Merge branch 'lash/use-timestamps' into 'master'

Use timestamps instead of blocks

See merge request grassrootseconomics/sarafu-token!4

python/tests/test_basic.py

@@ -3,6 +3,7 @@ import os
 import unittest
 import json
 import logging
+import datetime
 
 # third-party imports
 import web3
@@ -18,9 +19,11 @@ logging.getLogger('eth.vm').setLevel(logging.WARNING)
 testdir = os.path.dirname(__file__)
 
 #BLOCKTIME = 5 # seconds
-TAX_LEVEL = 10000 * 2 # 2%
+TAX_LEVEL = int(10000 * 2) # 2%
+# calc "1-(0.98)^(1/518400)" <- 518400 = 30 days of blocks
+# 0.00000003897127107225
 #PERIOD = int(60/BLOCKTIME) * 60 * 24 * 30 # month
-PERIOD = 10
+PERIOD = 1
 
 
 class Test(unittest.TestCase):
@@ -48,12 +51,15 @@ class Test(unittest.TestCase):
         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]})
+        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)
         self.contract = self.w3.eth.contract(abi=self.abi, address=r.contractAddress)
 
         self.start_block = self.w3.eth.blockNumber
+        b = self.w3.eth.getBlock(self.start_block)
+        self.start_time = b['timestamp']
+
 
     def tearDown(self):
         pass
@@ -61,10 +67,31 @@ class Test(unittest.TestCase):
 
     def test_hello(self):
         self.assertEqual(self.contract.functions.actualPeriod().call(), 1)
-        self.eth_tester.mine_blocks(PERIOD)
+        self.eth_tester.time_travel(self.start_time + 61)
         self.assertEqual(self.contract.functions.actualPeriod().call(), 2)
 
 
+
+    def test_apply_demurrage(self):
+        modifier = 10 * (10 ** 37)
+        demurrage_modifier = self.contract.functions.demurrageModifier().call()
+        demurrage_modifier &= (1 << 128) - 1
+        self.assertEqual(modifier, demurrage_modifier)
+
+        self.eth_tester.time_travel(self.start_time + 59)
+        demurrage_modifier = self.contract.functions.demurrageModifier().call()
+        demurrage_modifier &= (1 << 128) - 1
+        self.assertEqual(modifier, demurrage_modifier)
+
+        self.eth_tester.time_travel(self.start_time + 61)
+        tx_hash = self.contract.functions.applyDemurrage().transact()
+        r = self.w3.eth.getTransactionReceipt(tx_hash)
+
+        demurrage_modifier = self.contract.functions.demurrageModifier().call()
+        demurrage_modifier &= (1 << 128) - 1
+        self.assertEqual(int(98 * (10 ** 36)), demurrage_modifier)
+
+
     def test_mint(self):
         tx_hash = self.contract.functions.mintTo(self.w3.eth.accounts[1], 1024).transact()
         r = self.w3.eth.getTransactionReceipt(tx_hash)
@@ -80,6 +107,26 @@ class Test(unittest.TestCase):
         balance = self.contract.functions.balanceOf(self.w3.eth.accounts[1]).call()
         self.assertEqual(balance, 2000)
 
+        self.eth_tester.time_travel(self.start_time + 61)
+        balance = self.contract.functions.balanceOf(self.w3.eth.accounts[1]).call()
+        self.assertEqual(balance, int(2000 * 0.98))
+
+    
+    def test_base_amount(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.time_travel(self.start_time + 61)
+
+        self.contract.functions.applyDemurrage().transact()
+        demurrage_modifier = self.contract.functions.demurrageModifier().call()
+        demurrage_amount = self.contract.functions.toDemurrageAmount(demurrage_modifier).call()
+        logg.debug('d {} {}'.format(demurrage_modifier.to_bytes(32, 'big').hex(), demurrage_amount))
+
+        a = self.contract.functions.toBaseAmount(1000).call();
+        self.assertEqual(a, 1020)
+
 
     def test_transfer(self):
         tx_hash = self.contract.functions.mintTo(self.w3.eth.accounts[1], 1024).transact()
@@ -128,60 +175,5 @@ class Test(unittest.TestCase):
         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)
-
-
 if __name__ == '__main__':
     unittest.main()

python/tests/test_period.py

@@ -0,0 +1,80 @@
+# 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__)
+
+#BLOCKTIME = 5 # seconds
+TAX_LEVEL = 10000 * 2 # 2%
+#PERIOD = int(60/BLOCKTIME) * 60 * 24 * 30 # month
+PERIOD = 1
+
+
+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 * (10 ** 32), 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
+        b = self.w3.eth.getBlock(self.start_block)
+        self.start_time = b['timestamp']
+
+
+    def tearDown(self):
+        pass
+
+
+    def test_period(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)
+
+        self.eth_tester.time_travel(self.start_time + 61)
+        tx_hash = self.contract.functions.changePeriod().transact()
+        r = self.w3.eth.getTransactionReceipt(tx_hash)
+        self.assertEqual(r.status, 1)
+
+        redistribution = self.contract.functions.redistributions(1).call()
+        self.assertEqual(2, self.contract.functions.toRedistributionPeriod(redistribution).call())
+        self.assertEqual(2, self.contract.functions.actualPeriod().call())
+
+
+if __name__ == '__main__':
+    unittest.main()

python/tests/test_pure.py

@@ -0,0 +1,107 @@
+# standard imports
+import os
+import unittest
+import json
+import logging
+import math
+
+# 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__)
+
+#BLOCKTIME = 5 # seconds
+TAX_LEVEL = int((10000 * 2) * (10 ** 32)) # 2%
+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
+
+
+    def test_tax_period(self):
+        t = self.contract.functions.taxLevel().call()
+        logg.debug('taxlevel {}'.format(t))
+
+        a = self.contract.functions.toTaxPeriodAmount(1000000, 0).call()
+        self.assertEqual(a, 1000000)
+
+        a = self.contract.functions.toTaxPeriodAmount(1000000, 1).call()
+        self.assertEqual(a, 980000)
+
+        a = self.contract.functions.toTaxPeriodAmount(1000000, 2).call()
+        self.assertEqual(a, 960400)
+
+        a = self.contract.functions.toTaxPeriodAmount(980000, 1).call()
+        self.assertEqual(a, 960400)
+
+
+    def test_fractional_state(self):
+        with self.assertRaises(eth_tester.exceptions.TransactionFailed):
+            self.contract.functions.remainder(2, 1).call();
+
+        with self.assertRaises(eth_tester.exceptions.TransactionFailed):
+            remainder = self.contract.functions.remainder(0, 100001).call();
+
+        remainder = self.contract.functions.remainder(1, 2).call();
+        self.assertEqual(remainder, 0);
+   
+        whole = 5000001
+        parts = 20000
+        expect = whole - (math.floor(whole/parts) * parts) 
+        remainder = self.contract.functions.remainder(parts, whole).call();
+        self.assertEqual(remainder, expect)
+
+        parts = 30000
+        expect = whole - (math.floor(whole/parts) * parts) 
+        remainder = self.contract.functions.remainder(parts, whole).call();
+        self.assertEqual(remainder, expect)
+
+        parts = 40001
+        expect = whole - (math.floor(whole/parts) * parts) 
+        remainder = self.contract.functions.remainder(parts, whole).call();
+        self.assertEqual(remainder, expect)
+
+if __name__ == '__main__':
+    unittest.main()

python/tests/test_redistribution.py

@@ -0,0 +1,198 @@
+# 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__)
+
+#BLOCKTIME = 5 # seconds
+TAX_LEVEL = 10000 * 2 # 2%
+#PERIOD = int(60/BLOCKTIME) * 60 * 24 * 30 # month
+PERIOD = 1
+
+
+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 * (10 ** 32), 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
+        b = self.w3.eth.getBlock(self.start_block)
+        self.start_time = b['timestamp']
+
+
+    def tearDown(self):
+        pass
+
+
+    def debug_periods(self):
+        pactual = self.contract.functions.actualPeriod().call()
+        pstart = self.contract.functions.periodStart().call()
+        pduration = self.contract.functions.periodDuration().call()
+        blocknumber = self.w3.eth.blockNumber;
+        logg.debug('actual {} start {} duration {} blocknumber {}'.format(pactual, pstart, pduration, blocknumber))
+
+
+    # TODO: check receipt log outputs
+    def test_redistribution_storage(self):
+        self.contract.functions.mintTo(self.w3.eth.accounts[1], 1000000).transact()
+        self.contract.functions.mintTo(self.w3.eth.accounts[2], 1000000).transact()
+
+        external_address = web3.Web3.toChecksumAddress('0x' + os.urandom(20).hex())
+        tx_hash = self.contract.functions.transfer(external_address, 1000000).transact({'from': self.w3.eth.accounts[2]})
+        tx_hash = self.contract.functions.transfer(external_address, 999999).transact({'from': self.w3.eth.accounts[1]})
+        r = self.w3.eth.getTransactionReceipt(tx_hash)
+        logg.debug('tx before {}'.format(r))
+        self.assertEqual(r.status, 1)
+
+        self.eth_tester.time_travel(self.start_time + 61)
+
+        redistribution = self.contract.functions.redistributions(0).call();
+        self.assertEqual(redistribution.hex(), '000000000100000000000000000000000000000000001e848000000000000001')
+
+        tx_hash = self.contract.functions.mintTo(self.w3.eth.accounts[0], 1000000).transact()
+        r = self.w3.eth.getTransactionReceipt(tx_hash)
+        self.assertEqual(r.status, 1)
+
+        redistribution = self.contract.functions.redistributions(1).call()
+        self.assertEqual(redistribution.hex(), '000000000000000000000000000000000000000000002dc6c000000000000002')
+    
+
+    def test_redistribution_balance_on_zero_participants(self):
+        supply = 1000000000000
+        tx_hash = self.contract.functions.mintTo(self.w3.eth.accounts[1], supply).transact()
+        r = self.w3.eth.getTransactionReceipt(tx_hash)
+
+        self.eth_tester.time_travel(self.start_time + 61)
+
+        tx_hash = self.contract.functions.applyDemurrage().transact()
+        r = self.w3.eth.getTransactionReceipt(tx_hash)
+        logg.debug('r {}'.format(r))
+        self.assertEqual(r.status, 1)
+        tx_hash = self.contract.functions.changePeriod().transact()
+        rr = self.w3.eth.getTransactionReceipt(tx_hash)
+        self.assertEqual(rr.status, 1)
+
+        redistribution = self.contract.functions.redistributions(0).call();
+        supply = self.contract.functions.totalSupply().call()
+
+        sink_increment = int(supply * (TAX_LEVEL / 1000000))
+        for l in r['logs']:
+            if l.topics[0].hex() == '0xa0717e54e02bd9829db5e6e998aec0ae9de796b8d150a3cc46a92ab869697755': # event Decayed(uint256,uint256,uint256,uint256)
+                period = int.from_bytes(l.topics[1], 'big')
+                self.assertEqual(period, 2)
+                b = bytes.fromhex(l.data[2:])
+                remainder = int.from_bytes(b, 'big')
+                self.assertEqual(remainder, int((1000000 - TAX_LEVEL) * (10 ** 32)))
+                logg.debug('period {} remainder {}'.format(period, remainder))
+
+        sink_balance = self.contract.functions.balanceOf(self.sink_address).call()
+        logg.debug('{} {}'.format(sink_increment, sink_balance))
+        self.assertEqual(sink_balance, int(sink_increment * 0.98))
+        self.assertEqual(sink_balance, int(sink_increment * (1000000 - TAX_LEVEL) / 1000000))
+
+        balance = self.contract.functions.balanceOf(self.w3.eth.accounts[1]).call()
+        self.assertEqual(balance, supply - sink_increment)
+
+
+    def test_redistribution_two_of_ten(self):
+        mint_amount = 100000000
+        z = 0
+        for i in range(10):
+            self.contract.functions.mintTo(self.w3.eth.accounts[i], mint_amount).transact()
+            z += mint_amount
+
+        initial_balance = self.contract.functions.balanceOf(self.w3.eth.accounts[1]).call()
+
+        spend_amount = 1000000
+        external_address = web3.Web3.toChecksumAddress('0x' + os.urandom(20).hex())
+        self.contract.functions.transfer(external_address, spend_amount).transact({'from': self.w3.eth.accounts[1]})
+        tx_hash = self.contract.functions.transfer(external_address, spend_amount).transact({'from': self.w3.eth.accounts[2]})
+        r = self.w3.eth.getTransactionReceipt(tx_hash)
+        # No cheating!
+        self.contract.functions.transfer(self.w3.eth.accounts[3], spend_amount).transact({'from': self.w3.eth.accounts[3]})
+        # Cheapskate!
+        self.contract.functions.transfer(external_address, spend_amount-1).transact({'from': self.w3.eth.accounts[4]})
+
+        self.assertEqual(r.status, 1)
+
+        self.eth_tester.time_travel(self.start_time + 61)
+
+        self.contract.functions.applyDemurrage().transact()
+        self.contract.functions.changePeriod().transact()
+
+        bummer_balance = self.contract.functions.balanceOf(self.w3.eth.accounts[3]).call()
+        self.assertEqual(bummer_balance, mint_amount - (mint_amount * (TAX_LEVEL / 1000000)))
+        logg.debug('bal {} '.format(bummer_balance))
+
+        bummer_balance = self.contract.functions.balanceOf(self.w3.eth.accounts[1]).call()
+        spender_balance = mint_amount - spend_amount
+        spender_decayed_balance = int(spender_balance - (spender_balance * (TAX_LEVEL / 1000000)))
+        self.assertEqual(bummer_balance, spender_decayed_balance)
+        logg.debug('bal {} '.format(bummer_balance))
+
+        tx_hash = self.contract.functions.applyRedistributionOnAccount(self.w3.eth.accounts[1]).transact()
+        r = self.w3.eth.getTransactionReceipt(tx_hash)
+        logg.debug('log {}'.format(r.logs))
+
+        self.contract.functions.applyRedistributionOnAccount(self.w3.eth.accounts[2]).transact()
+
+        redistribution_data = self.contract.functions.redistributions(0).call()
+        logg.debug('redist data {}'.format(redistribution_data.hex()))
+
+        account_period_data = self.contract.functions.accountPeriod(self.w3.eth.accounts[1]).call()
+        logg.debug('account period {}'.format(account_period_data))
+
+        actual_period = self.contract.functions.actualPeriod().call()
+        logg.debug('period {}'.format(actual_period))
+
+        redistribution = int((z / 2) * (TAX_LEVEL / 1000000))
+        spender_new_base_balance = ((mint_amount - spend_amount) + redistribution)
+        spender_new_decayed_balance = int(spender_new_base_balance - (spender_new_base_balance * (TAX_LEVEL / 1000000)))
+
+        spender_actual_balance = self.contract.functions.balanceOf(self.w3.eth.accounts[1]).call()
+        logg.debug('rrr {} {}'.format(redistribution, spender_new_decayed_balance))
+
+        self.assertEqual(spender_actual_balance, spender_new_decayed_balance)
+
+
+if __name__ == '__main__':
+    unittest.main()
+
+ 

solidity/RedistributedDemurrageToken.sol

@@ -6,15 +6,17 @@ pragma solidity > 0.6.11;
 contract RedistributedDemurrageToken {
 
 	address public owner;
-	uint256 public decimals;
 	string public name;
 	string public symbol;
+	uint256 public decimals;
 	uint256 public totalSupply;
+	uint256 public minimumParticipantSpend;
+	uint256 constant ppmDivider = 100000000000000000000000000000000;
 
-	uint256 public periodStart;
+	uint256 public immutable periodStart; // timestamp
-	uint256 public periodDuration;
+	uint256 public immutable periodDuration; // duration in SECONDS
-	uint256 public taxLevel; // PPM
+	uint256 public immutable taxLevel; // PPM per MINUTE
-	uint256 public demurrageModifier; // PPM
+	uint256 public demurrageModifier; // PPM uint128(block) | uint128(ppm)
 
 	bytes32[] public redistributions; // uint1(isFractional) | uint1(unused) | uint38(participants) | uint160(value) | uint56(period)
 	mapping (address => bytes32) account; // uint20(unused) | uint56(period) | uint160(value)
@@ -27,22 +29,24 @@ contract RedistributedDemurrageToken {
 	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 Decayed(uint256 indexed _period, uint256 indexed _periodCount, uint256 indexed _oldAmount, uint256 _newAmount);
 	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 {
+	constructor(string memory _name, string memory _symbol, uint8 _decimals, uint256 _taxLevelMinute, uint256 _periodMinutes, address _defaultSinkAddress) public {
 		owner = msg.sender;
 		minter[owner] = true;
-		periodStart = block.number;
+		periodStart = block.timestamp;
-		periodDuration = _period;
+		periodDuration = _periodMinutes * 60;
-		taxLevel = _taxLevel;
 		name = _name;
 		symbol = _symbol;
 		decimals = _decimals;
-		demurrageModifier = 1000000;
+		demurrageModifier = ppmDivider * 1000000; // Emulates 38 decimal places
+		demurrageModifier |= (1 << 128);
+		taxLevel = _taxLevelMinute; // 38 decimal places
 		sinkAddress = _defaultSinkAddress;
 		bytes32 initialRedistribution = toRedistribution(0, 0, 1);
 		redistributions.push(initialRedistribution);
+		minimumParticipantSpend = 10 ** uint256(_decimals);
 	}
 
 	// Given address will be allowed to call the mintTo() function
@@ -51,13 +55,24 @@ contract RedistributedDemurrageToken {
 		minter[_minter] = true;
 		return true;
 	}
-	
+
 	/// ERC20
 	function balanceOf(address _account) public view returns (uint256) {
-		uint256 baseBalance = getBaseBalance(_account);
+		uint256 baseBalance;
-		uint256 inverseModifier = 1000000 - demurrageModifier;
+		uint256 anchorDemurrageAmount;
-		uint256 balanceModifier = (inverseModifier * baseBalance) / 1000000;
+		uint256 anchorDemurragePeriod;
-		return baseBalance - balanceModifier;
+		uint256 currentDemurrageAmount;
+		uint256 periodCount;
+
+		baseBalance = getBaseBalance(_account);
+		anchorDemurrageAmount = toDemurrageAmount(demurrageModifier);
+		anchorDemurragePeriod = toDemurragePeriod(demurrageModifier);
+
+		periodCount = actualPeriod() - toDemurragePeriod(demurrageModifier);
+
+		currentDemurrageAmount = toTaxPeriodAmount(anchorDemurrageAmount, periodCount);
+
+		return (baseBalance * currentDemurrageAmount) / (ppmDivider * 1000000);
 	}
 
 	/// Balance unmodified by demurrage
@@ -69,7 +84,11 @@ contract RedistributedDemurrageToken {
 	function increaseBaseBalance(address _account, uint256 _delta) private returns (bool) {
 		uint256 oldBalance;
 		uint256 newBalance;
-		
+	
+		if (_delta == 0) {
+			return false;
+		}
+
 		oldBalance = getBaseBalance(_account);
 		newBalance = oldBalance + _delta;
 		require(uint160(newBalance) > uint160(oldBalance), 'ERR_WOULDWRAP'); // revert if increase would result in a wrapped value
@@ -83,6 +102,10 @@ contract RedistributedDemurrageToken {
 		uint256 oldBalance;
 	       	uint256 newBalance;
 
+		if (_delta == 0) {
+			return false;
+		}
+
 		oldBalance = getBaseBalance(_account);	
 		require(oldBalance >= _delta, 'ERR_OVERSPEND'); // overspend guard
 		newBalance = oldBalance - _delta;
@@ -96,8 +119,8 @@ contract RedistributedDemurrageToken {
 	function mintTo(address _beneficiary, uint256 _amount) external returns (bool) {
 		require(minter[msg.sender]);
 
-		// TODO: get base amount for minting
+		applyDemurrage();
-		applyTax();
+		changePeriod();
 		totalSupply += _amount;
 		increaseBaseBalance(_beneficiary, _amount);
 		emit Mint(msg.sender, _beneficiary, _amount);
@@ -162,7 +185,7 @@ contract RedistributedDemurrageToken {
 
 	// Get the demurrage period of the current block number
 	function actualPeriod() public view returns (uint256) {
-		return (block.number - periodStart) / periodDuration + 1;
+		return (block.timestamp - periodStart) / periodDuration + 1;
 	}
 
 	// Add an entered demurrage period to the redistribution array
@@ -198,7 +221,7 @@ contract RedistributedDemurrageToken {
 		uint256 truncatedResult;
 
 		if (_numParts == 0) { // no division by zero please
-			return _sumWhole;
+			revert('ERR_NUMPARTS_ZERO');
 		}
 		require(_numParts < _sumWhole); // At least you are never LESS than the sum of your parts. Think about that.
 
@@ -207,24 +230,79 @@ contract RedistributedDemurrageToken {
 		return _sumWhole - truncatedResult;
 	}
 
+	// Called in the edge case where participant number is 0. It will override the participant count to 1.
+	// Returns the remainder sent to the sink address
+	function applyDefaultRedistribution(bytes32 _redistribution) private returns (uint256) {
+		uint256 redistributionSupply;
+		uint256 redistributionPeriod;
+		uint256 unit;
+		uint256 truncatedResult;
+
+		redistributionSupply = toRedistributionSupply(_redistribution);
+
+		unit = (redistributionSupply * taxLevel) / 1000000;
+		truncatedResult = (unit * 1000000) / taxLevel;
+
+		if (truncatedResult < redistributionSupply) {
+			redistributionPeriod = toRedistributionPeriod(_redistribution); // since we reuse period here, can possibly be optimized by passing period instead
+			redistributions[redistributionPeriod-1] &= 0x0000000000ffffffffffffffffffffffffffffffffffffffffffffffffffffff; // just to be safe, zero out all participant count data, in this case there will be only one
+			redistributions[redistributionPeriod-1] |= 0x8000000001000000000000000000000000000000000000000000000000000000;
+		}
+
+		increaseBaseBalance(sinkAddress, unit / ppmDivider); //truncatedResult);
+		return unit;
+	}
+
 	// 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;
+		uint256 periodSupply;
-
-		redistribution = redistributions[_period-1];
 
 		if (_remainder == 0) {
 			return false;
 		}
-		redistribution |= 0x8000000000000000000000000000000000000000000000000000000000000000;
+
-		increaseBaseBalance(sinkAddress, _remainder);
+		redistributions[_period-1] |= 0x8000000000000000000000000000000000000000000000000000000000000000;
+
+		periodSupply = toRedistributionSupply(redistributions[_period-1]);
+		increaseBaseBalance(sinkAddress, periodSupply - _remainder);
+		return true;
+	}
+
+
+	function toDemurrageAmount(uint256 _demurrage) public pure returns (uint256) {
+		return _demurrage & 0x00000000000000000000000000000000ffffffffffffffffffffffffffffffff;
+	}
+
+	function toDemurragePeriod(uint256 _demurrage) public pure returns (uint256) {
+		return (_demurrage & 0xffffffffffffffffffffffffffffffff00000000000000000000000000000000) >> 128;
+	}
+
+	function applyDemurrage() public returns (bool) {
+		uint256 epochPeriodCount;
+		uint256 periodCount;
+		uint256 lastDemurrageAmount;
+		uint256 newDemurrageAmount;
+
+		epochPeriodCount = actualPeriod();
+		//epochPeriodCount = (block.timestamp - periodStart) / periodDuration; // toDemurrageTime(demurrageModifier);
+		periodCount = epochPeriodCount - toDemurragePeriod(demurrageModifier);
+		if (periodCount == 0) {
+			return false;
+		}
+		lastDemurrageAmount = toDemurrageAmount(demurrageModifier);
+		newDemurrageAmount = toTaxPeriodAmount(lastDemurrageAmount, periodCount);
+		demurrageModifier = 0;
+		demurrageModifier |= (newDemurrageAmount & 0x00000000000000000000000000000000ffffffffffffffffffffffffffffffff);
+		demurrageModifier |= (epochPeriodCount << 128);
+		emit Decayed(epochPeriodCount, periodCount, lastDemurrageAmount, newDemurrageAmount);
 		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) {
+	//function applyTax() public returns (uint256) {
+	function changePeriod() public returns (uint256) {
 		bytes32 currentRedistribution;
 		bytes32 nextRedistribution;
 		uint256 currentPeriod;
@@ -235,29 +313,33 @@ contract RedistributedDemurrageToken {
 		if (currentRedistribution == bytes32(0x00)) {
 			return demurrageModifier;
 		}
-		demurrageModifier -= (demurrageModifier * taxLevel) / 1000000;
+		//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
+		if (currentParticipants == 0) {
-		applyRemainderOnPeriod(currentRemainder, currentPeriod);
+			currentRemainder = applyDefaultRedistribution(currentRedistribution);
-		emit Taxed(currentPeriod, currentRemainder);
+		} else {
+			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);
+		}
 		return demurrageModifier;
 	}
 
 	// Calculate a value reduced by demurrage by the given period
 	function toTaxPeriodAmount(uint256 _value, uint256 _period) public view returns (uint256) {
 		uint256 valueFactor;
+		uint256 truncatedTaxLevel;
 	      
-	       	// TODO: doesn't work for solidity as floats are missing and using ints linearly increases the order of magnitude  	
+		// TODO: if can't get to work, reverse the iteration from current period.
-		// valueFactor = 1000000 * (((1000000-taxLevel)/1000000) ** _period);
 		valueFactor = 1000000;
-		for (uint256 i = 0; i < _period; i++) {
+		truncatedTaxLevel = taxLevel / ppmDivider;
-			valueFactor = (valueFactor * taxLevel) / 1000000;
-		}
 
+		for (uint256 i = 0; i < _period; i++) {
+			valueFactor = valueFactor - ((valueFactor * truncatedTaxLevel) / 1000000);
+		}
 		return (valueFactor * _value) / 1000000;
 	}
 
@@ -282,9 +364,8 @@ contract RedistributedDemurrageToken {
 		}
 
 		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) * (taxLevel / 1000000)) / ppmDivider;
-		baseValue = supply / participants;
+		value = toTaxPeriodAmount(baseValue, period - 1);
-		value = toTaxPeriodAmount(baseValue, period-1);
 
 		account[_account] &= bytes32(0x000000000000000000000000ffffffffffffffffffffffffffffffffffffffff);
 		increaseBaseBalance(_account, value);
@@ -295,7 +376,21 @@ contract RedistributedDemurrageToken {
 
 	// Inflates the given amount according to the current demurrage modifier
 	function toBaseAmount(uint256 _value) public view returns (uint256) {
-		return (_value * 1000000) / demurrageModifier;
+		return (_value * ppmDivider * 1000000) / toDemurrageAmount(demurrageModifier);
+	}
+
+	// ERC20, triggers tax and/or redistribution
+	function approve(address _spender, uint256 _value) public returns (bool) {
+		uint256 baseValue;
+
+		applyDemurrage();
+		changePeriod();
+		applyRedistributionOnAccount(msg.sender);
+
+		baseValue = toBaseAmount(_value);
+		allowance[msg.sender][_spender] += baseValue;
+		emit Approval(msg.sender, _spender, _value);
+		return true;
 	}
 
 	// ERC20, triggers tax and/or redistribution
@@ -303,7 +398,8 @@ contract RedistributedDemurrageToken {
 		uint256 baseValue;
 		bool result;
 
-		applyTax();
+		applyDemurrage();
+		changePeriod();
 		applyRedistributionOnAccount(msg.sender);
 
 		// TODO: Prefer to truncate the result, instead it seems to round to nearest :/
@@ -313,29 +409,14 @@ contract RedistributedDemurrageToken {
 		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();
+		applyDemurrage();
+		changePeriod();
 		applyRedistributionOnAccount(msg.sender);
 
 		baseValue = toBaseAmount(_value);
@@ -345,16 +426,17 @@ contract RedistributedDemurrageToken {
 		return result;
 	}
 
-	// ERC20, triggers tax and/or redistribution
+	// ERC20 transfer backend for transfer, transferFrom
-	function approve(address _spender, uint256 _value) public returns (bool) {
+	function transferBase(address _from, address _to, uint256 _value) private returns (bool) {
-		uint256 baseValue;
+		uint256 period;
 
-		applyTax();
+		decreaseBaseBalance(_from, _value);
-		applyRedistributionOnAccount(msg.sender);
+		increaseBaseBalance(_to, _value);
 
-		baseValue = toBaseAmount(_value);
+		period = actualPeriod();
-		allowance[msg.sender][_spender] += baseValue;
+		if (_value >= minimumParticipantSpend && accountPeriod(_from) != period && _from != _to) {
-		emit Approval(msg.sender, _spender, _value);
+			registerAccountPeriod(_from, period);
+		}
 		return true;
 	}
 }