[ERC5643] NFTの所有権をサブスクのように管理できる仕組みを理解しよう！

interface IERC5643 {
    /// @notice Emitted when a subscription expiration changes
    /// @dev When a subscription is canceled, the expiration value should also be 0.
    event SubscriptionUpdate(uint256 indexed tokenId, uint64 expiration);

    /// @notice Renews the subscription to an NFT
    /// Throws if `tokenId` is not a valid NFT
    /// @param tokenId The NFT to renew the subscription for
    /// @param duration The number of seconds to extend a subscription for
    function renewSubscription(uint256 tokenId, uint64 duration) external payable;

    /// @notice Cancels the subscription of an NFT
    /// @dev Throws if `tokenId` is not a valid NFT
    /// @param tokenId The NFT to cancel the subscription for
    function cancelSubscription(uint256 tokenId) external payable;

    /// @notice Gets the expiration date of a subscription
    /// @dev Throws if `tokenId` is not a valid NFT
    /// @param tokenId The NFT to get the expiration date of
    /// @return The expiration date of the subscription
    function expiresAt(uint256 tokenId) external view returns(uint64);

    /// @notice Determines whether a subscription can be renewed
    /// @dev Throws if `tokenId` is not a valid NFT
    /// @param tokenId The NFT to get the expiration date of
    /// @return The renewability of a the subscription
    function isRenewable(uint256 tokenId) external view returns(bool);
}

// SPDX-License-Identifier: CC0-1.0
pragma solidity ^0.8.13;

import "forge-std/Test.sol";
import "../src/ERC5643.sol";

contract ERC5643Mock is ERC5643 {
    constructor(string memory name_, string memory symbol_) ERC5643(name_, symbol_) {}

    function mint(address to, uint256 tokenId) public {
        _mint(to, tokenId);
    }
}

contract ERC5643Test is Test {
    event SubscriptionUpdate(uint256 indexed tokenId, uint64 expiration);

    address user1;
    uint256 tokenId;
    ERC5643Mock erc5643;

    function setUp() public {
        tokenId = 1;
        user1 = address(0x1);

        erc5643 = new ERC5643Mock("erc5369", "ERC5643");
        erc5643.mint(user1, tokenId);
    }

    function testRenewalValid() public {
        vm.warp(1000);
        vm.prank(user1);
        vm.expectEmit(true, true, false, true);
        emit SubscriptionUpdate(tokenId, 3000);
        erc5643.renewSubscription(tokenId, 2000);
    }

    function testRenewalNotOwner() public {
        vm.expectRevert("Caller is not owner nor approved");
        erc5643.renewSubscription(tokenId, 2000);
    }

    function testCancelValid() public {
        vm.prank(user1);
        vm.expectEmit(true, true, false, true);
        emit SubscriptionUpdate(tokenId, 0);
        erc5643.cancelSubscription(tokenId);
    }

    function testCancelNotOwner() public {
        vm.expectRevert("Caller is not owner nor approved");
        erc5643.cancelSubscription(tokenId);
    }

    function testExpiresAt() public {
        vm.warp(1000);

        assertEq(erc5643.expiresAt(tokenId), 0);
        vm.startPrank(user1);
        erc5643.renewSubscription(tokenId, 2000);
        assertEq(erc5643.expiresAt(tokenId), 3000);

        erc5643.cancelSubscription(tokenId);
        assertEq(erc5643.expiresAt(tokenId), 0);
    }
}

// SPDX-License-Identifier: CC0-1.0
pragma solidity ^0.8.13;

import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "./IERC5643.sol";

contract ERC5643 is ERC721, IERC5643 {
    mapping(uint256 => uint64) private _expirations;

    constructor(string memory name_, string memory symbol_) ERC721(name_, symbol_) {}

    function renewSubscription(uint256 tokenId, uint64 duration) external payable {
        require(_isApprovedOrOwner(msg.sender, tokenId), "Caller is not owner nor approved");

        uint64 currentExpiration = _expirations[tokenId];
        uint64 newExpiration;
        if (currentExpiration == 0) {
            newExpiration = uint64(block.timestamp) + duration;
        } else {
            if (!_isRenewable(tokenId)) {
                revert SubscriptionNotRenewable();
            }
            newExpiration = currentExpiration + duration;
        }

        _expirations[tokenId] = newExpiration;

        emit SubscriptionUpdate(tokenId, newExpiration);
    }

    function cancelSubscription(uint256 tokenId) external payable {
        require(_isApprovedOrOwner(msg.sender, tokenId), "Caller is not owner nor approved");
        delete _expirations[tokenId];
        emit SubscriptionUpdate(tokenId, 0);
    }

    function expiresAt(uint256 tokenId) external view returns(uint64) {
        return _expirations[tokenId];
    }

    function isRenewable(uint256 tokenId) external pure returns(bool) {
        return true;
    }

    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
        return interfaceId == type(IERC5643).interfaceId || super.supportsInterface(interfaceId);
    }
}