[ERC5700] NFTにNFTを紐付けたり解除する仕組みを理解しよう！

/// @title ERC-721 Bindable Token Standard
/// @dev See https://eips.ethereum.org/ERCS/eip-5700
///  Note: the ERC-165 identifier for this interface is 0x82a34a7d.
interface IERC721Bindable /* is IERC721 */ {

    /// @notice This event emits when an unbound token is bound to an NFT.
    /// @param operator The address approved to perform the binding.
    /// @param from The address of the unbound token owner.
    /// @param bindAddress The contract address of the NFT being bound to.
    /// @param bindId The identifier of the NFT being bound to.
    /// @param tokenId The identifier of binding token.
    event Bind(
        address indexed operator,
        address indexed from,
        address indexed bindAddress,
        uint256 bindId,
        uint256 tokenId
    );

    /// @notice This event emits when an NFT-bound token is unbound.
    /// @param operator The address approved to perform the unbinding.
    /// @param from The owner of the NFT the token is bound to.
    /// @param to The address of the new unbound token owner.
    /// @param bindAddress The contract address of the NFT being unbound from.
    /// @param bindId The identifier of the NFT being unbound from.
    /// @param tokenId The identifier of the unbinding token.
    event Unbind(
        address indexed operator,
        address indexed from,
        address to,
        address indexed bindAddress,
        uint256 bindId,
        uint256 tokenId
    );

    /// @notice Binds token `tokenId` to NFT `bindId` at address `bindAddress`.
    /// @dev The function MUST throw unless `msg.sender` is the current owner, 
    ///  an authorized operator, or the approved address for the token. It also
    ///  MUST throw if the token is already bound or if `from` is not the token
    ///  owner. Finally, it MUST throw if the NFT contract does not support the
    ///  ERC-721 interface or if the NFT being bound to does not exist. Before 
    ///  binding, token ownership MUST be transferred to the contract address of
    ///  the NFT. On bind completion, the function MUST emit `Transfer` & `Bind` 
    ///  events to reflect the implicit token transfer and subsequent bind.
    /// @param from The address of the unbound token owner.
    /// @param bindAddress The contract address of the NFT being bound to.
    /// @param bindId The identifier of the NFT being bound to.
    /// @param tokenId The identifier of the binding token.
    function bind(
        address from,
        address bindAddress,
        uint256 bindId,
        uint256 tokenId
    ) external;

    /// @notice Unbinds token `tokenId` from NFT `bindId` at address `bindAddress`.
    /// @dev The function MUST throw unless `msg.sender` is the current owner, 
    ///  an authorized operator, or the approved address for the NFT the token
    ///  is bound to. It also MUST throw if the token is unbound, if `from` is
    ///  not the owner of the bound NFT, or if `to` is the zero address. After
    ///  unbinding, token ownership MUST be transferred to `to`, during which
    ///  the function MUST check if `to` is a valid contract (code size > 0),
    ///  and if so, call `onERC721Received`, throwing if the wrong identifier is
    ///  returned. On unbind completion, the function MUST emit `Unbind` &
    ///  `Transfer` events to reflect the unbind and subsequent transfer.
    /// @param from The address of the owner of the NFT the token is bound to.
    /// @param to The address of the unbound token new owner.
    /// @param bindAddress The contract address of the NFT being unbound from.
    /// @param bindId The identifier of the NFT being unbound from.
    /// @param tokenId The identifier of the unbinding token.
    function unbind(
        address from,
        address to,
        address bindAddress,
        uint256 bindId,
        uint256 tokenId
    ) external;

    /// @notice Gets the NFT address and identifier token `tokenId` is bound to.
    /// @dev When the token is unbound, this function MUST return the zero
    ///  address for the address portion to indicate no binding exists.
    /// @param tokenId The identifier of the token being queried.
    /// @return The token-bound NFT contract address and numerical identifier.
    function binderOf(uint256 tokenId) external view returns (address, uint256);

    /// @notice Gets total tokens bound to NFT `bindId` at address `bindAddress`.
    /// @param bindAddress The contract address of the NFT being queried.
    /// @param bindId The identifier of the NFT being queried.
    /// @return The total number of tokens bound to the queried NFT.
    function boundBalanceOf(address bindAddress, uint256 bindId) external view returns (uint256);

struct Binder {
    address bindAddress;
    uint256 bindId;
}

mapping(address => mapping(uint256 => uint256)) public boundBalanceOf; 

mapping(uint256 => Binder) internal _bound;

bytes4 private constant _ERC165_INTERFACE_ID = 0x01ffc9a7;

bytes4 private constant _ERC721_BINDER_INTERFACE_ID = 0x2ac2d2bc;

bytes4 private constant _ERC721_BINDABLE_INTERFACE_ID = 0xd92c3ff0;

function binderOf(uint256 tokenId) public view returns (address, uint256) {
    Binder memory bound = _bound[tokenId];
    return (bound.bindAddress, bound.bindId);
}

function bind(
        address from,
        address bindAddress,
        uint256 bindId,
        uint256 tokenId
    ) public {
        if (
            _bound[tokenId].bindAddress != address(0) ||
            IERC721(bindAddress).ownerOf(bindId) == address(0)
        ) {
            revert BindInvalid();
        }

        if (from != _ownerOf[tokenId]) {
            revert OwnerInvalid();
        }

        if (
            msg.sender != from &&
            msg.sender != getApproved[tokenId] &&
            !_operatorApprovals[from][msg.sender]
        ) {
            revert SenderUnauthorized();
        }

        delete getApproved[tokenId];

        unchecked {
            _balanceOf[from]--;
            _balanceOf[bindAddress]++;
            boundBalanceOf[bindAddress][bindId]++;
        }

        _ownerOf[tokenId] = bindAddress;
        _bound[tokenId] = Binder(bindAddress, bindId);

        emit Transfer(from, bindAddress, tokenId);
        emit Bind(msg.sender, from,  bindAddress, bindId, tokenId);

}

function unbind(
        address from,
        address to,
        address bindAddress,
        uint256 bindId,
        uint256 tokenId
    ) public {
        Binder memory bound = _bound[tokenId];
        if (
            bound.bindAddress != bindAddress ||
            bound.bindId != bindId ||
            _ownerOf[tokenId] != bindAddress
        ) {
            revert BindInvalid();
        }

        IERC721 binder = IERC721(bindAddress);

        if (from != binder.ownerOf(bindId)) {
            revert OwnerInvalid();
        }

        if (
            msg.sender != from &&
            msg.sender != binder.getApproved(tokenId) &&
            !binder.isApprovedForAll(from, msg.sender)
        ) {
            revert SenderUnauthorized();
        }

        if (to == address(0)) {
            revert ReceiverInvalid();
        }

        delete getApproved[tokenId];

        unchecked {
            _balanceOf[to]++;
            _balanceOf[bindAddress]--;
            boundBalanceOf[bindAddress][bindId]--;
        }

        _ownerOf[tokenId] = to;
        delete _bound[tokenId];

        emit Unbind(msg.sender, from, to, bindAddress, bindId, tokenId);
        emit Transfer(bindAddress, to, tokenId);

		if (
			to.code.length != 0 &&
				IERC721Receiver(to).onERC721Received(msg.sender, bindAddress, tokenId, "")
                !=
                IERC721Receiver.onERC721Received.selector
		) {
			revert SafeTransferUnsupported();
        }

}

function supportsInterface(bytes4 id) public pure override(ERC721, IERC165) returns (bool) {
    return super.supportsInterface(id) || id == _ERC721_BINDABLE_INTERFACE_ID;
}

/// @title ERC-1155 Bindable Token Standard
/// @dev See https://eips.ethereum.org/ERCS/eip-5700
///  Note: the ERC-165 identifier for this interface is 0xd0d555c6.
interface IERC1155Bindable /* is IERC1155 */ {

    /// @notice This event emits when token(s) are bound to an NFT.
    /// @param operator The address approved to perform the binding.
    /// @param from The owner address of the unbound tokens.
    /// @param bindAddress The contract address of the NFT being bound to.
    /// @param bindId The identifier of the NFT being bound to.
    /// @param tokenId The identifier of the binding token type.
    /// @param amount The number of tokens binding to the NFT.
    event Bind(
        address indexed operator,
        address indexed from,
        address indexed bindAddress,
        uint256 bindId,
        uint256 tokenId,
        uint256 amount
    );

    /// @notice This event emits when token(s) of different types are bound to an NFT.
    /// @param operator The address approved to perform the batch binding.
    /// @param from The owner address of the unbound tokens.
    /// @param bindAddress The contract address of the NFTs being bound to.
    /// @param bindId The identifier of the NFT being bound to.
    /// @param tokenIds The identifiers of the binding token types.
    /// @param amounts The number of tokens per type binding to the NFTs.
    event BindBatch(
        address indexed operator,
        address indexed from,
        address indexed bindAddress,
        uint256 bindId,
        uint256[] tokenIds,
        uint256[] amounts
    );

    /// @notice This event emits when token(s) are unbound from an NFT.
    /// @param operator The address approved to perform the unbinding.
    /// @param from The owner address of the NFT the tokens are bound to.
    /// @param to The address of the unbound tokens' new owner.
    /// @param bindAddress The contract address of the NFT being unbound from.
    /// @param bindId The identifier of the NFT being unbound from.
    /// @param tokenId The identifier of the unbinding token type.
    /// @param amount The number of tokens unbinding from the NFT.
    event Unbind(
        address indexed operator,
        address indexed from,
        address to,
        address indexed bindAddress,
        uint256 bindId,
        uint256 tokenId,
        uint256 amount
    );

    /// @notice This event emits when token(s) of different types are unbound from an NFT.
    /// @param operator The address approved to perform the batch binding.
    /// @param from The owner address of the unbound tokens.
    /// @param to The address of the unbound tokens' new owner.
    /// @param bindAddress The contract address of the NFTs being unbound from.
    /// @param bindId The identifier of the NFT being unbound from.
    /// @param tokenIds The identifiers of the unbinding token types.
    /// @param amounts The number of tokens per type unbinding from the NFTs.
    event UnbindBatch(
        address indexed operator,
        address indexed from,
        address to,
        address indexed bindAddress,
        uint256 bindId,
        uint256[] tokenIds,
        uint256[] amounts
    );

    /// @notice Binds `amount` tokens of `tokenId` to NFT `bindId` at address `bindAddress`.
    /// @dev The function MUST throw unless `msg.sender` is an approved operator
    ///  for `from`. It also MUST throw if the `from` owns fewer than `amount`
    ///  tokens. Finally, it MUST throw if the NFT contract does not support the
    ///  ERC-721 interface or if the NFT being bound to does not exist. Before 
    ///  binding, tokens MUST be transferred to the contract address of the NFT. 
    ///  On bind completion, the function MUST emit `Transfer` & `Bind` events 
    ///  to reflect the implicit token transfers and subsequent bind.
    /// @param from The owner address of the unbound tokens.
    /// @param bindAddress The contract address of the NFT being bound to.
    /// @param bindId The identifier of the NFT being bound to.
    /// @param tokenId The identifier of the binding token type.
    /// @param amount The number of tokens binding to the NFT.
    function bind(
        address from,
        address bindAddress,
        uint256 bindId,
        uint256 tokenId,
        uint256 amount
    ) external;

    /// @notice Binds `amounts` tokens of `tokenIds` to NFT `bindId` at address `bindAddress`.
    /// @dev The function MUST throw unless `msg.sender` is an approved operator
    ///  for `from`. It also MUST throw if the length of `amounts` is not the 
    ///  same as `tokenIds`, or if any balances of `tokenIds` for `from` is less
    ///  than that of `amounts`. Finally, it MUST throw if the NFT contract does 
    ///  not support the ERC-721 interface or if the bound NFT does not exist. 
    ///  Before binding, tokens MUST be transferred to the contract address of 
    ///  the NFT. On bind completion, the function MUST emit `TransferBatch` and
    ///  `BindBatch` events to reflect the batch token transfers and bind.
    /// @param from The owner address of the unbound tokens.
    /// @param bindAddress The contract address of the NFTs being bound to.
    /// @param bindId The identifier of the NFT being bound to.
    /// @param tokenIds The identifiers of the binding token types.
    /// @param amounts The number of tokens per type binding to the NFTs.
    function batchBind(
        address from,
        address bindAddress,
        uint256 bindId,
        uint256[] calldata tokenIds,
        uint256[] calldata amounts
    ) external;

    /// @notice Unbinds `amount` tokens of `tokenId` from NFT `bindId` at address `bindAddress`.
    /// @dev The function MUST throw unless `msg.sender` is an approved operator
    ///  for `from`. It also MUST throw if `from` is not the owner of the bound
    ///  NFT, if the NFT's token balance is fewer than `amount`, or if `to` is 
    ///  the zero address. After unbinding, tokens MUST be transferred to `to`,
    ///  during which the function MUST check if `to` is a valid contract (code 
    ///  size > 0), and if so, call `onERC1155Received`, throwing if the wrong \
    ///  identifier is returned. On unbind completion, the function MUST emit 
    ///  `Unbind` & `Transfer` events to reflect the unbind and transfers.
    /// @param from The owner address of the NFT the tokens are bound to.
    /// @param to The address of the unbound tokens' new owner.
    /// @param bindAddress The contract address of the NFT being unbound from.
    /// @param bindId The identifier of the NFT being unbound from.
    /// @param tokenId The identifier of the unbinding token type.
    /// @param amount The number of tokens unbinding from the NFT.
    function unbind(
        address from,
        address to,
        address bindAddress,
        uint256 bindId,
        uint256 tokenId,
        uint256 amount
    ) external;

    /// @notice Unbinds `amount` tokens of `tokenId` from NFT `bindId` at address `bindAddress`.
    /// @dev The function MUST throw unless `msg.sender` is an approved operator
    ///  for `from`. It also MUST throw if the length of `amounts` is not the
    ///  same as `tokenIds`, if any balances of `tokenIds` for the NFT is less 
    ///  than that of `amounts`, or if `to` is the zero addresss. After 
    ///  unbinding, tokens MUST be transferred to `to`, during which the 
    ///  function MUST check if `to` is a valid contract (code size > 0), and if 
    ///  so, call `onERC1155BatchReceived`, throwing if the wrong identifier is 
    ///  returned. On unbind completion, the function MUST emit `UnbindBatch` & 
    ///  `TransferBatch` events to reflect the batch unbind and transfers.
    /// @param from The owner address of the unbound tokens.
    /// @param to The address of the unbound tokens' new owner.
    /// @param bindAddress The contract address of the NFTs being unbound from.
    /// @param bindId The identifier of the NFT being unbound from.
    /// @param tokenIds The identifiers of the unbinding token types.
    /// @param amounts The number of tokens per type unbinding from the NFTs.
    function batchUnbind(
        address from,
        address to,
        address bindAddress,
        uint256 bindId,
        uint256[] calldata tokenIds,
        uint256[] calldata amounts
    ) external;

    /// @notice Gets the number of tokens of type `tokenId` bound to NFT `bindId` at address `bindAddress`.
    /// @param bindAddress The contract address of the bound NFT.
    /// @param bindId The identifier of the bound NFT.
    /// @param tokenId The identifier of the token type bound to the NFT.
    /// @return The number of tokens of type `tokenId` bound to the NFT.
    function boundBalanceOf(
        address bindAddress,
        uint256 bindId,
        uint256 tokenId
    ) external view returns (uint256);

    /// @notice Gets the number of tokens of types `bindIds` bound to NFTs `bindIds` at address `bindAddress`.
    /// @param bindAddress The contract address of the bound NFTs.
    /// @param bindIds The identifiers of the bound NFTs.
    /// @param tokenIds The identifiers of the token types bound to the NFTs.
    /// @return balances The bound balances for each token type / NFT pair.
    function boundBalanceOfBatch(
        address bindAddress,
        uint256[] calldata bindIds,
        uint256[] calldata tokenIds
    ) external view returns (uint256[] memory balances);

}

mapping(address => mapping(uint256 => mapping(uint256 => uint256))) public boundBalanceOf;

function boundBalanceOfBatch(
        address bindAddress,
        uint256[] calldata bindIds,
        uint256[] calldata tokenIds
    ) public view returns (uint256[] memory balances) {
        if (bindIds.length != tokenIds.length) {
            revert ArityMismatch();
        }

        balances = new uint256[](bindIds.length);

        unchecked {
            for (uint256 i = 0; i < bindIds.length; ++i) {
                balances[i] = boundBalanceOf[bindAddress][bindIds[i]][tokenIds[i]];
            }
        }
}

function batchBind(
        address from,
        address bindAddress,
        uint256 bindId,
        uint256[] calldata tokenIds,
        uint256[] calldata amounts
    ) public {
        if (msg.sender != from && !isApprovedForAll[from][msg.sender]) {
            revert SenderUnauthorized();
        }

        if (IERC721(bindAddress).ownerOf(bindId) == address(0)) {
            revert BindInvalid();
        }

        if (tokenIds.length != amounts.length) {
            revert ArityMismatch();
        }

        for (uint256 i = 0; i < tokenIds.length; i++) {
            _balanceOf[from][tokenIds[i]] -= amounts[i];
            _balanceOf[bindAddress][tokenIds[i]] += amounts[i];
            boundBalanceOf[bindAddress][bindId][tokenIds[i]] += amounts[i];
        }

		emit TransferBatch(msg.sender, from, bindAddress, tokenIds, amounts);
        emit BindBatch(msg.sender, from, bindAddress, bindId, tokenIds, amounts);

}

function batchUnbind(
        address from,
        address to,
        address bindAddress,
        uint256 bindId,
        uint256[] calldata tokenIds,
        uint256[] calldata amounts
    ) public {
        IERC721 binder = IERC721(bindAddress);

        if (binder.ownerOf(bindId) != from) {
            revert OwnerInvalid();
        }

        if (
            msg.sender != from &&
            msg.sender != binder.getApproved(bindId) &&
            !binder.isApprovedForAll(from, msg.sender)
        ) {
            revert SenderUnauthorized();
        }

        if (tokenIds.length != amounts.length) {
            revert ArityMismatch();
        }

        if (to == address(0)) {
            revert ReceiverInvalid();
        }

        for (uint256 i = 0; i < tokenIds.length; i++) {

            _balanceOf[to][tokenIds[i]] += amounts[i];
            _balanceOf[bindAddress][tokenIds[i]] -= amounts[i];
            boundBalanceOf[bindAddress][bindId][tokenIds[i]] -= amounts[i];
        }

        emit UnbindBatch(msg.sender, from, to, bindAddress, bindId, tokenIds, amounts);
		emit TransferBatch(msg.sender, from, bindAddress, tokenIds, amounts);

		if (
			to.code.length != 0 &&
				IERC1155Receiver(to).onERC1155BatchReceived(msg.sender, from, tokenIds, amounts, "")
                !=
                IERC1155Receiver.onERC1155BatchReceived.selector
		) {
			revert SafeTransferUnsupported();
        }
}