[EIP7681] ERC20とERC1155を組み合わせたERC404のような仕組みを理解しよう！

event Transfer(address indexed from, address indexed to, uint256 value);

event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);

event TransferSingle(address indexed operator, address indexed from, address indexed to, uint256 id, uint256 value);
event TransferBatch(
    address indexed operator,
    address indexed from,
    address indexed to,
    uint256[] ids,
    uint256[] values
);

interface IERC7681 /* is IERC20, IERC1155 */ {
    /// The contract MUST contain the following events
    /// ERC20 related events
    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);

    /// The contract MUST contain the following events
    /// ERC1155 related events
    event TransferSingle(address indexed _operator, address indexed _from, address indexed _to, uint256 _id, uint256 _value);
    event TransferBatch(address indexed _operator, address indexed _from, address indexed _to, uint256[] _ids, uint256[] _values);
    event ApprovalForAll(address indexed _owner, address indexed _operator, bool _approved);
    event URI(string _value, uint256 indexed _id);

    /// The contract MAY contain the following functions
    /// ERC20 related functions
    function name() public view returns (string);
    function symbol() public view returns (string);
    function decimals() public view returns (uint8);

    /// The contract MUST contain the following functions
    /// ERC20 related functions
    function totalSupply() public view returns (uint256);
    function balanceOf(address _owner) public view returns (uint256);
    function transfer(address _to, uint256 _value) public returns (bool);
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool);
    function approve(address _spender, uint256 _value) public returns (bool);
    function allowance(address _owner, address _spender) public view returns (uint256);

    /// The contract MUST contain the following functions
    /// ERC1155 related functions
    function balanceOf(address _owner, uint256 _id) external view returns (uint256);
    function balanceOfBatch(address[] calldata _owners, uint256[] calldata _ids) external view returns (uint256[] memory);
    function setApprovalForAll(address _operator, bool _approved) external;
    function isApprovedForAll(address _owner, address _operator) external view returns (bool);
    function safeTransferFrom(address _from, address _to, uint256 _id, uint256 _value, bytes calldata _data) external;
    function safeBatchTransferFrom(address _from, address _to, uint256[] calldata _ids, uint256[] calldata _values, bytes calldata _data) external;
}

interface IERC7681Skippable {
    /// @dev Emitted when the skip ERC1155 token status of `owner` is changed by any mechanism.
    ///
    /// This initial skip ERC1155 token status for `owner` can be dynamically chosen to
    /// be true or false, but any changes to it MUST emit this event.
    event SkipTokenSet(address indexed owner, bool status);

    /// @dev Returns true if ERC-1155 mints and transfers to `owner` SHOULD be
    /// skipped during ERC-20 to ERC-1155 synchronization. Otherwise false.
    /// 
    /// This method MAY revert
    ///
    /// If this method reverts:
    /// - Interacting code SHOULD interpret `setSkipToken` functionality as
    ///   unavailable (and hide any functionality to call `setSkipToken`).
    /// - The skip ERC1155 token status for `owner` SHOULD be interpreted as undefined.
    ///
    /// Once a true or false value has been returned for a given `owner`,
    /// this method MUST NOT revert for the given `owner`.
    function getSkipToken(address owner) external view returns (bool);

    /// @dev Sets the caller's skip ERC1155 token status.
    ///
    /// This method MAY revert
    /// (e.g. insufficient permissions, method not supported).
    ///
    /// Emits a {SkipTokenSet} event.
    function setSkipToken(bool status) external;
}