// SPDX-License-Identifier: MIT // OpenZeppelin Contracts (last updated v4.9.0) (token/ERC721/extensions/ERC721Wrapper.sol) pragma solidity ^0.8.20; import {IERC721, ERC721} from "../ERC721.sol"; import {IERC721Receiver} from "../IERC721Receiver.sol"; /** * @dev Extension of the ERC721 token contract to support token wrapping. * * Users can deposit and withdraw an "underlying token" and receive a "wrapped token" with a matching tokenId. This is useful * in conjunction with other modules. For example, combining this wrapping mechanism with {ERC721Votes} will allow the * wrapping of an existing "basic" ERC721 into a governance token. */ abstract contract ERC721Wrapper is ERC721, IERC721Receiver { IERC721 private immutable _underlying; /** * @dev The received ERC721 token couldn't be wrapped. */ error ERC721UnsupportedToken(address token); constructor(IERC721 underlyingToken) { _underlying = underlyingToken; } /** * @dev Allow a user to deposit underlying tokens and mint the corresponding tokenIds. */ function depositFor(address account, uint256[] memory tokenIds) public virtual returns (bool) { uint256 length = tokenIds.length; for (uint256 i = 0; i < length; ++i) { uint256 tokenId = tokenIds[i]; // This is an "unsafe" transfer that doesn't call any hook on the receiver. With underlying() being trusted // (by design of this contract) and no other contracts expected to be called from there, we are safe. // slither-disable-next-line reentrancy-no-eth underlying().transferFrom(_msgSender(), address(this), tokenId); _safeMint(account, tokenId); } return true; } /** * @dev Allow a user to burn wrapped tokens and withdraw the corresponding tokenIds of the underlying tokens. */ function withdrawTo(address account, uint256[] memory tokenIds) public virtual returns (bool) { uint256 length = tokenIds.length; for (uint256 i = 0; i < length; ++i) { uint256 tokenId = tokenIds[i]; // Setting an "auth" arguments enables the `_isAuthorized` check which verifies that the token exists // (from != 0). Therefore, it is not needed to verify that the return value is not 0 here. _update(address(0), tokenId, _msgSender()); // Checks were already performed at this point, and there's no way to retake ownership or approval from // the wrapped tokenId after this point, so it's safe to remove the reentrancy check for the next line. // slither-disable-next-line reentrancy-no-eth underlying().safeTransferFrom(address(this), account, tokenId); } return true; } /** * @dev Overrides {IERC721Receiver-onERC721Received} to allow minting on direct ERC721 transfers to * this contract. * * In case there's data attached, it validates that the operator is this contract, so only trusted data * is accepted from {depositFor}. * * WARNING: Doesn't work with unsafe transfers (eg. {IERC721-transferFrom}). Use {ERC721Wrapper-_recover} * for recovering in that scenario. */ function onERC721Received(address, address from, uint256 tokenId, bytes memory) public virtual returns (bytes4) { if (address(underlying()) != _msgSender()) { revert ERC721UnsupportedToken(_msgSender()); } _safeMint(from, tokenId); return IERC721Receiver.onERC721Received.selector; } /** * @dev Mint a wrapped token to cover any underlyingToken that would have been transferred by mistake. Internal * function that can be exposed with access control if desired. */ function _recover(address account, uint256 tokenId) internal virtual returns (uint256) { address owner = underlying().ownerOf(tokenId); if (owner != address(this)) { revert ERC721IncorrectOwner(address(this), tokenId, owner); } _safeMint(account, tokenId); return tokenId; } /** * @dev Returns the underlying token. */ function underlying() public view virtual returns (IERC721) { return _underlying; } }