/* solium-disable security/no-block-members */

pragma solidity ^0.4.23;

/**
 * @title ERC20Basic
 * @dev Simpler version of ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/179
 */
contract ERC20Basic {
    function totalSupply() public view returns (uint256);
    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);
}

/**
 * @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
            );
}


/**
 * @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 {
        require(token.transfer(to, value));
    }

    function safeTransferFrom(
            ERC20 token,
            address from,
            address to,
            uint256 value
            )
        internal
        {
            require(token.transferFrom(from, to, value));
        }

    function safeApprove(ERC20 token, address spender, uint256 value) internal {
        require(token.approve(spender, value));
    }
}


/**
 * @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 OwnershipRenounced(address indexed previousOwner);
    event OwnershipTransferred(
            address indexed previousOwner,
            address indexed newOwner
            );


    /**
     * @dev The Ownable constructor sets the original `owner` of the contract to the sender
     * account.
     */
    constructor() 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;
    }

    /**
     * @dev Allows the current owner to relinquish control of the contract.
     */
    // function renounceOwnership() public onlyOwner {
    //   emit OwnershipRenounced(owner);
    //   owner = address(0);
    // }
}


/**
 * @title SafeMath
 * @dev Math operations with safety checks that throw on error
 */
library SafeMath {

    /**
     * @dev Multiplies two numbers, throws on overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256 c) {
        if (a == 0) {
            return 0;
        }
        c = a * b;
        assert(c / a == b);
        return c;
    }

    /**
     * @dev Integer division of two numbers, truncating the quotient.
     */
    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 a / b;
    }

    /**
     * @dev Subtracts two numbers, throws on overflow (i.e. if subtrahend is greater than minuend).
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        assert(b <= a);
        return a - b;
    }

    /**
     * @dev Adds two numbers, throws on overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256 c) {
        c = a + b;
        assert(c >= a);
        return c;
    }
}



/**
 * @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
    //一下写死的数据会在上线的时候，根据实际情况替换
    address public beneficiary;    //最终受益人地址
    uint256 public cliff;                                          //第一次收益时间
    uint256 public start;                                          //合约开始时间
    uint256 public duration;                                       //最后一次收益时间
    bool public revocable;                                               //是否可以召回

    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
     */
    constructor(
            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);
        }
    }
}