Bump version

Add apply demurrage cli tool

See merge request cicnet/erc20-demurrage-token!9

.gitignore

@@ -0,0 +1,10 @@
+build/
+dist/
+*.egg-info
+__pycache__
+*.pyc
+gmon.out
+solidity/*.json
+solidity/*.bin
+.venv
+venv

.gitlab-ci.yml

@@ -0,0 +1,36 @@
+# To contribute improvements to CI/CD templates, please follow the Development guide at:
+# https://docs.gitlab.com/ee/development/cicd/templates.html
+# This specific template is located at:
+# https://gitlab.com/gitlab-org/gitlab/-/blob/master/lib/gitlab/ci/templates/Python.gitlab-ci.yml
+
+# Official language image. Look for the different tagged releases at:
+# https://hub.docker.com/r/library/python/tags/
+image: python:3.8
+
+# Change pip's cache directory to be inside the project directory since we can
+# only cache local items.
+variables:
+  PIP_CACHE_DIR: "$CI_PROJECT_DIR/.cache/pip"
+
+# Pip's cache doesn't store the python packages
+# https://pip.pypa.io/en/stable/reference/pip_install/#caching
+#
+# If you want to also cache the installed packages, you have to install
+# them in a virtualenv and cache it as well.
+cache:
+  paths:
+    - .cache/pip
+    - venv/
+
+before_script:
+  - cd ./python
+  - python --version  # For debugging
+  - pip install virtualenv
+  - virtualenv venv
+  - source venv/bin/activate
+
+test:
+  script:
+    - pip install -r requirements.txt -r test_requirements.txt --extra-index-url https://pip.grassrootseconomics.net
+    - bash run_tests.sh 
+

README.md

@@ -1,88 +1,95 @@
 # RedistributedDemurrageToken
 
+**this documentation is obsolete, will rewrite asap**
+
 ## Use Case
 * Network / Basic Income Token
   * 100 Sarafu is distributed to anyone in Kenya after user validation by the owner of a faucet which mints new Sarafu.
-  * Validated users are those that validate their phone number in Kenya.
-  * A monthly Sarafu holding tax aka ([demurrage](https://en.wikipedia.org/wiki/Demurrage_(currency))) of 2% is deducted from users 
-  * Each month (after a number of blocks) the total amount tax is distributed evenly out to _active_ users.
-    *  any single transaction by a user is considered _active_ (heartbeat) (possibly add minimum size of heartbeat in constructor (TODO))
+    * Validated users are those that validate their phone number in Kenya.
+  * A Sarafu holding tax aka ([demurrage](https://en.wikipedia.org/wiki/Demurrage_(currency))) of 0.000050105908373373% is charged from users per minute - such that over 1 month to total tax would be 2%. 
+  * After 1 week the total amount tax is distributed evenly out to _active_ users.
+    *  any single transaction by a user within that week is considered _active_ (heartbeat) 
   * This is meant to result in a disincentivization to hold (hodl) the Sarafu token and increase its usage as a medium of exchange rather than a store of value.
   * This token can be added to liquidity pools with other ERC20 tokens and or Community Inclusion Currencies (CICs) - and thereby act as a central network token and connect various tokens and CICs together.
   * Example 
-    -  With a demurrage of 2% - If there are 10 users all with balances of 1000 Sarafu and only 2 of them trade (assume they trade back and forth with no net balance change). 
+    -  With a demurrage of 2% (net per month) and a reward period of 1 month - If there are 10 users all with balances of 1000 Sarafu and only 2 of them trade that month (assume they trade back and forth with no net balance change). 
     - Then the resulting balances after one tax period of those two trading would be 1080 Sarafu while the remaining non-active users would be 980 Sarafu. If this behaviour continued in the next tax period, with the same two users only trading (with no net balance changes), they would have 1158.39999968 Sarafu and those users that are not trading would have their balances further reduced to 960.40 Sarafu. If this continued on ~forever those two active trading users would have the entire token supply and the non-trading users would eventually reach a zero balance.
     - this example calculation for 3 tax periods can be found here: https://gitlab.com/grassrootseconomics/cic-docs/-/blob/master/demurrage-redist-sarafu.ods
 
+## Nomenclature
 
-## Variables
-
-* Inputs to Constructor (Set only once during contract deployment can't be changed )  
-  * `Demurrage` aka Decay amount: A percentage of token supply that will be charged once per - aka `period` and evenly redistributed to _active_ users 
-  * Demurrage Period (blocks)- aka `period`: The number of blocks (equivalent to a time frame) over which a new Holding Fee is applied and redistributed. 
-  * Inflated Balance: The inflated balance of each user is stored for bookkeeping.
-  * Number of Decimals: Resolution on token (TODO) (Default 6)
-  * Minimum Activity Volume: (TODO) the minimum transaction amount to be considered active
-  * Sink Token Address: Rounding errors and if no one trades the tax goes to this address
+* `Demurrage` aka Decay amount: A percentage of token supply that will be charged once per minute and evenly redistributed to _active_ users every Demurrage Period (minutes)
+* Base balance: The inflated balance of each user is stored for bookkeeping.
+* Sink Token Address: Rounding errors and if no one trades the tax goes to this address
+* Demurrage Period (minutes)- aka `period`: The number of minutes over which a user must be _active_ to receive tax-redistibution. 
 
 
 ## Ownership
 
 * Contract creator is owner
-* Ownership can be transferred (also to ownership void contract "no more changes can be made")
+* Ownership can be transferred
 
 
 ## Mint
 
-* Owner can add minters
+* Owner can add minters and remove
   - A faucet contract would be a minter and choose the amount of tokens to mint and distribute to new _validated_ users.
   - The interface says the amount and is at the caller's discretion per contract call. _validation_ is outside of this contract.
+* A minter can remove itself
 * Minters can mint any amount
 
 
 ## Demurrage
-* Holding Tax (`demurrage`) is applied when a **mint** or **transfer** is triggered for first time/block in a new `period`; (it can also be triggered explicitly)
-  - Supply _stays the same_.
-  - Updates `demurrageModifier` which represents the accumulated tax value and is an exponential decay step (of size `demurrage`) for each `period`
-    - `demurrageModifier = (1-demurrage)^period` 
-      - e.g. a `demurrage` of 2% at a `period` of 1 would be give a `demurrageModifier = (1-0.02)^1 = 0.98`.
-      - e.g. a `demurrage` of 2% at a `period` of 2 would be give a `demurrageModifier = (1-0.02)^2 = 0.9604`.
+* Holding Tax (`demurrage`) is applied when a **mint** or **transfer**; (it can also be triggered explicitly)
+  - Note that the token supply _stays the same_ but a virtual _balance output_ is created.
+  - Updates `demurrageModifier` which represents the accumulated tax value and is an exponential decay step (of size `demurrage`) for each minute that has passed.
+    - `demurrageModifier = (1-demurrage)^(minute_passed)` 
+      - e.g. a `demurrage` of 2% after the 1st minute would be give a `demurrageModifier = (1-0.02)^1 = 0.98`.
+      - e.g. a `demurrage` after the 2nd minute would be give a `demurrageModifier = (1-0.02)^2 = 0.9604`.
 * All client-facing values (_balance output_ , _transfer inputs_) are adjusted with `demurrageModifier`.
   - e.g. `_balance output_ = user_balance - user_balance * demurrageModifier`
-* Edge case: `approve` call, which may be called on either side of a period.
 
 
 ## Redistribution
 
-* One redistribution entry is added to storage for each period;
+* One redistribution entry is added to storage for each `period`;
   - When `mint` is triggered, the new totalsupply is stored to the entry
   - When `transfer` is triggered, and the account did not yet participate in the `period`, the entry's participant count is incremented. 
 * Account must have "participated" in a period to be redistribution beneficiary.
-* Redistribution is applied when an account triggers a **transfer** for the first time in a new period;
+* Redistribution is applied when an account triggers a **transfer** for the first time in a new `period`;
   - Check if user has participated in `period`. (_active_ user heartbeat)
-  - Each _active_ user balance is increased by `(total supply at end of period * demurrageModifier ) / number_of_active_participants` via minting
+  - Each _active_ user balance in the `period` is increased by `(total supply at end of period * demurrageModifier ) / number_of_active_participants` via minting
   - Participation field is zeroed out for that user.
-* Fractions must be rounded down (TODO)
-  - Remainder is "dust" and should be sent to a dedicated "sink" token address (TODO)
-  - If no one is _active_ all taxes go to the same sink address
+* Fractions must be rounded down
+  - Remainder is "dust" and should be sent to a dedicated Sink Token Address.
+  - If no one is _active_ all taxes go to the Sink Token Address.
 
 
 ## Data structures
 
-* One word per account:
-  - bits 000-159: value
-  - bits 160-255: period
-  - (we have more room here in case we want to cram something else in)
-* One word per redistribution period:
-  - bits 000-055: period
-  - bits 056-215: supply
-  - bits 216-253: participant count
-  - bits     254: Set if individual redistribution amounts are fractions (TODO)
-  - bits     255: Set if "dust" has been transferred to sink (TODO)
+* One word per `account`:
+  - bits 000-071: value
+  - bits 072-103: period
+  - bits 104-255: (Unused)
+* One word per `redistributions` period:
+  - bits 000-031: period
+  - bits 032-103: supply
+  - bits 104-139: participant count
+  - bits 140-159: demurrage modifier
+  - bits 160-254: (Unused)
+  - bits     255: Set if individual redistribution amounts are fractions
+
+### Notes
+
+Accumulated demurrage modifier in `demurrageModifier` is 128 bit, but will be _truncated_ do 20 bits in `redistributions`. The 128 bit resolution is to used to reduce the impact of fractional drift of the long-term accumulation of the demurrage modifier. However, the demurrage snapshot values used in `redistributions` are parts-per-million and can be fully contained within a 20-bit value.
 
 
 ## QA
 
 * Basic python tests in place
-* How to determine and generate test vectors, and how to adapt them to scripts.
+* How to determine and generate sufficient test vectors, and how to adapt them to scripts.
 * Audit sources?
+
+## Known issues
+
+* A `transferFrom` following an `approve` call, when called across period thresholds, may fail if margin to demurraged amount is insufficient.

python/CHANGELOG

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+- 0.3.0
+	* Smart contracts use abdk math libraries, all exponential operations are static gas cost
+	* Add expiry features, after which balances are frozen and no more transfers or demurrage will occur
+	* Add sealable features for supply, sink address, expiry and minters (when sealed cannot be changed)
+	* Deployer script now takes demurrage amount as ppm instead of literal growth fraction
+	* Retire old multi and cap contracts
+	* Replace contract bitfields for redistributions with structs
+- 0.1.1
+	* Settable demurrage steps for apply demurrage cli tool
+- 0.1.0
+	* Dependency upgrades
+- 0.0.11
+	* Apply demurrage cli tool
+- 0.0.10
+	* Settable sink address
+- 0.0.9
+	* Correct redistribution amount for SingleNocap contract
+- 0.0.2
+	* Move to chainlib-eth
+- 0.0.1
+	* Interface for redistributed and non-redistributed, with or without cap

python/MANIFEST.in

@@ -0,0 +1 @@
+include erc20_demurrage_token/data/* erc20_demurrage_token/data/config/*.ini *requirements.txt

python/erc20_demurrage_token/__init__.py

@@ -0,0 +1,5 @@
+from .token import (
+        DemurrageToken,
+        DemurrageTokenSettings,
+        DemurrageRedistribution,
+        )

python/erc20_demurrage_token/data/__init__.py

@@ -0,0 +1,3 @@
+import os
+
+data_dir = os.path.realpath(os.path.dirname(__file__))

python/erc20_demurrage_token/data/config/eth.ini

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+[eth]
+provider=http://localhost:8545

python/erc20_demurrage_token/data/config/session.ini

@@ -0,0 +1,2 @@
+[session]
+chain_spec=

python/erc20_demurrage_token/data/config/token.ini

@@ -0,0 +1,8 @@
+[token]
+redistribution_period=10800
+demurrage_level=50
+supply_limit=0
+symbol=RDT
+name=Redistributed Demurraged Token
+decimals=6
+sink_address=

python/erc20_demurrage_token/demurrage.py

@@ -0,0 +1,67 @@
+# standard imports
+import logging
+import datetime
+import math
+
+# eternal imports
+from chainlib.eth.constant import ZERO_ADDRESS
+
+# local imports
+from .token import DemurrageToken
+
+logg = logging.getLogger(__name__)
+
+
+class DemurrageCalculator:
+
+    def __init__(self, interest_f_minute):
+
+        self.r_min = interest_f_minute
+        self.r_hour = 1 - ((1 -self.r_min) ** 60)
+        self.r_day = 1 - ((1 -self.r_hour) ** 24)
+        #self.r_week = interest_f_day ** 7
+        logg.info('demurrage calculator set with min {:.32f} hour {:.32f} day {:.32f}'.format(self.r_min, self.r_hour, self.r_day))
+
+
+    def amount_since(self, amount, timestamp):
+        delta = datetime.datetime.utcnow() - datetime.datetime.fromtimestamp(timestamp)
+        adjusted_amount = amount * ((1 - self.r_day) ** (delta.days))
+        logg.debug('adjusted for {} days {} -> {}'.format(delta.days, amount, adjusted_amount))
+
+        remainder = delta.seconds
+        remainder_hours = math.floor(remainder / (60 * 60))
+        adjusted_delta = adjusted_amount * ((1 - self.r_hour) ** remainder_hours)
+        adjusted_amount -= (adjusted_amount - adjusted_delta)
+        logg.debug('adjusted for {} hours {} -> {} delta {}'.format(remainder_hours, amount, adjusted_amount, adjusted_delta))
+
+        remainder -= (remainder_hours * (60 * 60))
+        remainder_minutes = math.floor(remainder / 60)
+        adjusted_delta = adjusted_amount * ((1 - self.r_min) ** remainder_minutes)
+        adjusted_amount -= (adjusted_amount - adjusted_delta)
+        logg.debug('adjusted for {} minutes {} -> {} delta {}'.format(remainder_minutes, amount, adjusted_amount, adjusted_delta))
+
+        return adjusted_amount
+
+    
+    def amount_since_slow(self, amount, timestamp):
+        delta = datetime.datetime.utcnow() - datetime.datetime.fromtimestamp(timestamp)
+        remainder_minutes = math.floor(delta.total_seconds() / 60)
+        adjusted_amount = amount * ((1 - self.r_min) ** remainder_minutes)
+        logg.debug('adjusted for {} minutes {} -> {} delta {}'.format(remainder_minutes, amount, adjusted_amount, amount - adjusted_amount))
+
+        return adjusted_amount
+
+
+    @staticmethod
+    def from_contract(rpc, chain_spec, contract_address, sender_address=ZERO_ADDRESS):
+        c = DemurrageToken(chain_spec)
+        o = c.tax_level(contract_address, sender_address=sender_address)
+        r = rpc.do(o)
+        taxlevel_i = c.parse_tax_level(r)
+
+        o = c.resolution_factor(contract_address, sender_address=sender_address)
+        r = rpc.do(o)
+        divider = c.parse_resolution_factor(r)
+        logg.debug('taxlevel {} f {}'.format(taxlevel_i, divider))
+        taxlevel_f = taxlevel_i / divider
+        return DemurrageCalculator(taxlevel_f)

python/erc20_demurrage_token/expiry.py

@@ -0,0 +1,36 @@
+# external imports
+from chainlib.eth.tx import (
+        TxFactory,
+        TxFormat,
+        )
+from chainlib.eth.contract import (
+        ABIContractEncoder,
+        ABIContractType,
+        abi_decode_single,
+        )
+from chainlib.eth.constant import ZERO_ADDRESS
+
+
+class ExpiryContract(TxFactory):
+
+    def set_expire_period(self, contract_address, sender_address, expire_timestamp, tx_format=TxFormat.JSONRPC):
+        enc = ABIContractEncoder()
+        enc.method('setExpirePeriod')
+        enc.typ(ABIContractType.UINT256)
+        enc.uint256(expire_timestamp)
+        data = enc.get()
+        tx = self.template(sender_address, contract_address, use_nonce=True)
+        tx = self.set_code(tx, data)
+        tx = self.finalize(tx, tx_format)
+        return tx
+
+
+    def expires(self, contract_address, sender_address=ZERO_ADDRESS):
+        return self.call_noarg('expires', contract_address, sender_address=sender_address)
+
+
+    @classmethod
+    def parse_expires(self, v):
+        return abi_decode_single(ABIContractType.UINT256, v)
+
+

python/erc20_demurrage_token/runnable/deploy.py

@@ -0,0 +1,175 @@
+"""Deploy sarafu token
+
+.. moduleauthor:: Louis Holbrook <dev@holbrook.no>
+.. pgp:: 0826EDA1702D1E87C6E2875121D2E7BB88C2A746 
+
+"""
+
+# standard imports
+import sys
+import os
+import json
+import argparse
+import logging
+
+# external imports
+import confini
+from funga.eth.signer import EIP155Signer
+from funga.eth.keystore.dict import DictKeystore
+from chainlib.chain import ChainSpec
+from chainlib.eth.nonce import (
+        RPCNonceOracle,
+        OverrideNonceOracle,
+        )
+from chainlib.eth.gas import (
+        RPCGasOracle,
+        OverrideGasOracle,
+        )
+from chainlib.eth.connection import EthHTTPConnection
+from chainlib.eth.tx import receipt
+from chainlib.eth.constant import ZERO_ADDRESS
+import chainlib.eth.cli
+from chainlib.eth.cli.arg import (
+        Arg,
+        ArgFlag,
+        process_args,
+        )
+from chainlib.eth.cli.config import (
+        Config,
+        process_config,
+        )
+from chainlib.eth.cli.log import process_log
+from chainlib.eth.settings import process_settings
+from chainlib.eth.address import to_checksum_address
+from chainlib.settings import ChainSettings
+
+from dexif import to_fixed
+
+# local imports
+import erc20_demurrage_token
+from erc20_demurrage_token import (
+        DemurrageToken,
+        DemurrageTokenSettings,
+        )
+
+logg = logging.getLogger()
+
+script_dir = os.path.dirname(__file__)
+data_dir = os.path.join(script_dir, '..', 'data')
+
+config_dir = os.path.join(data_dir, 'config')
+
+
+def process_config_local(config, arg, args, flags):
+    config.add(args.token_name, 'TOKEN_NAME')
+    config.add(args.token_symbol, 'TOKEN_SYMBOL')
+    config.add(args.token_decimals, 'TOKEN_DECIMALS')
+    sink_address = to_checksum_address(args.sink_address)
+    config.add(sink_address, 'TOKEN_SINK_ADDRESS')
+    config.add(args.redistribution_period, 'TOKEN_REDISTRIBUTION_PERIOD')
+
+    v = args.demurrage_level / 1000000
+    if v >= 1.0:
+        raise ValueError('demurrage level must be less than 100%')
+    demurrage_level = to_fixed(v)
+    config.add(demurrage_level, 'TOKEN_DEMURRAGE_LEVEL')
+    return config
+
+
+arg_flags = ArgFlag()
+arg = Arg(arg_flags)
+flags = arg_flags.STD_WRITE | arg_flags.WALLET
+
+argparser = chainlib.eth.cli.ArgumentParser(arg_flags)
+argparser = process_args(argparser, arg, flags)
+argparser.add_argument('--name', dest='token_name', type=str, help='Token name')
+argparser.add_argument('--symbol', dest='token_symbol', required=True, type=str, help='Token symbol')
+argparser.add_argument('--decimals', dest='token_decimals', type=int, help='Token decimals')
+argparser.add_argument('--sink-address', dest='sink_address', type=str, help='demurrage level,ppm per minute') 
+argparser.add_argument('--redistribution-period', type=int, help='redistribution period, minutes (0 = deactivate)') # default 10080 = week
+argparser.add_argument('--demurrage-level', dest='demurrage_level', type=int, help='demurrage level, ppm per period') 
+args = argparser.parse_args()
+
+logg = process_log(args, logg)
+
+config = Config()
+config = process_config(config, arg, args, flags)
+config = process_config_local(config, arg, args, flags)
+logg.debug('config loaded:\n{}'.format(config))
+
+settings = ChainSettings()
+settings = process_settings(settings, config)
+logg.debug('settings loaded:\n{}'.format(settings))
+
+
+#extra_args = {
+#        'redistribution_period': 'TOKEN_REDISTRIBUTION_PERIOD',
+#        'demurrage_level': 'TOKEN_DEMURRAGE_LEVEL',
+#        'supply_limit': 'TOKEN_SUPPLY_LIMIT',
+#        'token_name': 'TOKEN_NAME',
+#        'token_symbol': 'TOKEN_SYMBOL',
+#        'token_decimals': 'TOKEN_DECIMALS',
+#        'sink_address': 'TOKEN_SINK_ADDRESS',
+#        'multi': None,
+#        }
+#config = chainlib.eth.cli.Config.from_args(args, arg_flags, extra_args=extra_args, default_fee_limit=DemurrageToken.gas(), base_config_dir=config_dir)
+#
+#if not bool(config.get('TOKEN_NAME')):
+#    logg.info('token name not set, using symbol {} as name'.format(config.get('TOKEN_SYMBOL')))
+#    config.add(config.get('TOKEN_SYMBOL'), 'TOKEN_NAME', True)
+#
+#if config.get('TOKEN_SUPPLY_LIMIT') == None:
+#    config.add(0, 'TOKEN_SUPPLY_LIMIT', True)
+#
+#if config.get('TOKEN_REDISTRIBUTION_PERIOD') == None:
+#    config.add(10800, 'TOKEN_REDISTRIBUTION_PERIOD', True)
+#logg.debug('config loaded:\n{}'.format(config))
+#
+#wallet = chainlib.eth.cli.Wallet()
+#wallet.from_config(config)
+#
+#rpc = chainlib.eth.cli.Rpc(wallet=wallet)
+#conn = rpc.connect_by_config(config)
+#
+#chain_spec = ChainSpec.from_chain_str(config.get('CHAIN_SPEC'))
+
+def main():
+    conn = settings.get('CONN')
+    c = DemurrageToken(
+            settings.get('CHAIN_SPEC'),
+            signer=settings.get('SIGNER'),
+            gas_oracle=settings.get('FEE_ORACLE'),
+            nonce_oracle=settings.get('NONCE_ORACLE'),
+            )
+    token_settings = DemurrageTokenSettings()
+    token_settings.name = config.get('TOKEN_NAME')
+    token_settings.symbol = config.get('TOKEN_SYMBOL')
+    token_settings.decimals = int(config.get('TOKEN_DECIMALS'))
+    token_settings.demurrage_level = int(config.get('TOKEN_DEMURRAGE_LEVEL'))
+    token_settings.period_minutes = int(config.get('TOKEN_REDISTRIBUTION_PERIOD'))
+    token_settings.sink_address = config.get('TOKEN_SINK_ADDRESS')
+
+    (tx_hash_hex, o) = c.constructor(
+            settings.get('SENDER_ADDRESS'),
+            token_settings,
+            )
+    if settings.get('RPC_SEND'):
+        conn.do(o)
+        if config.true('_WAIT'):
+            r = conn.wait(tx_hash_hex)
+            if r['status'] == 0:
+                sys.stderr.write('EVM revert while deploying contract. Wish I had more to tell you')
+                sys.exit(1)
+            # TODO: pass through translator for keys (evm tester uses underscore instead of camelcase)
+            address = r['contractAddress']
+
+            print(address)
+        else:
+            print(tx_hash_hex)
+
+    else:
+        print(o)
+
+
+if __name__ == '__main__':
+    main()

python/erc20_demurrage_token/seal.py

@@ -0,0 +1,66 @@
+# standard imports
+import enum
+
+# external imports
+from chainlib.eth.constant import ZERO_ADDRESS
+from chainlib.jsonrpc import JSONRPCRequest
+from chainlib.eth.tx import (
+        TxFactory,
+        TxFormat,
+        )
+from chainlib.eth.contract import (
+        ABIContractEncoder,
+        ABIContractType,
+        abi_decode_single,
+        )
+from hexathon import (
+        add_0x,
+        )
+
+class ContractState(enum.IntEnum):
+    MINTER_STATE = 1
+    SINK_STATE = 2
+    EXPIRY_STATE = 4
+    CAP_STATE = 8
+
+CONTRACT_SEAL_STATE_MAX = 0
+
+for v in dir(ContractState):
+    if len(v) > 6 and v[-6:] == '_STATE':
+       CONTRACT_SEAL_STATE_MAX += getattr(ContractState, v).value
+
+
+class SealedContract(TxFactory):
+
+    def seal(self, contract_address, sender_address, seal, tx_format=TxFormat.JSONRPC):
+        enc = ABIContractEncoder()
+        enc.method('seal')
+        enc.typ(ABIContractType.UINT256)
+        enc.uint256(seal)
+        data = enc.get()
+        tx = self.template(sender_address, contract_address, use_nonce=True)
+        tx = self.set_code(tx, data)
+        tx = self.finalize(tx, tx_format)
+        return tx
+
+
+    def is_sealed(self, contract_address, v, sender_address=ZERO_ADDRESS, id_generator=None):
+        j = JSONRPCRequest(id_generator)
+        o = j.template()
+        o['method'] = 'eth_call'
+        enc = ABIContractEncoder()
+        enc.method('isSealed')
+        enc.typ(ABIContractType.UINT256)
+        enc.uint256(v)
+        data = add_0x(enc.get())
+        tx = self.template(sender_address, contract_address)
+        tx = self.set_code(tx, data)
+        o['params'].append(self.normalize(tx))
+        o['params'].append('latest')
+        o = j.finalize(o)
+        return o
+
+
+    @classmethod
+    def parse_is_sealed(self, v):
+        return abi_decode_single(ABIContractType.BOOLEAN, v)

python/erc20_demurrage_token/sim/__init__.py

@@ -0,0 +1,2 @@
+from .sim import DemurrageTokenSimulation
+from .error import TxLimitException

python/erc20_demurrage_token/sim/error.py

@@ -0,0 +1,2 @@
+class TxLimitException(RuntimeError):
+    pass

python/erc20_demurrage_token/sim/sim.py

@@ -0,0 +1,302 @@
+# standard imports
+import logging
+
+# external imports
+from chainlib.chain import ChainSpec
+from chainlib.eth.unittest.ethtester import create_tester_signer
+from chainlib.eth.unittest.base import TestRPCConnection
+from chainlib.eth.tx import (
+        receipt,
+        Tx,
+        )
+from chainlib.eth.nonce import RPCNonceOracle
+from chainlib.eth.gas import (
+        OverrideGasOracle,
+        Gas,
+        )
+from chainlib.eth.address import to_checksum_address
+from chainlib.eth.block import (
+        block_latest,
+        block_by_number,
+        block_by_hash,
+        )
+from funga.eth.keystore.dict import DictKeystore
+from funga.eth.signer import EIP155Signer
+from hexathon import (
+        strip_0x,
+        add_0x,
+        )
+
+# local imports
+from erc20_demurrage_token import DemurrageToken
+from erc20_demurrage_token.sim.error import TxLimitException
+
+logg = logging.getLogger(__name__)
+
+
+class DemurrageTokenSimulation:
+
+    def __init__(self, chain_str, settings, redistribute=True, cap=0, actors=1):
+        self.chain_spec = ChainSpec.from_chain_str(chain_str)
+        self.accounts = []
+        self.redistribute = redistribute
+        self.keystore = DictKeystore()
+        self.signer = EIP155Signer(self.keystore)
+        self.eth_helper = create_tester_signer(self.keystore)
+        self.eth_backend = self.eth_helper.backend
+        self.gas_oracle = OverrideGasOracle(limit=100000, price=1)
+        self.rpc = TestRPCConnection(None, self.eth_helper, self.signer)
+        for a in self.keystore.list():
+            self.accounts.append(add_0x(to_checksum_address(a)))
+        settings.sink_address = self.accounts[0]
+
+        self.actors = []
+        for i in range(actors):
+            idx = i % 10
+            address = self.keystore.new()
+            self.actors.append(address)
+            self.accounts.append(address)
+
+            nonce_oracle = RPCNonceOracle(self.accounts[idx], conn=self.rpc)
+            c = Gas(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle, gas_oracle=self.gas_oracle)
+            (tx_hash, o) = c.create(self.accounts[idx], address, 100000 * 1000000)
+            self.rpc.do(o)
+            o = receipt(tx_hash)
+            r = self.rpc.do(o)
+            if r['status'] != 1:
+                raise RuntimeError('failed gas transfer to account #{}: {} from {}'.format(i, address, self.accounts[idx]))
+            logg.info('added actor account #{}: {} block {}'.format(i, address, r['block_number']))
+
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.constructor(self.accounts[0], settings, redistribute=redistribute, cap=cap)
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        if (r['status'] != 1):
+            raise RuntimeError('contract deployment failed')
+        self.address = r['contract_address']
+        logg.info('deployed contract to {} block {}'.format(self.address, r['block_number']))
+
+        o = block_latest()
+        r = self.rpc.do(o)
+        self.last_block = r
+        self.start_block = self.last_block
+
+        o = block_by_number(r)
+        r = self.rpc.do(o)
+        self.last_timestamp = r['timestamp']
+        self.start_timestamp = self.last_timestamp
+
+        nonce_oracle = RPCNonceOracle(self.accounts[0], conn=self.rpc)
+        o = c.decimals(self.address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        self.decimals = c.parse_decimals(r)
+
+        self.period_seconds = settings.period_minutes * 60
+
+        self.period = 1
+        self.period_txs = []
+        self.period_tx_limit = self.period_seconds - 1
+        self.sink_address = settings.sink_address
+
+        logg.info('intialized at block {} timestamp {} period {} demurrage level {} sink address {} (first address in keystore)'.format(
+                self.last_block,
+                self.last_timestamp,
+                settings.period_minutes,
+                settings.demurrage_level,
+                settings.sink_address,
+                )
+            )
+
+        self.eth_helper.disable_auto_mine_transactions()
+
+        self.caller_contract = DemurrageToken(self.chain_spec)
+        self.caller_address = self.accounts[0]
+
+
+    def __check_limit(self):
+        if self.period_tx_limit == len(self.period_txs):
+            raise TxLimitException('reached period tx limit {}'.format(self.period_tx_limit))
+
+
+    def __check_tx(self, tx_hash):
+        o = receipt(tx_hash)
+        rcpt = self.rpc.do(o)
+        if rcpt['status'] == 0:
+            raise RuntimeError('tx {} (block {} index {}) failed'.format(tx_hash, self.last_block, rcpt['transaction_index']))
+        logg.debug('tx {} block {} index {} verified'.format(tx_hash, self.last_block, rcpt['transaction_index']))
+
+
+    def get_now(self):
+        o = block_latest()
+        r = self.rpc.do(o)
+        o = block_by_number(r, include_tx=False)
+        r = self.rpc.do(o)
+        return r['timestamp']
+
+
+    def get_minutes(self):
+        t = self.get_now()
+        return int((t - self.start_timestamp) / 60)
+
+
+    def get_start(self):
+        return self.start_timestamp
+
+
+    def get_period(self):
+        o = self.caller_contract.actual_period(self.address, sender_address=self.caller_address)
+        r = self.rpc.do(o)
+        return self.caller_contract.parse_actual_period(r)
+
+
+    def get_demurrage(self):
+        o = self.caller_contract.demurrage_amount(self.address, sender_address=self.caller_address)
+        r = self.rpc.do(o)
+        logg.info('demrrage amount {}'.format(r))
+        return float(self.caller_contract.parse_demurrage_amount(r) / (10 ** 38))
+
+
+    def get_supply(self):
+        o = self.caller_contract.total_supply(self.address, sender_address=self.caller_address)
+        r = self.rpc.do(o)
+        supply = self.caller_contract.parse_total_supply(r)
+        return supply
+
+
+    def from_units(self, v):
+        return v * (10 ** self.decimals)
+
+
+    def mint(self, recipient, value):
+        self.__check_limit()
+        nonce_oracle = RPCNonceOracle(self.accounts[0], conn=self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle, gas_oracle=self.gas_oracle)
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], recipient, value)
+        self.rpc.do(o)
+        self.__next_block()
+        self.__check_tx(tx_hash)
+        self.period_txs.append(tx_hash)
+        logg.info('mint {} tokens to {} - {}'.format(value, recipient, tx_hash))
+        return tx_hash
+
+
+    def transfer(self, sender, recipient, value):
+        nonce_oracle = RPCNonceOracle(sender, conn=self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle, gas_oracle=self.gas_oracle)
+        (tx_hash, o) = c.transfer(self.address, sender, recipient, value)
+        self.rpc.do(o)
+        self.__next_block()
+        self.__check_tx(tx_hash)
+        self.period_txs.append(tx_hash)
+        logg.info('transfer {} tokens from {} to {} - {}'.format(value, sender, recipient, tx_hash))
+        return tx_hash
+
+
+    def balance(self, holder, base=False):
+        o = None
+        if base:
+            o = self.caller_contract.base_balance_of(self.address, holder, sender_address=self.caller_address)
+        else:
+            o = self.caller_contract.balance_of(self.address, holder, sender_address=self.caller_address)
+        r = self.rpc.do(o)
+        return self.caller_contract.parse_balance(r)
+
+
+    def __next_block(self):
+        hsh = self.eth_helper.mine_block()
+        o = block_by_hash(hsh)
+        r = self.rpc.do(o)
+
+        for tx_hash in r['transactions']:
+            o = receipt(tx_hash)
+            rcpt = self.rpc.do(o)
+            if rcpt['status'] == 0:
+                raise RuntimeError('tx {} (block {} index {}) failed'.format(tx_hash, self.last_block, rcpt['transaction_index']))
+            logg.debug('tx {} (block {} index {}) verified'.format(tx_hash, self.last_block, rcpt['transaction_index']))
+
+        logg.debug('now at block {} timestamp {}'.format(r['number'], r['timestamp']))
+
+
+    def next(self):
+        target_timestamp = self.start_timestamp + (self.period * self.period_seconds)
+        logg.info('warping to {}, {} from start {}'.format(target_timestamp, target_timestamp - self.start_timestamp, self.start_timestamp))
+        self.last_timestamp = target_timestamp 
+
+        o = block_latest()
+        r = self.rpc.do(o)
+        self.last_block = r
+        o = block_by_number(r)
+        r = self.rpc.do(o)
+        cursor_timestamp = r['timestamp'] + 1
+
+        nonce_oracle = RPCNonceOracle(self.accounts[2], conn=self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle, gas_oracle=self.gas_oracle)
+
+        i = 0
+        while cursor_timestamp < target_timestamp:
+            logg.info('mining block on {}'.format(cursor_timestamp))
+            (tx_hash, o) = c.apply_demurrage(self.address, self.accounts[2])
+            self.rpc.do(o)
+            self.eth_helper.time_travel(cursor_timestamp + 60)
+            self.__next_block()
+            o = receipt(tx_hash)
+            r = self.rpc.do(o)
+            if r['status'] == 0:
+                raise RuntimeError('demurrage fast-forward failed on step {} timestamp {} block timestamp {} target {}'.format(i, cursor_timestamp, target_timestamp))
+            cursor_timestamp += 60*60 # 1 hour
+            o = block_by_number(r['block_number'])
+            b = self.rpc.do(o)
+            logg.info('block mined on timestamp {} (delta {}) block number {}'.format(b['timestamp'], b['timestamp'] - self.start_timestamp, b['number']))
+            i += 1
+
+        
+        (tx_hash, o) = c.apply_demurrage(self.address, self.accounts[2])
+        self.rpc.do(o)
+
+        nonce_oracle = RPCNonceOracle(self.accounts[3], conn=self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle, gas_oracle=self.gas_oracle)
+        (tx_hash, o) = c.change_period(self.address, self.accounts[3])
+        self.rpc.do(o)
+        self.eth_helper.time_travel(target_timestamp + 1)
+        self.__next_block()
+    
+        o = block_latest()
+        r = self.rpc.do(o)
+        o = block_by_number(self.last_block)
+        r = self.rpc.do(o)
+        self.last_block = r['number']
+        block_base = self.last_block
+        logg.info('block before demurrage execution {} {}'.format(r['timestamp'], r['number']))
+
+        if self.redistribute:
+            for actor in self.actors:
+                nonce_oracle = RPCNonceOracle(actor, conn=self.rpc)
+                c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle, gas_oracle=self.gas_oracle)
+                (tx_hash, o) = c.apply_redistribution_on_account(self.address, actor, actor)
+                self.rpc.do(o)
+
+            nonce_oracle = RPCNonceOracle(self.sink_address, conn=self.rpc)
+            c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle, gas_oracle=self.gas_oracle)
+            (tx_hash, o) = c.apply_redistribution_on_account(self.address, self.sink_address, self.sink_address)
+            self.rpc.do(o)
+
+        self.__next_block()
+
+        o = block_latest()
+        self.last_block = self.rpc.do(o)
+
+        o = block_by_number(self.last_block)
+        r = self.rpc.do(o)
+        for tx_hash in r['transactions']:
+            o = receipt(tx_hash)
+            rcpt = self.rpc.do(o)
+            if rcpt['status'] == 0:
+                raise RuntimeError('demurrage step failed on block {}'.format(self.last_block))
+
+        self.last_timestamp = r['timestamp']
+        logg.debug('next concludes at block {} timestamp {}, {} after start'.format(self.last_block, self.last_timestamp, self.last_timestamp - self.start_timestamp))
+        self.period += 1
+        self.period_txs = []
+
+        return (self.last_block, self.last_timestamp)

python/erc20_demurrage_token/token.py

@@ -0,0 +1,656 @@
+# standard imports
+import os
+import logging
+
+# external imports
+from chainlib.eth.tx import (
+        TxFactory,
+        TxFormat,
+        )
+from chainlib.hash import keccak256_string_to_hex
+from chainlib.eth.contract import (
+        ABIContractEncoder,
+        ABIContractDecoder,
+        ABIContractType,
+        abi_decode_single,
+        )
+from chainlib.eth.constant import ZERO_ADDRESS
+from chainlib.jsonrpc import JSONRPCRequest
+from eth_erc20 import ERC20
+from hexathon import (
+        add_0x,
+        strip_0x,
+        )
+from dexif import from_fixed
+
+# local imports
+from erc20_demurrage_token.data import data_dir
+from erc20_demurrage_token.seal import SealedContract
+from erc20_demurrage_token.expiry import ExpiryContract
+
+logg = logging.getLogger(__name__)
+
+
+class DemurrageRedistribution:
+    
+    def __init__(self, v):
+        d = ABIContractDecoder()
+        v = strip_0x(v)
+        d.typ(ABIContractType.UINT256)
+        d.typ(ABIContractType.UINT256)
+        d.typ(ABIContractType.BYTES32)
+        d.val(v[:64])
+        d.val(v[64:128])
+        d.val(v[128:192])
+        r = d.decode()
+
+        self.period = r[0]
+        self.value = r[1]
+        self.demurrage = from_fixed(r[2])
+
+
+    def __str__(self):
+        return 'period {} value {} demurrage {}'.format(self.period, self.value, self.demurrage)
+
+
+class DemurrageTokenSettings:
+
+    def __init__(self):
+        self.name = None
+        self.symbol = None
+        self.decimals = None
+        self.demurrage_level = None
+        self.period_minutes = None
+        self.sink_address = None
+
+
+    def __str__(self):
+        return 'name {} demurrage level {} period minutes {} sink address {}'.format(
+                self.name,
+                self.demurrage_level,
+                self.period_minutes,
+                self.sink_address,
+                )
+
+
+class DemurrageToken(ERC20, SealedContract, ExpiryContract):
+
+    __abi = {}
+    __bytecode = {}
+
+    def constructor(self, sender_address, settings, tx_format=TxFormat.JSONRPC):
+        code = DemurrageToken.bytecode()
+        enc = ABIContractEncoder()
+        enc.string(settings.name)
+        enc.string(settings.symbol)
+        enc.uint256(settings.decimals)
+        enc.uint256(settings.demurrage_level)
+        enc.uint256(settings.period_minutes)
+        enc.address(settings.sink_address)
+        code += enc.get()
+        tx = self.template(sender_address, None, use_nonce=True)
+        tx = self.set_code(tx, code)
+        return self.finalize(tx, tx_format)
+
+
+    @staticmethod
+    def gas(code=None):
+        return 4000000
+
+
+    @staticmethod
+    def abi(multi=True):
+        name = 'DemurrageTokenSingleNocap'
+        if DemurrageToken.__abi.get(name) == None:
+            f = open(os.path.join(data_dir, name + '.json'), 'r')
+            DemurrageToken.__abi[name] = json.load(f)
+            f.close()
+        return DemurrageToken.__abi[name]
+
+
+    @staticmethod
+    def bytecode(multi=True):
+        name = 'DemurrageTokenSingleNocap'
+        if DemurrageToken.__bytecode.get(name) == None:
+            f = open(os.path.join(data_dir, name + '.bin'), 'r')
+            DemurrageToken.__bytecode[name] = f.read()
+            f.close()
+        return DemurrageToken.__bytecode[name]
+
+
+    def increase_allowance(self, contract_address, sender_address, address, value, tx_format=TxFormat.JSONRPC):
+        enc = ABIContractEncoder()
+        enc.method('increaseAllowance')
+        enc.typ(ABIContractType.ADDRESS)
+        enc.typ(ABIContractType.UINT256)
+        enc.address(address)
+        enc.uint256(value)
+        data = enc.get()
+        tx = self.template(sender_address, contract_address, use_nonce=True)
+        tx = self.set_code(tx, data)
+        tx = self.finalize(tx, tx_format)
+        return tx
+
+
+    def decrease_allowance(self, contract_address, sender_address, address, value, tx_format=TxFormat.JSONRPC):
+        enc = ABIContractEncoder()
+        enc.method('decreaseAllowance')
+        enc.typ(ABIContractType.ADDRESS)
+        enc.typ(ABIContractType.UINT256)
+        enc.address(address)
+        enc.uint256(value)
+        data = enc.get()
+        tx = self.template(sender_address, contract_address, use_nonce=True)
+        tx = self.set_code(tx, data)
+        tx = self.finalize(tx, tx_format)
+        return tx
+
+
+    def add_minter(self, contract_address, sender_address, address, tx_format=TxFormat.JSONRPC):
+        enc = ABIContractEncoder()
+        enc.method('addMinter')
+        enc.typ(ABIContractType.ADDRESS)
+        enc.address(address)
+        data = enc.get()
+        tx = self.template(sender_address, contract_address, use_nonce=True)
+        tx = self.set_code(tx, data)
+        tx = self.finalize(tx, tx_format)
+        return tx
+
+
+    def set_max_supply(self, contract_address, sender_address, cap, tx_format=TxFormat.JSONRPC):
+        enc = ABIContractEncoder()
+        enc.method('setMaxSupply')
+        enc.typ(ABIContractType.UINT256)
+        enc.uint256(cap)
+        data = enc.get()
+        tx = self.template(sender_address, contract_address, use_nonce=True)
+        tx = self.set_code(tx, data)
+        tx = self.finalize(tx, tx_format)
+        return tx
+
+    def remove_minter(self, contract_address, sender_address, address, tx_format=TxFormat.JSONRPC):
+        enc = ABIContractEncoder()
+        enc.method('removeMinter')
+        enc.typ(ABIContractType.ADDRESS)
+        enc.address(address)
+        data = enc.get()
+        tx = self.template(sender_address, contract_address, use_nonce=True)
+        tx = self.set_code(tx, data)
+        tx = self.finalize(tx, tx_format)
+        return tx
+
+
+    def mint_to(self, contract_address, sender_address, address, value, tx_format=TxFormat.JSONRPC):
+        enc = ABIContractEncoder()
+        enc.method('mintTo')
+        enc.typ(ABIContractType.ADDRESS)
+        enc.typ(ABIContractType.UINT256)
+        enc.address(address)
+        enc.uint256(value)
+        data = enc.get()
+        tx = self.template(sender_address, contract_address, use_nonce=True)
+        tx = self.set_code(tx, data)
+        tx = self.finalize(tx, tx_format)
+        return tx
+
+
+    def burn(self, contract_address, sender_address, value, tx_format=TxFormat.JSONRPC):
+        enc = ABIContractEncoder()
+        enc.method('burn')
+        enc.typ(ABIContractType.UINT256)
+        enc.uint256(value)
+        data = enc.get()
+        tx = self.template(sender_address, contract_address, use_nonce=True)
+        tx = self.set_code(tx, data)
+        tx = self.finalize(tx, tx_format)
+        return tx
+
+
+    def total_burned(self, contract_address, sender_address=ZERO_ADDRESS, id_generator=None):
+        j = JSONRPCRequest(id_generator)
+        o = j.template()
+        o['method'] = 'eth_call'
+        enc = ABIContractEncoder()
+        enc.method('totalBurned')
+        data = add_0x(enc.get())
+        tx = self.template(sender_address, contract_address)
+        tx = self.set_code(tx, data)
+        o['params'].append(self.normalize(tx))
+        o['params'].append('latest')
+        o = j.finalize(o)
+        return o
+
+
+    def to_base_amount(self, contract_address, value, sender_address=ZERO_ADDRESS, id_generator=None):
+        j = JSONRPCRequest(id_generator)
+        o = j.template()
+        o['method'] = 'eth_call'
+        enc = ABIContractEncoder()
+        enc.method('toBaseAmount')
+        enc.typ(ABIContractType.UINT256)
+        enc.uint256(value)
+        data = add_0x(enc.get())
+        tx = self.template(sender_address, contract_address)
+        tx = self.set_code(tx, data)
+        o['params'].append(self.normalize(tx))
+        o['params'].append('latest')
+        o = j.finalize(o)
+        return o
+
+
+    def remainder(self, contract_address, parts, whole, sender_address=ZERO_ADDRESS, id_generator=None):
+        j = JSONRPCRequest(id_generator)
+        o = j.template()
+        o['method'] = 'eth_call'
+        enc = ABIContractEncoder()
+        enc.method('remainder')
+        enc.typ(ABIContractType.UINT256)
+        enc.typ(ABIContractType.UINT256)
+        enc.uint256(parts)
+        enc.uint256(whole)
+        data = add_0x(enc.get())
+        tx = self.template(sender_address, contract_address)
+        tx = self.set_code(tx, data)
+        o['params'].append(self.normalize(tx))
+        o['params'].append('latest')
+        o = j.finalize(o)
+        return o
+
+
+    def redistributions(self, contract_address, idx, sender_address=ZERO_ADDRESS, id_generator=None):
+        j = JSONRPCRequest(id_generator)
+        o = j.template()
+        o['method'] = 'eth_call'
+        enc = ABIContractEncoder()
+        enc.method('redistributions')
+        enc.typ(ABIContractType.UINT256)
+        enc.uint256(idx)
+        data = add_0x(enc.get())
+        tx = self.template(sender_address, contract_address)
+        tx = self.set_code(tx, data)
+        o['params'].append(self.normalize(tx))
+        o['params'].append('latest')
+        o = j.finalize(o)
+        return o
+
+
+    def account_period(self, contract_address, address, sender_address=ZERO_ADDRESS, id_generator=None):
+        j = JSONRPCRequest(id_generator)
+        o = j.template()
+        o['method'] = 'eth_call'
+        enc = ABIContractEncoder()
+        enc.method('accountPeriod')
+        enc.typ(ABIContractType.ADDRESS)
+        enc.address(address)
+        data = add_0x(enc.get())
+        tx = self.template(sender_address, contract_address)
+        tx = self.set_code(tx, data)
+        o['params'].append(self.normalize(tx))
+        o['params'].append('latest')
+        o = j.finalize(o)
+        return o
+
+
+    def to_redistribution(self, contract_address, participants, demurrage_modifier, value, period, sender_address=ZERO_ADDRESS, id_generator=None):
+        j = JSONRPCRequest(id_generator)
+        o = j.template()
+        o['method'] = 'eth_call'
+        enc = ABIContractEncoder()
+        enc.method('toRedistribution')
+        enc.typ(ABIContractType.UINT256)
+        enc.typ_literal('int128')
+        enc.typ(ABIContractType.UINT256)
+        enc.typ(ABIContractType.UINT256)
+        enc.uint256(participants)
+        enc.uint256(demurrage_modifier)
+        enc.uint256(value)
+        enc.uint256(period)
+        data = add_0x(enc.get())
+        tx = self.template(sender_address, contract_address)
+        tx = self.set_code(tx, data)
+        o['params'].append(self.normalize(tx))
+        o['params'].append('latest')
+        o = j.finalize(o)
+        return o
+
+
+
+    def to_redistribution_period(self, contract_address, redistribution, sender_address=ZERO_ADDRESS, id_generator=None):
+        j = JSONRPCRequest(id_generator)
+        o = j.template()
+        o['method'] = 'eth_call'
+        enc = ABIContractEncoder()
+        enc.method('toRedistributionPeriod')
+        v = strip_0x(redistribution)
+        enc.typ_literal('(uint32,uint72,uint64)')
+        enc.bytes32(v[:64])
+        enc.bytes32(v[64:128])
+        enc.bytes32(v[128:192])
+        data = add_0x(enc.get())
+        tx = self.template(sender_address, contract_address)
+        tx = self.set_code(tx, data)
+        o['params'].append(self.normalize(tx))
+        o['params'].append('latest')
+        o = j.finalize(o)
+        return o
+
+
+#    def to_redistribution_participants(self, contract_address, redistribution, sender_address=ZERO_ADDRESS, id_generator=None):
+#        j = JSONRPCRequest(id_generator)
+#        o = j.template()
+#        o['method'] = 'eth_call'
+#        enc = ABIContractEncoder()
+#        enc.method('toRedistributionParticipants')
+#        v = strip_0x(redistribution)
+#        enc.typ_literal('(uint32,uint72,uint104)')
+#        #enc.typ(ABIContractType.BYTES32)
+#        enc.bytes32(v[:64])
+#        enc.bytes32(v[64:128])
+#        enc.bytes32(v[128:192])
+#        data = add_0x(enc.get())
+#        tx = self.template(sender_address, contract_address)
+#        tx = self.set_code(tx, data)
+#        o['params'].append(self.normalize(tx))
+#        o['params'].append('latest')
+#        o = j.finalize(o)
+#        return o
+#
+
+    def to_redistribution_supply(self, contract_address, redistribution, sender_address=ZERO_ADDRESS, id_generator=None):
+        j = JSONRPCRequest(id_generator)
+        o = j.template()
+        o['method'] = 'eth_call'
+        enc = ABIContractEncoder()
+        enc.method('toRedistributionSupply')
+        v = strip_0x(redistribution)
+        enc.typ_literal('(uint32,uint72,uint64)')
+        enc.bytes32(v[:64])
+        enc.bytes32(v[64:128])
+        enc.bytes32(v[128:192])
+        data = add_0x(enc.get())
+        tx = self.template(sender_address, contract_address)
+        tx = self.set_code(tx, data)
+        o['params'].append(self.normalize(tx))
+        o['params'].append('latest')
+        o = j.finalize(o)
+        return o
+
+
+    def to_redistribution_demurrage_modifier(self, contract_address, redistribution, sender_address=ZERO_ADDRESS, id_generator=None):
+        j = JSONRPCRequest(id_generator)
+        o = j.template()
+        o['method'] = 'eth_call'
+        enc = ABIContractEncoder()
+        enc.method('toRedistributionDemurrageModifier')
+        v = strip_0x(redistribution)
+        enc.typ_literal('(uint32,uint72,uint64)')
+        enc.bytes32(v[:64])
+        enc.bytes32(v[64:128])
+        enc.bytes32(v[128:192])
+        data = add_0x(enc.get())
+        tx = self.template(sender_address, contract_address)
+        tx = self.set_code(tx, data)
+        o['params'].append(self.normalize(tx))
+        o['params'].append('latest')
+        o = j.finalize(o)
+        return o
+
+
+    def base_balance_of(self, contract_address, address, sender_address=ZERO_ADDRESS, id_generator=None):
+        j = JSONRPCRequest(id_generator)
+        o = j.template()
+        o['method'] = 'eth_call'
+        enc = ABIContractEncoder()
+        enc.method('baseBalanceOf')
+        enc.typ(ABIContractType.ADDRESS)
+        enc.address(address)
+        data = add_0x(enc.get())
+        tx = self.template(sender_address, contract_address)
+        tx = self.set_code(tx, data)
+        o['params'].append(self.normalize(tx))
+        o['params'].append('latest')
+        o = j.finalize(o)
+        return o
+
+
+    def set_sink_address(self, contract_address, sender_address, address, tx_format=TxFormat.JSONRPC):
+        enc = ABIContractEncoder()
+        enc.method('setSinkAddress')
+        enc.typ(ABIContractType.ADDRESS)
+        enc.address(address)
+        data = enc.get()
+        tx = self.template(sender_address, contract_address, use_nonce=True)
+        tx = self.set_code(tx, data)
+        tx = self.finalize(tx, tx_format)
+        return tx
+
+
+    def apply_demurrage(self, contract_address, sender_address, limit=0, tx_format=TxFormat.JSONRPC):
+        if limit == 0:
+            return self.transact_noarg('applyDemurrage', contract_address, sender_address)
+
+        enc = ABIContractEncoder()
+        enc.method('applyDemurrageLimited')
+        enc.typ(ABIContractType.UINT256)
+        enc.uint256(limit)
+        data = enc.get()
+        tx = self.template(sender_address, contract_address, use_nonce=True)
+        tx = self.set_code(tx, data)
+        tx = self.finalize(tx, tx_format)
+        return tx
+
+
+    def change_period(self, contract_address, sender_address):
+        return self.transact_noarg('changePeriod', contract_address, sender_address)
+
+
+    def apply_redistribution_on_account(self, contract_address, sender_address, address, tx_format=TxFormat.JSONRPC):
+        enc = ABIContractEncoder()
+        enc.method('applyRedistributionOnAccount')
+        enc.typ(ABIContractType.ADDRESS)
+        enc.address(address)
+        data = enc.get()
+        tx = self.template(sender_address, contract_address, use_nonce=True)
+        tx = self.set_code(tx, data)
+        tx = self.finalize(tx, tx_format)
+        return tx
+
+
+
+
+    def tax_level(self, contract_address, sender_address=ZERO_ADDRESS):
+        return self.call_noarg('taxLevel', contract_address, sender_address=sender_address)
+
+
+    def resolution_factor(self, contract_address, sender_address=ZERO_ADDRESS):
+        return self.call_noarg('resolutionFactor', contract_address, sender_address=sender_address)
+
+
+    def actual_period(self, contract_address, sender_address=ZERO_ADDRESS):
+        return self.call_noarg('actualPeriod', contract_address, sender_address=sender_address)
+
+
+    def period_start(self, contract_address, sender_address=ZERO_ADDRESS):
+        return self.call_noarg('periodStart', contract_address, sender_address=sender_address)
+
+
+    def period_duration(self, contract_address, sender_address=ZERO_ADDRESS):
+        return self.call_noarg('periodDuration', contract_address, sender_address=sender_address)
+
+
+    def demurrage_amount(self, contract_address, sender_address=ZERO_ADDRESS):
+        return self.call_noarg('demurrageAmount', contract_address, sender_address=sender_address)
+
+
+    def demurrage_timestamp(self, contract_address, sender_address=ZERO_ADDRESS):
+        return self.call_noarg('demurrageTimestamp', contract_address, sender_address=sender_address)
+
+
+    def max_supply(self, contract_address, sender_address=ZERO_ADDRESS):
+        return self.call_noarg('maxSupply', contract_address, sender_address=sender_address)
+
+
+#    def grow_by(self, contract_address, value, period, sender_address=ZERO_ADDRESS, id_generator=None):
+#        j = JSONRPCRequest(id_generator)
+#        o = j.template()
+#        o['method'] = 'eth_call'
+#        enc = ABIContractEncoder()
+#        enc.method('growBy')
+#        enc.typ(ABIContractType.UINT256)
+#        enc.typ(ABIContractType.UINT256)
+#        enc.uint256(value)
+#        enc.uint256(period)
+#        data = add_0x(enc.get())
+#        tx = self.template(sender_address, contract_address)
+#        tx = self.set_code(tx, data)
+#        o['params'].append(self.normalize(tx))
+#        o['params'].append('latest')
+#        o = j.finalize(o)
+#        return o
+#
+
+    def decay_by(self, contract_address, value, period, sender_address=ZERO_ADDRESS, id_generator=None):
+        j = JSONRPCRequest(id_generator)
+        o = j.template()
+        o['method'] = 'eth_call'
+        enc = ABIContractEncoder()
+        enc.method('decayBy')
+        enc.typ(ABIContractType.UINT256)
+        enc.typ(ABIContractType.UINT256)
+        enc.uint256(value)
+        enc.uint256(period)
+        data = add_0x(enc.get())
+        tx = self.template(sender_address, contract_address)
+        tx = self.set_code(tx, data)
+        o['params'].append(self.normalize(tx))
+        o['params'].append('latest')
+        o = j.finalize(o)
+        return o
+
+
+    def get_distribution(self, contract_address, supply, demurrage_amount, sender_address=ZERO_ADDRESS, id_generator=None):
+        j = JSONRPCRequest(id_generator)
+        o = j.template()
+        o['method'] = 'eth_call'
+        enc = ABIContractEncoder()
+        enc.method('getDistribution')
+        enc.typ(ABIContractType.UINT256)
+        enc.typ_literal('int128')
+        enc.uint256(supply)
+        enc.uint256(demurrage_amount)
+        data = add_0x(enc.get())
+        tx = self.template(sender_address, contract_address)
+        tx = self.set_code(tx, data)
+        o['params'].append(self.normalize(tx))
+        o['params'].append('latest')
+        o = j.finalize(o)
+        return o
+
+
+    def get_distribution_from_redistribution(self, contract_address, redistribution, sender_address=ZERO_ADDRESS, id_generator=None):
+        j = JSONRPCRequest(id_generator)
+        o = j.template()
+        o['method'] = 'eth_call'
+        enc = ABIContractEncoder()
+        enc.method('getDistributionFromRedistribution')
+        v = strip_0x(redistribution)
+        enc.typ_literal('(uint32,uint72,uint64)')
+        enc.bytes32(v[:64])
+        enc.bytes32(v[64:128])
+        enc.bytes32(v[128:192])
+        data = add_0x(enc.get())
+        tx = self.template(sender_address, contract_address)
+        tx = self.set_code(tx, data)
+        o['params'].append(self.normalize(tx))
+        o['params'].append('latest')
+        o = j.finalize(o)
+        return o
+
+
+
+    @classmethod
+    def parse_actual_period(self, v):
+        return abi_decode_single(ABIContractType.UINT256, v)
+
+
+    @classmethod
+    def parse_period_start(self, v):
+        return abi_decode_single(ABIContractType.UINT256, v)
+
+
+    @classmethod
+    def parse_period_duration(self, v):
+        return abi_decode_single(ABIContractType.UINT256, v)
+
+
+    @classmethod
+    def parse_demurrage_amount(self, v):
+        #        return abi_decode_single(ABIContractType.UINT256, v)
+        return from_fixed(v)
+
+
+    @classmethod
+    def parse_remainder(self, v):
+        return abi_decode_single(ABIContractType.UINT256, v)
+
+
+    @classmethod
+    def parse_to_base_amount(self, v):
+        return abi_decode_single(ABIContractType.UINT256, v)
+
+    
+    @classmethod
+    def parse_redistributions(self, v):
+        return strip_0x(v)
+        
+
+    @classmethod
+    def parse_account_period(self, v):
+        return abi_decode_single(ABIContractType.ADDRESS, v)
+
+
+    @classmethod
+    def parse_to_redistribution_period(self, v):
+        return abi_decode_single(ABIContractType.UINT256, v)
+
+
+    @classmethod
+    def parse_to_redistribution_item(self, v):
+        return abi_decode_single(ABIContractType.UINT256, v)
+
+
+    @classmethod
+    def parse_supply_cap(self, v):
+        return abi_decode_single(ABIContractType.UINT256, v)
+
+
+    @classmethod
+    def parse_grow_by(self, v):
+        return abi_decode_single(ABIContractType.UINT256, v)
+
+
+    @classmethod
+    def parse_decay_by(self, v):
+        return abi_decode_single(ABIContractType.UINT256, v)
+
+
+    @classmethod
+    def parse_get_distribution(self, v):
+        return abi_decode_single(ABIContractType.UINT256, v)
+
+
+    @classmethod
+    def parse_tax_level(self, v):
+        return abi_decode_single(ABIContractType.UINT256, v)
+
+
+    @classmethod
+    def parse_resolution_factor(self, v):
+        return abi_decode_single(ABIContractType.UINT256, v)
+
+
+    @classmethod
+    def parse_total_burned(self, v):
+        return abi_decode_single(ABIContractType.UINT256, v)
+

python/erc20_demurrage_token/unittest/__init__.py

@@ -0,0 +1 @@
+from .base import *

python/erc20_demurrage_token/unittest/base.py

@@ -0,0 +1,150 @@
+# standard imports
+import logging
+import os
+import math
+
+# external imports
+from chainlib.eth.unittest.ethtester import EthTesterCase
+from chainlib.eth.tx import (
+        receipt,
+        )
+from chainlib.eth.block import (
+        block_latest,
+        block_by_number,
+        )
+from chainlib.eth.nonce import RPCNonceOracle
+from chainlib.eth.constant import ZERO_ADDRESS
+
+# local imports
+from erc20_demurrage_token import (
+        DemurrageTokenSettings,
+        DemurrageToken,
+        )
+from dexif import *
+
+logg = logging.getLogger()
+
+#BLOCKTIME = 5 # seconds
+TAX_LEVEL = int(10000 * 2) # 2%
+# calc "1-(0.98)^(1/518400)" <- 518400 = 30 days of blocks
+# 0.00000003897127107225
+PERIOD = 43200
+
+
+class TestTokenDeploy:
+
+    """tax level is ppm, 1000000 = 100%"""
+    def __init__(self, rpc, token_symbol='FOO', token_name='Foo Token', sink_address=ZERO_ADDRESS, tax_level=TAX_LEVEL, period=PERIOD):
+        self.tax_level = tax_level
+        self.period_seconds = period * 60
+
+        self.settings = DemurrageTokenSettings()
+        self.settings.name = token_name
+        self.settings.symbol = token_symbol
+        self.settings.decimals = 6
+        tax_level_input = to_fixed((1 - (tax_level / 1000000)) ** (1 / period))
+        self.settings.demurrage_level = tax_level_input
+        self.settings.period_minutes = period
+        self.settings.sink_address = sink_address
+        self.sink_address = self.settings.sink_address
+        logg.debug('using demurrage token settings: {}'.format(self.settings))
+
+        o = block_latest()
+        self.start_block = rpc.do(o)
+        
+        o = block_by_number(self.start_block, include_tx=False)
+        r = rpc.do(o)
+
+        try:
+            self.start_time = int(r['timestamp'], 16)
+        except TypeError:
+            self.start_time = int(r['timestamp'])
+
+
+    def deploy(self, rpc, deployer_address, interface, supply_cap=0):
+        tx_hash = None
+        o = None
+        (tx_hash, o) = interface.constructor(deployer_address, self.settings)
+
+        r = rpc.do(o)
+        o = receipt(tx_hash)
+        r = rpc.do(o)
+        assert r['status'] == 1
+        self.start_block = r['block_number']
+        self.address = r['contract_address']
+
+        o = block_by_number(r['block_number'])
+        r = rpc.do(o)
+        self.start_time = r['timestamp']
+
+        return self.address
+
+
+class TestDemurrage(EthTesterCase):
+
+    def setUp(self):
+        super(TestDemurrage, self).setUp()
+        period = PERIOD
+        try:
+            period = getattr(self, 'period')
+        except AttributeError as e:
+            pass
+        self.deployer = TestTokenDeploy(self.rpc, period=period, sink_address=self.accounts[9])
+        self.default_supply = 0
+        self.default_supply_cap = 0
+        self.start_block = None
+        self.address = None
+        self.start_time = None
+
+
+    def deploy(self, interface):
+        self.address = self.deployer.deploy(self.rpc, self.accounts[0], interface, supply_cap=self.default_supply_cap)
+        self.start_block = self.deployer.start_block
+        self.start_time = self.deployer.start_time
+        self.tax_level = self.deployer.tax_level
+        self.period_seconds = self.deployer.period_seconds
+        self.sink_address = self.deployer.sink_address
+
+        logg.debug('contract address {} start block {} start time {}'.format(self.address, self.start_block, self.start_time))
+
+
+    def assert_within(self, v, target, tolerance_ppm):
+        lower_target = target - (target * (tolerance_ppm / 1000000))
+        higher_target = target + (target * (tolerance_ppm / 1000000))
+        #self.assertGreaterEqual(v, lower_target)
+        #self.assertLessEqual(v, higher_target)
+        if v >= lower_target and v <= higher_target:
+            logg.debug('asserted within {} <= {} <= {}'.format(lower_target, v, higher_target))
+            return
+        raise AssertionError('{} not within lower {} and higher {}'.format(v, lower_target, higher_target))
+
+
+    def assert_within_lower(self, v, target, tolerance_ppm):
+        lower_target = target - (target * (tolerance_ppm / 1000000))
+        self.assertGreaterEqual(v, lower_target)
+        self.assertLessEqual(v, target)
+        logg.debug('asserted within lower {} <= {} <= {}'.format(lower_target, v, target))
+
+
+    def assert_equal_decimals(self, v, target, precision):
+        target = int(target * (10 ** precision))
+        target = target / (10 ** precision)
+        self.assertEqual(v, target)
+
+
+    def tearDown(self):
+        pass
+
+
+class TestDemurrageDefault(TestDemurrage):
+
+    def setUp(self):
+        super(TestDemurrageDefault, self).setUp()
+   
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+        self.deploy(c)
+
+        self.default_supply = 10**12
+        self.default_supply_cap = self.default_supply

python/erc20_demurrage_token/unittest/newbase.py

@@ -0,0 +1,146 @@
+# standard imports
+import logging
+import os
+import math
+
+# external imports
+from chainlib.eth.unittest.ethtester import EthTesterCase
+from chainlib.eth.tx import (
+        receipt,
+        )
+from chainlib.eth.block import (
+        block_latest,
+        block_by_number,
+        )
+from chainlib.eth.nonce import RPCNonceOracle
+from chainlib.eth.constant import ZERO_ADDRESS
+
+# local imports
+from erc20_demurrage_token import (
+        DemurrageTokenSettings,
+        DemurrageToken,
+        )
+from dexif import *
+
+logg = logging.getLogger()
+
+TAX_LEVEL = int(10000 * 2) # 2%
+PERIOD = 43200 # 30 days in minutes
+
+class TestTokenDeploy:
+
+    """tax level is ppm, 1000000 = 100%"""
+    def __init__(self, rpc, token_symbol='FOO', token_name='Foo Token', sink_address=ZERO_ADDRESS, supply=10**12, tax_level=TAX_LEVEL, period=PERIOD):
+        self.tax_level = tax_level
+        self.period_seconds = period * 60
+
+        self.settings = DemurrageTokenSettings()
+        self.settings.name = token_name
+        self.settings.symbol = token_symbol
+        self.settings.decimals = 6
+        tax_level_input = to_fixed((1 - (tax_level / 1000000)) ** (1 / period))
+        self.settings.demurrage_level = tax_level_input
+        self.settings.period_minutes = period
+        self.settings.sink_address = sink_address
+        self.sink_address = self.settings.sink_address
+        logg.debug('using demurrage token settings: {}'.format(self.settings))
+
+        o = block_latest()
+        self.start_block = rpc.do(o)
+        
+        o = block_by_number(self.start_block, include_tx=False)
+        r = rpc.do(o)
+
+        try:
+            self.start_time = int(r['timestamp'], 16)
+        except TypeError:
+            self.start_time = int(r['timestamp'])
+
+        self.default_supply = supply
+        self.default_supply_cap = 0
+
+
+    def deploy(self, rpc, deployer_address, interface, supply_cap=0):
+        tx_hash = None
+        o = None
+        (tx_hash, o) = interface.constructor(deployer_address, self.settings, redistribute=False, cap=0)
+
+        r = rpc.do(o)
+        o = receipt(tx_hash)
+        r = rpc.do(o)
+        assert r['status'] == 1
+        self.start_block = r['block_number']
+        self.address = r['contract_address']
+
+        o = block_by_number(r['block_number'])
+        r = rpc.do(o)
+        self.start_time = r['timestamp']
+
+        return self.address
+
+
+class TestDemurrage(EthTesterCase):
+
+    def setUp(self):
+        super(TestDemurrage, self).setUp()
+        period = PERIOD
+        try:
+            period = getattr(self, 'period')
+        except AttributeError as e:
+            pass
+        self.deployer = TestTokenDeploy(self.rpc, period=period)
+        self.default_supply = self.deployer.default_supply
+        self.default_supply_cap = self.deployer.default_supply_cap
+        self.start_block = None
+        self.address = None
+        self.start_time = None
+
+
+    def deploy(self, interface):
+        self.address = self.deployer.deploy(self.rpc, self.accounts[0], interface, supply_cap=self.default_supply_cap)
+        self.start_block = self.deployer.start_block
+        self.start_time = self.deployer.start_time
+        self.tax_level = self.deployer.tax_level
+        self.period_seconds = self.deployer.period_seconds
+        self.sink_address = self.deployer.sink_address
+
+        logg.debug('contract address {} start block {} start time {}'.format(self.address, self.start_block, self.start_time))
+
+
+    def assert_within(self, v, target, tolerance_ppm):
+        lower_target = target - (target * (tolerance_ppm / 1000000))
+        higher_target = target + (target * (tolerance_ppm / 1000000))
+        #self.assertGreaterEqual(v, lower_target)
+        #self.assertLessEqual(v, higher_target)
+        if v >= lower_target and v <= higher_target:
+            logg.debug('asserted within {} <= {} <= {}'.format(lower_target, v, higher_target))
+            return
+        raise AssertionError('{} not within lower {} and higher {}'.format(v, lower_target, higher_target))
+
+
+    def assert_within_lower(self, v, target, tolerance_ppm):
+        lower_target = target - (target * (tolerance_ppm / 1000000))
+        self.assertGreaterEqual(v, lower_target)
+        self.assertLessEqual(v, target)
+        logg.debug('asserted within lower {} <= {} <= {}'.format(lower_target, v, target))
+
+
+    def assert_equal_decimals(self, v, target, precision):
+        target = int(target * (10 ** precision))
+        target = target / (10 ** precision)
+        self.assertEqual(v, target)
+
+
+    def tearDown(self):
+        pass
+
+
+class TestDemurrageDefault(TestDemurrage):
+
+    def setUp(self):
+        super(TestDemurrageDefault, self).setUp()
+   
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+        self.deploy(c)

python/examples/sim.py

@@ -0,0 +1,76 @@
+# standard imports
+import logging
+
+# local imports
+from erc20_demurrage_token import DemurrageTokenSettings
+from erc20_demurrage_token.sim import DemurrageTokenSimulation
+
+logging.basicConfig(level=logging.WARNING)
+logg = logging.getLogger()
+
+decay_per_minute = 0.000050105908373373 # equals approx 2% per month
+
+# parameters for simulation object
+settings = DemurrageTokenSettings()
+settings.name = 'Simulated Demurrage Token'
+settings.symbol = 'SIM'
+settings.decimals = 6
+settings.demurrage_level = int(decay_per_minute*(10**40))
+settings.period_minutes = 10800 # 1 week in minutes
+chain = 'evm:foochain:42'
+cap = (10 ** 6) * (10 ** 12)
+
+# instantiate simulation
+sim = DemurrageTokenSimulation(chain, settings, redistribute=True, cap=cap, actors=10)
+
+# name the usual suspects
+alice = sim.actors[0]
+bob = sim.actors[1]
+carol = sim.actors[2]
+
+# mint and transfer (every single action advances one block, and one second in time)
+sim.mint(alice, sim.from_units(100)) # 10000000 tokens
+sim.mint(bob, sim.from_units(100))
+sim.transfer(alice, carol, sim.from_units(50))
+
+# check that balances have been updated
+assert sim.balance(alice) == sim.from_units(50)
+assert sim.balance(bob) == sim.from_units(100)
+assert sim.balance(carol) == sim.from_units(50)
+
+# advance to next redistribution period
+sim.next()
+
+# inspect balances
+print('alice balance: demurraged {:>9d} base {:>9d}'.format(sim.balance(alice), sim.balance(alice, base=True)))
+print('bob balance:   demurraged {:>9d} base {:>9d}'.format(sim.balance(bob), sim.balance(bob, base=True)))
+print('carol balance: demurraged {:>9d} base {:>9d}'.format(sim.balance(carol), sim.balance(carol, base=True)))
+print('sink balance:  demurraged {:>9d} base {:>9d}'.format(sim.balance(sim.sink_address), sim.balance(sim.sink_address, base=True)))
+
+# get times
+minutes = sim.get_minutes()
+start = sim.get_now()
+timestamp = sim.get_start()
+period = sim.get_period()
+print('start {} now {} period {} minutes passed {}'.format(start, timestamp, period, minutes))
+
+
+contract_demurrage = 1 - sim.get_demurrage_modifier()    # demurrage in percent (float)
+frontend_demurrage = ((1 - decay_per_minute) ** minutes / 100)   # corresponding demurrage modifier (float)
+demurrage_delta = contract_demurrage - frontend_demurrage      # difference between demurrage in contract and demurrage calculated in frontend
+
+alice_checksum = 50000000 - (50000000 * frontend_demurrage) + (200000000 * frontend_demurrage) # alice's balance calculated with frontend demurrage
+print("""alice frontend balance {}
+alice contract balance {}
+frontend demurrage {}
+contract demurrage {}
+demurrage delta {}""".format(
+    alice_checksum,
+    sim.balance(alice),
+    frontend_demurrage,
+    contract_demurrage,
+    demurrage_delta),
+)
+
+balance_sum = sim.balance(alice) + sim.balance(bob) + sim.balance(carol)
+print('sum of contract demurraged balances {}'.format(balance_sum))

python/examples/sim_noredistribute.py

@@ -0,0 +1,80 @@
+# standard imports
+import logging
+
+# local imports
+from erc20_demurrage_token import DemurrageTokenSettings
+from erc20_demurrage_token.sim import DemurrageTokenSimulation
+
+logging.basicConfig(level=logging.INFO)
+logg = logging.getLogger()
+
+decay_per_minute = 0.00000050105908373373 # equals approx 2% per month
+
+# parameters for simulation object
+settings = DemurrageTokenSettings()
+settings.name = 'Simulated Demurrage Token'
+settings.symbol = 'SIM'
+settings.decimals = 6
+settings.demurrage_level = int(decay_per_minute*(10**38))
+#settings.period_minutes = 1 # 1 week in minutes
+settings.period_minutes = 60*24*7
+chain = 'evm:foochain:42'
+cap = (10 ** 6) * (10 ** 12)
+#cap = 0
+
+# instantiate simulation
+sim = DemurrageTokenSimulation(chain, settings, redistribute=False, cap=cap, actors=10)
+
+# name the usual suspects
+alice = sim.actors[0]
+bob = sim.actors[1]
+carol = sim.actors[2]
+
+# mint and transfer (every single action advances one block, and one second in time)
+sim.mint(alice, sim.from_units(100)) # 10000000 tokens
+sim.mint(bob, sim.from_units(100))
+sim.transfer(alice, carol, sim.from_units(50))
+
+# check that balances have been updated
+#assert sim.balance(alice) == sim.from_units(50)
+#assert sim.balance(bob) == sim.from_units(100)
+#assert sim.balance(carol) == sim.from_units(50)
+
+# advance to next redistribution period
+sim.next()
+
+# inspect balances
+print('alice balance: demurraged {:>9d} base {:>9d}'.format(sim.balance(alice), sim.balance(alice, base=True)))
+print('bob balance:   demurraged {:>9d} base {:>9d}'.format(sim.balance(bob), sim.balance(bob, base=True)))
+print('carol balance: demurraged {:>9d} base {:>9d}'.format(sim.balance(carol), sim.balance(carol, base=True)))
+print('sink balance:  demurraged {:>9d} base {:>9d}'.format(sim.balance(sim.sink_address), sim.balance(sim.sink_address, base=True)))
+
+# get times
+minutes = sim.get_minutes()
+timestamp = sim.get_now()
+start = sim.get_start()
+period = sim.get_period()
+print('start {} now {} period {} minutes passed {}'.format(start, timestamp, period, minutes))
+
+
+contract_demurrage = 1 - sim.get_demurrage()    # demurrage in percent (float)
+frontend_demurrage = 1.0 - ((1 - decay_per_minute) ** minutes)   # corresponding demurrage modifier (float)
+demurrage_delta = contract_demurrage - frontend_demurrage      # difference between demurrage in contract and demurrage calculated in frontend
+
+alice_checksum = 50000000 - (50000000 * frontend_demurrage) + (200000000 * frontend_demurrage) # alice's balance calculated with frontend demurrage
+#print("""alice frontend balance {}
+print("""alice contract balance {}
+frontend demurrage {:.38f}
+contract demurrage {:.38f}
+demurrage delta {:.38f}""".format(
+    alice_checksum,
+    sim.balance(alice),
+    frontend_demurrage,
+    contract_demurrage,
+    demurrage_delta),
+)
+
+balance_sum = sim.balance(alice) + sim.balance(bob) + sim.balance(carol) + sim.balance(sim.sink_address)
+supply = sim.get_supply()
+print('sum of contract demurraged balances {}'.format(balance_sum))
+print('total token supply {}'.format(supply))

python/requirements.txt

@@ -0,0 +1,4 @@
+chainlib-eth~=0.4.11
+eth-erc20~=0.5.0
+funga-eth~=0.6.0
+dexif~=0.0.1

python/run_tests.sh

@@ -0,0 +1,14 @@
+#!/bin/bash
+
+set -a
+set -e
+set -x
+default_pythonpath=$PYTHONPATH:.
+export PYTHONPATH=${default_pythonpath:-.}
+>&2 echo using pythonpath $PYTHONPATH
+for f in `ls tests/test_*.py`; do
+	python $f
+done
+set +x
+set +e
+set +a

python/setup.cfg

@@ -0,0 +1,43 @@
+[metadata]
+name = erc20-demurrage-token
+version = 0.3.1
+description = ERC20 token with redistributed continual demurrage
+author = Louis Holbrook
+author_email = dev@holbrook.no
+url = https://gitlab.com/ccicnet/erc20-demurrage-token
+keywords =
+	ethereum
+	blockchain
+	cryptocurrency
+	erc20
+classifiers =
+	Programming Language :: Python :: 3
+	Operating System :: OS Independent
+	Development Status :: 3 - Alpha
+	Environment :: No Input/Output (Daemon)
+	Intended Audience :: Developers
+	License :: OSI Approved :: GNU General Public License v3 or later (GPLv3+)
+	Topic :: Internet
+	#Topic :: Blockchain :: EVM
+license = GPL3
+licence_files =
+	LICENSE
+
+[options]
+include_package_data = True
+python_requires = >= 3.7
+packages =
+	erc20_demurrage_token
+	erc20_demurrage_token.runnable
+	erc20_demurrage_token.data
+	erc20_demurrage_token.sim
+	erc20_demurrage_token.unittest
+
+[options.package_data]
+* =
+ 	data/DemurrageToken*.bin
+ 	data/DemurrageToken*.json
+
+[options.entry_points]
+console_scripts =
+	erc20-demurrage-token-deploy = erc20_demurrage_token.runnable.deploy:main

python/setup.py

@@ -0,0 +1,31 @@
+from setuptools import setup
+
+requirements = []
+f = open('requirements.txt', 'r')
+while True:
+    l = f.readline()
+    if l == '':
+        break
+    requirements.append(l.rstrip())
+f.close()
+
+test_requirements = []
+f = open('test_requirements.txt', 'r')
+while True:
+    l = f.readline()
+    if l == '':
+        break
+    test_requirements.append(l.rstrip())
+f.close()
+
+
+setup(
+        package_data={
+            '': [
+                'data/MintableFactor.bin',
+                ],
+            },
+        include_package_data=True,
+        install_requires=requirements,
+        tests_require=test_requirements,
+        )

python/test_requirements.txt

@@ -0,0 +1,2 @@
+eth_tester==0.5.0b3
+py-evm==0.3.0a20

python/tests/bench.old

@@ -0,0 +1,228 @@
+# standard imports
+import os
+import unittest
+import json
+import logging
+
+# third-party imports
+import web3
+import eth_tester
+import eth_abi
+
+logging.basicConfig(level=logging.DEBUG)
+logg = logging.getLogger()
+
+logging.getLogger('web3').setLevel(logging.WARNING)
+logging.getLogger('eth.vm').setLevel(logging.WARNING)
+
+testdir = os.path.dirname(__file__)
+
+TAX_LEVEL = 10000 * 2 # 2%
+
+
+class Test(unittest.TestCase):
+
+    contract = None
+
+    def setUp(self):
+        eth_params = eth_tester.backends.pyevm.main.get_default_genesis_params({
+            'gas_limit': 9000000,
+            })
+
+        f = open(os.path.join(testdir, '../../solidity/RedistributedDemurrageToken.bin'), 'r')
+        self.bytecode = f.read()
+        f.close()
+
+        f = open(os.path.join(testdir, '../../solidity/RedistributedDemurrageToken.json'), 'r')
+        self.abi = json.load(f)
+        f.close()
+
+        backend = eth_tester.PyEVMBackend(eth_params)
+        self.eth_tester =  eth_tester.EthereumTester(backend)
+        provider = web3.Web3.EthereumTesterProvider(self.eth_tester)
+        self.w3 = web3.Web3(provider)
+        self.sink_address = self.w3.eth.accounts[9]
+
+    def tearDown(self):
+        pass
+
+
+    def test_construct(self):
+            period = 10
+            c = self.w3.eth.contract(abi=self.abi, bytecode=self.bytecode)
+            tx_hash = c.constructor('Foo Token', 'FOO', 6, TAX_LEVEL * (10 ** 32), period, self.sink_address).transact({'from': self.w3.eth.accounts[0]})
+            r = self.w3.eth.getTransactionReceipt(tx_hash)
+            print('construct: {}'.format(r['gasUsed']))
+
+
+    def test_gas_changeperiod(self):
+        period = 43200
+        for i in range(5):
+            c = self.w3.eth.contract(abi=self.abi, bytecode=self.bytecode)
+            tx_hash = c.constructor('Foo Token', 'FOO', 6, TAX_LEVEL * (10 ** 32), period, self.sink_address).transact({'from': self.w3.eth.accounts[0]})
+            r = self.w3.eth.getTransactionReceipt(tx_hash)
+            contract = self.w3.eth.contract(abi=self.abi, address=r.contractAddress)
+
+            start_block = self.w3.eth.blockNumber
+            b = self.w3.eth.getBlock(start_block)
+            start_time = b['timestamp']
+
+            period_seconds = period * 60
+            self.eth_tester.time_travel(start_time + period_seconds + (60 * (10 ** i)))
+            tx_hash = contract.functions.changePeriod().transact()
+            r = self.w3.eth.getTransactionReceipt(tx_hash)
+
+            print('changePeriod {} ({}): {}'.format(i, 60 * (10 ** i), r['gasUsed']))
+
+
+    def test_mint(self):
+            period = 10
+            c = self.w3.eth.contract(abi=self.abi, bytecode=self.bytecode)
+            tx_hash = c.constructor('Foo Token', 'FOO', 6, TAX_LEVEL * (10 ** 32), period, self.sink_address).transact({'from': self.w3.eth.accounts[0]})
+            r = self.w3.eth.getTransactionReceipt(tx_hash)
+            contract = self.w3.eth.contract(abi=self.abi, address=r.contractAddress)
+
+            start_block = self.w3.eth.blockNumber
+            b = self.w3.eth.getBlock(start_block)
+            start_time = b['timestamp']
+
+            tx_hash = contract.functions.mintTo(self.w3.eth.accounts[1], 1000000).transact({'from': self.w3.eth.accounts[0]})
+            r = self.w3.eth.getTransactionReceipt(tx_hash)
+            print ('mintTo: {}'.format(r['gasUsed']))
+
+
+    def test_transfer(self):
+            period = 10
+            c = self.w3.eth.contract(abi=self.abi, bytecode=self.bytecode)
+            tx_hash = c.constructor('Foo Token', 'FOO', 6, TAX_LEVEL * (10 ** 32), period, self.sink_address).transact({'from': self.w3.eth.accounts[0]})
+            r = self.w3.eth.getTransactionReceipt(tx_hash)
+            contract = self.w3.eth.contract(abi=self.abi, address=r.contractAddress)
+
+            start_block = self.w3.eth.blockNumber
+            b = self.w3.eth.getBlock(start_block)
+            start_time = b['timestamp']
+
+            contract.functions.mintTo(self.w3.eth.accounts[1], 1000000).transact({'from': self.w3.eth.accounts[0]})
+
+            tx_hash = contract.functions.transfer(self.w3.eth.accounts[2], 1000000).transact({'from': self.w3.eth.accounts[1]})
+            r = self.w3.eth.getTransactionReceipt(tx_hash)
+            print ('transfer: {}'.format(r['gasUsed']))
+
+
+    def test_approve(self):
+            period = 10
+            c = self.w3.eth.contract(abi=self.abi, bytecode=self.bytecode)
+            tx_hash = c.constructor('Foo Token', 'FOO', 6, TAX_LEVEL * (10 ** 32), period, self.sink_address).transact({'from': self.w3.eth.accounts[0]})
+            r = self.w3.eth.getTransactionReceipt(tx_hash)
+            contract = self.w3.eth.contract(abi=self.abi, address=r.contractAddress)
+
+            start_block = self.w3.eth.blockNumber
+            b = self.w3.eth.getBlock(start_block)
+            start_time = b['timestamp']
+
+            contract.functions.mintTo(self.w3.eth.accounts[1], 1000000).transact({'from': self.w3.eth.accounts[0]})
+
+            tx_hash = contract.functions.approve(self.w3.eth.accounts[2], 1000000).transact({'from': self.w3.eth.accounts[1]})
+            r = self.w3.eth.getTransactionReceipt(tx_hash)
+            print ('approve: {}'.format(r['gasUsed']))
+
+
+    def test_transferfrom(self):
+            period = 10
+            c = self.w3.eth.contract(abi=self.abi, bytecode=self.bytecode)
+            tx_hash = c.constructor('Foo Token', 'FOO', 6, TAX_LEVEL * (10 ** 32), period, self.sink_address).transact({'from': self.w3.eth.accounts[0]})
+            r = self.w3.eth.getTransactionReceipt(tx_hash)
+            contract = self.w3.eth.contract(abi=self.abi, address=r.contractAddress)
+
+            start_block = self.w3.eth.blockNumber
+            b = self.w3.eth.getBlock(start_block)
+            start_time = b['timestamp']
+
+            contract.functions.mintTo(self.w3.eth.accounts[1], 1000000).transact({'from': self.w3.eth.accounts[0]})
+
+            contract.functions.approve(self.w3.eth.accounts[2], 1000000).transact({'from': self.w3.eth.accounts[1]})
+
+            tx_hash = contract.functions.transferFrom(self.w3.eth.accounts[1], self.w3.eth.accounts[3], 1000000).transact({'from': self.w3.eth.accounts[2]})
+            r = self.w3.eth.getTransactionReceipt(tx_hash)
+            print ('transferFrom: {}'.format(r['gasUsed']))
+
+
+    def test_redistribute_default(self):
+            period = 10
+            c = self.w3.eth.contract(abi=self.abi, bytecode=self.bytecode)
+            tx_hash = c.constructor('Foo Token', 'FOO', 6, TAX_LEVEL * (10 ** 32), period, self.sink_address).transact({'from': self.w3.eth.accounts[0]})
+            r = self.w3.eth.getTransactionReceipt(tx_hash)
+            contract = self.w3.eth.contract(abi=self.abi, address=r.contractAddress)
+
+            start_block = self.w3.eth.blockNumber
+            b = self.w3.eth.getBlock(start_block)
+            start_time = b['timestamp']
+
+            for i in range(100):
+                addr = web3.Web3.toChecksumAddress('0x' + os.urandom(20).hex())
+                contract.functions.mintTo(addr, 1000000 * (i+1)).transact({'from': self.w3.eth.accounts[0]})
+
+            self.eth_tester.time_travel(start_time + period * 60 + 1)
+            redistribution = contract.functions.redistributions(0).call()
+            tx_hash = contract.functions.changePeriod().transact({'from': self.w3.eth.accounts[2]})
+            r = self.w3.eth.getTransactionReceipt(tx_hash)
+            print ('chainPeriod -> defaultRedistribution: {}'.format(r['gasUsed']))
+
+
+    def test_redistribution_account(self):
+            period = 10
+            c = self.w3.eth.contract(abi=self.abi, bytecode=self.bytecode)
+            tx_hash = c.constructor('Foo Token', 'FOO', 6, TAX_LEVEL * (10 ** 32), period, self.sink_address).transact({'from': self.w3.eth.accounts[0]})
+            r = self.w3.eth.getTransactionReceipt(tx_hash)
+            contract = self.w3.eth.contract(abi=self.abi, address=r.contractAddress)
+
+            start_block = self.w3.eth.blockNumber
+            b = self.w3.eth.getBlock(start_block)
+            start_time = b['timestamp']
+
+            contract.functions.mintTo(self.w3.eth.accounts[1], 1000000).transact({'from': self.w3.eth.accounts[0]})
+            contract.functions.transfer(self.w3.eth.accounts[2], 1000000).transact({'from': self.w3.eth.accounts[1]})
+
+            for i in range(100):
+                addr = web3.Web3.toChecksumAddress('0x' + os.urandom(20).hex())
+                contract.functions.mintTo(addr, 1000000 * (i+1)).transact({'from': self.w3.eth.accounts[0]})
+
+            self.eth_tester.time_travel(start_time + period * 60 + 1)
+            redistribution = contract.functions.redistributions(0).call()
+            tx_hash = contract.functions.applyRedistributionOnAccount(self.w3.eth.accounts[1]).transact({'from': self.w3.eth.accounts[2]})
+            r = self.w3.eth.getTransactionReceipt(tx_hash)
+            self.assertEqual(r.logs[0].topics[0].hex(), '0x9a2a887706623ad3ff7fc85652deeceabe9fe1e00466c597972079ee91ea40d3')
+            print ('redistribute account: {}'.format(r['gasUsed']))
+
+
+    def test_redistribution_account_transfer(self):
+            period = 10
+            c = self.w3.eth.contract(abi=self.abi, bytecode=self.bytecode)
+            tx_hash = c.constructor('Foo Token', 'FOO', 6, TAX_LEVEL * (10 ** 32), period, self.sink_address).transact({'from': self.w3.eth.accounts[0]})
+            r = self.w3.eth.getTransactionReceipt(tx_hash)
+            contract = self.w3.eth.contract(abi=self.abi, address=r.contractAddress)
+
+            start_block = self.w3.eth.blockNumber
+            b = self.w3.eth.getBlock(start_block)
+            start_time = b['timestamp']
+
+            contract.functions.mintTo(self.w3.eth.accounts[1], 2000000).transact({'from': self.w3.eth.accounts[0]})
+            contract.functions.transfer(self.w3.eth.accounts[2], 1000000).transact({'from': self.w3.eth.accounts[1]})
+
+            for i in range(10):
+                addr = web3.Web3.toChecksumAddress('0x' + os.urandom(20).hex())
+                contract.functions.mintTo(addr, 1000000 * (i+1)).transact({'from': self.w3.eth.accounts[0]})
+
+            self.eth_tester.time_travel(start_time + period * 60 + 1)
+            redistribution = contract.functions.redistributions(0).call()
+            contract.functions.changePeriod().transact({'from': self.w3.eth.accounts[0]})
+            tx_hash = contract.functions.transfer(self.w3.eth.accounts[3], 100000).transact({'from': self.w3.eth.accounts[1]})
+            r = self.w3.eth.getTransactionReceipt(tx_hash)
+            self.assertEqual(r.logs[0].topics[0].hex(), '0x9a2a887706623ad3ff7fc85652deeceabe9fe1e00466c597972079ee91ea40d3')
+            print ('redistribute account: {}'.format(r['gasUsed']))
+
+
+if __name__ == '__main__':
+    unittest.main()
+
+ 

python/tests/bench_gas.py

@@ -0,0 +1,167 @@
+# standard imports
+import os
+import unittest
+import json
+import logging
+import datetime
+
+# external imports
+from chainlib.eth.constant import ZERO_ADDRESS
+from chainlib.eth.nonce import RPCNonceOracle
+from chainlib.eth.tx import receipt
+from chainlib.eth.block import (
+        block_latest,
+        block_by_number,
+    )
+
+# local imports
+from erc20_demurrage_token import DemurrageToken
+
+# test imports
+from erc20_demurrage_token.unittest import TestDemurrageDefault
+
+logging.basicConfig(level=logging.INFO)
+logg = logging.getLogger()
+
+testdir = os.path.dirname(__file__)
+
+
+
+class BenchBasic(TestDemurrageDefault):
+
+    def setUp(self):
+        super(BenchBasic, self).setUp()
+        self.bench = {
+    'mint': None,
+    'transfer_light': None,
+    'transfer_heavy': None,
+    'approve': None,
+    'transfer_from': None,
+    'period_light': None,
+    'period_heavy': None,
+    'period_catchup': None,
+    'demurrage': None,
+        }
+
+
+    def test_bench_min(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[1], 1024)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+        self.bench['mint'] = r['gas_used']
+        
+        nonce_oracle = RPCNonceOracle(self.accounts[1], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.transfer(self.address, self.accounts[1], self.accounts[2], 512)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+        self.bench['transfer_light'] = r['gas_used']
+
+        (tx_hash, o) = c.approve(self.address, self.accounts[1], self.accounts[0], 512)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+        self.bench['approve'] = r['gas_used']
+
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.transfer_from(self.address, self.accounts[0], self.accounts[1], self.accounts[3], 256)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+        self.bench['transfer_from'] = r['gas_used']
+
+        z = 0
+        for i in range(100):
+            self.backend.time_travel(self.start_time + int(self.period_seconds / 2) + (10 * (i * (i + 1))))
+            (tx_hash, o) = c.apply_demurrage(self.address, self.accounts[0])
+            r = self.rpc.do(o)
+            o = receipt(tx_hash)
+            r = self.rpc.do(o)
+            self.assertEqual(r['status'], 1)
+            z += r['gas_used']
+            logg.info('demurrage round {} gas {}'.format(i, r['gas_used']))
+        z /= 100
+        self.bench['demurrage'] = int(z)
+
+        z = 0
+        for i in range(100):
+            self.backend.time_travel(self.start_time + (self.period_seconds * (i + 1)))
+            (tx_hash, o) = c.change_period(self.address, self.accounts[0])
+            r = self.rpc.do(o)
+            o = receipt(tx_hash)
+            r = self.rpc.do(o)
+            self.assertEqual(r['status'], 1)
+            z += r['gas_used']
+            logg.info('period with demurrage round {} gas {}'.format(i, r['gas_used']))
+
+        z /= 100
+        self.bench['period_heavy'] = int(z)
+
+        z = 0
+        for i in range(100):
+            self.backend.time_travel(self.start_time + (self.period_seconds * ((i + 101))))
+            (tx_hash, o) = c.apply_demurrage(self.address, self.accounts[0])
+            r = self.rpc.do(o)
+            o = receipt(tx_hash)
+            r = self.rpc.do(o)
+            self.assertEqual(r['status'], 1)
+
+            (tx_hash, o) = c.change_period(self.address, self.accounts[0])
+            r = self.rpc.do(o)
+            o = receipt(tx_hash)
+            r = self.rpc.do(o)
+            self.assertEqual(r['status'], 1)
+            z += r['gas_used']
+            logg.info('period without demurrage round {} gas {}'.format(i, r['gas_used']))
+
+        z /= 100
+        self.bench['period_light'] = int(z)
+
+        z = 0
+        self.backend.time_travel(self.start_time + (self.period_seconds * 401))
+        for i in range(100):
+            (tx_hash, o) = c.change_period(self.address, self.accounts[0])
+            r = self.rpc.do(o)
+            o = receipt(tx_hash)
+            r = self.rpc.do(o)
+            self.assertEqual(r['status'], 1)
+            z += r['gas_used']
+            logg.info('period catchup round {} gas {}'.format(i, r['gas_used']))
+
+        z /= 100
+        self.bench['period_catchup'] = int(z)
+
+        self.backend.time_travel(self.start_time + (self.period_seconds * 501))
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[2], 1024)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+        self.backend.time_travel(self.start_time + (self.period_seconds * 502))
+
+        nonce_oracle = RPCNonceOracle(self.accounts[2], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.transfer(self.address, self.accounts[2], self.accounts[4], 1)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+        self.bench['transfer_heavy'] = r['gas_used']
+
+        print(json.dumps(self.bench))
+
+
+
+
+
+if __name__ == '__main__':
+    unittest.main()

python/tests/sim/tests_sim.py

@@ -0,0 +1,73 @@
+# standard imports
+import unittest
+import logging
+
+# local imports
+from erc20_demurrage_token import DemurrageTokenSettings
+from erc20_demurrage_token.sim import DemurrageTokenSimulation
+
+logging.basicConfig(level=logging.INFO)
+logg = logging.getLogger()
+
+
+class TestSim(unittest.TestCase):
+
+    def setUp(self):
+        self.cap = 0
+        settings = DemurrageTokenSettings()
+        settings.name = 'Simulated Demurrage Token'
+        settings.symbol = 'SIM'
+        settings.decimals = 6
+        settings.demurrage_level = 5010590837337300000000000000000000 # equals approx 2% per month
+        settings.period_minutes = 10800 # 1 week in minutes
+        self.sim = DemurrageTokenSimulation('evm:foochain:42', settings, redistribute=True, cap=self.cap, actors=10)
+
+
+    def test_mint(self):
+        self.sim.mint(self.sim.actors[0], 1024)
+        self.sim.next()
+        balance = self.sim.balance(self.sim.actors[0])
+        self.assertEqual(balance, 1023)
+
+
+    def test_transfer(self):
+        self.sim.mint(self.sim.actors[0], 1024)
+        self.sim.transfer(self.sim.actors[0], self.sim.actors[1], 500)
+        self.sim.next()
+        balance = self.sim.balance(self.sim.actors[0])
+        self.assertEqual(balance, 523)
+
+        balance = self.sim.balance(self.sim.actors[1])
+        self.assertEqual(balance, 499)
+
+
+    def test_more_periods(self):
+        self.sim.mint(self.sim.actors[0], 1024)
+        self.sim.mint(self.sim.actors[1], 1024)
+        self.sim.next()
+
+        self.sim.mint(self.sim.actors[0], 1024)
+        self.sim.next()
+
+        balance = self.sim.balance(self.sim.actors[0])
+        self.assertEqual(balance, 2047)
+
+
+    def test_demurrage(self):
+        self.sim.mint(self.sim.actors[0], self.sim.from_units(100))
+        self.sim.mint(self.sim.actors[1], self.sim.from_units(100))
+        self.sim.transfer(self.sim.actors[0], self.sim.actors[2], self.sim.from_units(10))
+        self.sim.next()
+
+        balance = self.sim.balance(self.sim.actors[0])
+        self.assertEqual(balance, 90005520)
+        
+        balance = self.sim.balance(self.sim.actors[1])
+        self.assertEqual(balance, 99995000)
+
+        balance = self.sim.balance(self.sim.actors[1], base=True)
+        self.assertEqual(balance, 100000000)
+
+
+if __name__ == '__main__':
+    unittest.main()

python/tests/sim/tests_sim_limit.py

@@ -0,0 +1,35 @@
+# standard imports
+import unittest
+import logging
+
+# local imports
+from erc20_demurrage_token import DemurrageTokenSettings
+from erc20_demurrage_token.sim import (
+        DemurrageTokenSimulation,
+        TxLimitException,
+        )
+
+logging.basicConfig(level=logging.INFO)
+logg = logging.getLogger()
+
+class TestLimit(unittest.TestCase):
+
+    def setUp(self):
+        self.cap = 0
+        settings = DemurrageTokenSettings()
+        settings.name = 'Simulated Demurrage Token'
+        settings.symbol = 'SIM'
+        settings.decimals = 6
+        settings.demurrage_level = 1
+        settings.period_minutes = 1
+        self.sim = DemurrageTokenSimulation('evm:foochain:42', settings, redistribute=True, cap=self.cap, actors=1)
+
+
+    def test_limit(self):
+        with self.assertRaises(TxLimitException):
+            for i in range(60):
+                self.sim.mint(self.sim.actors[0], i)
+        
+
+if __name__ == '__main__':
+    unittest.main()

python/tests/test_amounts.py

@@ -0,0 +1,123 @@
+# standard imports
+import os
+import unittest
+import json
+import logging
+
+# external imports
+from chainlib.eth.constant import ZERO_ADDRESS
+from chainlib.eth.nonce import RPCNonceOracle
+from chainlib.eth.tx import receipt
+
+# local imports
+from erc20_demurrage_token import DemurrageToken
+
+# test imports
+from erc20_demurrage_token.unittest import TestDemurrageDefault
+
+logging.basicConfig(level=logging.DEBUG)
+logg = logging.getLogger()
+
+testdir = os.path.dirname(__file__)
+
+class TestAmounts(TestDemurrageDefault):
+
+    def test_mints(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[1], 1000)
+        r = self.rpc.do(o)
+
+        self.backend.time_travel(self.start_time + self.period_seconds)
+
+        (tx_hash, o) = c.apply_demurrage(self.address, self.accounts[0])
+        r = self.rpc.do(o)
+        
+        o = c.balance_of(self.address, self.accounts[1], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance(r)
+        self.assertEqual(balance, 980)
+
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[1], 1000)
+        r = self.rpc.do(o)
+
+        o = c.balance_of(self.address, self.accounts[1], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance(r)
+        self.assert_within_lower(balance, 1980, 750)
+
+        self.backend.time_travel(self.start_time + self.period_seconds * 2)
+
+        (tx_hash, o) = c.apply_demurrage(self.address, self.accounts[0])
+        r = self.rpc.do(o)
+        
+        o = c.balance_of(self.address, self.accounts[1], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance(r)
+
+        expected_balance = ((1 - self.tax_level / 1000000) ** 10) * 1000
+        expected_balance += ((1 - self.tax_level / 1000000) ** 20) * 1000
+        #self.assert_within_lower(balance, expected_balance, 500)
+        self.assertEqual(balance, 1940)
+
+    def test_transfers(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[1], 2000)
+        r = self.rpc.do(o)
+
+        self.backend.time_travel(self.start_time + self.period_seconds)
+
+        (tx_hash, o) = c.apply_demurrage(self.address, self.accounts[0])
+        r = self.rpc.do(o)
+ 
+        o = c.balance_of(self.address, self.accounts[1], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance(r)
+        self.assertEqual(balance, 1960)
+
+        nonce_oracle = RPCNonceOracle(self.accounts[1], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.transfer(self.address, self.accounts[1], self.accounts[2], 500)
+        r = self.rpc.do(o)
+     
+        o = c.balance_of(self.address, self.accounts[1], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance(r)
+        self.assertEqual(balance, 1460)
+
+        o = c.balance_of(self.address, self.accounts[2], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance(r)
+        self.assert_within_lower(balance, 500, 2000)
+
+
+    def test_dynamic_amount(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[1], 2000)
+        r = self.rpc.do(o)
+
+        cases = [
+            (60, 1960),
+            (120, 1920),
+            (180, 1882),
+            (240, 1844),
+            (300, 1807),
+            (360, 1771),
+            (420, 1736),
+            (480, 1701),
+            (540, 1667),
+            (600, 1634),
+                ]
+        for case in cases:
+            self.backend.time_travel(self.start_time + int(case[0] * (self.period_seconds / 60)))
+
+            o = c.balance_of(self.address, self.accounts[1], sender_address=self.accounts[0])
+            r = self.rpc.do(o)
+            balance = c.parse_balance(r)
+            self.assert_within_lower(balance, case[1], 10000)
+
+
+if __name__ == '__main__':
+    unittest.main()

python/tests/test_basic.py

@@ -3,184 +3,353 @@ import os
 import unittest
 import json
 import logging
+import datetime
 
-# third-party imports
-import web3
-import eth_tester
-import eth_abi
+# external imports
+from chainlib.eth.constant import ZERO_ADDRESS
+from chainlib.eth.nonce import RPCNonceOracle
+from chainlib.eth.tx import receipt
+from chainlib.eth.block import (
+        block_latest,
+        block_by_number,
+    )
+
+# local imports
+from erc20_demurrage_token import DemurrageToken
+
+# test imports
+from erc20_demurrage_token.unittest import TestDemurrageDefault
 
 logging.basicConfig(level=logging.DEBUG)
 logg = logging.getLogger()
 
-logging.getLogger('web3').setLevel(logging.WARNING)
-logging.getLogger('eth.vm').setLevel(logging.WARNING)
-
 testdir = os.path.dirname(__file__)
 
-#BLOCKTIME = 5 # seconds
-TAX_LEVEL = 10000 * 2 # 2%
-#PERIOD = int(60/BLOCKTIME) * 60 * 24 * 30 # month
-PERIOD = 10
-
-
-class Test(unittest.TestCase):
-
-    contract = None
-
-    def setUp(self):
-        eth_params = eth_tester.backends.pyevm.main.get_default_genesis_params({
-            'gas_limit': 9000000,
-            })
-
-        f = open(os.path.join(testdir, '../../solidity/RedistributedDemurrageToken.bin'), 'r')
-        self.bytecode = f.read()
-        f.close()
-
-        f = open(os.path.join(testdir, '../../solidity/RedistributedDemurrageToken.json'), 'r')
-        self.abi = json.load(f)
-        f.close()
-
-
-        backend = eth_tester.PyEVMBackend(eth_params)
-        self.eth_tester =  eth_tester.EthereumTester(backend)
-        provider = web3.Web3.EthereumTesterProvider(self.eth_tester)
-        self.w3 = web3.Web3(provider)
-        self.sink_address = self.w3.eth.accounts[9]
-
-        c = self.w3.eth.contract(abi=self.abi, bytecode=self.bytecode)
-        tx_hash = c.constructor('Foo Token', 'FOO', 6, TAX_LEVEL, PERIOD, self.sink_address).transact({'from': self.w3.eth.accounts[0]})
-
-        r = self.w3.eth.getTransactionReceipt(tx_hash)
-        self.contract = self.w3.eth.contract(abi=self.abi, address=r.contractAddress)
-
-        self.start_block = self.w3.eth.blockNumber
-
-    def tearDown(self):
-        pass
 
+class TestBasic(TestDemurrageDefault):
 
     def test_hello(self):
-        self.assertEqual(self.contract.functions.actualPeriod().call(), 1)
-        self.eth_tester.mine_blocks(PERIOD)
-        self.assertEqual(self.contract.functions.actualPeriod().call(), 2)
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        o = c.actual_period(self.address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        
+        self.backend.time_travel(self.start_time + self.period_seconds + 1)
+        o = c.actual_period(self.address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
 
 
-    def test_mint(self):
-        tx_hash = self.contract.functions.mintTo(self.w3.eth.accounts[1], 1024).transact()
-        r = self.w3.eth.getTransactionReceipt(tx_hash)
-        self.assertEqual(r.status, 1)
+    def test_balance(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[1], 1024)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
 
-        balance = self.contract.functions.balanceOf(self.w3.eth.accounts[1]).call()
+        o = c.balance_of(self.address, self.accounts[1], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance_of(r)
         self.assertEqual(balance, 1024)
 
-        tx_hash = self.contract.functions.mintTo(self.w3.eth.accounts[1], 976).transact()
-        r = self.w3.eth.getTransactionReceipt(tx_hash)
-        self.assertEqual(r.status, 1)
 
-        balance = self.contract.functions.balanceOf(self.w3.eth.accounts[1]).call()
+    def test_apply_demurrage_limited(self):
+        #modifier = (10 ** 28)
+        modifier = 1
+
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+        o = c.demurrage_amount(self.address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        demurrage_amount = c.parse_demurrage_amount(r)
+        self.assertEqual(modifier, demurrage_amount)
+
+        self.backend.time_travel(self.start_time + (60 * 43200))
+        (tx_hash, o) = c.apply_demurrage(self.address, sender_address=self.accounts[0], limit=20000)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        o = c.demurrage_amount(self.address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        demurrage_amount = c.parse_demurrage_amount(r)
+        self.assert_equal_decimals(0.9906, demurrage_amount, 4)
+
+
+    def test_apply_demurrage(self):
+        #modifier = (10 ** 28)
+        modifier = 1
+
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+        o = c.demurrage_amount(self.address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        demurrage_amount = c.parse_demurrage_amount(r)
+        self.assertEqual(modifier, demurrage_amount)
+
+        o = block_latest()
+        r = self.rpc.do(o)
+        o = block_by_number(r)
+        b = self.rpc.do(o)
+        logg.debug('block {} start {}'.format(b['timestamp'], self.start_time))
+
+        self.backend.time_travel(self.start_time + (60 * 43200))
+        (tx_hash, o) = c.apply_demurrage(self.address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        o = c.demurrage_amount(self.address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        demurrage_amount = c.parse_demurrage_amount(r)
+        self.assert_equal_decimals(0.98, demurrage_amount, 2)
+
+        self.backend.time_travel(self.start_time + (60 * 43200 * 2))
+        (tx_hash, o) = c.apply_demurrage(self.address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+        o = c.demurrage_amount(self.address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        demurrage_amount = c.parse_demurrage_amount(r)
+        modifier_base = 1000000 - self.tax_level
+        modifier = int(modifier_base * (10 ** 22)) # 38 decimal places minus 6 (1000000)
+        self.assert_equal_decimals(0.9604, demurrage_amount, 4)
+
+
+    def test_mint_balance(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[1], 1024)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        o = c.balance_of(self.address, self.accounts[1], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance_of(r)
+        self.assertEqual(balance, 1024)
+
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[1], 976)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+        o = c.balance_of(self.address, self.accounts[1], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance_of(r)
         self.assertEqual(balance, 2000)
 
 
+        self.backend.time_travel(self.start_time + (60 * 43200))
+        (tx_hash, o) = c.apply_demurrage(self.address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        o = c.balance_of(self.address, self.accounts[1], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance_of(r)
+        self.assertEqual(balance, int(2000 * 0.98))
+
+
+    def test_minter_control(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[1], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[1], self.accounts[2], 1024)
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 0)
+            
+        (tx_hash, o) = c.add_minter(self.address, self.accounts[1], self.accounts[1])
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 0)
+
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.add_minter(self.address, self.accounts[0], self.accounts[1])
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        nonce_oracle = RPCNonceOracle(self.accounts[1], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[1], self.accounts[2], 1024)
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        (tx_hash, o) = c.add_minter(self.address, self.accounts[1], self.accounts[2])
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 0)
+
+        (tx_hash, o) = c.remove_minter(self.address, self.accounts[1], self.accounts[1])
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[1], self.accounts[2], 1024)
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 0)
+            
+
+    def test_base_amount(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[1], 1024)
+        self.rpc.do(o)
+
+        self.backend.time_travel(self.start_time + (60 * 43200))
+        (tx_hash, o) = c.apply_demurrage(self.address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        o = c.to_base_amount(self.address, 1000, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        amount = c.parse_to_base_amount(r)
+        self.assertEqual(amount, 1020)
+
+
     def test_transfer(self):
-        tx_hash = self.contract.functions.mintTo(self.w3.eth.accounts[1], 1024).transact()
-        r = self.w3.eth.getTransactionReceipt(tx_hash)
-        self.assertEqual(r.status, 1)
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
 
-        tx_hash = self.contract.functions.transfer(self.w3.eth.accounts[2], 500).transact({'from': self.w3.eth.accounts[1]})
-        r = self.w3.eth.getTransactionReceipt(tx_hash)
-        self.assertEqual(r.status, 1)
-        logg.debug('tx {}'.format(r))
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[1], 1024)
+        self.rpc.do(o)
 
-        balance_alice = self.contract.functions.balanceOf(self.w3.eth.accounts[1]).call()
-        self.assertEqual(balance_alice, 524)
+        nonce_oracle = RPCNonceOracle(self.accounts[1], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.transfer(self.address, self.accounts[1], self.accounts[2], 500)
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
 
-        balance_bob = self.contract.functions.balanceOf(self.w3.eth.accounts[2]).call()
-        self.assertEqual(balance_bob, 500)
+        o = c.balance_of(self.address, self.accounts[1], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance_of(r)
+        self.assertEqual(balance, 524)
 
-        tx_hash = self.contract.functions.transfer(self.w3.eth.accounts[2], 500).transact({'from': self.w3.eth.accounts[1]})
-        r = self.w3.eth.getTransactionReceipt(tx_hash)
-        self.assertEqual(r.status, 1)
-        logg.debug('tx {}'.format(r))
+        o = c.balance_of(self.address, self.accounts[2], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance_of(r)
+        self.assertEqual(balance, 500)
+
+        nonce_oracle = RPCNonceOracle(self.accounts[2], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.transfer(self.address, self.accounts[2], self.accounts[1], 500)
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+      
+    def test_approve(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.approve(self.address, self.accounts[0], self.accounts[1], 500)
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+ 
+        (tx_hash, o) = c.approve(self.address, self.accounts[0], self.accounts[1], 600)
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 0)
+
+        (tx_hash, o) = c.approve(self.address, self.accounts[0], self.accounts[1], 0)
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        (tx_hash, o) = c.approve(self.address, self.accounts[0], self.accounts[1], 600)
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        (tx_hash, o) = c.increase_allowance(self.address, self.accounts[0], self.accounts[1], 200)
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        (tx_hash, o) = c.decrease_allowance(self.address, self.accounts[0], self.accounts[1], 800)
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        (tx_hash, o) = c.approve(self.address, self.accounts[0], self.accounts[1], 42)
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
 
 
     def test_transfer_from(self):
-        tx_hash = self.contract.functions.mintTo(self.w3.eth.accounts[1], 1024).transact()
-        r = self.w3.eth.getTransactionReceipt(tx_hash)
-        self.assertEqual(r.status, 1)
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[1], 1024)
+        self.rpc.do(o)
 
-        tx_hash = self.contract.functions.approve(self.w3.eth.accounts[2], 500).transact({'from': self.w3.eth.accounts[1]})
-        r = self.w3.eth.getTransactionReceipt(tx_hash)
-        self.assertEqual(r.status, 1)
-        logg.debug('tx {}'.format(r))
+        nonce_oracle = RPCNonceOracle(self.accounts[1], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.approve(self.address, self.accounts[1], self.accounts[2], 500)
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+        
+        o = c.balance_of(self.address, self.accounts[1], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance_of(r)
+        self.assertEqual(balance, 1024)
 
-        balance_alice = self.contract.functions.balanceOf(self.w3.eth.accounts[1]).call()
-        self.assertEqual(balance_alice, 1024)
+        nonce_oracle = RPCNonceOracle(self.accounts[2], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.transfer_from(self.address, self.accounts[2], self.accounts[1], self.accounts[3], 500)
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+ 
+        o = c.balance_of(self.address, self.accounts[1], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance_of(r)
+        self.assertEqual(balance, 524)
 
-        tx_hash = self.contract.functions.transferFrom(self.w3.eth.accounts[1], self.w3.eth.accounts[3], 500).transact({'from': self.w3.eth.accounts[2]})
-        r = self.w3.eth.getTransactionReceipt(tx_hash)
-        self.assertEqual(r.status, 1)
-        logg.debug('tx {}'.format(r))
+        o = c.balance_of(self.address, self.accounts[3], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance_of(r)
+        self.assertEqual(balance, 500)
 
-        balance_alice = self.contract.functions.balanceOf(self.w3.eth.accounts[1]).call()
-        self.assertEqual(balance_alice, 524)
-
-        balance_alice = self.contract.functions.balanceOf(self.w3.eth.accounts[3]).call()
-        self.assertEqual(balance_alice, 500)
-
-
-    def test_apply_tax(self):
-        self.eth_tester.mine_blocks(PERIOD)
-        tx_hash = self.contract.functions.applyTax().transact()
-        r = self.w3.eth.getTransactionReceipt(tx_hash)
-        self.assertEqual(self.contract.functions.redistributionCount().call(), 2)
-        self.assertEqual(self.contract.functions.demurrageModifier().call(), 980000)
-
-        self.eth_tester.mine_blocks(PERIOD)
-        tx_hash = self.contract.functions.applyTax().transact()
-        r = self.w3.eth.getTransactionReceipt(tx_hash)
-        self.assertEqual(self.contract.functions.redistributionCount().call(), 3)
-        self.assertEqual(self.contract.functions.demurrageModifier().call(), 960400)
-
-
-    def test_tax_balance(self):
-        tx_hash = self.contract.functions.mintTo(self.w3.eth.accounts[1], 1000).transact()
-        r = self.w3.eth.getTransactionReceipt(tx_hash)
-        self.assertEqual(r.status, 1)
-
-        self.eth_tester.mine_blocks(PERIOD)
-        tx_hash = self.contract.functions.applyTax().transact()
-        r = self.w3.eth.getTransactionReceipt(tx_hash)
-        self.assertEqual(r.status, 1)
-
-        balance = self.contract.functions.balanceOf(self.w3.eth.accounts[1]).call()
-        self.assertEqual(balance, 980)
-
-    
-    def test_taxed_transfer(self):
-        tx_hash = self.contract.functions.mintTo(self.w3.eth.accounts[1], 1000000).transact()
-        r = self.w3.eth.getTransactionReceipt(tx_hash)
-        self.assertEqual(r.status, 1)
-
-        self.eth_tester.mine_blocks(PERIOD)
-        tx_hash = self.contract.functions.applyTax().transact()
-        r = self.w3.eth.getTransactionReceipt(tx_hash)
-        self.assertEqual(r.status, 1)
-
-        balance_alice = self.contract.functions.balanceOf(self.w3.eth.accounts[1]).call()
-        self.assertEqual(balance_alice, 980000)
-
-        tx_hash = self.contract.functions.transfer(self.w3.eth.accounts[2], 500000).transact({'from': self.w3.eth.accounts[1]})
-        r = self.w3.eth.getTransactionReceipt(tx_hash)
-        logg.debug('r {}'.format(r))
-        self.assertEqual(r.status, 1)
-
-        balance_alice = self.contract.functions.balanceOf(self.w3.eth.accounts[1]).call()
-        balance_alice_trunc = int(balance_alice/1000)*1000
-        self.assertEqual(balance_alice_trunc, 480000)
-
-        balance_bob = self.contract.functions.balanceOf(self.w3.eth.accounts[2]).call()
-        balance_bob_trunc = int(balance_bob/1000)*1000
-        self.assertEqual(balance_bob_trunc, 500000)
+        (tx_hash, o) = c.transfer_from(self.address, self.accounts[2], self.accounts[1], self.accounts[3], 1)
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 0)
 
 
 if __name__ == '__main__':

python/tests/test_cap.py

@@ -0,0 +1,66 @@
+import os
+import unittest
+import json
+import logging
+
+# external imports
+from chainlib.eth.constant import ZERO_ADDRESS
+from chainlib.eth.nonce import RPCNonceOracle
+from chainlib.eth.tx import receipt
+from chainlib.eth.block import block_latest
+from chainlib.eth.address import to_checksum_address
+from hexathon import (
+        strip_0x,
+        add_0x,
+        )
+
+# local imports
+from erc20_demurrage_token import DemurrageToken
+
+# test imports
+from erc20_demurrage_token.unittest import TestDemurrageDefault
+
+logging.basicConfig(level=logging.DEBUG)
+logg = logging.getLogger()
+
+testdir = os.path.dirname(__file__)
+
+
+class TestCap(TestDemurrageDefault):
+
+    def test_cap(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+        o = c.total_supply(self.address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        logg.debug('r {}'.format(r))
+
+        (tx_hash, o) = c.set_max_supply(self.address, self.accounts[0], self.default_supply_cap)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        o = c.max_supply(self.address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        cap = c.parse_supply_cap(r)
+        self.assertEqual(cap, self.default_supply_cap)
+
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[1], self.default_supply_cap)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[2], 1)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 0)
+
+
+if __name__ == '__main__':
+    unittest.main()

python/tests/test_expiry.py

@@ -0,0 +1,98 @@
+# standard imports
+import os
+import unittest
+import json
+import logging
+import datetime
+
+# external imports
+from chainlib.eth.constant import ZERO_ADDRESS
+from chainlib.eth.nonce import RPCNonceOracle
+from chainlib.eth.tx import receipt
+from chainlib.eth.block import (
+        block_latest,
+        block_by_number,
+    )
+
+# local imports
+from erc20_demurrage_token import DemurrageToken
+
+# test imports
+from erc20_demurrage_token.unittest import TestDemurrageDefault
+
+logging.basicConfig(level=logging.DEBUG)
+logg = logging.getLogger()
+
+testdir = os.path.dirname(__file__)
+
+
+class TestExpire(TestDemurrageDefault):
+
+    def test_expires(self):
+        mint_amount = self.default_supply
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+        for i in range(3):
+            (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[i+1], mint_amount)
+            r = self.rpc.do(o)
+
+        (tx_hash, o) = c.set_expire_period(self.address, self.accounts[0], 2)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        o = c.expires(self.address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        expiry_time = c.parse_expires(r)
+
+        self.backend.time_travel(expiry_time + 60)
+        o = block_latest()
+        r = self.rpc.do(o)
+        o = block_by_number(r)
+        r = self.rpc.do(o)
+        self.assertGreaterEqual(r['timestamp'], expiry_time)
+        
+        nonce_oracle = RPCNonceOracle(self.sink_address, self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.transfer(self.address, self.sink_address, self.accounts[2], 1)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        (tx_hash, o) = c.transfer(self.address, self.sink_address, self.accounts[2], 1)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 0)
+
+        o = c.balance_of(self.address, self.accounts[1], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance(r)
+        self.assert_within(balance, 0.9604 * mint_amount, 1)
+
+        o = c.total_supply(self.address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        supply = c.parse_balance(r)
+
+        (tx_hash, o) = c.change_period(self.address, self.sink_address)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        o = c.balance_of(self.address, self.sink_address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance(r)
+
+        o = c.decay_by(self.address, supply, int((expiry_time - self.start_time) / 60), sender_address=self.sink_address)
+        r = self.rpc.do(o)
+        target_balance = c.parse_balance(r)
+
+        self.assert_within_lower(balance, supply - target_balance, 0.0001)
+
+
+if __name__ == '__main__':
+    unittest.main()

python/tests/test_growth.py

@@ -0,0 +1,66 @@
+# standard imports
+import os
+import unittest
+import json
+import logging
+import datetime
+
+# external imports
+from chainlib.eth.constant import ZERO_ADDRESS
+from chainlib.eth.nonce import RPCNonceOracle
+from chainlib.eth.tx import receipt
+from chainlib.eth.block import (
+        block_latest,
+        block_by_number,
+    )
+
+# local imports
+from erc20_demurrage_token import DemurrageToken
+
+# test imports
+from erc20_demurrage_token.unittest import TestDemurrageDefault
+
+logging.basicConfig(level=logging.DEBUG)
+logg = logging.getLogger()
+
+testdir = os.path.dirname(__file__)
+
+
+class TestGrowth(TestDemurrageDefault):
+
+    def test_decay_by(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+        v = 1000000000
+        o = c.decay_by(self.address, v, 20000, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        g = c.parse_decay_by(r)
+        self.assertEqual(int(g), 990690498)
+       
+        o = c.decay_by(self.address, v, 43200, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        g = c.parse_decay_by(r)
+        self.assertEqual(int(g), 980000000)
+
+
+    def test_decay_steps(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+        v = 1000000000
+        o = c.decay_by(self.address, v, 43200, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        gr = c.parse_decay_by(r)
+
+        v = 1000000000
+        for i in range(100):
+            o = c.decay_by(self.address, v, 432, sender_address=self.accounts[0])
+            r = self.rpc.do(o)
+            v = c.parse_decay_by(r)
+
+        self.assert_within_lower(int(v), int(gr), 0.1)
+
+
+if __name__ == '__main__':
+    unittest.main()

python/tests/test_period.py

@@ -0,0 +1,237 @@
+# standard imports
+import os
+import unittest
+import json
+import logging
+
+# external imports
+from chainlib.eth.constant import ZERO_ADDRESS
+from chainlib.eth.nonce import RPCNonceOracle
+from chainlib.eth.tx import (
+        receipt,
+        TxFactory,
+        TxFormat,
+        )
+from chainlib.eth.contract import (
+        ABIContractEncoder,
+        ABIContractType,
+        )
+from hexathon import same as hex_same
+from hexathon import strip_0x
+from dexif import from_fixed
+
+# local imports
+from erc20_demurrage_token import DemurrageToken
+from erc20_demurrage_token import DemurrageRedistribution
+
+# test imports
+from erc20_demurrage_token.unittest import TestDemurrageDefault
+
+logging.basicConfig(level=logging.DEBUG)
+logg = logging.getLogger()
+
+testdir = os.path.dirname(__file__)
+
+class TestPeriod(TestDemurrageDefault):
+
+    def test_period_and_amount(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[1], 1024)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        for i in range(100):
+            self.backend.time_travel(self.start_time + int((self.period_seconds / 100) * (i + 1)))
+            (tx_hash, o) = c.apply_demurrage(self.address, self.accounts[0], 0)
+            self.rpc.do(o)
+            o = receipt(tx_hash)
+            r = self.rpc.do(o)
+            self.assertEqual(r['status'], 1)
+
+        for lg in r['logs']:
+            if hex_same(lg['topics'][0], '1c9c74563c32efd114cb36fb5e432d9386c8254d08456614804a33a3088ab736'):
+                self.assert_equal_decimals(0.98, from_fixed(strip_0x(lg['data'])), 2)
+
+
+    def test_period_demurrage(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[1], 1024)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        self.backend.time_travel(self.start_time + self.period_seconds + int(self.period_seconds / 2))
+        (tx_hash, o) = c.change_period(self.address, self.accounts[0])
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        for lg in r['logs']:
+            if hex_same(lg['topics'][0], '1c9c74563c32efd114cb36fb5e432d9386c8254d08456614804a33a3088ab736'):
+                self.assert_equal_decimals(0.9701, from_fixed(strip_0x(lg['data'])), 4)
+
+        o = c.redistributions(self.address, 1, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        redistribution_data = c.parse_redistributions(r)
+        redistribution = DemurrageRedistribution(redistribution_data)
+        logg.debug('fixxx {}'.format(redistribution.demurrage))
+
+
+    def test_period(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[1], 1024)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        self.backend.time_travel(self.start_time + self.period_seconds)
+
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.change_period(self.address, self.accounts[0])
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        o = c.redistributions(self.address, 1, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        redistribution = c.parse_redistributions(r)
+
+        o = c.to_redistribution_period(self.address, redistribution, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        period = c.parse_to_redistribution_period(r)
+        self.assertEqual(2, period)
+
+        o = c.actual_period(self.address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        period = c.parse_actual_period(r)
+        self.assertEqual(2, period)
+
+        o = c.to_redistribution_demurrage_modifier(self.address, redistribution, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        period = from_fixed(r)
+        redistro = DemurrageRedistribution(redistribution)
+        logg.debug('redistro {} {}'.format(redistro, period))
+
+        self.backend.time_travel(self.start_time + self.period_seconds * 2)
+
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.change_period(self.address, self.accounts[0])
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        o = c.redistributions(self.address, 2, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        redistribution = c.parse_redistributions(r)
+
+        o = c.to_redistribution_demurrage_modifier(self.address, redistribution, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        period = from_fixed(r)
+
+        # allow test code float rounding error to billionth
+        modifier = (1 - (self.tax_level / 1000000)) ** ((self.period_seconds * 2) / 60)
+        modifier *= 10 ** 9 
+        modifier = int(modifier) * (10 ** (28 - 9))
+
+        period /= (10 ** (28 - 9))
+        period = int(period) * (10 ** (28 - 9))
+        self.assertEqual(modifier, period)
+
+
+    def test_change_sink(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+        o = c.balance_of(self.address, ZERO_ADDRESS, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance_of(r)
+        self.assertEqual(balance, 0)
+
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[1], 102400000000)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        self.backend.time_travel(self.start_time + self.period_seconds + 1)
+
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.change_period(self.address, self.accounts[0])
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        o = c.balance_of(self.address, self.sink_address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance_of(r)
+        self.assertGreater(balance, 0)
+        old_sink_balance = balance
+
+        o = c.balance_of(self.address, self.accounts[3], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance_of(r)
+        self.assertEqual(balance, 0)
+
+        nonce_oracle = RPCNonceOracle(self.accounts[5], self.rpc)
+        c = TxFactory(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        enc = ABIContractEncoder()
+        enc.method('setSinkAddress')
+        enc.typ(ABIContractType.ADDRESS)
+        enc.address(self.accounts[3])
+        data = enc.get()
+        o = c.template(self.accounts[5], self.address, use_nonce=True)
+        o = c.set_code(o, data)
+        (tx_hash, o) = c.finalize(o, TxFormat.JSONRPC)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 0)
+
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = TxFactory(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        enc = ABIContractEncoder()
+        enc.method('setSinkAddress')
+        enc.typ(ABIContractType.ADDRESS)
+        enc.address(self.accounts[3])
+        data = enc.get()
+        o = c.template(self.accounts[0], self.address, use_nonce=True)
+        o = c.set_code(o, data)
+        (tx_hash, o) = c.finalize(o, TxFormat.JSONRPC)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        self.backend.time_travel(self.start_time + (self.period_seconds * 2) + 1)
+
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.change_period(self.address, self.accounts[0])
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        o = c.balance_of(self.address, self.sink_address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance_of(r)
+        self.assertLess(balance, old_sink_balance)
+
+        o = c.balance_of(self.address, self.accounts[3], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance_of(r)
+        self.assertGreater(balance, 0)
+
+
+if __name__ == '__main__':
+    unittest.main()

python/tests/test_redistribution_single.py

@@ -0,0 +1,205 @@
+# standard imports
+import os
+import unittest
+import json
+import logging
+
+# external imports
+from chainlib.eth.constant import ZERO_ADDRESS
+from chainlib.eth.nonce import RPCNonceOracle
+from chainlib.eth.tx import receipt
+from chainlib.eth.block import (
+        block_latest,
+        block_by_number,
+        )
+from chainlib.eth.address import to_checksum_address
+from hexathon import (
+        strip_0x,
+        add_0x,
+        same as hex_same,
+        )
+from dexif import from_fixed
+
+# local imports
+from erc20_demurrage_token import DemurrageToken
+
+# test imports
+from erc20_demurrage_token.unittest import TestDemurrageDefault
+
+logging.basicConfig(level=logging.INFO)
+logg = logging.getLogger()
+
+testdir = os.path.dirname(__file__)
+
+class TestRedistribution(TestDemurrageDefault):
+
+
+    def test_redistribution_periods(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+        demurrage = (1 - (self.tax_level / 1000000)) * (10**28)
+        supply = self.default_supply
+
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[0], supply)
+        self.rpc.do(o)
+
+        for i in range(1, 100):
+            logg.info('execute time travel to period {}'.format(i))
+            self.backend.time_travel(self.start_time + (self.period_seconds * i))
+            (tx_hash, o) = c.change_period(self.address, self.accounts[0])
+            self.rpc.do(o)
+            o = receipt(tx_hash)
+            r = self.rpc.do(o)
+            self.assertEqual(r['status'], 1)
+
+            redistribution_value = 0
+            for lg in r['logs']:
+                if hex_same(lg['topics'][0], '0x9a2a887706623ad3ff7fc85652deeceabe9fe1e00466c597972079ee91ea40d3'):
+                    redistribution_value = int(strip_0x(lg['data']), 16)
+
+            o = c.redistributions(self.address, i, sender_address=self.accounts[0])
+            redistribution = self.rpc.do(o)
+
+            o = c.to_redistribution_demurrage_modifier(self.address, redistribution, sender_address=self.accounts[0])
+            r = self.rpc.do(o)
+            demurrage = from_fixed(r)
+
+            o = c.redistributions(self.address, i-1, sender_address=self.accounts[0])
+            redistribution = self.rpc.do(o)
+
+            o = c.to_redistribution_demurrage_modifier(self.address, redistribution, sender_address=self.accounts[0])
+            r = self.rpc.do(o)
+            demurrage_previous = from_fixed(r)
+
+            o = c.balance_of(self.address, self.sink_address, sender_address=self.accounts[0])
+            r = self.rpc.do(o)
+            balance_sink = c.parse_balance(r)
+
+            o = c.balance_of(self.address, self.accounts[0], sender_address=self.accounts[0])
+            r = self.rpc.do(o)
+            balance_minter = c.parse_balance(r)
+
+            logg.info('testing redistro {} sink {} mint {} adds up to {} supply {} with demurrage between {} and {}'.format(redistribution_value, balance_sink, balance_minter, balance_sink + balance_minter, supply, demurrage_previous, demurrage))
+
+            self.assert_within(balance_minter + balance_sink, supply, 10)
+
+
+    def test_redistribution_catchup_periods(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+        demurrage = (1 - (self.tax_level / 1000000)) * (10**28)
+        supply = self.default_supply
+
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[0], supply)
+        self.rpc.do(o)
+
+        self.backend.time_travel(self.start_time + (self.period_seconds * 100))
+
+        balance_minter = None
+        balance_sink = None
+        real_supply = None
+
+        for i in range(1, 101):
+            (tx_hash, o) = c.change_period(self.address, self.accounts[0])
+            self.rpc.do(o)
+            o = receipt(tx_hash)
+            r = self.rpc.do(o)
+            self.assertEqual(r['status'], 1)
+
+            o = c.balance_of(self.address, self.sink_address, sender_address=self.accounts[0])
+            r = self.rpc.do(o)
+            balance_sink = c.parse_balance(r)
+
+            o = c.balance_of(self.address, self.accounts[0], sender_address=self.accounts[0])
+            r = self.rpc.do(o)
+            balance_minter = c.parse_balance(r)
+            
+            real_supply = balance_sink + balance_minter
+            logg.info('period {} testing sink {} mint {} adds up to supply {} of original {} (delta {})'.format(i, balance_sink, balance_minter, real_supply, supply, supply - real_supply))
+
+        i = 100
+        o = c.redistributions(self.address, i, sender_address=self.accounts[0])
+        redistribution = self.rpc.do(o)
+
+        o = c.to_redistribution_demurrage_modifier(self.address, redistribution, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        demurrage = c.parse_to_redistribution_item(r)
+
+        o = c.redistributions(self.address, i-1, sender_address=self.accounts[0])
+        redistribution = self.rpc.do(o)
+
+        o = c.to_redistribution_demurrage_modifier(self.address, redistribution, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        demurrage_previous = c.parse_to_redistribution_item(r)
+
+        o = c.balance_of(self.address, self.sink_address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance_sink = c.parse_balance(r)
+
+        o = c.balance_of(self.address, self.accounts[0], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance_minter = c.parse_balance(r)
+
+        logg.debug('testing sink {} mint {} adds up to supply {} with demurrage between {} and {}'.format(balance_sink, balance_minter, real_supply, demurrage_previous, demurrage))
+
+        self.assert_within_lower(balance_minter + balance_sink, supply, 0.1)
+
+
+#    def test_redistribution_boundaries(self):
+#        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+#        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+#
+#        demurrage = (1 - (self.tax_level / 1000000)) * (10**28)
+#        supply = self.default_supply
+#
+#        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[0], supply)
+#        self.rpc.do(o)
+#
+#        o = c.balance_of(self.address, self.sink_address, sender_address=self.accounts[0])
+#        r = self.rpc.do(o)
+#        balance = c.parse_balance(r)
+#        logg.debug('balance before {} supply {}'.format(balance, supply))
+#
+#        self.backend.time_travel(self.start_time + self.period_seconds)
+#        (tx_hash, o) = c.change_period(self.address, self.accounts[0])
+#        r = self.rpc.do(o)
+#
+#        o = receipt(tx_hash)
+#        r = self.rpc.do(o)
+#        self.assertEqual(r['status'], 1)
+#
+#        o = c.redistributions(self.address, 1, sender_address=self.accounts[0])
+#        r = self.rpc.do(o)
+#        oo = c.to_redistribution_supply(self.address, r, sender_address=self.accounts[0])
+#        rr = self.rpc.do(oo)
+#        oo = c.to_redistribution_demurrage_modifier(self.address, r, sender_address=self.accounts[0])
+#        rr = self.rpc.do(oo)
+#
+#        o = c.balance_of(self.address, self.sink_address, sender_address=self.accounts[0])
+#        r = self.rpc.do(o)
+#        balance = c.parse_balance(r)
+#
+#        self.backend.time_travel(self.start_time + self.period_seconds * 2 + 1)
+#        (tx_hash, o) = c.change_period(self.address, self.accounts[0])
+#        r = self.rpc.do(o)
+#
+#        o = receipt(tx_hash)
+#        r = self.rpc.do(o)
+#        self.assertEqual(r['status'], 1)
+#
+#        o = c.redistributions(self.address, 2, sender_address=self.accounts[0])
+#        r = self.rpc.do(o)
+#        oo = c.to_redistribution_supply(self.address, r, sender_address=self.accounts[0])
+#        rr = self.rpc.do(oo)
+#        oo = c.to_redistribution_demurrage_modifier(self.address, r, sender_address=self.accounts[0])
+#        rr = self.rpc.do(oo)
+#
+#        o = c.balance_of(self.address, self.sink_address, sender_address=self.accounts[0])
+#        r = self.rpc.do(o)
+#        balance = c.parse_balance(r)
+
+
+if __name__ == '__main__':
+    unittest.main()

python/tests/test_redistribution_unit.py

@@ -0,0 +1,202 @@
+import os
+import unittest
+import json
+import logging
+
+# external imports
+from chainlib.eth.constant import ZERO_ADDRESS
+from chainlib.eth.nonce import RPCNonceOracle
+from chainlib.eth.tx import receipt
+from chainlib.eth.block import (
+        block_latest,
+        block_by_number,
+        )
+from chainlib.eth.address import to_checksum_address
+from hexathon import (
+        strip_0x,
+        add_0x,
+        )
+from dexif import to_fixed
+
+# local imports
+from erc20_demurrage_token import DemurrageToken
+from erc20_demurrage_token import DemurrageRedistribution
+
+# test imports
+from erc20_demurrage_token.unittest import TestDemurrageDefault
+
+logging.basicConfig(level=logging.DEBUG)
+logg = logging.getLogger()
+
+testdir = os.path.dirname(__file__)
+
+
+class TestRedistribution(TestDemurrageDefault):
+
+
+    # TODO: move to "pure" test file when getdistribution is implemented in all contracts
+    def test_distribution_direct(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+        demurrage = (1 - (self.tax_level / 1000000)) * (10**28)
+        supply = self.default_supply
+
+        #o = c.get_distribution(self.address, supply, demurrage, sender_address=self.accounts[0])
+        o = c.get_distribution(self.address, supply, to_fixed(self.tax_level / 1000000), sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        distribution = c.parse_get_distribution(r)
+        expected_distribution = self.default_supply * (self.tax_level / 1000000)
+        self.assert_within(distribution, expected_distribution, 100)
+
+
+    def test_distribution_from_redistribution(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+        demurrage = (1 - (self.tax_level / 100000)) * (10**28)
+
+        supply = self.default_supply
+
+        o = c.to_redistribution(self.address, 0, to_fixed(self.tax_level / 1000000), supply, 2, sender_address=self.accounts[0])
+        redistribution = self.rpc.do(o)
+
+        o = c.get_distribution_from_redistribution(self.address, redistribution, self.accounts[0])
+        r = self.rpc.do(o)
+        distribution = c.parse_get_distribution(r)
+        expected_distribution = (self.default_supply * (self.tax_level / 1000000))
+        logg.debug('distribution {} supply {}'.format(distribution, self.default_supply))
+        self.assert_within(distribution, expected_distribution, 1000)
+
+
+    def test_single_step_basic(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+        mint_amount = 100000000
+
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[1], mint_amount)
+        self.rpc.do(o)
+
+        self.backend.time_travel(self.start_time + self.period_seconds)
+
+        (tx_hash, o) = c.change_period(self.address, self.accounts[0])
+        self.rpc.do(o)
+
+        expected_balance = int(mint_amount - ((self.tax_level / 1000000) * mint_amount))
+
+        o = c.balance_of(self.address, ZERO_ADDRESS, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance(r)
+
+        logg.debug('balance {}'.format(balance))
+
+        o = c.balance_of(self.address, self.accounts[1], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance(r)
+
+        self.assertEqual(balance, expected_balance)
+
+
+    def test_single_step_multi(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+        mint_amount = 100000000
+
+        for i in range(3):
+            (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[i+1], mint_amount)
+            self.rpc.do(o)
+    
+        self.backend.time_travel(self.start_time + self.period_seconds)
+
+        (tx_hash, o) = c.change_period(self.address, self.accounts[0])
+        self.rpc.do(o)
+
+        expected_balance = int(mint_amount - ((self.tax_level / 1000000) * mint_amount))
+
+        for i in range(3):
+            o = c.balance_of(self.address, self.accounts[i+1], sender_address=self.accounts[0])
+            r = self.rpc.do(o)
+            balance = c.parse_balance(r)
+            self.assertEqual(balance, expected_balance)
+
+
+    def test_single_step_transfer(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+        mint_amount = self.default_supply
+        half_mint_amount = int(mint_amount / 2)
+
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[1], mint_amount)
+        self.rpc.do(o)
+
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[2], mint_amount)
+        self.rpc.do(o)
+    
+        nonce_oracle = RPCNonceOracle(self.accounts[1], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.transfer(self.address, self.accounts[1], self.accounts[3], half_mint_amount)
+        self.rpc.do(o)
+
+        self.backend.time_travel(self.start_time + self.period_seconds)
+
+        (tx_hash, o) = c.change_period(self.address, self.accounts[1])
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        # check that we have crossed into new period, this will throw if not
+        o = c.redistributions(self.address, 1, sender_address=self.accounts[0])
+        self.rpc.do(o)
+
+        demurrage_amount = int((self.tax_level / 1000000) * mint_amount)
+
+        expected_balance = mint_amount - demurrage_amount
+        o = c.balance_of(self.address, self.accounts[2], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance(r)
+        self.assert_within(balance, expected_balance, 10)
+
+        half_demurrage_amount = int((self.tax_level / 1000000) * half_mint_amount)
+
+        expected_balance = half_mint_amount - half_demurrage_amount
+        o = c.balance_of(self.address, self.accounts[1], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance(r)
+        self.assertEqual(balance, expected_balance)
+
+        o = c.balance_of(self.address, self.accounts[3], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance(r)
+        self.assertEqual(balance, expected_balance)
+
+        o = c.total_supply(self.address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        supply = c.parse_total_supply(r)
+
+        o = c.redistributions(self.address, 0, sender_address=self.accounts[0])
+        redistribution = self.rpc.do(o)
+        o = c.to_redistribution_supply(self.address, redistribution, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        supply = c.parse_to_redistribution_item(r)
+        o = c.to_redistribution_demurrage_modifier(self.address, redistribution, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        #demurrage = c.parse_to_redistribution_item(r)
+        #logg.debug('\nrediistribution {}\ndemurrage {}\nsupply {}'.format(redistribution, demurrage, supply))
+        redistro_item = DemurrageRedistribution(redistribution)
+        logg.debug('redistribution {}'.format(redistro_item))
+
+        expected_balance = int(supply * (self.tax_level / 1000000))
+        expected_balance_tolerance = 1
+
+        o = c.balance_of(self.address, self.sink_address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance(r)
+        self.assert_within_lower(balance, expected_balance, 1000)
+
+
+if __name__ == '__main__':
+    unittest.main()

python/tests/test_seal.py

@@ -0,0 +1,195 @@
+# standard imports
+import os
+import unittest
+import json
+import logging
+import datetime
+
+# external imports
+from chainlib.eth.constant import ZERO_ADDRESS
+from chainlib.eth.nonce import RPCNonceOracle
+from chainlib.eth.tx import receipt
+from chainlib.eth.block import (
+        block_latest,
+        block_by_number,
+    )
+
+# local imports
+from erc20_demurrage_token import DemurrageToken
+from erc20_demurrage_token.seal import ContractState
+from erc20_demurrage_token.seal import CONTRACT_SEAL_STATE_MAX
+
+# test imports
+from erc20_demurrage_token.unittest import TestDemurrageDefault
+
+logging.basicConfig(level=logging.DEBUG)
+logg = logging.getLogger()
+
+testdir = os.path.dirname(__file__)
+
+
+
+class TestSeal(TestDemurrageDefault):
+
+    def test_seal_dup(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+        (tx_hash, o) = c.seal(self.address, self.accounts[0], 1)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        (tx_hash, o) = c.seal(self.address, self.accounts[0], 1)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 0)
+
+
+    def test_seal_all(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+        (tx_hash, o) = c.seal(self.address, self.accounts[0], CONTRACT_SEAL_STATE_MAX)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        o = c.is_sealed(self.address, 0, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        self.assertTrue(c.parse_is_sealed(r))
+
+
+    def test_seal_minter(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+    
+        (tx_hash, o) = c.add_minter(self.address, self.accounts[0], self.accounts[1])
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        (tx_hash, o) = c.seal(self.address, self.accounts[0], ContractState.MINTER_STATE)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        (tx_hash, o) = c.add_minter(self.address, self.accounts[0], self.accounts[2])
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 0)
+
+        o = c.is_sealed(self.address, ContractState.MINTER_STATE, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        self.assertTrue(c.parse_is_sealed(r))
+
+
+    def test_seal_expiry(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+    
+        (tx_hash, o) = c.set_expire_period(self.address, self.accounts[0], 10)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        (tx_hash, o) = c.set_expire_period(self.address, self.accounts[0], 20)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        (tx_hash, o) = c.seal(self.address, self.accounts[0], ContractState.EXPIRY_STATE)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        (tx_hash, o) = c.set_expire_period(self.address, self.accounts[0], 21)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 0)
+
+        o = c.is_sealed(self.address, ContractState.EXPIRY_STATE, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        self.assertTrue(c.parse_is_sealed(r))
+
+
+    def test_seal_set_sink_address(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+    
+        (tx_hash, o) = c.set_sink_address(self.address, self.accounts[0], self.accounts[3])
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        (tx_hash, o) = c.set_sink_address(self.address, self.accounts[0], self.accounts[4])
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        (tx_hash, o) = c.seal(self.address, self.accounts[0], ContractState.SINK_STATE)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        (tx_hash, o) = c.set_sink_address(self.address, self.accounts[0], self.accounts[5])
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 0)
+
+        o = c.is_sealed(self.address, ContractState.SINK_STATE, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        self.assertTrue(c.parse_is_sealed(r))
+
+
+    def test_seal_cap(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+    
+        (tx_hash, o) = c.set_max_supply(self.address, self.accounts[0], 100)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        (tx_hash, o) = c.set_max_supply(self.address, self.accounts[0], 200)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        (tx_hash, o) = c.seal(self.address, self.accounts[0], ContractState.CAP_STATE)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        (tx_hash, o) = c.set_max_supply(self.address, self.accounts[0], 300)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 0)
+
+        o = c.is_sealed(self.address, ContractState.CAP_STATE, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        self.assertTrue(c.parse_is_sealed(r))
+
+
+if __name__ == '__main__':
+    unittest.main()
+
+

python/tests/test_single.py

@@ -0,0 +1,96 @@
+import os
+import unittest
+import json
+import logging
+
+# external imports
+from chainlib.eth.constant import ZERO_ADDRESS
+from chainlib.eth.nonce import RPCNonceOracle
+from chainlib.eth.tx import receipt
+from chainlib.eth.block import block_latest
+from chainlib.eth.address import to_checksum_address
+from hexathon import (
+        strip_0x,
+        add_0x,
+        )
+from dexif import to_fixed
+
+# local imports
+from erc20_demurrage_token import DemurrageToken
+
+# test imports
+from erc20_demurrage_token.unittest import TestDemurrageDefault
+
+logging.basicConfig(level=logging.DEBUG)
+logg = logging.getLogger()
+
+testdir = os.path.dirname(__file__)
+
+
+class TestRedistributionSingle(TestDemurrageDefault):
+
+    def test_single_even_if_multiple(self):
+        mint_amount = 100000000
+
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+        for i in range(3):
+            (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[i+1], mint_amount)
+            r = self.rpc.do(o)
+
+        external_address = to_checksum_address('0x' + os.urandom(20).hex())
+        nonce_oracle = RPCNonceOracle(self.accounts[2], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.transfer(self.address, self.accounts[2], external_address, int(mint_amount) * 0.1)
+        r = self.rpc.do(o)
+
+        nonce_oracle = RPCNonceOracle(self.accounts[3], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.transfer(self.address, self.accounts[3], external_address, int(mint_amount) * 0.2)
+        r = self.rpc.do(o)
+
+        self.backend.time_travel(self.start_time + self.period_seconds + 1)
+        (tx_hash, o) = c.apply_demurrage(self.address, self.accounts[3])
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        rcpt = self.rpc.do(o)
+        self.assertEqual(rcpt['status'], 1)
+
+        (tx_hash, o) = c.change_period(self.address, self.accounts[3])
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        tax_modifier = 0.98
+        o = c.balance_of(self.address, self.accounts[1], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance(r)
+        self.assertEqual(balance, int(mint_amount * tax_modifier))
+
+        o = c.balance_of(self.address, self.accounts[2], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance(r)
+        base_amount = mint_amount - int(mint_amount * 0.1)
+        self.assertEqual(balance, int(base_amount * tax_modifier)) #(base_amount - (base_amount * (self.tax_level / 1000000))))
+
+        o = c.balance_of(self.address, self.accounts[3], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance(r)
+        base_amount = mint_amount - int(mint_amount * 0.2)
+        self.assertEqual(balance, int(base_amount * tax_modifier)) #(base_amount - (base_amount * (self.tax_level / 1000000))))
+
+        o = c.total_supply(self.address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        new_supply = c.parse_total_supply(r)
+
+        o = c.balance_of(self.address, self.sink_address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        balance = c.parse_balance(r)
+        expected_balance = new_supply - (new_supply * tax_modifier)
+        self.assert_within_lower(balance, expected_balance, 1)
+
+
+if __name__ == '__main__':
+    unittest.main()

solidity/DemurrageTokenSingleNocap.sol

@@ -0,0 +1,703 @@
+pragma solidity >= 0.8.0;
+
+
+import "aux/ABDKMath64x64.sol";
+
+// SPDX-License-Identifier: GPL-3.0-or-later
+contract DemurrageTokenSingleNocap {
+
+	struct redistributionItem {
+		uint32 period;
+		uint72 value;
+		uint64 demurrage;
+	}
+	redistributionItem[] public redistributions; // uint51(unused) | uint64(demurrageModifier) | uint36(participants) | uint72(value) | uint32(period)
+
+	// Account balances
+	mapping (address => uint256) account;
+	
+	// Cached demurrage amount, ppm with 38 digit resolution
+	//uint128 public demurrageAmount;
+	int128 public demurrageAmount;
+
+	// Cached demurrage timestamp; the timestamp for which demurrageAmount was last calculated
+	uint256 public demurrageTimestamp;
+
+	// Implements EIP172
+	address public owner;
+
+	address newOwner;
+
+	// Implements ERC20
+	string public name;
+
+	// Implements ERC20
+	string public symbol;
+
+	// Implements ERC20
+	uint256 public immutable decimals;
+
+	// Implements ERC20
+	//uint256 public totalSupply;
+	uint256 supply;
+
+	// Last executed period
+	uint256 public lastPeriod;
+
+	// Last sink redistribution amount
+	uint256 public totalSink;
+
+	// Value of burnt tokens (burnt tokens do not decay)
+	uint256 public burned;
+
+	// 128 bit resolution of the demurrage divisor
+	// (this constant x 1000000 is contained within 128 bits)
+	//uint256 constant nanoDivider = 100000000000000000000000000; // now nanodivider, 6 zeros less
+
+	// remaining decimal positions of nanoDivider to reach 38, equals precision in growth and decay
+	//uint256 constant growthResolutionFactor = 1000000000000;
+
+	// demurrage decimal width; 38 places
+	//uint256 public immutable resolutionFactor = nanoDivider * growthResolutionFactor; 
+
+	// Timestamp of start of periods (time which contract constructor was called)
+	uint256 public immutable periodStart;
+
+	// Duration of a single redistribution period in seconds
+	uint256 public immutable periodDuration;
+
+	// Demurrage in ppm per minute
+	//uint256 public immutable taxLevel;
+	// 64x64
+	int128 public immutable taxLevel;
+		
+	// Addresses allowed to mint new tokens
+	mapping (address => bool) minter;
+
+	// Storage for ERC20 approve/transferFrom methods
+	mapping (address => mapping (address => uint256 ) ) allowance; // holder -> spender -> amount (amount is subject to demurrage)
+
+	// Address to send unallocated redistribution tokens
+	address public sinkAddress; 
+
+	// timestamp when token contract expires
+	uint256 public expires;
+	bool expired;
+
+	// supply xap
+	uint256 public maxSupply;
+
+	// Implements ERC20
+	event Transfer(address indexed _from, address indexed _to, uint256 _value);
+
+	// Implements ERC20
+	event Approval(address indexed _owner, address indexed _spender, uint256 _value);
+
+	// New tokens minted
+	event Mint(address indexed _minter, address indexed _beneficiary, uint256 _value);
+
+	// New demurrage cache milestone calculated
+	event Decayed(uint256 indexed _period, uint256 indexed _periodCount, int128 indexed _oldAmount, int128 _newAmount);
+
+	// When a new period threshold has been crossed
+	event Period(uint256 _period);
+
+	// Redistribution applied on a single eligible account
+	event Redistribution(address indexed _account, uint256 indexed _period, uint256 _value);
+
+	// Temporary event used in development, will be removed on prod
+	//event Debug(bytes32 _foo);
+	event Debug(int128 indexed _foo, uint256 indexed _bar);
+
+	// Emitted when tokens are burned
+	event Burn(address indexed _burner, uint256 _value);
+
+	// EIP173
+	event OwnershipTransferred(address indexed previousOwner, address indexed newOwner); // EIP173
+
+	event SealStateChange(uint256 _sealState);
+
+	event Expired(uint256 _timestamp);
+
+	event Cap(uint256 indexed _oldCap, uint256 _newCap);
+
+	// property sealing 
+	uint256 public sealState;
+	uint8 constant MINTER_STATE = 1;
+	uint8 constant SINK_STATE = 2;
+	uint8 constant EXPIRY_STATE = 4;
+	uint8 constant CAP_STATE = 8;
+	uint256 constant public maxSealState = 15;
+
+
+	constructor(string memory _name, string memory _symbol, uint8 _decimals, int128 _taxLevel, uint256 _periodMinutes, address _defaultSinkAddress) {
+		require(_taxLevel < (1 << 64));
+		redistributionItem memory initialRedistribution;
+
+		//require(ABDKMath64x64.toUInt(_taxLevel) == 0);
+
+		// ACL setup
+		owner = msg.sender;
+		minter[owner] = true;
+
+		// ERC20 setup
+		name = _name;
+		symbol = _symbol;
+		decimals = _decimals;
+
+		// Demurrage setup
+		demurrageTimestamp = block.timestamp;
+		periodStart = demurrageTimestamp;
+		periodDuration = _periodMinutes * 60;
+		demurrageAmount = ABDKMath64x64.fromUInt(1);
+
+		taxLevel = ABDKMath64x64.ln(_taxLevel);
+		initialRedistribution = toRedistribution(0, demurrageAmount, 0, 1);
+		redistributions.push(initialRedistribution);
+
+		// Misc settings
+		sinkAddress = _defaultSinkAddress;
+	}
+
+	function seal(uint256 _state) public returns(uint256) {
+		require(_state < 16, 'ERR_INVALID_STATE');
+		require(_state & sealState == 0, 'ERR_ALREADY_LOCKED');
+		sealState |= _state;
+		emit SealStateChange(sealState);
+		return uint256(sealState);
+	}
+
+	function isSealed(uint256 _state) public returns(bool) {
+		require(_state < maxSealState);
+		if (_state == 0) {
+			return sealState == maxSealState;
+		}
+		return _state & sealState == _state;
+	}
+
+	function setExpirePeriod(uint256 _expirePeriod) public {
+		uint256 r;
+
+		require(!isSealed(EXPIRY_STATE));
+		require(!expired);
+		require(msg.sender == owner);
+		r = periodStart + (_expirePeriod * periodDuration);
+		require(r > expires);
+		expires = r;
+	}
+	
+	function setMaxSupply(uint256 _cap) public {
+		require(!isSealed(CAP_STATE));
+		require(msg.sender == owner);
+		require(_cap > totalSupply());
+		emit Cap(maxSupply, _cap);
+		maxSupply = _cap;
+	}
+
+	// Change sink address for redistribution
+	function setSinkAddress(address _sinkAddress) public {
+		require(!isSealed(SINK_STATE));
+		require(msg.sender == owner);
+		sinkAddress = _sinkAddress;
+	}
+
+	// Expire the contract if expire is set and we have gone over the threshold.
+	// Finalizes demurrage up to the timestamp of the expiry. 
+	// The first approve, transfer or transferFrom call that hits the ex == 2 will get the tx mined. but without the actual effect. Otherwise we would have to wait until an external egent called applyExpiry to get the correct final balance.
+	function applyExpiry() public returns(uint8) {
+		if (expired) {
+			return 1;
+		}
+		if (expires == 0) {
+			return 0;
+		}
+		if (block.timestamp >= expires) {
+			applyDemurrageLimited(expires - demurrageTimestamp / 60);
+			expired = true;
+			emit Expired(block.timestamp);
+			changePeriod();
+			return 2;
+		}
+		return 0;
+	}
+
+	// Given address will be allowed to call the mintTo() function
+	function addMinter(address _minter) public returns (bool) {
+		require(!isSealed(MINTER_STATE));
+		require(msg.sender == owner);
+		minter[_minter] = true;
+		return true;
+	}
+
+	// Given address will no longer be allowed to call the mintTo() function
+	function removeMinter(address _minter) public returns (bool) {
+		require(!isSealed(MINTER_STATE));
+		require(msg.sender == owner || _minter == msg.sender);
+		minter[_minter] = false;
+		return true;
+	}
+
+	/// Implements ERC20
+	function balanceOf(address _account) public view returns (uint256) {
+		int128 baseBalance;
+		int128 currentDemurragedAmount;
+		uint256 periodCount;
+		uint8 expiryState;
+
+		baseBalance = ABDKMath64x64.fromUInt(baseBalanceOf(_account));
+
+		periodCount = getMinutesDelta(demurrageTimestamp);
+
+		currentDemurragedAmount = ABDKMath64x64.mul(baseBalance, demurrageAmount);
+		return decayBy(ABDKMath64x64.toUInt(currentDemurragedAmount), periodCount);
+	}
+
+	// Balance unmodified by demurrage
+	function baseBalanceOf(address _account) public view returns (uint256) {
+		return account[_account];
+	}
+
+	/// Increases base balance for a single account
+	function increaseBaseBalance(address _account, uint256 _delta) private returns (bool) {
+		uint256 oldBalance;
+		uint256 newBalance;
+		uint256 workAccount;
+
+		workAccount = uint256(account[_account]);
+	
+		if (_delta == 0) {
+			return false;
+		}
+
+		oldBalance = baseBalanceOf(_account);
+		account[_account] = oldBalance + _delta;
+		return true;
+	}
+
+	/// Decreases base balance for a single account
+	function decreaseBaseBalance(address _account, uint256 _delta) private returns (bool) {
+		uint256 oldBalance;
+	       	uint256 newBalance;
+		uint256 workAccount;
+
+		workAccount = uint256(account[_account]);
+
+		if (_delta == 0) {
+			return false;
+		}
+
+		oldBalance = baseBalanceOf(_account);	
+		require(oldBalance >= _delta, 'ERR_OVERSPEND'); // overspend guard
+		account[_account] = oldBalance - _delta;
+		return true;
+	}
+
+	// Creates new tokens out of thin air, and allocates them to the given address
+	// Triggers tax
+	function mintTo(address _beneficiary, uint256 _amount) external returns (bool) {
+		uint256 baseAmount;
+
+		require(applyExpiry() == 0);
+		require(minter[msg.sender], 'ERR_ACCESS');
+changePeriod();
+		if (maxSupply > 0) {
+			require(supply + _amount <= maxSupply);
+		}
+		supply += _amount;
+
+		baseAmount = toBaseAmount(_amount);
+		increaseBaseBalance(_beneficiary, baseAmount);
+		emit Mint(msg.sender, _beneficiary, _amount);
+		saveRedistributionSupply();
+		return true;
+	}
+
+	// Deserializes the redistribution word
+	function toRedistribution(uint256 _participants, int128 _demurrageModifier, uint256 _value, uint256 _period) public pure returns(redistributionItem memory) {
+		redistributionItem memory redistribution;
+
+		redistribution.period = uint32(_period);
+		redistribution.value = uint72(_value);
+		redistribution.demurrage = uint64(uint128(_demurrageModifier) & 0xffffffffffffffff);
+		return redistribution;
+
+	}
+
+	// Serializes the demurrage period part of the redistribution word
+	function toRedistributionPeriod(redistributionItem memory _redistribution) public pure returns (uint256) {
+		return uint256(_redistribution.period);
+	}
+
+	// Serializes the supply part of the redistribution word
+	function toRedistributionSupply(redistributionItem memory _redistribution) public pure returns (uint256) {
+		return uint256(_redistribution.value);
+	}
+
+	// Serializes the number of participants part of the redistribution word
+	function toRedistributionDemurrageModifier(redistributionItem memory _redistribution) public pure returns (int128) {
+		int128 r;
+
+		r = int128(int64(_redistribution.demurrage) & int128(0x0000000000000000ffffffffffffffff));
+		if (r == 0) {
+			r = ABDKMath64x64.fromUInt(1);
+		}
+		return r;
+	}
+
+	// Client accessor to the redistributions array length
+	function redistributionCount() public view returns (uint256) {
+		return redistributions.length;
+	}
+
+	// Save the current total supply amount to the current redistribution period
+	function saveRedistributionSupply() private returns (bool) {
+		redistributionItem memory currentRedistribution;
+		uint256 grownSupply;
+
+		grownSupply = totalSupply();
+		currentRedistribution = redistributions[redistributions.length-1];
+		currentRedistribution.value = uint72(grownSupply);
+
+		redistributions[redistributions.length-1] = currentRedistribution;
+		return true;
+	}
+
+	// Get the demurrage period of the current block number
+	function actualPeriod() public view returns (uint128) {
+		return uint128((block.timestamp - periodStart) / periodDuration + 1);
+	}
+
+	// Retrieve next redistribution if the period threshold has been crossed
+	function checkPeriod() private view returns (redistributionItem memory) {
+		redistributionItem memory lastRedistribution;
+		redistributionItem memory emptyRedistribution;
+		uint256 currentPeriod;
+
+		lastRedistribution =  redistributions[lastPeriod];
+		currentPeriod = this.actualPeriod();
+		if (currentPeriod <= toRedistributionPeriod(lastRedistribution)) {
+			return emptyRedistribution;
+		}
+		return lastRedistribution;
+	}
+
+	function getDistribution(uint256 _supply, int128 _demurrageAmount) public view returns (uint256) {
+		int128 difference;
+
+		difference = ABDKMath64x64.mul(ABDKMath64x64.fromUInt(_supply), ABDKMath64x64.sub(ABDKMath64x64.fromUInt(1), _demurrageAmount));
+		return _supply - ABDKMath64x64.toUInt(difference);
+			
+	}
+
+	function getDistributionFromRedistribution(redistributionItem memory _redistribution) public returns (uint256) {
+		uint256 redistributionSupply;
+		int128 redistributionDemurrage;
+
+		redistributionSupply = toRedistributionSupply(_redistribution);
+		redistributionDemurrage = toRedistributionDemurrageModifier(_redistribution);
+		return getDistribution(redistributionSupply, redistributionDemurrage);
+	}
+
+	// Returns the amount sent to the sink address
+	function applyDefaultRedistribution(redistributionItem memory _redistribution) private returns (uint256) {
+		uint256 unit;
+		uint256 baseUnit;
+	
+		unit = totalSupply() - getDistributionFromRedistribution(_redistribution);	
+		baseUnit = toBaseAmount(unit) - totalSink;
+		increaseBaseBalance(sinkAddress, baseUnit);
+		emit Redistribution(sinkAddress, _redistribution.period, unit);
+		lastPeriod += 1;
+		totalSink += baseUnit;
+		return unit;
+	}
+
+	// Recalculate the demurrage modifier for the new period
+	// Note that the supply for the consecutive period will be taken at the time of code execution, and thus not necessarily at the time when the redistribution period threshold was crossed.
+	function changePeriod() public returns (bool) {
+		redistributionItem memory currentRedistribution;
+		redistributionItem memory nextRedistribution;
+		redistributionItem memory lastRedistribution;
+		uint256 currentPeriod;
+		int128 lastDemurrageAmount;
+		int128 nextRedistributionDemurrage;
+		uint256 demurrageCounts;
+		uint256 nextPeriod;
+
+		applyDemurrage();
+		currentRedistribution = checkPeriod();
+		if (isEmptyRedistribution(currentRedistribution)) {
+			return false;
+		}
+
+		// calculate the decay from previous redistributino
+		lastRedistribution = redistributions[lastPeriod];
+		currentPeriod = toRedistributionPeriod(currentRedistribution);
+		nextPeriod = currentPeriod + 1;
+		lastDemurrageAmount = toRedistributionDemurrageModifier(lastRedistribution);
+		demurrageCounts = (periodDuration * currentPeriod) / 60;
+		// TODO refactor decayby to take int128 then DRY with it
+		nextRedistributionDemurrage = ABDKMath64x64.exp(ABDKMath64x64.mul(taxLevel, ABDKMath64x64.fromUInt(demurrageCounts)));
+		nextRedistribution = toRedistribution(0, nextRedistributionDemurrage, totalSupply(), nextPeriod);
+		redistributions.push(nextRedistribution);
+
+		applyDefaultRedistribution(nextRedistribution);
+		emit Period(nextPeriod);
+		return true;
+	}
+
+	// Calculate the time delta in whole minutes passed between given timestamp and current timestamp
+	function getMinutesDelta(uint256 _lastTimestamp) public view returns (uint256) {
+		return (block.timestamp - _lastTimestamp) / 60;
+	}
+
+	// Calculate and cache the demurrage value corresponding to the (period of the) time of the method call
+	function applyDemurrage() public returns (uint256) {
+		return applyDemurrageLimited(0);
+	}
+
+	// returns true if expired
+	function applyDemurrageLimited(uint256 _rounds) public returns (uint256) {
+		int128 v;
+		uint256 periodCount;
+		int128 periodPoint;
+		int128 lastDemurrageAmount;
+
+		if (expired) {
+			return 0; 
+		}
+
+		periodCount = getMinutesDelta(demurrageTimestamp);
+		if (periodCount == 0) {
+			return 0;
+		}
+		lastDemurrageAmount = demurrageAmount;
+	
+		// safety limit for exponential calculation to ensure that we can always
+		// execute this code no matter how much time passes.			
+		if (_rounds > 0 && _rounds < periodCount) {
+			periodCount = _rounds;
+		}
+
+		periodPoint = ABDKMath64x64.fromUInt(periodCount);
+		v = ABDKMath64x64.mul(taxLevel, periodPoint);
+		v = ABDKMath64x64.exp(v);
+		demurrageAmount = ABDKMath64x64.mul(demurrageAmount, v);
+
+		demurrageTimestamp = demurrageTimestamp + (periodCount * 60);
+		emit Decayed(demurrageTimestamp, periodCount, lastDemurrageAmount, demurrageAmount);
+		return periodCount;
+	}
+
+	// Return timestamp of start of period threshold
+	function getPeriodTimeDelta(uint256 _periodCount) public view returns (uint256) {
+		return periodStart + (_periodCount * periodDuration);
+	}
+
+	// Amount of demurrage cycles inbetween the current timestamp and the given target time
+	function demurrageCycles(uint256 _target) public view returns (uint256) {
+		return (block.timestamp - _target) / 60;
+	}
+
+	function isEmptyRedistribution(redistributionItem memory _redistribution) public pure returns(bool) {
+		if (_redistribution.period > 0) {
+			return false;
+		}
+		if (_redistribution.value > 0) {
+			return false;
+		}
+		if (_redistribution.demurrage > 0) {
+			return false;
+		}
+		return true;
+	}
+
+
+	// Calculate a value reduced by demurrage by the given period
+	function decayBy(uint256 _value, uint256 _period)  public view returns (uint256) {
+		int128 valuePoint;
+		int128 periodPoint;
+		int128 v;
+	
+		valuePoint = ABDKMath64x64.fromUInt(_value);
+		periodPoint = ABDKMath64x64.fromUInt(_period);
+
+		v = ABDKMath64x64.mul(taxLevel, periodPoint);
+		v = ABDKMath64x64.exp(v);
+		v = ABDKMath64x64.mul(valuePoint, v);
+		return ABDKMath64x64.toUInt(v);
+	}
+
+
+	// Inflates the given amount according to the current demurrage modifier
+	function toBaseAmount(uint256 _value) public view returns (uint256) {
+		int128 r;
+		r = ABDKMath64x64.div(ABDKMath64x64.fromUInt(_value), demurrageAmount);
+		return ABDKMath64x64.toUInt(r);
+	}
+
+	// Implements ERC20, triggers tax and/or redistribution
+	function approve(address _spender, uint256 _value) public returns (bool) {
+		uint256 baseValue;
+		uint8 ex;
+
+		ex = applyExpiry();
+		if (ex == 2) {
+			return false;	
+		} else if (ex > 0) {
+			revert('EXPIRED');
+		}
+		if (allowance[msg.sender][_spender] > 0) {
+			require(_value == 0, 'ZERO_FIRST');
+		}
+		
+		changePeriod();
+
+		baseValue = toBaseAmount(_value);
+		allowance[msg.sender][_spender] = baseValue;
+		emit Approval(msg.sender, _spender, _value);
+		return true;
+	}
+
+	// Reduce allowance by amount
+	function decreaseAllowance(address _spender, uint256 _value) public returns (bool) {
+		uint256 baseValue;
+
+		baseValue = toBaseAmount(_value);
+		require(allowance[msg.sender][_spender] >= baseValue);
+		
+		changePeriod();
+
+		allowance[msg.sender][_spender] -= baseValue;
+		emit Approval(msg.sender, _spender, allowance[msg.sender][_spender]);
+		return true;
+	}
+
+	// Increase allowance by amount
+	function increaseAllowance(address _spender, uint256 _value) public returns (bool) {
+		uint256 baseValue;
+
+		changePeriod();
+
+		baseValue = toBaseAmount(_value);
+
+		allowance[msg.sender][_spender] += baseValue;
+		emit Approval(msg.sender, _spender, allowance[msg.sender][_spender]);
+		return true;
+	}
+
+	// Implements ERC20, triggers tax and/or redistribution
+	function transfer(address _to, uint256 _value) public returns (bool) {
+		uint256 baseValue;
+		bool result;
+		uint8 ex;
+
+		ex = applyExpiry();
+		if (ex == 2) {
+			return false;	
+		} else if (ex > 0) {
+			revert('EXPIRED');
+		}
+		changePeriod();
+
+		baseValue = toBaseAmount(_value);
+		result = transferBase(msg.sender, _to, baseValue);
+		emit Transfer(msg.sender, _to, _value);
+		return result;
+	}
+
+	// Implements ERC20, triggers tax and/or redistribution
+	function transferFrom(address _from, address _to, uint256 _value) public returns (bool) {
+		uint256 baseValue;
+		bool result;
+		uint8 ex;
+
+		ex = applyExpiry();
+		if (ex == 2) {
+			return false;	
+		} else if (ex > 0) {
+			revert('EXPIRED');
+		}
+		changePeriod();
+
+		baseValue = toBaseAmount(_value);
+		require(allowance[_from][msg.sender] >= baseValue);
+
+		allowance[_from][msg.sender] -= baseValue;
+		result = transferBase(_from, _to, baseValue);
+
+		emit Transfer(_from, _to, _value);
+		return result;
+	}
+
+	// ERC20 transfer backend for transfer, transferFrom
+	function transferBase(address _from, address _to, uint256 _value) private returns (bool) {
+		uint256 period;
+
+		decreaseBaseBalance(_from, _value);
+		increaseBaseBalance(_to, _value);
+
+		return true;
+	}
+
+	// Implements EIP173
+	function transferOwnership(address _newOwner) public returns (bool) {
+		require(msg.sender == owner);
+		newOwner = _newOwner;
+	}
+
+	// Implements OwnedAccepter
+	function acceptOwnership() public returns (bool) {
+		address oldOwner;
+
+		require(msg.sender == newOwner);
+		oldOwner = owner; 
+		owner = newOwner;
+		newOwner = address(0);
+		emit OwnershipTransferred(oldOwner, owner);
+	}
+
+	// Explicitly and irretrievably burn tokens
+	// Only token minters can burn tokens
+	function burn(uint256 _value) public {
+		require(applyExpiry() == 0);
+		require(minter[msg.sender]);
+		require(_value <= account[msg.sender]);
+		uint256 _delta = toBaseAmount(_value);
+
+		//applyDemurrage();
+		decreaseBaseBalance(msg.sender, _delta);
+		burned += _value;
+		emit Burn(msg.sender, _value);
+	}
+
+	// Implements ERC20
+	function totalSupply() public view returns (uint256) {
+		return supply - burned;
+	}
+
+	// Return total number of burned tokens
+	function totalBurned() public view returns (uint256) {
+		return burned;
+	}
+
+	// Implements EIP165
+	function supportsInterface(bytes4 _sum) public pure returns (bool) {
+		if (_sum == 0xc6bb4b70) { // ERC20
+			return true;
+		}
+		if (_sum == 0x449a52f8) { // Minter
+			return true;
+		}
+		if (_sum == 0x01ffc9a7) { // EIP165
+			return true;
+		}
+		if (_sum == 0x9493f8b2) { // EIP173
+			return true;
+		}
+		if (_sum == 0x37a47be4) { // OwnedAccepter
+			return true;
+		}
+		return false;
+	}
+}

solidity/Makefile

@@ -1,16 +1,22 @@
 SOLC = /usr/bin/solc
 
-all:
-	$(SOLC) RedistributedDemurrageToken.sol --abi --evm-version byzantium | awk 'NR>3' > RedistributedDemurrageToken.json
-	$(SOLC) RedistributedDemurrageToken.sol --bin --evm-version byzantium | awk 'NR>3' > RedistributedDemurrageToken.bin
-	truncate -s -1 RedistributedDemurrageToken.bin
+all: single_nocap
+
+single_nocap:
+	$(SOLC) DemurrageTokenSingleNocap.sol --abi --evm-version byzantium | awk 'NR==4' > DemurrageTokenSingleNocap.json
+	$(SOLC) DemurrageTokenSingleNocap.sol --bin --evm-version byzantium | awk 'NR==4' > DemurrageTokenSingleNocap.bin
+	truncate -s -1 DemurrageTokenSingleNocap.bin
+
+single: single_nocap
 
 test: all
 	python ../python/tests/test_basic.py
 	python ../python/tests/test_period.py
 	python ../python/tests/test_redistribution.py
+	python ../python/tests/test_pure.py
 
 install: all
-	cp -v RedistributedDemurrageToken.{json,bin} ../python/eth_address_declarator/data/
+	cp -v DemurrageToken*.json ../python/erc20_demurrage_token/data/
+	cp -v DemurrageToken*.bin ../python/erc20_demurrage_token/data/
 	
 .PHONY: test install

solidity/RedistributedDemurrageToken.sol

@@ -1,360 +0,0 @@
-pragma solidity > 0.6.11;
-
-// SPDX-License-Identifier: GPL-3.0-or-later
-
-// TODO: assign bitmask values to contants 
-contract RedistributedDemurrageToken {
-
-	address public owner;
-	uint256 public decimals;
-	string public name;
-	string public symbol;
-	uint256 public totalSupply;
-
-	uint256 public periodStart;
-	uint256 public periodDuration;
-	uint256 public taxLevel; // PPM
-	uint256 public demurrageModifier; // PPM
-
-	bytes32[] public redistributions; // uint1(isFractional) | uint1(unused) | uint38(participants) | uint160(value) | uint56(period)
-	mapping (address => bytes32) account; // uint20(unused) | uint56(period) | uint160(value)
-	mapping (address => bool) minter;
-	mapping (address => mapping (address => uint256 ) ) allowance; // holder -> spender -> amount (amount is subject to demurrage)
-
-	address sinkAddress; // receives redistribuion remainders
-
-	event Transfer(address indexed _from, address indexed _to, uint256 _value);
-	event Approval(address indexed _owner, address indexed _spender, uint256 _value);
-	event Mint(address indexed _minter, address indexed _beneficiary, uint256 _value);
-	//event Debug(uint256 _foo);
-	event Taxed(uint256 indexed _period, uint256 remainder);
-	event Redistribution(address indexed _account, uint256 indexed _period, uint256 _value);
-
-	constructor(string memory _name, string memory _symbol, uint8 _decimals, uint32 _taxLevel, uint256 _period, address _defaultSinkAddress) public {
-		owner = msg.sender;
-		minter[owner] = true;
-		periodStart = block.number;
-		periodDuration = _period;
-		taxLevel = _taxLevel;
-		name = _name;
-		symbol = _symbol;
-		decimals = _decimals;
-		demurrageModifier = 1000000;
-		sinkAddress = _defaultSinkAddress;
-		bytes32 initialRedistribution = toRedistribution(0, 0, 1);
-		redistributions.push(initialRedistribution);
-	}
-
-	// Given address will be allowed to call the mintTo() function
-	function addMinter(address _minter) public returns (bool) {
-		require(msg.sender == owner);
-		minter[_minter] = true;
-		return true;
-	}
-	
-	/// ERC20
-	function balanceOf(address _account) public view returns (uint256) {
-		uint256 baseBalance = getBaseBalance(_account);
-		uint256 inverseModifier = 1000000 - demurrageModifier;
-		uint256 balanceModifier = (inverseModifier * baseBalance) / 1000000;
-		return baseBalance - balanceModifier;
-	}
-
-	/// Balance unmodified by demurrage
-	function getBaseBalance(address _account) private view returns (uint256) {
-		return uint256(account[_account]) & 0x00ffffffffffffffffffffffffffffffffffffffff;
-	}
-
-	/// Increases base balance for a single account
-	function increaseBaseBalance(address _account, uint256 _delta) private returns (bool) {
-		uint256 oldBalance;
-		uint256 newBalance;
-		
-		oldBalance = getBaseBalance(_account);
-		newBalance = oldBalance + _delta;
-		require(uint160(newBalance) > uint160(oldBalance), 'ERR_WOULDWRAP'); // revert if increase would result in a wrapped value
-		account[_account] &= bytes32(0xffffffffffffffffffffffff0000000000000000000000000000000000000000);
-		account[_account] |= bytes32(newBalance & 0x00ffffffffffffffffffffffffffffffffffffffff);
-		return true;
-	}
-
-	/// Decreases base balance for a single account
-	function decreaseBaseBalance(address _account, uint256 _delta) private returns (bool) {
-		uint256 oldBalance;
-	       	uint256 newBalance;
-
-		oldBalance = getBaseBalance(_account);	
-		require(oldBalance >= _delta, 'ERR_OVERSPEND'); // overspend guard
-		newBalance = oldBalance - _delta;
-		account[_account] &= bytes32(0xffffffffffffffffffffffff0000000000000000000000000000000000000000);
-		account[_account] |= bytes32(newBalance & 0x00ffffffffffffffffffffffffffffffffffffffff);
-		return true;
-	}
-
-	// Creates new tokens out of thin air, and allocates them to the given address
-	// Triggers tax
-	function mintTo(address _beneficiary, uint256 _amount) external returns (bool) {
-		require(minter[msg.sender]);
-
-		// TODO: get base amount for minting
-		applyTax();
-		totalSupply += _amount;
-		increaseBaseBalance(_beneficiary, _amount);
-		emit Mint(msg.sender, _beneficiary, _amount);
-		saveRedistributionSupply();
-		return true;
-	}
-
-	// Deserializes the redistribution word
-	function toRedistribution(uint256 _participants, uint256 _value, uint256 _period) private pure returns(bytes32) {
-		bytes32 redistribution;
-
-		redistribution |= bytes32((_participants & 0x7fffffffff) << 216);
-		redistribution |= bytes32((_value & 0xffffffffffffffffffffffff) << 56);
-		redistribution |= bytes32(_period & 0xffffffffffffff);
-		return redistribution;
-	}
-
-	// Serializes the demurrage period part of the redistribution word
-	function toRedistributionPeriod(bytes32 redistribution) public pure returns (uint256) {
-		return uint256(redistribution & 0x00000000000000000000000000000000000000000000000000ffffffffffffff);
-	}
-
-	// Serializes the supply part of the redistribution word
-	function toRedistributionSupply(bytes32 redistribution) public pure returns (uint256) {
-		return uint256(redistribution & 0x0000000000ffffffffffffffffffffffffffffffffffffffff00000000000000) >> 56;
-	}
-
-	// Serializes the number of participants part of the redistribution word
-	function toRedistributionParticipants(bytes32 redistribution) public pure returns (uint256) {
-		return uint256(redistribution & 0x7fffffffff000000000000000000000000000000000000000000000000000000) >> 216;
-	}
-
-	// Client accessor to the redistributions array length
-	function redistributionCount() public view returns (uint256) {
-		return redistributions.length;
-	}
-
-	// Add number of participants for the current redistribution period by one
-	function incrementRedistributionParticipants() private returns (bool) {
-		uint256 currentRedistribution;
-		uint256 participants;
-
-		currentRedistribution = uint256(redistributions[redistributions.length-1]);
-		participants = ((currentRedistribution & 0x7fffffffff000000000000000000000000000000000000000000000000000000) >> 216) + 1;
-		currentRedistribution &= 0x8000000000ffffffffffffffffffffffffffffffffffffffffffffffffffffff;
-		currentRedistribution |= participants << 216;
-
-		//emit Debug(participants);
-		redistributions[redistributions.length-1] = bytes32(currentRedistribution);
-	}
-
-	// Save the current total supply amount to the current redistribution period
-	function saveRedistributionSupply() private returns (bool) {
-		uint256 currentRedistribution;
-
-		currentRedistribution = uint256(redistributions[redistributions.length-1]);
-		currentRedistribution &= 0xffffffffff0000000000000000000000000000000000000000ffffffffffffff;
-		currentRedistribution |= totalSupply << 56;
-
-		redistributions[redistributions.length-1] = bytes32(currentRedistribution);
-	}
-
-	// Get the demurrage period of the current block number
-	function actualPeriod() public view returns (uint256) {
-		return (block.number - periodStart) / periodDuration + 1;
-	}
-
-	// Add an entered demurrage period to the redistribution array
-	function checkPeriod() private view returns (bytes32) {
-		bytes32 lastRedistribution;
-		uint256 currentPeriod;
-
-		lastRedistribution =  redistributions[redistributions.length-1];
-		currentPeriod = this.actualPeriod();
-		if (currentPeriod <= toRedistributionPeriod(lastRedistribution)) {
-			return bytes32(0x00);
-		}
-		return lastRedistribution;
-	}
-
-	// Deserialize the pemurrage period for the given account is participating in
-	function accountPeriod(address _account) public view returns (uint256) {
-		return (uint256(account[_account]) & 0xffffffffffffffffffffffff0000000000000000000000000000000000000000) >> 160;
-	}
-
-	// Save the given demurrage period as the currently participation period for the given address
-	function registerAccountPeriod(address _account, uint256 _period) private returns (bool) {
-		account[_account] &= 0x000000000000000000000000ffffffffffffffffffffffffffffffffffffffff;
-		account[_account] |= bytes32(_period << 160);
-		incrementRedistributionParticipants();
-	}
-
-	// Determine whether the unit number is rounded down, rounded up or evenly divides.
-	// Returns 0 if evenly distributed, or the remainder as a positive number
-	// A _numParts value 0 will be interpreted as the value 1
-	function remainder(uint256 _numParts, uint256 _sumWhole) public pure returns (uint256) {
-		uint256 unit;
-		uint256 truncatedResult;
-
-		if (_numParts == 0) { // no division by zero please
-			return _sumWhole;
-		}
-		require(_numParts < _sumWhole); // At least you are never LESS than the sum of your parts. Think about that.
-
-		unit = _sumWhole / _numParts;
-		truncatedResult = unit * _numParts;
-		return _sumWhole - truncatedResult;
-	}
-
-	// sets the remainder bit for the given period and books the remainder to the sink address balance
-	// returns false if no change was made
-	function applyRemainderOnPeriod(uint256 _remainder, uint256 _period) private returns (bool) {
-		bytes32 redistribution;
-
-		redistribution = redistributions[_period-1];
-
-		if (_remainder == 0) {
-			return false;
-		}
-		redistribution |= 0x8000000000000000000000000000000000000000000000000000000000000000;
-		increaseBaseBalance(sinkAddress, _remainder);
-		return true;
-	}
-
-	// Recalculate the demurrage modifier for the new period
-	// After this, all REPORTED balances will have been reduced by the corresponding ratio (but the effecive totalsupply stays the same)
-	function applyTax() public returns (uint256) {
-		bytes32 currentRedistribution;
-		bytes32 nextRedistribution;
-		uint256 currentPeriod;
-		uint256 currentParticipants;
-		uint256 currentRemainder;
-
-		currentRedistribution = checkPeriod();
-		if (currentRedistribution == bytes32(0x00)) {
-			return demurrageModifier;
-		}
-		demurrageModifier -= (demurrageModifier * taxLevel) / 1000000;
-		currentPeriod = toRedistributionPeriod(currentRedistribution);
-		nextRedistribution = toRedistribution(0, totalSupply, currentPeriod + 1);
-		redistributions.push(nextRedistribution);
-
-		currentParticipants = toRedistributionParticipants(currentRedistribution);
-		currentRemainder = remainder(currentParticipants, totalSupply); // we can use totalSupply directly because it will always be the same as the recorded supply on the current redistribution
-		applyRemainderOnPeriod(currentRemainder, currentPeriod);
-		emit Taxed(currentPeriod, currentRemainder);
-		return demurrageModifier;
-	}
-
-	// Calculate a value reduced by demurrage by the given period
-	function toTaxPeriodAmount(uint256 _value, uint256 _period) public view returns (uint256) {
-		uint256 valueFactor;
-	      
-	       	// TODO: doesn't work for solidity as floats are missing and using ints linearly increases the order of magnitude  	
-		// valueFactor = 1000000 * (((1000000-taxLevel)/1000000) ** _period);
-		valueFactor = 1000000;
-		for (uint256 i = 0; i < _period; i++) {
-			valueFactor = (valueFactor * taxLevel) / 1000000;
-		}
-
-		return (valueFactor * _value) / 1000000;
-	}
-
-	// If the given account is participating in a period and that period has been crossed
-	// THEN increase the base value of the account with its share of the value reduction of the period
-	function applyRedistributionOnAccount(address _account) public returns (bool) {
-		bytes32 periodRedistribution;
-		uint256 supply;
-		uint256 participants;
-		uint256 baseValue;
-		uint256 value;
-		uint256 period;
-	       
-		period = accountPeriod(_account);
-		if (period == 0 || period >= actualPeriod()) {
-			return false;
-		}
-		periodRedistribution = redistributions[period-1];
-		participants = toRedistributionParticipants(periodRedistribution);
-		if (participants == 0) {
-			return false;
-		}
-
-		supply = toRedistributionSupply(periodRedistribution);
-		// TODO: Make sure value for balance increases round down, and that we can do a single allocation to a sink account with the difference. We can use the highest bit in "participants" for that.
-		baseValue = supply / participants;
-		value = toTaxPeriodAmount(baseValue, period-1);
-
-		account[_account] &= bytes32(0x000000000000000000000000ffffffffffffffffffffffffffffffffffffffff);
-		increaseBaseBalance(_account, value);
-
-		emit Redistribution(_account, period, value);
-		return true;
-	}
-
-	// Inflates the given amount according to the current demurrage modifier
-	function toBaseAmount(uint256 _value) public view returns (uint256) {
-		return (_value * 1000000) / demurrageModifier;
-	}
-
-	// ERC20, triggers tax and/or redistribution
-	function transfer(address _to, uint256 _value) public returns (bool) {
-		uint256 baseValue;
-		bool result;
-
-		applyTax();
-		applyRedistributionOnAccount(msg.sender);
-
-		// TODO: Prefer to truncate the result, instead it seems to round to nearest :/
-		baseValue = toBaseAmount(_value);
-		result = transferBase(msg.sender, _to, baseValue);
-
-		return result;
-	}
-
-	// ERC20 transfer backend for transfer, transferFrom
-	function transferBase(address _from, address _to, uint256 _value) private returns (bool) {
-		uint256 period;
-
-		if (!decreaseBaseBalance(_from, _value)) {
-			revert('ERR_TX_DECREASEBALANCE');
-		}
-		if (!increaseBaseBalance(_to, _value)) {
-			revert('ERR_TX_INCREASEBALANCE');
-		}
-		period = actualPeriod();
-		if (_value > 0 && accountPeriod(_from) != period) {
-			registerAccountPeriod(_from, period);
-		}
-		return true;
-	}
-
-	// ERC20, triggers tax and/or redistribution
-	function transferFrom(address _from, address _to, uint256 _value) public returns (bool) {
-		uint256 baseValue;
-		bool result;
-
-		applyTax();
-		applyRedistributionOnAccount(msg.sender);
-
-		baseValue = toBaseAmount(_value);
-		require(allowance[_from][msg.sender] >= baseValue);
-
-		result = transferBase(_from, _to, baseValue);
-		return result;
-	}
-
-	// ERC20, triggers tax and/or redistribution
-	function approve(address _spender, uint256 _value) public returns (bool) {
-		uint256 baseValue;
-
-		applyTax();
-		applyRedistributionOnAccount(msg.sender);
-
-		baseValue = toBaseAmount(_value);
-		allowance[msg.sender][_spender] += baseValue;
-		emit Approval(msg.sender, _spender, _value);
-		return true;
-	}
-}

solidity/aux/ABDKMath64x64.sol

@@ -0,0 +1,752 @@
+// SPDX-License-Identifier: BSD-4-Clause
+/*
+ * ABDK Math 64.64 Smart Contract Library.  Copyright © 2019 by ABDK Consulting.
+ * Author: Mikhail Vladimirov <mikhail.vladimirov@gmail.com>
+ */
+pragma solidity ^0.8.0;
+
+/**
+ * Smart contract library of mathematical functions operating with signed
+ * 64.64-bit fixed point numbers.  Signed 64.64-bit fixed point number is
+ * basically a simple fraction whose numerator is signed 128-bit integer and
+ * denominator is 2^64.  As long as denominator is always the same, there is no
+ * need to store it, thus in Solidity signed 64.64-bit fixed point numbers are
+ * represented by int128 type holding only the numerator.
+ */
+library ABDKMath64x64 {
+  /*
+   * Minimum value signed 64.64-bit fixed point number may have. 
+   */
+  int128 private constant MIN_64x64 = -0x80000000000000000000000000000000;
+
+  /*
+   * Maximum value signed 64.64-bit fixed point number may have. 
+   */
+  int128 private constant MAX_64x64 = 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF;
+
+  /**
+   * Convert signed 256-bit integer number into signed 64.64-bit fixed point
+   * number.  Revert on overflow.
+   *
+   * @param x signed 256-bit integer number
+   * @return signed 64.64-bit fixed point number
+   */
+  function fromInt (int256 x) internal pure returns (int128) {
+    unchecked {
+      require (x >= -0x8000000000000000 && x <= 0x7FFFFFFFFFFFFFFF);
+      return int128 (x << 64);
+    }
+  }
+
+  /**
+   * Convert signed 64.64 fixed point number into signed 64-bit integer number
+   * rounding down.
+   *
+   * @param x signed 64.64-bit fixed point number
+   * @return signed 64-bit integer number
+   */
+  function toInt (int128 x) internal pure returns (int64) {
+    unchecked {
+      return int64 (x >> 64);
+    }
+  }
+
+  /**
+   * Convert unsigned 256-bit integer number into signed 64.64-bit fixed point
+   * number.  Revert on overflow.
+   *
+   * @param x unsigned 256-bit integer number
+   * @return signed 64.64-bit fixed point number
+   */
+  function fromUInt (uint256 x) internal pure returns (int128) {
+    unchecked {
+      require (x <= 0x7FFFFFFFFFFFFFFF);
+      return int128 (int256 (x << 64));
+    }
+  }
+
+  /**
+   * Convert signed 64.64 fixed point number into unsigned 64-bit integer
+   * number rounding down.  Revert on underflow.
+   *
+   * @param x signed 64.64-bit fixed point number
+   * @return unsigned 64-bit integer number
+   */
+  function toUInt (int128 x) internal pure returns (uint64) {
+    unchecked {
+      require (x >= 0);
+      return uint64 (uint128 (x >> 64));
+    }
+  }
+
+  /**
+   * Convert signed 128.128 fixed point number into signed 64.64-bit fixed point
+   * number rounding down.  Revert on overflow.
+   *
+   * @param x signed 128.128-bin fixed point number
+   * @return signed 64.64-bit fixed point number
+   */
+  function from128x128 (int256 x) internal pure returns (int128) {
+    unchecked {
+      int256 result = x >> 64;
+      require (result >= MIN_64x64 && result <= MAX_64x64);
+      return int128 (result);
+    }
+  }
+
+  /**
+   * Convert signed 64.64 fixed point number into signed 128.128 fixed point
+   * number.
+   *
+   * @param x signed 64.64-bit fixed point number
+   * @return signed 128.128 fixed point number
+   */
+  function to128x128 (int128 x) internal pure returns (int256) {
+    unchecked {
+      return int256 (x) << 64;
+    }
+  }
+
+  /**
+   * Calculate x + y.  Revert on overflow.
+   *
+   * @param x signed 64.64-bit fixed point number
+   * @param y signed 64.64-bit fixed point number
+   * @return signed 64.64-bit fixed point number
+   */
+  function add (int128 x, int128 y) internal pure returns (int128) {
+    unchecked {
+      int256 result = int256(x) + y;
+      require (result >= MIN_64x64 && result <= MAX_64x64);
+      return int128 (result);
+    }
+  }
+
+  /**
+   * Calculate x - y.  Revert on overflow.
+   *
+   * @param x signed 64.64-bit fixed point number
+   * @param y signed 64.64-bit fixed point number
+   * @return signed 64.64-bit fixed point number
+   */
+  function sub (int128 x, int128 y) internal pure returns (int128) {
+    unchecked {
+      int256 result = int256(x) - y;
+      require (result >= MIN_64x64 && result <= MAX_64x64);
+      return int128 (result);
+    }
+  }
+
+  /**
+   * Calculate x * y rounding down.  Revert on overflow.
+   *
+   * @param x signed 64.64-bit fixed point number
+   * @param y signed 64.64-bit fixed point number
+   * @return signed 64.64-bit fixed point number
+   */
+  function mul (int128 x, int128 y) internal pure returns (int128) {
+    unchecked {
+      int256 result = int256(x) * y >> 64;
+      require (result >= MIN_64x64 && result <= MAX_64x64);
+      return int128 (result);
+    }
+  }
+
+  /**
+   * Calculate x * y rounding towards zero, where x is signed 64.64 fixed point
+   * number and y is signed 256-bit integer number.  Revert on overflow.
+   *
+   * @param x signed 64.64 fixed point number
+   * @param y signed 256-bit integer number
+   * @return signed 256-bit integer number
+   */
+  function muli (int128 x, int256 y) internal pure returns (int256) {
+    unchecked {
+      if (x == MIN_64x64) {
+        require (y >= -0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF &&
+          y <= 0x1000000000000000000000000000000000000000000000000);
+        return -y << 63;
+      } else {
+        bool negativeResult = false;
+        if (x < 0) {
+          x = -x;
+          negativeResult = true;
+        }
+        if (y < 0) {
+          y = -y; // We rely on overflow behavior here
+          negativeResult = !negativeResult;
+        }
+        uint256 absoluteResult = mulu (x, uint256 (y));
+        if (negativeResult) {
+          require (absoluteResult <=
+            0x8000000000000000000000000000000000000000000000000000000000000000);
+          return -int256 (absoluteResult); // We rely on overflow behavior here
+        } else {
+          require (absoluteResult <=
+            0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF);
+          return int256 (absoluteResult);
+        }
+      }
+    }
+  }
+
+  /**
+   * Calculate x * y rounding down, where x is signed 64.64 fixed point number
+   * and y is unsigned 256-bit integer number.  Revert on overflow.
+   *
+   * @param x signed 64.64 fixed point number
+   * @param y unsigned 256-bit integer number
+   * @return unsigned 256-bit integer number
+   */
+  function mulu (int128 x, uint256 y) internal pure returns (uint256) {
+    unchecked {
+      if (y == 0) return 0;
+
+      require (x >= 0);
+
+      uint256 lo = (uint256 (int256 (x)) * (y & 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF)) >> 64;
+      uint256 hi = uint256 (int256 (x)) * (y >> 128);
+
+      require (hi <= 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF);
+      hi <<= 64;
+
+      require (hi <=
+        0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF - lo);
+      return hi + lo;
+    }
+  }
+
+  /**
+   * Calculate x / y rounding towards zero.  Revert on overflow or when y is
+   * zero.
+   *
+   * @param x signed 64.64-bit fixed point number
+   * @param y signed 64.64-bit fixed point number
+   * @return signed 64.64-bit fixed point number
+   */
+  function div (int128 x, int128 y) internal pure returns (int128) {
+    unchecked {
+      require (y != 0);
+      int256 result = (int256 (x) << 64) / y;
+      require (result >= MIN_64x64 && result <= MAX_64x64);
+      return int128 (result);
+    }
+  }
+
+  /**
+   * Calculate x / y rounding towards zero, where x and y are signed 256-bit
+   * integer numbers.  Revert on overflow or when y is zero.
+   *
+   * @param x signed 256-bit integer number
+   * @param y signed 256-bit integer number
+   * @return signed 64.64-bit fixed point number
+   */
+  function divi (int256 x, int256 y) internal pure returns (int128) {
+    unchecked {
+      require (y != 0);
+
+      bool negativeResult = false;
+      if (x < 0) {
+        x = -x; // We rely on overflow behavior here
+        negativeResult = true;
+      }
+      if (y < 0) {
+        y = -y; // We rely on overflow behavior here
+        negativeResult = !negativeResult;
+      }
+      uint128 absoluteResult = divuu (uint256 (x), uint256 (y));
+      if (negativeResult) {
+        require (absoluteResult <= 0x80000000000000000000000000000000);
+        return -int128 (absoluteResult); // We rely on overflow behavior here
+      } else {
+        require (absoluteResult <= 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF);
+        return int128 (absoluteResult); // We rely on overflow behavior here
+      }
+    }
+  }
+
+  /**
+   * Calculate x / y rounding towards zero, where x and y are unsigned 256-bit
+   * integer numbers.  Revert on overflow or when y is zero.
+   *
+   * @param x unsigned 256-bit integer number
+   * @param y unsigned 256-bit integer number
+   * @return signed 64.64-bit fixed point number
+   */
+  function divu (uint256 x, uint256 y) internal pure returns (int128) {
+    unchecked {
+      require (y != 0);
+      uint128 result = divuu (x, y);
+      require (result <= uint128 (MAX_64x64));
+      return int128 (result);
+    }
+  }
+
+  /**
+   * Calculate -x.  Revert on overflow.
+   *
+   * @param x signed 64.64-bit fixed point number
+   * @return signed 64.64-bit fixed point number
+   */
+  function neg (int128 x) internal pure returns (int128) {
+    unchecked {
+      require (x != MIN_64x64);
+      return -x;
+    }
+  }
+
+  /**
+   * Calculate |x|.  Revert on overflow.
+   *
+   * @param x signed 64.64-bit fixed point number
+   * @return signed 64.64-bit fixed point number
+   */
+  function abs (int128 x) internal pure returns (int128) {
+    unchecked {
+      require (x != MIN_64x64);
+      return x < 0 ? -x : x;
+    }
+  }
+
+  /**
+   * Calculate 1 / x rounding towards zero.  Revert on overflow or when x is
+   * zero.
+   *
+   * @param x signed 64.64-bit fixed point number
+   * @return signed 64.64-bit fixed point number
+   */
+  function inv (int128 x) internal pure returns (int128) {
+    unchecked {
+      require (x != 0);
+      int256 result = int256 (0x100000000000000000000000000000000) / x;
+      require (result >= MIN_64x64 && result <= MAX_64x64);
+      return int128 (result);
+    }
+  }
+
+  /**
+   * Calculate arithmetics average of x and y, i.e. (x + y) / 2 rounding down.
+   *
+   * @param x signed 64.64-bit fixed point number
+   * @param y signed 64.64-bit fixed point number
+   * @return signed 64.64-bit fixed point number
+   */
+  function avg (int128 x, int128 y) internal pure returns (int128) {
+    unchecked {
+      return int128 ((int256 (x) + int256 (y)) >> 1);
+    }
+  }
+
+  /**
+   * Calculate geometric average of x and y, i.e. sqrt (x * y) rounding down.
+   * Revert on overflow or in case x * y is negative.
+   *
+   * @param x signed 64.64-bit fixed point number
+   * @param y signed 64.64-bit fixed point number
+   * @return signed 64.64-bit fixed point number
+   */
+  function gavg (int128 x, int128 y) internal pure returns (int128) {
+    unchecked {
+      int256 m = int256 (x) * int256 (y);
+      require (m >= 0);
+      require (m <
+          0x4000000000000000000000000000000000000000000000000000000000000000);
+      return int128 (sqrtu (uint256 (m)));
+    }
+  }
+
+  /**
+   * Calculate x^y assuming 0^0 is 1, where x is signed 64.64 fixed point number
+   * and y is unsigned 256-bit integer number.  Revert on overflow.
+   *
+   * @param x signed 64.64-bit fixed point number
+   * @param y uint256 value
+   * @return signed 64.64-bit fixed point number
+   */
+  function pow (int128 x, uint256 y) internal pure returns (int128) {
+    unchecked {
+      bool negative = x < 0 && y & 1 == 1;
+
+      uint256 absX = uint128 (x < 0 ? -x : x);
+      uint256 absResult;
+      absResult = 0x100000000000000000000000000000000;
+
+      if (absX <= 0x10000000000000000) {
+        absX <<= 63;
+        while (y != 0) {
+          if (y & 0x1 != 0) {
+            absResult = absResult * absX >> 127;
+          }
+          absX = absX * absX >> 127;
+
+          if (y & 0x2 != 0) {
+            absResult = absResult * absX >> 127;
+          }
+          absX = absX * absX >> 127;
+
+          if (y & 0x4 != 0) {
+            absResult = absResult * absX >> 127;
+          }
+          absX = absX * absX >> 127;
+
+          if (y & 0x8 != 0) {
+            absResult = absResult * absX >> 127;
+          }
+          absX = absX * absX >> 127;
+
+          y >>= 4;
+        }
+
+        absResult >>= 64;
+      } else {
+        uint256 absXShift = 63;
+        if (absX < 0x1000000000000000000000000) { absX <<= 32; absXShift -= 32; }
+        if (absX < 0x10000000000000000000000000000) { absX <<= 16; absXShift -= 16; }
+        if (absX < 0x1000000000000000000000000000000) { absX <<= 8; absXShift -= 8; }
+        if (absX < 0x10000000000000000000000000000000) { absX <<= 4; absXShift -= 4; }
+        if (absX < 0x40000000000000000000000000000000) { absX <<= 2; absXShift -= 2; }
+        if (absX < 0x80000000000000000000000000000000) { absX <<= 1; absXShift -= 1; }
+
+        uint256 resultShift = 0;
+        while (y != 0) {
+          require (absXShift < 64);
+
+          if (y & 0x1 != 0) {
+            absResult = absResult * absX >> 127;
+            resultShift += absXShift;
+            if (absResult > 0x100000000000000000000000000000000) {
+              absResult >>= 1;
+              resultShift += 1;
+            }
+          }
+          absX = absX * absX >> 127;
+          absXShift <<= 1;
+          if (absX >= 0x100000000000000000000000000000000) {
+              absX >>= 1;
+              absXShift += 1;
+          }
+
+          y >>= 1;
+        }
+
+        require (resultShift < 64);
+        absResult >>= 64 - resultShift;
+      }
+      int256 result = negative ? -int256 (absResult) : int256 (absResult);
+      require (result >= MIN_64x64 && result <= MAX_64x64);
+      return int128 (result);
+    }
+  }
+
+  /**
+   * Calculate sqrt (x) rounding down.  Revert if x < 0.
+   *
+   * @param x signed 64.64-bit fixed point number
+   * @return signed 64.64-bit fixed point number
+   */
+  function sqrt (int128 x) internal pure returns (int128) {
+    unchecked {
+      require (x >= 0);
+      return int128 (sqrtu (uint256 (int256 (x)) << 64));
+    }
+  }
+
+  /**
+   * Calculate binary logarithm of x.  Revert if x <= 0.
+   *
+   * @param x signed 64.64-bit fixed point number
+   * @return signed 64.64-bit fixed point number
+   */
+  function log_2 (int128 x) internal pure returns (int128) {
+    unchecked {
+      require (x > 0);
+
+      int256 msb = 0;
+      int256 xc = x;
+      if (xc >= 0x10000000000000000) { xc >>= 64; msb += 64; }
+      if (xc >= 0x100000000) { xc >>= 32; msb += 32; }
+      if (xc >= 0x10000) { xc >>= 16; msb += 16; }
+      if (xc >= 0x100) { xc >>= 8; msb += 8; }
+      if (xc >= 0x10) { xc >>= 4; msb += 4; }
+      if (xc >= 0x4) { xc >>= 2; msb += 2; }
+      if (xc >= 0x2) msb += 1;  // No need to shift xc anymore
+
+      int256 result = msb - 64 << 64;
+      uint256 ux = uint256 (int256 (x)) << uint256 (127 - msb);
+      for (int256 bit = 0x8000000000000000; bit > 0; bit >>= 1) {
+        ux *= ux;
+        uint256 b = ux >> 255;
+        ux >>= 127 + b;
+        result += bit * int256 (b);
+      }
+
+      return int128 (result);
+    }
+  }
+
+  /**
+   * Calculate natural logarithm of x.  Revert if x <= 0.
+   *
+   * @param x signed 64.64-bit fixed point number
+   * @return signed 64.64-bit fixed point number
+   */
+  function ln (int128 x) internal pure returns (int128) {
+    unchecked {
+      require (x > 0);
+
+      return int128 (int256 (
+          uint256 (int256 (log_2 (x))) * 0xB17217F7D1CF79ABC9E3B39803F2F6AF >> 128));
+    }
+  }
+
+  /**
+   * Calculate binary exponent of x.  Revert on overflow.
+   *
+   * @param x signed 64.64-bit fixed point number
+   * @return signed 64.64-bit fixed point number
+   */
+  function exp_2 (int128 x) internal pure returns (int128) {
+    unchecked {
+      require (x < 0x400000000000000000); // Overflow
+
+      if (x < -0x400000000000000000) return 0; // Underflow
+
+      uint256 result = 0x80000000000000000000000000000000;
+
+      if (x & 0x8000000000000000 > 0)
+        result = result * 0x16A09E667F3BCC908B2FB1366EA957D3E >> 128;
+      if (x & 0x4000000000000000 > 0)
+        result = result * 0x1306FE0A31B7152DE8D5A46305C85EDEC >> 128;
+      if (x & 0x2000000000000000 > 0)
+        result = result * 0x1172B83C7D517ADCDF7C8C50EB14A791F >> 128;
+      if (x & 0x1000000000000000 > 0)
+        result = result * 0x10B5586CF9890F6298B92B71842A98363 >> 128;
+      if (x & 0x800000000000000 > 0)
+        result = result * 0x1059B0D31585743AE7C548EB68CA417FD >> 128;
+      if (x & 0x400000000000000 > 0)
+        result = result * 0x102C9A3E778060EE6F7CACA4F7A29BDE8 >> 128;
+      if (x & 0x200000000000000 > 0)
+        result = result * 0x10163DA9FB33356D84A66AE336DCDFA3F >> 128;
+      if (x & 0x100000000000000 > 0)
+        result = result * 0x100B1AFA5ABCBED6129AB13EC11DC9543 >> 128;
+      if (x & 0x80000000000000 > 0)
+        result = result * 0x10058C86DA1C09EA1FF19D294CF2F679B >> 128;
+      if (x & 0x40000000000000 > 0)
+        result = result * 0x1002C605E2E8CEC506D21BFC89A23A00F >> 128;
+      if (x & 0x20000000000000 > 0)
+        result = result * 0x100162F3904051FA128BCA9C55C31E5DF >> 128;
+      if (x & 0x10000000000000 > 0)
+        result = result * 0x1000B175EFFDC76BA38E31671CA939725 >> 128;
+      if (x & 0x8000000000000 > 0)
+        result = result * 0x100058BA01FB9F96D6CACD4B180917C3D >> 128;
+      if (x & 0x4000000000000 > 0)
+        result = result * 0x10002C5CC37DA9491D0985C348C68E7B3 >> 128;
+      if (x & 0x2000000000000 > 0)
+        result = result * 0x1000162E525EE054754457D5995292026 >> 128;
+      if (x & 0x1000000000000 > 0)
+        result = result * 0x10000B17255775C040618BF4A4ADE83FC >> 128;
+      if (x & 0x800000000000 > 0)
+        result = result * 0x1000058B91B5BC9AE2EED81E9B7D4CFAB >> 128;
+      if (x & 0x400000000000 > 0)
+        result = result * 0x100002C5C89D5EC6CA4D7C8ACC017B7C9 >> 128;
+      if (x & 0x200000000000 > 0)
+        result = result * 0x10000162E43F4F831060E02D839A9D16D >> 128;
+      if (x & 0x100000000000 > 0)
+        result = result * 0x100000B1721BCFC99D9F890EA06911763 >> 128;
+      if (x & 0x80000000000 > 0)
+        result = result * 0x10000058B90CF1E6D97F9CA14DBCC1628 >> 128;
+      if (x & 0x40000000000 > 0)
+        result = result * 0x1000002C5C863B73F016468F6BAC5CA2B >> 128;
+      if (x & 0x20000000000 > 0)
+        result = result * 0x100000162E430E5A18F6119E3C02282A5 >> 128;
+      if (x & 0x10000000000 > 0)
+        result = result * 0x1000000B1721835514B86E6D96EFD1BFE >> 128;
+      if (x & 0x8000000000 > 0)
+        result = result * 0x100000058B90C0B48C6BE5DF846C5B2EF >> 128;
+      if (x & 0x4000000000 > 0)
+        result = result * 0x10000002C5C8601CC6B9E94213C72737A >> 128;
+      if (x & 0x2000000000 > 0)
+        result = result * 0x1000000162E42FFF037DF38AA2B219F06 >> 128;
+      if (x & 0x1000000000 > 0)
+        result = result * 0x10000000B17217FBA9C739AA5819F44F9 >> 128;
+      if (x & 0x800000000 > 0)
+        result = result * 0x1000000058B90BFCDEE5ACD3C1CEDC823 >> 128;
+      if (x & 0x400000000 > 0)
+        result = result * 0x100000002C5C85FE31F35A6A30DA1BE50 >> 128;
+      if (x & 0x200000000 > 0)
+        result = result * 0x10000000162E42FF0999CE3541B9FFFCF >> 128;
+      if (x & 0x100000000 > 0)
+        result = result * 0x100000000B17217F80F4EF5AADDA45554 >> 128;
+      if (x & 0x80000000 > 0)
+        result = result * 0x10000000058B90BFBF8479BD5A81B51AD >> 128;
+      if (x & 0x40000000 > 0)
+        result = result * 0x1000000002C5C85FDF84BD62AE30A74CC >> 128;
+      if (x & 0x20000000 > 0)
+        result = result * 0x100000000162E42FEFB2FED257559BDAA >> 128;
+      if (x & 0x10000000 > 0)
+        result = result * 0x1000000000B17217F7D5A7716BBA4A9AE >> 128;
+      if (x & 0x8000000 > 0)
+        result = result * 0x100000000058B90BFBE9DDBAC5E109CCE >> 128;
+      if (x & 0x4000000 > 0)
+        result = result * 0x10000000002C5C85FDF4B15DE6F17EB0D >> 128;
+      if (x & 0x2000000 > 0)
+        result = result * 0x1000000000162E42FEFA494F1478FDE05 >> 128;
+      if (x & 0x1000000 > 0)
+        result = result * 0x10000000000B17217F7D20CF927C8E94C >> 128;
+      if (x & 0x800000 > 0)
+        result = result * 0x1000000000058B90BFBE8F71CB4E4B33D >> 128;
+      if (x & 0x400000 > 0)
+        result = result * 0x100000000002C5C85FDF477B662B26945 >> 128;
+      if (x & 0x200000 > 0)
+        result = result * 0x10000000000162E42FEFA3AE53369388C >> 128;
+      if (x & 0x100000 > 0)
+        result = result * 0x100000000000B17217F7D1D351A389D40 >> 128;
+      if (x & 0x80000 > 0)
+        result = result * 0x10000000000058B90BFBE8E8B2D3D4EDE >> 128;
+      if (x & 0x40000 > 0)
+        result = result * 0x1000000000002C5C85FDF4741BEA6E77E >> 128;
+      if (x & 0x20000 > 0)
+        result = result * 0x100000000000162E42FEFA39FE95583C2 >> 128;
+      if (x & 0x10000 > 0)
+        result = result * 0x1000000000000B17217F7D1CFB72B45E1 >> 128;
+      if (x & 0x8000 > 0)
+        result = result * 0x100000000000058B90BFBE8E7CC35C3F0 >> 128;
+      if (x & 0x4000 > 0)
+        result = result * 0x10000000000002C5C85FDF473E242EA38 >> 128;
+      if (x & 0x2000 > 0)
+        result = result * 0x1000000000000162E42FEFA39F02B772C >> 128;
+      if (x & 0x1000 > 0)
+        result = result * 0x10000000000000B17217F7D1CF7D83C1A >> 128;
+      if (x & 0x800 > 0)
+        result = result * 0x1000000000000058B90BFBE8E7BDCBE2E >> 128;
+      if (x & 0x400 > 0)
+        result = result * 0x100000000000002C5C85FDF473DEA871F >> 128;
+      if (x & 0x200 > 0)
+        result = result * 0x10000000000000162E42FEFA39EF44D91 >> 128;
+      if (x & 0x100 > 0)
+        result = result * 0x100000000000000B17217F7D1CF79E949 >> 128;
+      if (x & 0x80 > 0)
+        result = result * 0x10000000000000058B90BFBE8E7BCE544 >> 128;
+      if (x & 0x40 > 0)
+        result = result * 0x1000000000000002C5C85FDF473DE6ECA >> 128;
+      if (x & 0x20 > 0)
+        result = result * 0x100000000000000162E42FEFA39EF366F >> 128;
+      if (x & 0x10 > 0)
+        result = result * 0x1000000000000000B17217F7D1CF79AFA >> 128;
+      if (x & 0x8 > 0)
+        result = result * 0x100000000000000058B90BFBE8E7BCD6D >> 128;
+      if (x & 0x4 > 0)
+        result = result * 0x10000000000000002C5C85FDF473DE6B2 >> 128;
+      if (x & 0x2 > 0)
+        result = result * 0x1000000000000000162E42FEFA39EF358 >> 128;
+      if (x & 0x1 > 0)
+        result = result * 0x10000000000000000B17217F7D1CF79AB >> 128;
+
+      result >>= uint256 (int256 (63 - (x >> 64)));
+      require (result <= uint256 (int256 (MAX_64x64)));
+
+      return int128 (int256 (result));
+    }
+  }
+
+  /**
+   * Calculate natural exponent of x.  Revert on overflow.
+   *
+   * @param x signed 64.64-bit fixed point number
+   * @return signed 64.64-bit fixed point number
+   */
+  function exp (int128 x) internal pure returns (int128) {
+    unchecked {
+      require (x < 0x400000000000000000); // Overflow
+
+      if (x < -0x400000000000000000) return 0; // Underflow
+
+      return exp_2 (
+          int128 (int256 (x) * 0x171547652B82FE1777D0FFDA0D23A7D12 >> 128));
+    }
+  }
+
+  /**
+   * Calculate x / y rounding towards zero, where x and y are unsigned 256-bit
+   * integer numbers.  Revert on overflow or when y is zero.
+   *
+   * @param x unsigned 256-bit integer number
+   * @param y unsigned 256-bit integer number
+   * @return unsigned 64.64-bit fixed point number
+   */
+  function divuu (uint256 x, uint256 y) private pure returns (uint128) {
+    unchecked {
+      require (y != 0);
+
+      uint256 result;
+
+      if (x <= 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF)
+        result = (x << 64) / y;
+      else {
+        uint256 msb = 192;
+        uint256 xc = x >> 192;
+        if (xc >= 0x100000000) { xc >>= 32; msb += 32; }
+        if (xc >= 0x10000) { xc >>= 16; msb += 16; }
+        if (xc >= 0x100) { xc >>= 8; msb += 8; }
+        if (xc >= 0x10) { xc >>= 4; msb += 4; }
+        if (xc >= 0x4) { xc >>= 2; msb += 2; }
+        if (xc >= 0x2) msb += 1;  // No need to shift xc anymore
+
+        result = (x << 255 - msb) / ((y - 1 >> msb - 191) + 1);
+        require (result <= 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF);
+
+        uint256 hi = result * (y >> 128);
+        uint256 lo = result * (y & 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF);
+
+        uint256 xh = x >> 192;
+        uint256 xl = x << 64;
+
+        if (xl < lo) xh -= 1;
+        xl -= lo; // We rely on overflow behavior here
+        lo = hi << 128;
+        if (xl < lo) xh -= 1;
+        xl -= lo; // We rely on overflow behavior here
+
+        assert (xh == hi >> 128);
+
+        result += xl / y;
+      }
+
+      require (result <= 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF);
+      return uint128 (result);
+    }
+  }
+
+  /**
+   * Calculate sqrt (x) rounding down, where x is unsigned 256-bit integer
+   * number.
+   *
+   * @param x unsigned 256-bit integer number
+   * @return unsigned 128-bit integer number
+   */
+  function sqrtu (uint256 x) private pure returns (uint128) {
+    unchecked {
+      if (x == 0) return 0;
+      else {
+        uint256 xx = x;
+        uint256 r = 1;
+        if (xx >= 0x100000000000000000000000000000000) { xx >>= 128; r <<= 64; }
+        if (xx >= 0x10000000000000000) { xx >>= 64; r <<= 32; }
+        if (xx >= 0x100000000) { xx >>= 32; r <<= 16; }
+        if (xx >= 0x10000) { xx >>= 16; r <<= 8; }
+        if (xx >= 0x100) { xx >>= 8; r <<= 4; }
+        if (xx >= 0x10) { xx >>= 4; r <<= 2; }
+        if (xx >= 0x4) { r <<= 1; }
+        r = (r + x / r) >> 1;
+        r = (r + x / r) >> 1;
+        r = (r + x / r) >> 1;
+        r = (r + x / r) >> 1;
+        r = (r + x / r) >> 1;
+        r = (r + x / r) >> 1;
+        r = (r + x / r) >> 1; // Seven iterations should be enough
+        uint256 r1 = x / r;
+        return uint128 (r < r1 ? r : r1);
+      }
+    }
+  }
+}

solidity/aux/LICENSE.md

@@ -0,0 +1,28 @@
+Copyright (c) 2019, [ABDK Consulting](https://abdk.consulting/)
+
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+1. Redistributions of source code must retain the above copyright notice, this
+   list of conditions and the following disclaimer.
+2. Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+3. All advertising materials mentioning features or use of this software must
+   display the following acknowledgement: This product includes software
+   developed by ABDK Consulting.
+4. Neither the name of ABDK Consulting nor the names of its contributors may be
+   used to endorse or promote products derived from this software without
+   specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY ABDK CONSULTING ''AS IS'' AND ANY EXPRESS OR
+IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
+SHALL ABDK CONSULTING BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
+OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
+IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
+OF SUCH DAMAGE.