TokenLocker.sol

// SPDX-License-Identifier: MIT
// wtf.academy
pragma solidity ^0.8.0;

import "../31_ERC20/IERC20.sol";
import "../31_ERC20/ERC20.sol";

/**
 * @dev ERC20代币时间锁合约。受益人在锁仓一段时间后才能取出代币。
 */
contract TokenLocker {

    // 事件
    event TokenLockStart(address indexed beneficiary, address indexed token, uint256 startTime, uint256 lockTime);
    event Release(address indexed beneficiary, address indexed token, uint256 releaseTime, uint256 amount);

    // 被锁仓的ERC20代币合约
    IERC20 public immutable token;
    // 受益人地址
    address public immutable beneficiary;
    // 锁仓时间(秒)
    uint256 public immutable lockTime;
    // 锁仓起始时间戳(秒)
    uint256 public immutable startTime;

    /**
     * @dev 部署时间锁合约，初始化代币合约地址，受益人地址和锁仓时间。
     * @param token_: 被锁仓的ERC20代币合约
     * @param beneficiary_: 受益人地址
     * @param lockTime_: 锁仓时间(秒)
     */
    constructor(
        IERC20 token_,
        address beneficiary_,
        uint256 lockTime_
    ) {
        require(lockTime_ > 0, "TokenLock: lock time should greater than 0");
        token = token_;
        beneficiary = beneficiary_;
        lockTime = lockTime_;
        startTime = block.timestamp;

        emit TokenLockStart(beneficiary_, address(token_), block.timestamp, lockTime_);
    }

    /**
     * @dev 在锁仓时间过后，将代币释放给受益人。
     */
    function release() public {
        require(block.timestamp >= startTime+lockTime, "TokenLock: current time is before release time");

        uint256 amount = token.balanceOf(address(this));
        require(amount > 0, "TokenLock: no tokens to release");

        token.transfer(beneficiary, amount);

        emit Release(msg.sender, address(token), block.timestamp, amount);
    }
}