[ERC6786] ロイヤリティを集計して受け取ることができる仕組みを理解しよう！

// @title Royalty Debt Registry
/// Note: the ERC-165 identifier for this interface is 0x253b27b0

interface IERC6786 {

    // Logged when royalties were paid for a NFT
    /// @notice Emitted when royalties are paid for the NFT with address tokenAddress and id tokenId
    event RoyaltiesPaid(address indexed tokenAddress, uint256 indexed tokenId, uint256 amount);

    /// @notice sends msg.value to the creator of a NFT
    /// @dev Reverts if there are no on-chain informations about the creator
    /// @param tokenAddress The address of NFT contract
    /// @param tokenId The NFT id
    function payRoyalties(address tokenAddress, uint256 tokenId) external payable;

    /// @notice Get the amount of royalties which was paid for a NFT
    /// @dev 
    /// @param tokenAddress The address of NFT contract
    /// @param tokenId The NFT id
    /// @return The amount of royalties paid for the NFT
    function getPaidRoyalties(address tokenAddress, uint256 tokenId) external view returns (uint256);
}

// SPDX-License-Identifier: CC0-1.0
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/utils/introspection/ERC165.sol";
import "./IERC6786.sol";
import "./utils/IERC2981.sol";

contract ERC6786 is IERC6786, ERC165 {

    //Mapping from token (address and id) to the amount of paid royalties
    mapping(address => mapping(uint256 => uint256)) private _paidRoyalties;

    /*
     *     bytes4(keccak256('payRoyalties(address,uint256)')) == 0xf511f0e9
     *     bytes4(keccak256('getPaidRoyalties(address,uint256)')) == 0xd02ad759
     *
     *     => 0xf511f0e9 ^ 0xd02ad759 == 0x253b27b0
     */
    bytes4 private constant _INTERFACE_ID_ERC6786 = 0x253b27b0;

    /*
     * bytes4(keccak256('royaltyInfo(uint256,uint256)')) == 0x2a55205a
     */
    bytes4 private constant _INTERFACE_ID_ERC2981 = 0x2a55205a;

    /// @notice This is thrown when there is no creator related information
    /// @param tokenAddress -> the address of the contract
    /// @param tokenId -> the id of the NFT
    error CreatorError(address tokenAddress, uint256 tokenId);

    /// @notice This is thrown when the payment fails
    /// @param creator -> the address of the creator
    /// @param amount -> the amount to pay
    error PaymentError(address creator, uint256 amount);

    function checkRoyalties(address _contract) internal view returns (bool) {
        (bool success) = IERC165(_contract).supportsInterface(_INTERFACE_ID_ERC2981);
        return success;
    }

    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
        return
        interfaceId == type(IERC6786).interfaceId ||
        super.supportsInterface(interfaceId);
    }

    function payRoyalties(address tokenAddress, uint256 tokenId) external override payable {
        if (!checkRoyalties(tokenAddress)) {
            revert CreatorError(tokenAddress, tokenId);
        }
        (address creator,) = IERC2981(tokenAddress).royaltyInfo(tokenId, 0);
        (bool success,) = payable(creator).call{value : msg.value}("");
        if(!success) {
            revert PaymentError(creator, msg.value);
        }
        _paidRoyalties[tokenAddress][tokenId] += msg.value;

        emit RoyaltiesPaid(tokenAddress, tokenId, msg.value);
    }

    function getPaidRoyalties(address tokenAddress, uint256 tokenId) external view override returns (uint256) {
        return _paidRoyalties[tokenAddress][tokenId];
    }
}

// Mapping from token (address and id) to the amount of paid royalties
mapping(address => mapping(uint256 => uint256)) private _paidRoyalties;

/*
 * bytes4(keccak256('payRoyalties(address,uint256)')) == 0xf511f0e9
 * bytes4(keccak256('getPaidRoyalties(address,uint256)')) == 0xd02ad759
 *
 * => 0xf511f0e9 ^ 0xd02ad759 == 0x253b27b0
 */
bytes4 private constant _INTERFACE_ID_ERC6786 = 0x253b27b0;

/*
 * bytes4(keccak256('royaltyInfo(uint256,uint256)')) == 0x2a55205a
 */
bytes4 private constant _INTERFACE_ID_ERC2981 = 0x2a55205a;

/// @notice This is thrown when there is no creator related information
/// @param tokenAddress -> the address of the contract
/// @param tokenId -> the id of the NFT
error CreatorError(address tokenAddress, uint256 tokenId);

/// @notice This is thrown when the payment fails
/// @param creator -> the address of the creator
/// @param amount -> the amount to pay
error PaymentError(address creator, uint256 amount);

function checkRoyalties(address _contract) internal view returns (bool) {
    (bool success) = IERC165(_contract).supportsInterface(_INTERFACE_ID_ERC2981);
    return success;
}

/**
 * @dev See {IERC165-supportsInterface}.
 */
function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
    return
    interfaceId == type(IERC6786).interfaceId ||
    super.supportsInterface(interfaceId);
}

function payRoyalties(address tokenAddress, uint256 tokenId) external override payable {
    if (!checkRoyalties(tokenAddress)) {
        revert CreatorError(tokenAddress, tokenId);
    }
    (address creator,) = IERC2981(tokenAddress).royaltyInfo(tokenId, 0);
    (bool success,) = payable(creator).call{value : msg.value}("");
    if(!success) {
        revert PaymentError(creator, msg.value);
    }
    _paidRoyalties[tokenAddress][tokenId] += msg.value;

    emit RoyaltiesPaid(tokenAddress, tokenId, msg.value);
}

function getPaidRoyalties(address tokenAddress, uint256 tokenId) external view override returns (uint256) {
    return _paidRoyalties[tokenAddress][tokenId];
}