[ERC6909] ERC1155を使いやすくアップデートした仕組みを理解しよう！

- name: totalSupply
  type: function
  stateMutability: view

  inputs:
    - name: id
      type: uint256

  outputs:
    - name: amount
      type: uint256

- name: balanceOf
  type: function
  stateMutability: view

  inputs:
    - name: owner
      type: address
    - name: id
      type: uint256

  outputs:
    - name: amount
      type: uint256

- name: allowance
  type: function
  stateMutability: view

  inputs:
    - name: owner
      type: address
    - name: spender
      type: address
    - name: id
      type: uint256

  outputs:
    - name: amount
      type: uint256

- name: isOperator
  type: function
  stateMutability: view

  inputs:
    - name: owner
      type: address
    - name: spender
      type: address

  outputs:
    - name: status
      type: bool

- name: transfer
  type: function
  stateMutability: nonpayable

  inputs:
    - name: receiver
      type: address
    - name: id
      type: uint256
    - name: amount
      type: uint256

  outputs:
    - name: success
      type: bool

- name: transferFrom
  type: function
  stateMutability: nonpayable

  inputs:
    - name: sender
      type: address
    - name: receiver
      type: address
    - name: id
      type: uint256
    - name: amount
      type: uint256

  outputs:
    - name: success
      type: bool

- name: approve
  type: function
  stateMutability: nonpayable

  inputs:
    - name: spender
      type: address
    - name: id
      type: uint256
    - name: amount
      type: uint256

  outputs:
    - name: success
      type: bool

function setOperator(address spender, bool approved) nonpayable returns (bool success)

- name: Transfer
  type: event

  inputs:
    - name: sender
      indexed: true
      type: address
    - name: receiver
      indexed: true
      type: address
    - name: id
      indexed: true
      type: uint256
    - name: amount
      indexed: false
      type: uint256

- name: OperatorSet
  type: event

  inputs:
    - name: owner
      indexed: true
      type: address
    - name: spender
      indexed: true
      type: address
    - name: approved
      indexed: false
      type: bool

- name: Approval
  type: event

  inputs:
    - name: owner
      indexed: true
      type: address
    - name: spender
      indexed: true
      type: address
    - name: id
      indexed: true
      type: uint256
    - name: amount
      indexed: false
      type: uint256

- name: name
  type: function
  stateMutability: view

  inputs: []

  outputs:
    - name: name
      type: string

- name: symbol
  type: function
  stateMutability: view

  inputs: []

  outputs:
    - name: symbol
      type: string

- name: decimals
  type: function
  stateMutability: view

  inputs:
    - name: id
      type: uint256

  outputs:
  - name: amount
    type: uint8

- name: tokenURI
  type: function
  stateMutability: view

  inputs:
    - name: id
      type: uint256

  outputs:
    - name: uri
      type: string

{
  "title": "Asset Metadata",
  "type": "object",
  "properties": {
    "name": {
      "type": "string",
      "description": "Identifies the token"
    },
    "description": {
      "type": "string",
      "description": "Describes the token"
    },
    "image": {
      "type": "string",
      "description": "A URI pointing to an image resource."
    }
  }
}

// SPDX-License-Identifier: CC0-1.0
pragma solidity 0.8.19;

/// @title ERC6909 Multi-Token Reference Implementation
/// @author jtriley.eth
contract ERC6909 {
    /// @dev Thrown when owner balance for id is insufficient.
    /// @param owner The address of the owner.
    /// @param id The id of the token.
    error InsufficientBalance(address owner, uint256 id);

    /// @dev Thrown when spender allowance for id is insufficient.
    /// @param spender The address of the spender.
    /// @param id The id of the token.
    error InsufficientPermission(address spender, uint256 id);

    /// @notice The event emitted when a transfer occurs.
    /// @param sender The address of the sender.
    /// @param receiver The address of the receiver.
    /// @param id The id of the token.
    /// @param amount The amount of the token.
    event Transfer(address indexed sender, address indexed receiver, uint256 indexed id, uint256 amount);

    /// @notice The event emitted when an operator is set.
    /// @param owner The address of the owner.
    /// @param spender The address of the spender.
    /// @param approved The approval status.
    event OperatorSet(address indexed owner, address indexed spender, bool approved);

    /// @notice The event emitted when an approval occurs.
    /// @param owner The address of the owner.
    /// @param spender The address of the spender.
    /// @param id The id of the token.
    /// @param amount The amount of the token.
    event Approval(address indexed owner, address indexed spender, uint256 indexed id, uint256 amount);

    /// @notice The total supply of each id.
    mapping(uint256 id => uint256 amount) public totalSupply;

    /// @notice Owner balance of an id.
    mapping(address owner => mapping(uint256 id => uint256 amount)) public balanceOf;

    /// @notice Spender allowance of an id.
    mapping(address owner => mapping(address spender => mapping(uint256 id => uint256 amount))) public allowance;

    /// @notice Checks if a spender is approved by an owner as an operator.
    mapping(address owner => mapping(address spender => bool)) public isOperator;

    /// @notice Transfers an amount of an id from the caller to a receiver.
    /// @param receiver The address of the receiver.
    /// @param id The id of the token.
    /// @param amount The amount of the token.
    function transfer(address receiver, uint256 id, uint256 amount) public returns (bool) {
        if (balanceOf[msg.sender][id] < amount) revert InsufficientBalance(msg.sender, id);
        balanceOf[msg.sender][id] -= amount;
        balanceOf[receiver][id] += amount;
        emit Transfer(msg.sender, receiver, id, amount);
        return true;
    }

    /// @notice Transfers an amount of an id from a sender to a receiver.
    /// @param sender The address of the sender.
    /// @param receiver The address of the receiver.
    /// @param id The id of the token.
    /// @param amount The amount of the token.
    function transferFrom(address sender, address receiver, uint256 id, uint256 amount) public returns (bool) {
        if (sender != msg.sender && !isOperator[sender][msg.sender]) {
            uint256 senderAllowance = allowance[sender][msg.sender][id];
            if (senderAllowance < amount) revert InsufficientPermission(msg.sender, id);
            if (senderAllowance != type(uint256).max) {
                allowance[sender][msg.sender][id] = senderAllowance - amount;
            }
        }
        if (balanceOf[sender][id] < amount) revert InsufficientBalance(sender, id);
        balanceOf[sender][id] -= amount;
        balanceOf[receiver][id] += amount;
        emit Transfer(sender, receiver, id, amount);
        return true;
    }

    /// @notice Approves an amount of an id to a spender.
    /// @param spender The address of the spender.
    /// @param id The id of the token.
    /// @param amount The amount of the token.
    function approve(address spender, uint256 id, uint256 amount) public returns (bool) {
        allowance[msg.sender][spender][id] = amount;
        emit Approval(msg.sender, spender, id, amount);
        return true;
    }


    /// @notice Sets or removes a spender as an operator for the caller.
    /// @param spender The address of the spender.
    /// @param approved The approval status.
    function setOperator(address spender, bool approved) public returns (bool) {
        isOperator[msg.sender][spender] = approved;
        emit OperatorSet(msg.sender, spender, approved);
        return true;
    }

    /// @notice Checks if a contract implements an interface.
    /// @param interfaceId The interface identifier, as specified in ERC-165.
    /// @return supported True if the contract implements `interfaceId`.
    function supportsInterface(bytes4 interfaceId) public pure returns (bool supported) {
        return interfaceId == 0xb2e69f8a || interfaceId == 0x01ffc9a7;
    }

    function _mint(address receiver, uint256 id, uint256 amount) internal {
      // WARNING: important safety checks should precede calls to this method.
      balanceOf[receiver][id] += amount;
      totalSupply[id] += amount;
      emit Transfer(address(0), receiver, id, amount);
    }

    function _burn(address sender, uint256 id, uint256 amount) internal {
      // WARNING: important safety checks should precede calls to this method.
      balanceOf[sender][id] -= amount;
      totalSupply[id] -= amount;
      emit Transfer(sender, address(0), id, amount);
    }
}

contract ERC6909OperatorPrecedence {
  // -- snip --

  function transferFrom(address sender, address receiver, uint256 id, uint256 amount) public {
    // check if `isOperator` first
    if (msg.sender != sender && !isOperator[sender][msg.sender]) {
      require(allowance[sender][msg.sender][id] >= amount, "insufficient allowance");
      allowance[sender][msg.sender][id] -= amount;
    }
  
    // -- snip --
  }
}

contract ERC6909AllowancePrecedence {
  // -- snip --

  function transferFrom(address sender, address receiver, uint256 id, uint256 amount) public {
    // check if allowance is sufficient first
    if (msg.sender != sender && allowance[sender][msg.sender][id] < amount) {
      require(isOperator[sender][msg.sender], "insufficient allowance");
    }

    // ERROR: when allowance is insufficient, this panics due to arithmetic underflow, regardless of
    // whether the caller has operator permissions.
    allowance[sender][msg.sender][id] -= amount;

    // -- snip
  }
}