// File: /Users/daixu/KINE/Codes/kine-protocol/contracts/Address.sol



pragma solidity ^0.5.5;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following 
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // According to EIP-1052, 0x0 is the value returned for not-yet created accounts
        // and 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470 is returned
        // for accounts without code, i.e. `keccak256('')`
        bytes32 codehash;
        bytes32 accountHash = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470;
        // solhint-disable-next-line no-inline-assembly
        assembly { codehash := extcodehash(account) }
        return (codehash != accountHash && codehash != 0x0);
    }

    /**
     * @dev Converts an `address` into `address payable`. Note that this is
     * simply a type cast: the actual underlying value is not changed.
     *
     * _Available since v2.4.0._
     */
    function toPayable(address account) internal pure returns (address payable) {
        return address(uint160(account));
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     *
     * _Available since v2.4.0._
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        // solhint-disable-next-line avoid-call-value
        (bool success, ) = recipient.call.value(amount)("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }
}

// File: /Users/daixu/KINE/Codes/kine-protocol/contracts/Context.sol



pragma solidity ^0.5.0;

/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with GSN meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
contract Context {
    // Empty internal constructor, to prevent people from mistakenly deploying
    // an instance of this contract, which should be used via inheritance.
    constructor () internal { }
    // solhint-disable-previous-line no-empty-blocks

    function _msgSender() internal view returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

// File: /Users/daixu/KINE/Codes/kine-protocol/contracts/IERC20.sol



pragma solidity ^0.5.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP. Does not include
 * the optional functions; to access them see {ERC20Detailed}.
 */
interface IERC20 {
    /**
     * @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 `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, 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 `sender` to `recipient` 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 sender, address recipient, uint256 amount) external returns (bool);

    /**
     * @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);
}

// File: /Users/daixu/KINE/Codes/kine-protocol/contracts/KineSafeMath.sol



pragma solidity ^0.5.0;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */

/**
 * Original work from OpenZeppelin: https://github.com/OpenZeppelin/openzeppelin-contracts/blob/v2.5.0/contracts/math/SafeMath.sol
 * changes we made:
 * 1. add two methods that take errorMessage as input parameter
 */

library KineSafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     * - Addition cannot overflow.
     * added by Kine
     */
    function add(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, errorMessage);

        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot overflow.
     *
     * _Available since v2.4.0._
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     * - Multiplication cannot overflow.
     * added by Kine
     */
    function mul(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, errorMessage);

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     *
     * _Available since v2.4.0._
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     *
     * _Available since v2.4.0._
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

// File: /Users/daixu/KINE/Codes/kine-protocol/contracts/LPStakingRewards.sol



pragma solidity ^0.5.16;

import "./Math.sol";
import "./SafeERC20.sol";
import "./Ownable.sol";

contract ReentrancyGuard {
    uint256 private _guardCounter;

    constructor () internal {
        _guardCounter = 1;
    }

    modifier nonReentrant() {
        _guardCounter += 1;
        uint256 localCounter = _guardCounter;
        _;
        require(localCounter == _guardCounter, "ReentrancyGuard: reentrant call");
    }
}

contract LPStakingRewards is Ownable, ReentrancyGuard {
    using KineSafeMath for uint;
    using SafeERC20 for IERC20;

    event NewRewardDistribution(address oldRewardDistribution, address newRewardDistribution);
    event NewRewardDuration(uint oldRewardDuration, uint newRewardDuration);
    event NewRewardReleasePeriod(uint oldRewardReleasePeriod, uint newRewardReleasePeriod);
    event NewCooldownTime(uint oldCooldownTime, uint newCooldownTime);
    event Staked(address indexed user, uint amount);
    event Withdrawn(address indexed user, uint amount);
    event RewardAdded(uint reward);
    event RewardPaid(address indexed user, uint reward);

    /**
     * @notice This is for avoiding reward calculation overflow (see https://sips.synthetix.io/sips/sip-77)
     * 1.15792e59 < uint(-1) / 1e18
    */
    uint public constant REWARD_OVERFLOW_CHECK = 1.15792e59;

    IERC20 public rewardsToken;
    IERC20 public stakingToken;
    address public rewardDistribution;
    uint public rewardDuration;
    uint public rewardReleasePeriod;
    uint public startTime;
    uint public periodFinish = 0;
    uint public rewardRate = 0;
    uint public rewardPerTokenStored;
    uint public lastUpdateTime;
    uint public claimCooldownTime;
    uint public totalStakes = 0;

    struct AccountRewardDetail {
        uint lastClaimTime;
        uint rewardPerTokenUpdated;
        uint accruedReward;
    }

    mapping(address => AccountRewardDetail) public accountRewardDetails;
    mapping(address => uint) public accountStakes;

    constructor (address rewardsToken_, address stakingToken_, uint startTime_) public {
        rewardsToken = IERC20(rewardsToken_);
        stakingToken = IERC20(stakingToken_);
        startTime = startTime_;
    }

    modifier onlyRewardDistribution() {
        require(_msgSender() == rewardDistribution, "Caller is not reward distribution");
        _;
    }

    modifier checkStart() {
        require(block.timestamp >= startTime, "not started yet");
        _;
    }

    modifier afterCooldown(address staker) {
        require(accountRewardDetails[staker].lastClaimTime.add(claimCooldownTime) < block.timestamp, "claim cooling down");
        _;
    }

    modifier updateReward(address account) {
        rewardPerTokenStored = rewardPerToken();
        lastUpdateTime = lastTimeRewardApplicable();
        if (account != address(0)) {
            AccountRewardDetail storage rd = accountRewardDetails[account];
            rd.accruedReward = earned(account);
            rd.rewardPerTokenUpdated = rewardPerTokenStored;
            if (rd.lastClaimTime == 0) {
                rd.lastClaimTime = block.timestamp;
            }
        }
        _;
    }

    function lastTimeRewardApplicable() public view returns (uint) {
        return Math.min(block.timestamp, periodFinish);
    }

    function rewardPerToken() public view returns (uint) {
        if (totalStakes == 0) {
            return rewardPerTokenStored;
        }
        return
        rewardPerTokenStored.add(
            lastTimeRewardApplicable()
            .sub(lastUpdateTime)
            .mul(rewardRate)
            .mul(1e18)
            .div(totalStakes)
        );
    }

    function earned(address account) public view returns (uint) {
        return accountStakes[account]
        .mul(rewardPerToken().sub(accountRewardDetails[account].rewardPerTokenUpdated))
        .div(1e18)
        .add(accountRewardDetails[account].accruedReward);
    }

    function claimable(address account) external view returns (uint) {
        uint accountNewAccruedReward = earned(account);
        uint pastTime = block.timestamp.sub(accountRewardDetails[account].lastClaimTime);
        uint maturedReward = rewardReleasePeriod == 0 ? accountNewAccruedReward : accountNewAccruedReward.mul(pastTime).div(rewardReleasePeriod);
        if (maturedReward > accountNewAccruedReward) {
            maturedReward = accountNewAccruedReward;
        }
        return maturedReward;
    }

    function getRewardForDuration() external view returns (uint256) {
        return rewardRate.mul(rewardDuration);
    }

    function stake(uint256 amount) external nonReentrant checkStart updateReward(msg.sender) {
        require(amount > 0, "staking 0");
        stakingToken.safeTransferFrom(msg.sender, address(this), amount);
        totalStakes = totalStakes.add(amount);
        accountStakes[msg.sender] = accountStakes[msg.sender].add(amount);
        emit Staked(msg.sender, amount);
    }

    function withdraw(uint256 amount) public nonReentrant updateReward(msg.sender) {
        require(amount > 0, "withdrawing 0");
        totalStakes = totalStakes.sub(amount);
        accountStakes[msg.sender] = accountStakes[msg.sender].sub(amount);
        stakingToken.safeTransfer(msg.sender, amount);
        emit Withdrawn(msg.sender, amount);
    }

    function getReward() public nonReentrant afterCooldown(msg.sender) updateReward(msg.sender) {
        uint reward = accountRewardDetails[msg.sender].accruedReward;
        if (reward > 0) {
            uint pastTime = block.timestamp.sub(accountRewardDetails[msg.sender].lastClaimTime);
            uint maturedReward = rewardReleasePeriod == 0 ? reward : reward.mul(pastTime).div(rewardReleasePeriod);
            if (maturedReward > reward) {
                maturedReward = reward;
            }

            accountRewardDetails[msg.sender].accruedReward = reward.sub(maturedReward);
            accountRewardDetails[msg.sender].lastClaimTime = block.timestamp;
            rewardsToken.safeTransfer(msg.sender, maturedReward);
            emit RewardPaid(msg.sender, maturedReward);
        }
    }

    function exit() external {
        withdraw(accountStakes[msg.sender]);
        getReward();
    }


    function notifyRewardAmount(uint reward) external onlyRewardDistribution updateReward(address(0)) {
        if (block.timestamp > startTime) {
            if (block.timestamp >= periodFinish) {
                require(reward < REWARD_OVERFLOW_CHECK, "reward rate will overflow");
                rewardRate = reward.div(rewardDuration);
            } else {
                uint remaining = periodFinish.sub(block.timestamp);
                uint leftover = remaining.mul(rewardRate);
                require(reward.add(leftover) < REWARD_OVERFLOW_CHECK, "reward rate will overflow");
                rewardRate = reward.add(leftover).div(rewardDuration);
            }
            lastUpdateTime = block.timestamp;
            periodFinish = block.timestamp.add(rewardDuration);
            emit RewardAdded(reward);
        } else {
            require(reward < REWARD_OVERFLOW_CHECK, "reward rate will overflow");
            rewardRate = reward.div(rewardDuration);
            lastUpdateTime = startTime;
            periodFinish = startTime.add(rewardDuration);
            emit RewardAdded(reward);
        }
    }

    function _setRewardDistribution(address _rewardDistribution) external onlyOwner {
        address oldRewardDistribution = rewardDistribution;
        rewardDistribution = _rewardDistribution;
        emit NewRewardDistribution(oldRewardDistribution, _rewardDistribution);
    }

    function _setRewardDuration(uint newRewardDuration) external onlyOwner updateReward(address(0)) {
        uint oldRewardDuration = rewardDuration;
        rewardDuration = newRewardDuration;

        if (block.timestamp > startTime) {
            if (block.timestamp >= periodFinish) {
                rewardRate = 0;
            } else {
                uint remaining = periodFinish.sub(block.timestamp);
                uint leftover = remaining.mul(rewardRate);
                rewardRate = leftover.div(rewardDuration);
            }
            lastUpdateTime = block.timestamp;
            periodFinish = block.timestamp.add(rewardDuration);
        } else {
            rewardRate = rewardRate.mul(oldRewardDuration).div(rewardDuration);
            lastUpdateTime = startTime;
            periodFinish = startTime.add(rewardDuration);
        }

        emit NewRewardDuration(oldRewardDuration, newRewardDuration);
    }

    function _setRewardReleasePeriod(uint newRewardReleasePeriod) external onlyOwner updateReward(address(0)) {
        uint oldRewardReleasePeriod = rewardReleasePeriod;
        rewardReleasePeriod = newRewardReleasePeriod;
        emit NewRewardReleasePeriod(oldRewardReleasePeriod, newRewardReleasePeriod);
    }

    function _setCooldownTime(uint newCooldownTime) external onlyOwner {
        uint oldCooldownTime = claimCooldownTime;
        claimCooldownTime = newCooldownTime;
        emit NewCooldownTime(oldCooldownTime, newCooldownTime);
    }

}
// File: /Users/daixu/KINE/Codes/kine-protocol/contracts/Math.sol



pragma solidity ^0.5.0;

/**
 * @dev Standard math utilities missing in the Solidity language.
 */
library Math {
    /**
     * @dev Returns the largest of two numbers.
     */
    function max(uint256 a, uint256 b) internal pure returns (uint256) {
        return a >= b ? a : b;
    }

    /**
     * @dev Returns the smallest of two numbers.
     */
    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }

    /**
     * @dev Returns the average of two numbers. The result is rounded towards
     * zero.
     */
    function average(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b) / 2 can overflow, so we distribute
        return (a / 2) + (b / 2) + ((a % 2 + b % 2) / 2);
    }
}

// File: /Users/daixu/KINE/Codes/kine-protocol/contracts/Ownable.sol



pragma solidity ^0.5.0;

import "./Context.sol";
/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor () internal {
        address msgSender = _msgSender();
        _owner = msgSender;
        emit OwnershipTransferred(address(0), msgSender);
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(isOwner(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Returns true if the caller is the current owner.
     */
    function isOwner() public view returns (bool) {
        return _msgSender() == _owner;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public onlyOwner {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public onlyOwner {
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     */
    function _transferOwnership(address newOwner) internal {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

// File: /Users/daixu/KINE/Codes/kine-protocol/contracts/SafeERC20.sol



pragma solidity ^0.5.0;

import "./IERC20.sol";
import "./KineSafeMath.sol";
import "./Address.sol";

/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * 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 {
    using KineSafeMath for uint256;
    using Address for address;

    function safeTransfer(IERC20 token, address to, uint256 value) internal {
        callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
        callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }

    function safeApprove(IERC20 token, address spender, uint256 value) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        // solhint-disable-next-line max-line-length
        require((value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).add(value);
        callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
        callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves.

        // A Solidity high level call has three parts:
        //  1. The target address is checked to verify it contains contract code
        //  2. The call itself is made, and success asserted
        //  3. The return value is decoded, which in turn checks the size of the returned data.
        // solhint-disable-next-line max-line-length
        require(address(token).isContract(), "SafeERC20: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = address(token).call(data);
        require(success, "SafeERC20: low-level call failed");

        if (returndata.length > 0) { // Return data is optional
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}