hyperlane-monorepo/solidity/contracts/token/HypERC20Collateral.sol

// SPDX-License-Identifier: Apache-2.0
pragma solidity >=0.8.0;

import {TokenRouter} from "./libs/TokenRouter.sol";
import {TokenMessage} from "./libs/TokenMessage.sol";
import {MailboxClient} from "../client/MailboxClient.sol";

import {IERC20} from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import {SafeERC20} from "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";

/**
 * @title Hyperlane ERC20 Token Collateral that wraps an existing ERC20 with remote transfer functionality.
 * @author Abacus Works
 */
contract HypERC20Collateral is TokenRouter {
    using SafeERC20 for IERC20;

    IERC20 public immutable wrappedToken;

    /**
     * @notice Constructor
     * @param erc20 Address of the token to keep as collateral
     */
    constructor(address erc20, address _mailbox) TokenRouter(_mailbox) {
        wrappedToken = IERC20(erc20);
    }

    function balanceOf(
        address _account
    ) external view override returns (uint256) {
        return wrappedToken.balanceOf(_account);
    }

    /**
     * @dev Transfers `_amount` of `wrappedToken` from `msg.sender` to this contract.
     * @inheritdoc TokenRouter
     */
    function _transferFromSender(
        uint256 _amount
    ) internal override returns (bytes memory) {
        wrappedToken.safeTransferFrom(msg.sender, address(this), _amount);
        return bytes(""); // no metadata
    }

    /**
     * @dev Transfers `_amount` of `wrappedToken` from this contract to `_recipient`.
     * @inheritdoc TokenRouter
     */
    function _transferTo(
        address _recipient,
        uint256 _amount,
        bytes calldata // no metadata
    ) internal virtual override {
        wrappedToken.safeTransfer(_recipient, _amount);
    }
}