Vested KTX

// SPDX-License-Identifier: MIT

pragma solidity ^0.6.2;

/**
 * @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) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }

    /**
     * @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].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

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

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: value }(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data, string memory errorMessage) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.3._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.3._
     */
    function functionDelegateCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private pure returns(bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;

contract Governable {
    address public gov;

    constructor() public {
        gov = msg.sender;
    }

    modifier onlyGov() {
        require(msg.sender == gov, "Governable: forbidden");
        _;
    }

    function setGov(address _gov) external onlyGov {
        gov = _gov;
    }
}

// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
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);
}

// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;

interface IMintable {
    function isMinter(address _account) external returns (bool);
    function setMinter(address _minter, bool _isActive) external;
    function mint(address _account, uint256 _amount) external;
    function burn(address _account, uint256 _amount) external;
}

// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;

interface IRewardTracker {
    function depositBalances(address _account, address _depositToken) external view returns (uint256);
    function stakedAmounts(address _account) external view returns (uint256);
    function updateRewards() external;
    function stake(address _depositToken, uint256 _amount) external;
    function stakeForAccount(address _fundingAccount, address _account, address _depositToken, uint256 _amount) external;
    function unstake(address _depositToken, uint256 _amount) external;
    function unstakeForAccount(address _account, address _depositToken, uint256 _amount, address _receiver) external;
    function tokensPerInterval() external view returns (uint256);
    function claim(address _receiver) external returns (uint256);
    function claimForAccount(address _account, address _receiver) external returns (uint256);
    function claimable(address _account) external view returns (uint256);
    function averageStakedAmounts(address _account) external view returns (uint256);
    function cumulativeRewards(address _account) external view returns (uint256);
}

// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;

interface IVester {
    function rewardTracker() external view returns (address);

    function claimForAccount(address _account, address _receiver) external returns (uint256);

    function claimable(address _account) external view returns (uint256);
    function cumulativeClaimAmounts(address _account) external view returns (uint256);
    function claimedAmounts(address _account) external view returns (uint256);
    function pairAmounts(address _account) external view returns (uint256);
    function getVestedAmount(address _account) external view returns (uint256);
    function transferredAverageStakedAmounts(address _account) external view returns (uint256);
    function transferredCumulativeRewards(address _account) external view returns (uint256);
    function cumulativeRewardDeductions(address _account) external view returns (uint256);
    function bonusRewards(address _account) external view returns (uint256);

    function transferStakeValues(address _sender, address _receiver) external;
    function setTransferredAverageStakedAmounts(address _account, uint256 _amount) external;
    function setTransferredCumulativeRewards(address _account, uint256 _amount) external;
    function setCumulativeRewardDeductions(address _account, uint256 _amount) external;
    function setBonusRewards(address _account, uint256 _amount) external;

    function getMaxVestableAmount(address _account) external view returns (uint256);
    function getCombinedAverageStakedAmount(address _account) external view returns (uint256);
}

// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;

/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 */
contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor () internal {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and make it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        // On the first call to nonReentrant, _notEntered will be true
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;

        _;

        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }
}

// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;

import "./IERC20.sol";
import "../math/SafeMath.sol";
import "../utils/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 IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using SafeMath 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));
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    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. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(data, "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");
        }
    }
}

// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;

/**
 * @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.
 */
library SafeMath {
    /**
     * @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 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.
     */
    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 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.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        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.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;

import "../libraries/math/SafeMath.sol";
import "../libraries/token/IERC20.sol";
import "../libraries/token/SafeERC20.sol";
import "../libraries/utils/ReentrancyGuard.sol";

import "./interfaces/IRewardTracker.sol";
import "./interfaces/IVester.sol";
import "../tokens/interfaces/IMintable.sol";
import "../access/Governable.sol";

contract Vester is IVester, IERC20, ReentrancyGuard, Governable {
    using SafeMath for uint256;
    using SafeERC20 for IERC20;

    string public name;
    string public symbol;
    uint8 public decimals = 18;

    uint256 public vestingDuration;

    address public esToken;
    address public pairToken;
    address public claimableToken;

    address public override rewardTracker;

    uint256 public override totalSupply;
    uint256 public pairSupply;

    bool public hasMaxVestableAmount;

    mapping (address => uint256) public balances;
    mapping (address => uint256) public override pairAmounts;
    mapping (address => uint256) public override cumulativeClaimAmounts;
    mapping (address => uint256) public override claimedAmounts;
    mapping (address => uint256) public lastVestingTimes;

    mapping (address => uint256) public override transferredAverageStakedAmounts;
    mapping (address => uint256) public override transferredCumulativeRewards;
    mapping (address => uint256) public override cumulativeRewardDeductions;
    mapping (address => uint256) public override bonusRewards;

    mapping (address => bool) public isHandler;

    event Claim(address receiver, uint256 amount);
    event Deposit(address account, uint256 amount);
    event Withdraw(address account, uint256 claimedAmount, uint256 balance);
    event PairTransfer(address indexed from, address indexed to, uint256 value);

    constructor (
        string memory _name,
        string memory _symbol,
        uint256 _vestingDuration,
        address _esToken,
        address _pairToken,
        address _claimableToken,
        address _rewardTracker
    ) public {
        name = _name;
        symbol = _symbol;

        vestingDuration = _vestingDuration;

        esToken = _esToken;
        pairToken = _pairToken;
        claimableToken = _claimableToken;

        rewardTracker = _rewardTracker;

        if (rewardTracker != address(0)) {
            hasMaxVestableAmount = true;
        }
    }

    function setHandler(address _handler, bool _isActive) external onlyGov {
        isHandler[_handler] = _isActive;
    }

    function setHasMaxVestableAmount(bool _hasMaxVestableAmount) external onlyGov {
        hasMaxVestableAmount = _hasMaxVestableAmount;
    }

    function deposit(uint256 _amount) external nonReentrant {
        _deposit(msg.sender, _amount);
    }

    function depositForAccount(address _account, uint256 _amount) external nonReentrant {
        _validateHandler();
        _deposit(_account, _amount);
    }

    function claim() external nonReentrant returns (uint256) {
        return _claim(msg.sender, msg.sender);
    }

    function claimForAccount(address _account, address _receiver) external override nonReentrant returns (uint256) {
        _validateHandler();
        return _claim(_account, _receiver);
    }

    // to help users who accidentally send their tokens to this contract
    function withdrawToken(address _token, address _account, uint256 _amount) external onlyGov {
        IERC20(_token).safeTransfer(_account, _amount);
    }

    function withdraw() external nonReentrant {
        address account = msg.sender;
        address _receiver = account;
        _claim(account, _receiver);

        uint256 claimedAmount = cumulativeClaimAmounts[account];
        uint256 balance = balances[account];
        uint256 totalVested = balance.add(claimedAmount);
        require(totalVested > 0, "Vester: vested amount is zero");

        if (hasPairToken()) {
            uint256 pairAmount = pairAmounts[account];
            _burnPair(account, pairAmount);
            IERC20(pairToken).safeTransfer(_receiver, pairAmount);
        }

        IERC20(esToken).safeTransfer(_receiver, balance);
        _burn(account, balance);

        delete cumulativeClaimAmounts[account];
        delete claimedAmounts[account];
        delete lastVestingTimes[account];

        emit Withdraw(account, claimedAmount, balance);
    }

    function transferStakeValues(address _sender, address _receiver) external override nonReentrant {
        _validateHandler();

        transferredAverageStakedAmounts[_receiver] = getCombinedAverageStakedAmount(_sender);
        transferredAverageStakedAmounts[_sender] = 0;

        uint256 transferredCumulativeReward = transferredCumulativeRewards[_sender];
        uint256 cumulativeReward = IRewardTracker(rewardTracker).cumulativeRewards(_sender);

        transferredCumulativeRewards[_receiver] = transferredCumulativeReward.add(cumulativeReward);
        cumulativeRewardDeductions[_sender] = cumulativeReward;
        transferredCumulativeRewards[_sender] = 0;

        bonusRewards[_receiver] = bonusRewards[_sender];
        bonusRewards[_sender] = 0;
    }

    function setTransferredAverageStakedAmounts(address _account, uint256 _amount) external override nonReentrant {
        _validateHandler();
        transferredAverageStakedAmounts[_account] = _amount;
    }

    function setTransferredCumulativeRewards(address _account, uint256 _amount) external override nonReentrant {
        _validateHandler();
        transferredCumulativeRewards[_account] = _amount;
    }

    function setCumulativeRewardDeductions(address _account, uint256 _amount) external override nonReentrant {
        _validateHandler();
        cumulativeRewardDeductions[_account] = _amount;
    }

    function setBonusRewards(address _account, uint256 _amount) external override nonReentrant {
        _validateHandler();
        bonusRewards[_account] = _amount;
    }

    function claimable(address _account) public override view returns (uint256) {
        uint256 amount = cumulativeClaimAmounts[_account].sub(claimedAmounts[_account]);
        uint256 nextClaimable = _getNextClaimableAmount(_account);
        return amount.add(nextClaimable);
    }

    function getMaxVestableAmount(address _account) public override view returns (uint256) {
        if (!hasRewardTracker()) { return 0; }

        uint256 transferredCumulativeReward = transferredCumulativeRewards[_account];
        uint256 bonusReward = bonusRewards[_account];
        uint256 cumulativeReward = IRewardTracker(rewardTracker).cumulativeRewards(_account);
        uint256 maxVestableAmount = cumulativeReward.add(transferredCumulativeReward).add(bonusReward);

        uint256 cumulativeRewardDeduction = cumulativeRewardDeductions[_account];

        if (maxVestableAmount < cumulativeRewardDeduction) {
            return 0;
        }

        return maxVestableAmount.sub(cumulativeRewardDeduction);
    }

    function getCombinedAverageStakedAmount(address _account) public override view returns (uint256) {
        uint256 cumulativeReward = IRewardTracker(rewardTracker).cumulativeRewards(_account);
        uint256 transferredCumulativeReward = transferredCumulativeRewards[_account];
        uint256 totalCumulativeReward = cumulativeReward.add(transferredCumulativeReward);
        if (totalCumulativeReward == 0) { return 0; }

        uint256 averageStakedAmount = IRewardTracker(rewardTracker).averageStakedAmounts(_account);
        uint256 transferredAverageStakedAmount = transferredAverageStakedAmounts[_account];

        return averageStakedAmount
            .mul(cumulativeReward)
            .div(totalCumulativeReward)
            .add(
                transferredAverageStakedAmount.mul(transferredCumulativeReward).div(totalCumulativeReward)
            );
    }

    function getPairAmount(address _account, uint256 _esAmount) public view returns (uint256) {
        if (!hasRewardTracker()) { return 0; }

        uint256 combinedAverageStakedAmount = getCombinedAverageStakedAmount(_account);
        if (combinedAverageStakedAmount == 0) {
            return 0;
        }

        uint256 maxVestableAmount = getMaxVestableAmount(_account);
        if (maxVestableAmount == 0) {
            return 0;
        }

        return _esAmount.mul(combinedAverageStakedAmount).div(maxVestableAmount);
    }

    function hasRewardTracker() public view returns (bool) {
        return rewardTracker != address(0);
    }

    function hasPairToken() public view returns (bool) {
        return pairToken != address(0);
    }

    function getTotalVested(address _account) public view returns (uint256) {
        return balances[_account].add(cumulativeClaimAmounts[_account]);
    }

    function balanceOf(address _account) public view override returns (uint256) {
        return balances[_account];
    }

    // empty implementation, tokens are non-transferrable
    function transfer(address /* recipient */, uint256 /* amount */) public override returns (bool) {
        revert("Vester: non-transferrable");
    }

    // empty implementation, tokens are non-transferrable
    function allowance(address /* owner */, address /* spender */) public view virtual override returns (uint256) {
        return 0;
    }

    // empty implementation, tokens are non-transferrable
    function approve(address /* spender */, uint256 /* amount */) public virtual override returns (bool) {
        revert("Vester: non-transferrable");
    }

    // empty implementation, tokens are non-transferrable
    function transferFrom(address /* sender */, address /* recipient */, uint256 /* amount */) public virtual override returns (bool) {
        revert("Vester: non-transferrable");
    }

    function getVestedAmount(address _account) public override view returns (uint256) {
        uint256 balance = balances[_account];
        uint256 cumulativeClaimAmount = cumulativeClaimAmounts[_account];
        return balance.add(cumulativeClaimAmount);
    }

    function _mint(address _account, uint256 _amount) private {
        require(_account != address(0), "Vester: mint to the zero address");

        totalSupply = totalSupply.add(_amount);
        balances[_account] = balances[_account].add(_amount);

        emit Transfer(address(0), _account, _amount);
    }

    function _mintPair(address _account, uint256 _amount) private {
        require(_account != address(0), "Vester: mint to the zero address");

        pairSupply = pairSupply.add(_amount);
        pairAmounts[_account] = pairAmounts[_account].add(_amount);

        emit PairTransfer(address(0), _account, _amount);
    }

    function _burn(address _account, uint256 _amount) private {
        require(_account != address(0), "Vester: burn from the zero address");

        balances[_account] = balances[_account].sub(_amount, "Vester: burn amount exceeds balance");
        totalSupply = totalSupply.sub(_amount);

        emit Transfer(_account, address(0), _amount);
    }

    function _burnPair(address _account, uint256 _amount) private {
        require(_account != address(0), "Vester: burn from the zero address");

        pairAmounts[_account] = pairAmounts[_account].sub(_amount, "Vester: burn amount exceeds balance");
        pairSupply = pairSupply.sub(_amount);

        emit PairTransfer(_account, address(0), _amount);
    }

    function _deposit(address _account, uint256 _amount) private {
        require(_amount > 0, "Vester: invalid _amount");

        _updateVesting(_account);

        IERC20(esToken).safeTransferFrom(_account, address(this), _amount);

        _mint(_account, _amount);

        if (hasPairToken()) {
            uint256 pairAmount = pairAmounts[_account];
            uint256 nextPairAmount = getPairAmount(_account, balances[_account]);
            if (nextPairAmount > pairAmount) {
                uint256 pairAmountDiff = nextPairAmount.sub(pairAmount);
                IERC20(pairToken).safeTransferFrom(_account, address(this), pairAmountDiff);
                _mintPair(_account, pairAmountDiff);
            }
        }

        if (hasMaxVestableAmount) {
            uint256 maxAmount = getMaxVestableAmount(_account);
            require(getTotalVested(_account) <= maxAmount, "Vester: max vestable amount exceeded");
        }

        emit Deposit(_account, _amount);
    }

    function _updateVesting(address _account) private {
        uint256 amount = _getNextClaimableAmount(_account);
        lastVestingTimes[_account] = block.timestamp;

        if (amount == 0) {
            return;
        }

        // transfer claimableAmount from balances to cumulativeClaimAmounts
        _burn(_account, amount);
        cumulativeClaimAmounts[_account] = cumulativeClaimAmounts[_account].add(amount);

        IMintable(esToken).burn(address(this), amount);
    }

    function _getNextClaimableAmount(address _account) private view returns (uint256) {
        uint256 timeDiff = block.timestamp.sub(lastVestingTimes[_account]);

        uint256 balance = balances[_account];
        if (balance == 0) { return 0; }

        uint256 vestedAmount = getVestedAmount(_account);
        uint256 claimableAmount = vestedAmount.mul(timeDiff).div(vestingDuration);

        if (claimableAmount < balance) {
            return claimableAmount;
        }

        return balance;
    }

    function _claim(address _account, address _receiver) private returns (uint256) {
        _updateVesting(_account);
        uint256 amount = claimable(_account);
        claimedAmounts[_account] = claimedAmounts[_account].add(amount);
        IERC20(claimableToken).safeTransfer(_receiver, amount);
        emit Claim(_account, amount);
        return amount;
    }

    function _validateHandler() private view {
        require(isHandler[msg.sender], "Vester: forbidden");
    }
}

{
  "compilationTarget": {
    "contracts/staking/Vester.sol": "Vester"
  },
  "evmVersion": "istanbul",
  "libraries": {},
  "metadata": {
    "bytecodeHash": "ipfs"
  },
  "optimizer": {
    "enabled": true,
    "runs": 1
  },
  "remappings": []
}