// File: @openzeppelin/contracts/token/ERC20/IERC20.sol

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @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);
}

// File: @openzeppelin/contracts/math/SafeMath.sol

pragma solidity >=0.6.0 <0.8.0;

/**
 * @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.
 */
library SafeMath {
  /**
   * @dev Returns the addition of two unsigned integers, with an overflow flag.
   *
   * _Available since v3.4._
   */
  function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
    uint256 c = a + b;
    if (c < a) return (false, 0);
    return (true, c);
  }

  /**
   * @dev Returns the substraction of two unsigned integers, with an overflow flag.
   *
   * _Available since v3.4._
   */
  function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
    if (b > a) return (false, 0);
    return (true, a - b);
  }

  /**
   * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
   *
   * _Available since v3.4._
   */
  function tryMul(uint256 a, uint256 b) internal pure returns (bool, 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 (true, 0);
    uint256 c = a * b;
    if (c / a != b) return (false, 0);
    return (true, c);
  }

  /**
   * @dev Returns the division of two unsigned integers, with a division by zero flag.
   *
   * _Available since v3.4._
   */
  function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
    if (b == 0) return (false, 0);
    return (true, a / b);
  }

  /**
   * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
   *
   * _Available since v3.4._
   */
  function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
    if (b == 0) return (false, 0);
    return (true, a % b);
  }

  /**
   * @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) {
    require(b <= a, 'SafeMath: subtraction overflow');
    return a - b;
  }

  /**
   * @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) {
    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, reverting 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) {
    require(b > 0, 'SafeMath: division by zero');
    return a / b;
  }

  /**
   * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
   * reverting 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) {
    require(b > 0, 'SafeMath: modulo by zero');
    return a % b;
  }

  /**
   * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
   * overflow (when the result is negative).
   *
   * CAUTION: This function is deprecated because it requires allocating memory for the error
   * message unnecessarily. For custom revert reasons use {trySub}.
   *
   * 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);
    return a - b;
  }

  /**
   * @dev Returns the integer division of two unsigned integers, reverting with custom message on
   * division by zero. The result is rounded towards zero.
   *
   * CAUTION: This function is deprecated because it requires allocating memory for the error
   * message unnecessarily. For custom revert reasons use {tryDiv}.
   *
   * 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);
    return a / b;
  }

  /**
   * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
   * reverting with custom message when dividing by zero.
   *
   * CAUTION: This function is deprecated because it requires allocating memory for the error
   * message unnecessarily. For custom revert reasons use {tryMod}.
   *
   * 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;
  }
}

// File: @openzeppelin/contracts/utils/Address.sol

pragma solidity >=0.6.2 <0.8.0;

/**
 * @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 v3.4._
   */
  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 v3.4._
   */
  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);
      }
    }
  }
}

// File: @openzeppelin/contracts/token/ERC20/SafeERC20.sol

pragma solidity >=0.6.0 <0.8.0;

/**
 * @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');
    }
  }
}

// File: @openzeppelin/contracts/math/Math.sol

pragma solidity >=0.6.0 <0.8.0;

/**
 * @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: @openzeppelin/contracts/utils/Context.sol

pragma solidity >=0.6.0 <0.8.0;

/*
 * @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.
 */
abstract contract Context {
  function _msgSender() internal view virtual returns (address payable) {
    return msg.sender;
  }

  function _msgData() internal view virtual returns (bytes memory) {
    this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
    return msg.data;
  }
}

// File: @openzeppelin/contracts/access/Ownable.sol

pragma solidity >=0.6.0 <0.8.0;

/**
 * @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.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * 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.
 */
abstract 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 virtual returns (address) {
    return _owner;
  }

  /**
   * @dev Throws if called by any account other than the owner.
   */
  modifier onlyOwner() {
    require(owner() == _msgSender(), 'Ownable: caller is not the 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 virtual 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 virtual onlyOwner {
    require(newOwner != address(0), 'Ownable: new owner is the zero address');
    emit OwnershipTransferred(_owner, newOwner);
    _owner = newOwner;
  }
}

// File: contracts/MasterChefMod.sol

pragma solidity >=0.6.0 <0.8.0;

contract MasterChefMod is Ownable {
  using SafeMath for uint256;
  using SafeERC20 for IERC20;

  event Deposit(address indexed user, uint256 indexed pid, uint256 amount);
  event Withdraw(address indexed user, uint256 indexed pid, uint256 amount);
  event Claim(address indexed user, uint256 indexed pid, uint256 amount);
  event EmergencyWithdraw(address indexed user, uint256 indexed pid, uint256 amount);

  /// @notice Detail of each user.
  struct UserInfo {
    uint256 amount; // Number of tokens staked
    uint256 rewardDebt; // A base for future reward claims. Works as a threshold, updated on each reward claim
    //
    // At any point in time, pending user reward for a given pool is:
    // pending reward = (user.amount * pool.accRewardPerShare) - user.rewardFloor
    //
    // Whenever a user deposits or withdraws a pool token:
    //   1. The pool's `accRewardPerShare` (and `lastUpdate`) gets updated.
    //   2. User receives the pending reward sent to their address.
    //   3. User's `amount` gets updated.
    //   4. User's `rewardFloor` gets updated.
  }

  /// @notice Detail of each pool.
  struct PoolInfo {
    address token; // Token to stake.
    uint256 allocPoint; // How many allocation points assigned to this pool. Rewards to distribute per second.
    uint256 lastUpdateTime; // Last time that distribution happened.
    uint256 accRewardPerShare; // Accumulated rewards per share.
    uint256 totalStaked; // Amount of tokens staked in the pool.
    uint256 accUndistributedReward; // Accumulated rewards when a pool has no stake in it.
  }

  /// @dev Division precision.
  uint256 private precision = 1e18;

  /// @dev Reward token balance.
  uint256 public rewardTokenBalance;

  /// @notice Total allocation points. Must be the sum of all allocation points in all pools.
  uint256 public totalAllocPoint;

  /// @notice Time of the contract deployment.
  uint256 public timeDeployed;

  /// @notice Total rewards accumulated since contract deployment.
  uint256 public totalRewards;

  /// @notice Reward token.
  address public rewardToken;

  /// @notice Detail of each pool.
  PoolInfo[] public poolInfo;

  /// @notice Period in which the latest distribution of rewards will end.
  uint256 public periodFinish;

  /// @notice Reward rate per second. Has increased precision (when doing math with it, do div(precision))
  uint256 public rewardRate;

  ///  @notice New rewards are equaly split between the duration.
  uint256 public rewardsDuration;

  /// @notice Detail of each user who stakes tokens.
  mapping(uint256 => mapping(address => UserInfo)) public userInfo;
  mapping(address => bool) private poolToken;

  constructor(address _rewardToken, uint256 _rewardsDuration) {
    rewardToken = _rewardToken;
    rewardsDuration = _rewardsDuration;
    timeDeployed = block.timestamp;
    periodFinish = timeDeployed.add(rewardsDuration);
  }

  /// @notice Average reward per second generated since contract deployment.
  function avgRewardsPerSecondTotal() external view returns (uint256 avgPerSecond) {
    return totalRewards.div(block.timestamp.sub(timeDeployed));
  }

  /// @notice Total pools.
  function poolLength() external view returns (uint256) {
    return poolInfo.length;
  }

  /// @notice Display user rewards for a specific pool.
  function pendingReward(uint256 _pid, address _user) public view returns (uint256) {
    PoolInfo storage pool = poolInfo[_pid];
    UserInfo storage user = userInfo[_pid][_user];
    uint256 accRewardPerShare = pool.accRewardPerShare;

    if (pool.totalStaked != 0 && totalAllocPoint != 0) {
      accRewardPerShare = accRewardPerShare.add(
        _getPoolRewardsSinceLastUpdate(_pid).mul(precision).div(pool.totalStaked)
      );
    }

    return user.amount.mul(accRewardPerShare).div(precision).sub(user.rewardDebt);
  }

  /// @notice Add a new pool.
  function add(
    uint256 _allocPoint,
    address _token,
    bool _withUpdate
  ) public onlyOwner {
    if (_withUpdate) {
      massUpdatePools();
    }

    require(
      poolToken[address(_token)] == false,
      'MasterChefMod: Stake token has already been added'
    );

    totalAllocPoint = totalAllocPoint.add(_allocPoint);

    poolInfo.push(
      PoolInfo({
        token: _token,
        allocPoint: _allocPoint,
        lastUpdateTime: block.timestamp,
        accRewardPerShare: 0,
        totalStaked: 0,
        accUndistributedReward: 0
      })
    );

    poolToken[address(_token)] = true;
  }

  /// @notice Update the given pool's allocation point.
  function set(
    uint256 _pid,
    uint256 _allocPoint,
    bool _withUpdate
  ) public onlyOwner {
    if (_withUpdate) {
      massUpdatePools();
    }

    totalAllocPoint = totalAllocPoint.sub(poolInfo[_pid].allocPoint).add(_allocPoint);
    poolInfo[_pid].allocPoint = _allocPoint;
  }

  /// @notice Deposit tokens to pool for reward allocation.
  function deposit(uint256 _pid, uint256 _amount) public {
    PoolInfo storage pool = poolInfo[_pid];
    UserInfo storage user = userInfo[_pid][msg.sender];

    _updatePool(_pid);

    uint256 pending;

    if (pool.totalStaked == 0) {
      // Special case: no one was staking, the pool was accumulating rewards.
      pending = pool.accUndistributedReward;
      pool.accUndistributedReward = 0;
    }
    if (user.amount != 0) {
      pending = _getUserPendingReward(_pid);
    }

    _claimFromPool(_pid, pending);
    _transferAmountIn(_pid, _amount);
    _updateRewardDebt(_pid);

    emit Deposit(msg.sender, _pid, _amount);
  }

  // Withdraw tokens from pool. Claims rewards implicitly (only claims rewards when called with _amount = 0)
  function withdraw(uint256 _pid, uint256 _amount) public {
    UserInfo storage user = userInfo[_pid][msg.sender];
    require(user.amount >= _amount, 'MasterChefMod: Withdraw amount is greater than user stake.');

    _updatePool(_pid);
    _claimFromPool(_pid, _getUserPendingReward(_pid));
    _transferAmountOut(_pid, _amount);
    _updateRewardDebt(_pid);

    emit Withdraw(msg.sender, _pid, _amount);
  }

  // Withdraw without caring about rewards. EMERGENCY ONLY.
  // !Caution this will remove all your pending rewards!
  function emergencyWithdraw(uint256 _pid) public {
    PoolInfo storage pool = poolInfo[_pid];
    UserInfo storage user = userInfo[_pid][msg.sender];

    uint256 _amount = user.amount;
    user.amount = 0;
    user.rewardDebt = 0;
    pool.totalStaked = pool.totalStaked.sub(_amount);

    IERC20(pool.token).safeTransfer(address(msg.sender), _amount);
    emit EmergencyWithdraw(msg.sender, _pid, _amount);
    // No mass update dont update pending rewards
  }

  /// Adds and evenly distributes any rewards that were sent to the contract since last reward update.
  function updateRewards(uint256 amount) external onlyOwner {
    require(amount != 0, 'MasterChefMod: Reward amount must be greater than zero');

    IERC20(rewardToken).safeTransferFrom(msg.sender, address(this), amount);
    rewardTokenBalance = rewardTokenBalance.add(amount);

    if (totalAllocPoint == 0) {
      return;
    }

    massUpdatePools();

    // note: if increasing rewards after the last period has ended, just divide the amount by period length
    if (block.timestamp >= periodFinish) {
      rewardRate = amount.mul(precision).div(rewardsDuration);
    } else {
      uint256 periodSecondsLeft = periodFinish.sub(block.timestamp);
      uint256 periodRewardsLeft = periodSecondsLeft.mul(rewardRate);
      rewardRate = periodRewardsLeft.add(amount.mul(precision)).div(rewardsDuration);
    }

    totalRewards = totalRewards.add(amount);
    periodFinish = block.timestamp.add(rewardsDuration);
  }

  /// @notice Updates rewards for all pools by adding pending rewards.
  /// Can spend a lot of gas.
  function massUpdatePools() public {
    uint256 length = poolInfo.length;
    for (uint256 pid = 0; pid < length; ++pid) {
      _updatePool(pid);
    }
  }

  /// @notice Keeps pool properties (lastUpdateTime, accRewardPerShare, accUndistributedReward) up to date.
  function _updatePool(uint256 _pid) internal {
    if (totalAllocPoint == 0) return;

    PoolInfo storage pool = poolInfo[_pid];
    uint256 poolRewards = _getPoolRewardsSinceLastUpdate(_pid);

    if (pool.totalStaked == 0) {
      pool.accRewardPerShare = pool.accRewardPerShare.add(poolRewards);
      pool.accUndistributedReward = pool.accUndistributedReward.add(poolRewards);
    } else {
      pool.accRewardPerShare = pool.accRewardPerShare.add(
        poolRewards.mul(precision).div(pool.totalStaked)
      );
    }

    pool.lastUpdateTime = block.timestamp;
  }

  function _getPoolRewardsSinceLastUpdate(uint256 _pid)
    internal
    view
    returns (uint256 _poolRewards)
  {
    PoolInfo storage pool = poolInfo[_pid];
    uint256 lastTimeRewardApplicable = Math.min(block.timestamp, periodFinish);
    uint256 numSeconds = Math.max(lastTimeRewardApplicable.sub(pool.lastUpdateTime), 0);
    return numSeconds.mul(rewardRate).mul(pool.allocPoint).div(totalAllocPoint).div(precision);
  }

  function _safeRewardTokenTransfer(address _to, uint256 _amount)
    internal
    returns (uint256 _claimed)
  {
    _claimed = Math.min(_amount, rewardTokenBalance);
    IERC20(rewardToken).transfer(_to, _claimed);
    rewardTokenBalance = rewardTokenBalance.sub(_claimed);
  }

  function withdrawStuckTokens(address _token, uint256 _amount) public onlyOwner {
    require(_token != address(rewardToken), 'MasterChefMod: Cannot withdraw reward tokens');
    require(poolToken[address(_token)] == false, 'MasterChefMod: Cannot withdraw stake tokens');
    IERC20(_token).safeTransfer(msg.sender, _amount);
  }

  function _getUserPendingReward(uint256 _pid) internal view returns (uint256 _reward) {
    PoolInfo storage pool = poolInfo[_pid];
    UserInfo storage user = userInfo[_pid][msg.sender];
    return user.amount.mul(pool.accRewardPerShare).div(precision).sub(user.rewardDebt);
  }

  function _claimFromPool(uint256 _pid, uint256 _amount) internal {
    if (_amount != 0) {
      uint256 amountClaimed = _safeRewardTokenTransfer(msg.sender, _amount);
      emit Claim(msg.sender, _pid, amountClaimed);
    }
  }

  function _transferAmountIn(uint256 _pid, uint256 _amount) internal {
    PoolInfo storage pool = poolInfo[_pid];
    UserInfo storage user = userInfo[_pid][msg.sender];

    if (_amount != 0) {
      IERC20(pool.token).safeTransferFrom(msg.sender, address(this), _amount);
      user.amount = user.amount.add(_amount);
      pool.totalStaked = pool.totalStaked.add(_amount);
    }
  }

  function _transferAmountOut(uint256 _pid, uint256 _amount) internal {
    PoolInfo storage pool = poolInfo[_pid];
    UserInfo storage user = userInfo[_pid][msg.sender];

    if (_amount != 0) {
      IERC20(pool.token).safeTransfer(msg.sender, _amount);
      user.amount = user.amount.sub(_amount);
      pool.totalStaked = pool.totalStaked.sub(_amount);
    }
  }

  function _updateRewardDebt(uint256 _pid) internal {
    UserInfo storage user = userInfo[_pid][msg.sender];
    user.rewardDebt = user.amount.mul(poolInfo[_pid].accRewardPerShare).div(precision);
  }
}