pragma solidity ^0.4.18;

// File: contracts/math/SafeMath.sol

/**
 * @title SafeMath
 * @dev Math operations with safety checks that throw on error
 */
library SafeMath {
  function mul(uint256 a, uint256 b) internal pure returns (uint256) {
    if (a == 0) {
      return 0;
    }
    uint256 c = a * b;
    assert(c / a == b);
    return c;
  }

  function div(uint256 a, uint256 b) internal pure returns (uint256) {
    // assert(b > 0); // Solidity automatically throws when dividing by 0
    uint256 c = a / b;
    // assert(a == b * c + a % b); // There is no case in which this doesn't hold
    return c;
  }

  function sub(uint256 a, uint256 b) internal pure returns (uint256) {
    assert(b <= a);
    return a - b;
  }

  function add(uint256 a, uint256 b) internal pure returns (uint256) {
    uint256 c = a + b;
    assert(c >= a);
    return c;
  }
}

// File: contracts/ownership/Ownable.sol

/**
 * @title Ownable
 * @dev The Ownable contract has an owner address, and provides basic authorization control
 * functions, this simplifies the implementation of "user permissions".
 */
contract Ownable {
  address public owner;


  event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);


  /**
   * @dev The Ownable constructor sets the original `owner` of the contract to the sender
   * account.
   */
  function Ownable() public {
    owner = msg.sender;
  }


  /**
   * @dev Throws if called by any account other than the owner.
   */
  modifier onlyOwner() {
    require(msg.sender == owner);
    _;
  }


  /**
   * @dev Allows the current owner to transfer control of the contract to a newOwner.
   * @param newOwner The address to transfer ownership to.
   */
  function transferOwnership(address newOwner) public onlyOwner {
    require(newOwner != address(0));
    emit OwnershipTransferred(owner, newOwner);
    owner = newOwner;
  }

}

// File: contracts/token/ERC20Basic.sol

/**
 * @title ERC20Basic
 * @dev Simpler version of ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/179
 */
contract ERC20Basic {
  uint256 public totalSupply;
  function balanceOf(address who) public view returns (uint256);
  function transfer(address to, uint256 value) public returns (bool);
  event Transfer(address indexed from, address indexed to, uint256 value);
}

// File: contracts/token/ERC20.sol

/**
 * @title ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/20
 */
contract ERC20 is ERC20Basic {
  function allowance(address owner, address spender) public view returns (uint256);
  function transferFrom(address from, address to, uint256 value) public returns (bool);
  function approve(address spender, uint256 value) public returns (bool);
  event Approval(address indexed owner, address indexed spender, uint256 value);
}

// File: contracts/token/SafeERC20.sol

/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure.
 * To use this library you can add a `using SafeERC20 for ERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
  function safeTransfer(ERC20Basic token, address to, uint256 value) internal {
    assert(token.transfer(to, value));
  }

  function safeTransferFrom(ERC20 token, address from, address to, uint256 value) internal {
    assert(token.transferFrom(from, to, value));
  }

  function safeApprove(ERC20 token, address spender, uint256 value) internal {
    assert(token.approve(spender, value));
  }
}

// File: contracts/token/TokenVesting.sol

/* solium-disable security/no-block-members */

pragma solidity ^0.4.21;








/**
 * @title TokenVesting
 * @dev A token holder contract that can release its token balance gradually like a
 * typical vesting scheme, with a cliff and vesting period. Optionally revocable by the
 * owner.
 */
contract TokenVesting is Ownable {
    using SafeMath for uint256;
    using SafeERC20 for ERC20Basic;

    event Released(uint256 amount);

    event Revoked();

    // beneficiary of tokens after they are released
    address public beneficiary;

    uint256 public cliff;

    uint256 public start;

    uint256 public duration;

    bool public revocable;

    mapping (address => uint256) public released;

    mapping (address => bool) public revoked;

    /**
     * @dev Creates a vesting contract that vests its balance of any ERC20 token to the
     * _beneficiary, gradually in a linear fashion until _start + _duration. By then all
     * of the balance will have vested.
     * @param _beneficiary address of the beneficiary to whom vested tokens are transferred
     * @param _cliff duration in seconds of the cliff in which tokens will begin to vest
     * @param _duration duration in seconds of the period in which the tokens will vest
     * @param _revocable whether the vesting is revocable or not
     */
    function TokenVesting(
    address _beneficiary,
    uint256 _start,
    uint256 _cliff,
    uint256 _duration,
    bool _revocable
    )
    public
    {
        require(_beneficiary != address(0));
        require(_cliff <= _duration);

        beneficiary = _beneficiary;
        revocable = _revocable;
        duration = _duration;
        cliff = _start.add(_cliff);
        start = _start;
    }

    /**
     * @notice Transfers vested tokens to beneficiary.
     * @param token ERC20 token which is being vested
     */
    function release(ERC20Basic token) public {
        uint256 unreleased = releasableAmount(token);
        require(unreleased > 0);
        released[token] = released[token].add(unreleased);
        token.safeTransfer(beneficiary, unreleased);

        emit Released(unreleased);
    }

    /**
     * @notice Allows the owner to revoke the vesting. Tokens already vested
     * remain in the contract, the rest are returned to the owner.
     * @param token ERC20 token which is being vested
     */
    function revoke(ERC20Basic token) public onlyOwner {
        require(revocable);
        require(!revoked[token]);

        uint256 balance = token.balanceOf(this);

        uint256 unreleased = releasableAmount(token);
        uint256 refund = balance.sub(unreleased);

        revoked[token] = true;

        token.safeTransfer(owner, refund);

        emit Revoked();
    }

    /**
     * @dev Calculates the amount that has already vested but hasn't been released yet.
     * @param token ERC20 token which is being vested
     */
    function releasableAmount(ERC20Basic token) public view returns (uint256) {
        return vestedAmount(token).sub(released[token]);
    }

    /**
     * @dev Calculates the amount that has already vested.
     * @param token ERC20 token which is being vested
     */
    function vestedAmount(ERC20Basic token) public view returns (uint256) {
        uint256 currentBalance = token.balanceOf(this);
        uint256 totalBalance = currentBalance.add(released[token]);

        if (block.timestamp < cliff) {
            return 0;
        }
        else if (block.timestamp >= start.add(duration) || revoked[token]) {
            return totalBalance;
        }
        else {
            return totalBalance.mul(block.timestamp.sub(start)).div(duration);
        }
    }
}