cic-contracts/README.md

# Smart contract interfaces

## Technology

CIC smart contracts are implemented using the *solidity* programming
language for the (Ethereum Virtual Machine (EVM).

## Adopted standards

### Signing

### ERC - Direct use

The following well-known solidity interfaces are used directly.

- [ERC20 - Token Standard](https://eips.ethereum.org/EIPS/eip-20)

- [ERC165 - Standard Interface
  Detection](https://eips.ethereum.org/EIPS/eip-165)

- [ERC173 - Contract Ownership
  Standard](https://eips.ethereum.org/EIPS/eip-173)

- [ERC191 - Signed Data
  Standard](https://eips.ethereum.org/EIPS/eip-191)

- [ERC712 - Typed structured data hashing and
  signing](https://eips.ethereum.org/EIPS/eip-712)

- [ERC721 - Non-Fungible Token
  Standard](https://eips.ethereum.org/EIPS/eip-721)

- [ERC5007 - Time NFT (EIP-721 Time
  Extension)](https://eips.ethereum.org/EIPS/eip-5007)

- [ERC5192 - Minimal Soulbound
  NFTs](https://eips.ethereum.org/EIPS/eip-5192)

### ERCs Partial use

The following well-known solidity interfaces are partially implemented
in CIC native interfaces.

- [ERC5679 - Token Minting and
  Burning](https://eips.ethereum.org/EIPS/eip-5679) (See `Minter`,
  `Burner`)

## Native interfaces

### Accounts Index

Append-only list of addresses. Typically used for access control lists.

Addresses may be *added*, *removed*, aswell as *deactivated* and
*activated*. Deactivated accounts still count towards the `entryCount`.

The `entry` method is used to iterate the account list. The order of
which accounts are returned is not guaranteed. Any returned value
matching `address(0x00)` should be skipped, and not counted towards
`entryCount`.

May optionally record time when account was added.

ERC165 Interface identifier  
b7bca625

Solidity interface definition  
    interface IAccountsIndex {
        // Address added to store, index in array.
        event AddressAdded(uint256 indexed _idx, address _account);

        // Return number of entries in index.
        function entryCount() external view returns (uint256);

        // Return entry at the spceificed index.
        // Will revert if index is beyond array length.
        // An entry result of 0 means the entry should be skipped, and not count towards entry count.
        function entry(uint256) external view returns (address);

        // Add an entry to the index. Incresases the entry count.
        function add(address) external returns (bool);

        // Verify that the entry exists in the index.
        function have(address) external view returns (bool);

        // Retrieve the timestamp when account was added.
        // If time is not being tracked, a value of 0 should be returned.
        function time(address) external view returns (uint256);
    }

Reference implementation  
<git://holbrook.no/eth-accounts-index.git> (v0.5.1)

### Accounts Index Mutable

Extends the functionality of `Accounts Index` to allow changes to the
address list.

Addresses may be *added*, *removed*, aswell as *deactivated* and
*activated*. Deactivated accounts still count towards the `entryCount`.

ERC165 Interface identifier  
9479f0ae

Solidity interface definition  
    interface IAccountsIndexMutable {
        // Active status of address changed, and by whom changed.
        event AddressActive(address indexed _account, bool _active);

        // Address removed from store, and by whom removed.
        event AddressRemoved(address _account);

        // Remove an entry from the index. Reduces the entry count.
        function remove(address) external returns (bool);

        // Deactivate account but keep in index. Does not affect entry count.
        function deactivate(address) external returns (bool);

        // Activate previously deactivated account. Does not affect entry count.
        function activate(address) external returns (bool);

        // Check if account exists and is active;
        function isActive(address) external view returns (bool);
    }

Reference implementation  
<git://holbrook.no/eth-accounts-index.git> (v0.5.1)

### Burner

Attached to `ERC20` and `ERC721` tokens that may be *burned*.

Implements the `burn(...)` part of `ERC5679` for interoperability.

ERC165 Interface identifier  
bc4babdd

Solidity interface definition  
    interface IBurner {
        // Token(s) successfully burned; by who and how much.
        event Burn(address indexed _burner, uint256 _burned);

        // Satisfies ERC 5679
        function burn(address _from, uint256 _amount, bytes calldata _data) external;

        // Burn given amount of tokens held by signer.
        function burn(uint256 _burn) external returns (bool);

        // Burn all tokens held by signer.
        function burn() external returns (bool);

        // Total amount of tokens that have been burned.
        function totalBurned() external returns (uint256);

        // Total amount of tokens ever minted.
        // If totalSupply() is available (ERC20, ERC721 Enumerable), this equals totalSupply() + totalBurned().
        function totalMinted() external returns (uint256);
    }

Example implementation  
<https://git.grassecon.net/cicnet/erc20-demurrage-token.git>

### Chrono

Define a creation time for a resource.

Complements `ERC5007`.

ERC165 Interface identifier  
4db1ccd4

Solidity interface definition  
    interface IChrono {
        // Returns the timestamp of when a resource corresponding to _idx was first created.
        // int64 chosen as return value for simpler interoperability with ERC5007.
        function createTime(uint256 _idx) external returns(int64);
    }

Example implementation  
<https://git.defalsify.org/eth-erc721> (BadgeToken contract)

### Declarator

Permissionless store of signed claims made by an address about other
addresses, or addresses about themselves.

It is used to declare or respond to certifications of vouchers, NFT,
voucher members.

Addresses may be Externally Owned Accounts or smart contracts.

Claims may be made with or without topics. A missing topic is synonymous
with a topic value of `bytes32(0x00)`.

Any number of claims can be made about an address under any number of
topics. All claims must be stored, and returned in the order which they
were added.

ERC165 Interface identifier  
21b7493b

Solidity interface definition  
    interface IDeclarator {
        event DeclarationAdded(address indexed _declarator, address indexed _subject, bytes32 indexed _topic, bytes32 _proof);
        
        // Get all declarations for a subject (without topic) signed by a declarator
        function declaration(address _declarator, address _subject) external view returns ( bytes32[] memory );

        // Get all declarations for a subject for the given topic signed by a declarator
        function declaration(address _declarator, address _subject, bytes32 _topic) external view returns ( bytes32[] memory );

        // Get number of declarations the declarator has ever signed
        function declarationCount(address _declarator) external view returns ( uint256 );

        // Get the subject of a declarator's declarations at the specific index
        function declarationAddressAt(address _declarator, uint256 _idx) external view returns ( address );

        // Add a declaration for the subject
        function addDeclaration(address _subject, bytes32 _proof) external returns ( bool );

        // Add a declaration with topic for the subject
        function addDeclaration(address _subject, bytes32 _proof, bytes32 _topic) external returns ( bool );

        // Get the declarator that signed a declaration at the specificed index for a subject
        function declaratorAddressAt(address _subject, uint256 _idx) external view returns ( address );

        // Get the number of declarators that have signed for a subject
        function declaratorCount(address _subject) external view returns ( uint256 );
    }

Reference implementation  
<git://holbrook.no/eth-address-index.git>

### Digest

Allows encoding of digests according to a specific encoding scheme.

Primary use-case is the abstraction of self-describing
[Multhash](https://multiformats.io/multihash/) encoding.

A default encoding *must* always be defined, and the encoding of a valid
digest *must* succeed with the default encoding.

ERC165 Interface identifier  
982ab05d

Solidity interface definition  
    interface IDigest {
        // Returns the default digest encoding used by the contract instance.
        function defaultDigestEncoding() external view returns (uint256 _encoding);

        // Check if the given encoding has been implemented in the contract instance.
        function haveDigestEncoding(uint256 _codec) external view returns(bool);

        // Verify and encode the given digest for a specific hashing algorithm.
        // Returns a zero-length byte array if digest is invalid.
        // Must succeed if called with the defaultDigestEncoding and a valid digest.
        function encodeDigest(bytes memory _data, uint256 _encoding) external view returns (bytes memory);

        // Encodes the digest using the default digest encoding.
        // Returns a zero-length byte array if digest is invalid.
        // Must succeed with a valid digest.
        function encodeDigest(bytes memory _data) external view returns (bytes memory);
    }

Example implementation  
<git://holbrook.no/eth-event-msg.git>

### Expire

Defines an expiry time after which token balances or supply *cannot
change*.

A contract defining an expiry *must not* allow changing the expiration
time to a time in the past.

ERC165 Interface identifier  
841a0e94

Solidity interface definition  
    interface IExpire {
        // Contract has expired.
        event Expired(uint256 _timestamp);

        // Expiry time has changed.
        event ExpiryChange(uint256 indexed _oldTimestamp, uint256 _newTimestamp);

        // The current expiration timestamp.
        function expires() external returns (uint256);

        // Check expiry and apply expiration if expired.
        // Return values must be:
        // 0: not yet expired.
        // 1: already expired.
        // >1: expiry executed.
        function applyExpiry() external returns(uint8);
    }

Example implementation  
<https://git.grassecon.net/cicnet/erc20-demurrage-token.git>

### Faucet

Used for dispensing tokens to any address.

It can be used for gas tokens and *ERC20* alike.

The interface is the same whether the faucet is dispensing from existing
balance or minting new tokens.

The value dispersed *must* be the same for all addresses.

In general, four criteria are expected to exist in any combination for
limiting access to the faucet:

Time  
A recipient may only use the faucet again after some time has passed.

Balance threshold  
A recipient may only use the faucet after its balance is below a certain
amount.

Membership  
A recipient may only use the faucet if it has been added to an access
control list.

Capacity  
The contract has sufficient token funds to dispense the current defined
amount to dispense.

The *check(address)* contract call *must* evaluate all four criteria,
and *must* return `false` if any of the criteria are not met.

ERC165 Interface identifier  
1a3ac634

Solidity interface definition  
    interface IFaucet {
        // Tokens were given to an address
        event Give(address indexed _recipient, address indexed _token, uint256 _value);

        // The amount that the faucet disperses has changed
        event FaucetAmountChange(uint256 _value);

        // Address of token the faucet represents
        // The faucet will return gas tokens with the zero-address is returned.
        function token() external returns (address);

        // Amount of tokens the faucet gives out
        function tokenAmount() external returns (uint256);

        // Give tokens to the given recipient. Returns amount of tokens given.
        function giveTo(address _recipient) external returns (uint256);

        // Give tokens to yourself. Returns amount of tokens given.
        function gimme() external returns (uint256);

        // Check if faucet may be used in the current contract state by _recipient
        function check(address _recipient) external view returns (bool);

        // Returns timestamp when faucet may be used again by _recipient
        // If 0 is returned, the address has not yet been used.
        // A return value of max(uint256) indicates that the faucet may not be used again.
        function nextTime(address _recipient) external returns (uint256);

        // Returns the token balance under which faucet may be used again by _recipient
        // A return value of max(uint256) indicates that the faucet may be used regardless
        //   of the token balance of _recipient
        function nextBalance(address _recipient) external returns (uint256);
    }

Reference implementations  
- <git://holbrook.no/erc20-faucet.git>

- <git://holbrook.no/eth-faucet.git>

### Locator

This interface supports `ERC721 Metadata`, in particular the
`tokenURI(uint256)` call.

Off-chain resources in the CIC network *must* be defined in terms of
content addressed strings.

It *must* be possible to refer to all off-chain resources directly by
the content address.

Furthermore, it *should* be possible to refer to a resource by a
fully-qualified location on the web or an overlay network (e.g. tor).

ERC165 Interface identifier  
ed75b333

Solidity interface definition  
    interface ILocator {
        // URI that may or may not point to a specific resource location.
        function toURI(bytes memory _data) external view returns (string memory);

        // URL pointing to a specific resource location.
        function toURL(bytes memory _data) external view returns(string memory);
    }

Example implementation  
<git://holbrook.no/eth-event-msg.git>

#### Expressing locators in terms of numetic token id

Given the numeric token id `1234567890987654321` (`0x112210f4b16c1cb1`
hex), and a base url `https://contentgateway.grassecon.net`, the result
of the methods may be as follows:

`toURI(toHex(1234567890987654321))`  
-\>
`https://contentgateway.grassecon.net/000000000000000000000000000000000000000000000000112210f4b16c1cb1`

`toURL(toHex(1234567890987654321))`  
-\>
`https://contentgateway.grassecon.net/000000000000000000000000000000000000000000000000112210f4b16c1cb1`

`tokenURI(1234567890987654321)`  
-\>
`https://contentgateway.grassecon.net/000000000000000000000000000000000000000000000000112210f4b16c1cb1`

#### Expressing locators in terms of a digest

Given the data `foo`, the digest algorithm `sha256` and a base url
`https://contentgateway.grassecon.net`, the result of the methods may be
as follows:

`toURI(sha256(foo))`  
-\>
`"sha256:2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae"`

`toURL(sha256(foo))`  
-\>
`"https://contentgateway.grassecon.net/2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae"`

`tokenURI(toUint(sha256(foo)))`  
-\>
`"https://contentgateway.grassecon.net/2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae"`

#### Locator without URL

Given the data `foo`, the digest algorithm `sha256` and no base url, the
result of the methods may be as follows:

`toURI(sha256(foo))`  
-\>
`"sha256:2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae"`

`toURL(sha256(foo))`  
-\> `""`

`tokenURI(toUint(sha256(foo)))`  
-\>
`"sha256:2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae"`

### Minter

Attached to `ERC20` and `ERC721` tokens that may be minted.

Implements the `mint(...)` and `safeMint(...)` parts of `ERC5679` for
interoperability.

ERC165 Interface identifier  
5878bcf4

Solidity interface definition  
    interface IMinter {
        // Tokens are successfully minted; by who, to whom and how much
        event Mint(address indexed _minter, address indexed _beneficiary, uint256 value);

        // Mint the specified value of tokens to the specified recipient
        function mintTo(address _beneficiary, uint256 value) external returns (bool);

        // Satisfies ERC5679 for ERC20
        function mint(address _beneficiary, uint256 value, bytes calldata _data) external;

        // Satisfies ERC5679 for ERC721
        function safeMint(address _beneficiary, uint256 value, bytes calldata _data) external;
    }

Example implementation  
<https://git.grassecon.net/cicnet/erc20-demurrage-token.git>

### Msg

Enables a reference "message" to describe the contract using an
off-chain resource.

The reference may or may not be mutable.

The interface complements `Locator` and `MultiHash` to generate locators
for how to resolve the reference.

ERC165 Interface identifier  
a3002595

Solidity interface definition  
    interface IMsg {
        // Emitted when a new message digest has been set
        // Should not be emitted if the digest set is identical to the previous
        event Msg(bytes _msgDigest);

        // Get the current message content hash
        function getMsg() external view returns(bytes memory);
    }

Example implementation  
<git://holbrook.no/eth-event-msg.git>

### Registry

The Registry interface is a key-value store resolving well-known
contract identifier names to contract addresses.

It currently has two distinct uses in the CIC context:

1.  Entry-point to discover all relevant contracts of CIC networks.

2.  Unique (ERC20) token symbol resolver.

ERC165 Interface identifier  
effbf671

Solidity interface definition  
    interface IRegistryClient {
        // Address added to store with the given key
        event AddressKey(bytes32 indexed _key, address _address);

        // Return the address of the contract identified by the given byte string
        function addressOf(bytes32) external view returns (address);

        // Indexed accessor for the full list of registred identifiers
        function identifier(uint256) external view returns (bytes32);

        // Number of registered interfaces
        function identifierCount() external view returns (uint256);
    }

Contract registry implementation  
<git://holbrook.no/eth-contract-registry.git>

Token index implementation  
<git://holbrook.no/eth-contract-registry.git>

### Seal

Some smart contract parameters may need to be mutable over part of a
smart contract’s lifetime.

This interface provides a method to explicitly signal when certain
parameters have been rendered immutable.

The value of `sealState()` *must not* decrease, and must not exceed
`maxSealState`.

`maxSealState` is used to define that *all mutable parameters* have been
rendered immutable. The practical implications of this will vary between
contracts.

The implementer is encouraged to use simple, descriptive names in the
source code to describe the applicable seal states.

Use cases of sealing include:

- Whether more tokens can be minted

- Allow ownership of a contract to be transferred

- The expiry time of a token (see `Expire`)

ERC165 Interface identifier  
0d7491f8

Solidity interface definition  
    interface ISeal {
        // Seal state has changed.
        event SealStateChange(bool indexed _final, uint256 _sealState);

        // The current seal state.
        function sealState() external view returns(uint256);

        // The numeric seal state in everything sealable has been sealed.
        function maxSealState() external view returns(uint256);
    }

Example implementation  
<https://git.grassecon.net/cicnet/erc20-demurrage-token.git>

### TokenVend

This interface defines the mechanism for which a specific ERC20 token
may be exchanged for a different ERC20 token.

A typical use-case is generation of voting tokens based on a momentary
voucher balance. This is especially useful if the original ERC20 token
is subject to decay (demurrage).

The tokens used for exchange **SHOULD** be locked for the full duration
of holding the vended tokens.

The withdrawal function may or may not allow partial withdrawals.

ERC165 Interface identifier  
8a13249c

Solidity interface definition  
    interface ITokenVend {
        // A new vended token has been created.
        event TokenCreated(uint256 indexed _tokenIdx, uint256 indexed _supply, address _token);

        // Create corresponding vended tokens for the control token balance of the caller.  
        function getFor(address _token) external returns (uint256);

        // Recover control tokens that were used to retrieve the corresponding vended tokens.
        function withdrawFor(address _token) external returns (uint256);
    }

Reference implementations  
- <git://holbrook.no/erc20-vend.git>

### TokenVote

Execute elections with granular ERC20 token votes.

A proposal submitted for vote may or may not contain multiple options.
If multiple options are available, an ERC20 token holder may distribute
its vote among the options with the granularity of the token balance.

Voted tokens **SHOULD** be locked until the voting has finalized.

Finalization of voting should be callable by anyone.

ERC165 Interface identifier  
28091366

Solidity interface definition  
    interface ITokenVote {

        // A new proposal has been created.
        event ProposalAdded(uint256 indexed _blockDeadline, uint256 indexed voteTargetPpm, uint256 indexed _proposalIdx);

        // A proposal vote has been completed.
        // The proposal is identified by the serial number in _proposalIdx. It is up to the implementer to define how the proposal should be retrieved by index.
        // The proposal result may be in one of three states:
        // * Ratified (_cancelled == false, _insufficient == false)
        // * Cancelled (_cancelled == true, _insufficient == false)
        // * Not reached quorum (_cancelled == false, _insufficient == true)
        event ProposalCompleted(uint256 indexed _proposalIdx, bool indexed _cancelled, bool indexed _insufficient, uint256 _totalVote);

        // Propose a new vote.
        // Voting is active until one of:
        // * total cancel vote reach quorum (_targetVotePpm, ppm = parts-per-million).
        // * _blockWait blocks from now.
        function propose(bytes32 _description, uint256 _blockWait, uint24 _targetVotePpm) external returns (uint256);

        // Same as propose(...), but provide options to vote on.
        function proposeMulti(bytes32 _description, bytes32[] memory _options, uint256 _blockWait, uint24 _targetVotePpm) external returns (uint256);

        // Get number of options available for the proposal.
        // This decides the boundary of the index that can be used with voteOptions(...)
        // If the result is 0, vote(...) can be used aswell.
        function optionCount(uint256 _proposalIdx) external view returns(uint256);

        // Get proposal option. Assumes that proposal was created with proposeMulti(...)
        function getOption(uint256 _proposalIdx, uint256 _optionIdx) external view returns (bytes32);

        // Get vote count for the given option.
        // If proposal has no options, it should be called with _optionIdx = 0
        function voteCount(uint256 _proposalIdx, uint256 _optionIdx) external view returns(uint256);

        // Vote on a proposal without options.
        // Assumes that proposal was created with propose(...) and will fail otherwise.
        function vote(uint256 _value) external returns (bool);

        // Vote on a proposal option. Assumes that proposal was created with proposeMulti(...).
        // Must work with a non-option proposal if _optionIndex is 0.
        function voteOption(uint256 _optionIndex, uint256 _value) external returns (bool);

        // Vote to cancel a proposal.
        // If cancel has the majority:
        // * A vote without options will have rejected the proposal description.
        // * A vote with options will have rejected the proposal description as well as all option descriptions.
        function voteCancel(uint256 _value) external returns (bool);

        // Finalize the vote for a proposal.
        // May be called if deadline has been passed, or if:
            // * quorum has been reached with cancel votes.
        // * quorum has been reached and proposal has no/only one option.
        function finalize() external returns (bool);
    }

Reference implementations  
- <git://holbrook.no/evm-tokenvote.git>

### Writer

A complement to ERC173, which allows definition of a class of
super-users for a contract.

A super-user address may perform *more* actions than a "normal" address,
aswell as *some* actions normally limited to the *contract owner*.

If an *contract owner* is defined, No super-user should be able to
perform actions that *contract owner* cannot perform.

Typically, only the *contract owner*, if it is defined, can add or
remove a super-user.

Some use-case examples of super-user actions include:

- Mint new tokens.

- Change the amount dispensed by the faucet.

- Edit access control lists.

ERC165 Interface identifier  
abe1f1f5

Solidity interface definition  
    interface IWriter {
        // A writer has been added by _executor
        event WriterAdded(address _writer);

        // A writer has been removed by _executor
        event WriterDeleted(address _writer);

        // Add a new writer to the contract.
        function addWriter(address _writer) external returns (bool);

        // Remove existing writer from the contract.
        function deleteWriter(address _writer) external returns (bool);

        // Check whether the given address is a writer.
        function isWriter(address _writer) external returns (bool);
    }

Example implementation  
<https://git.grassecon.net/cicnet/erc20-demurrage-token.git>