openzeppelin-contracts/contracts/token/ERC20/TokenTimelock.sol

pragma solidity ^0.4.24;

import "./SafeERC20.sol";

/**
 * @title TokenTimelock
 * @dev TokenTimelock is a token holder contract that will allow a
 * beneficiary to extract the tokens after a given release time
 */
contract TokenTimelock {
  using SafeERC20 for IERC20;

  // ERC20 basic token contract being held
  IERC20 private _token;

  // beneficiary of tokens after they are released
  address private _beneficiary;

  // timestamp when token release is enabled
  uint256 private _releaseTime;

  constructor(
    IERC20 token,
    address beneficiary,
    uint256 releaseTime
  )
    public
  {
    // solium-disable-next-line security/no-block-members
    require(releaseTime > block.timestamp);
    _token = token;
    _beneficiary = beneficiary;
    _releaseTime = releaseTime;
  }

  /**
   * @return the token being held.
   */
  function token() public view returns(IERC20) {
    return _token;
  }

  /**
   * @return the beneficiary of the tokens.
   */
  function beneficiary() public view returns(address) {
    return _beneficiary;
  }

  /**
   * @return the time when the tokens are released.
   */
  function releaseTime() public view returns(uint256) {
    return _releaseTime;
  }

  /**
   * @notice Transfers tokens held by timelock to beneficiary.
   */
  function release() public {
    // solium-disable-next-line security/no-block-members
    require(block.timestamp >= _releaseTime);

    uint256 amount = _token.balanceOf(address(this));
    require(amount > 0);

    _token.safeTransfer(_beneficiary, amount);
  }
}