// File: /contracts/ESGLocker.sol



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

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";

contract ESGLocker {

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

    IERC20 public immutable token;
    
    address public immutable beneficiary;
    uint256 public immutable lockTime;
    uint256 public immutable startTime;

    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_);
    }

    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);
    }
}
// File: @openzeppelin/contracts/token/ERC20/IERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.6.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);

    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `to`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address to, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `from` to `to` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address from,
        address to,
        uint256 amount
    ) external returns (bool);
}