// File: contracts/AmmRewards.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.6.12;
pragma experimental ABIEncoderV2;

import {Ownable} from '@openzeppelin/contracts/access/Ownable.sol';
import {IERC20} from '@openzeppelin/contracts/token/ERC20/IERC20.sol';
import {SafeMath} from '@openzeppelin/contracts/math/SafeMath.sol';
import {SafeERC20} from '@openzeppelin/contracts/token/ERC20/SafeERC20.sol';
import {ReentrancyGuard} from '@openzeppelin/contracts/utils/ReentrancyGuard.sol';
import {SignedSafeMath} from './lib/SignedSafeMath.sol';
import {IRewarder} from './interfaces/IRewarder.sol';

contract AmmRewards is ReentrancyGuard, Ownable {
  using SafeMath for uint256;
  using SafeERC20 for IERC20;
  using SignedSafeMath for int256;

  /// @notice Info of each MCV2 user.
  /// `amount` LP token amount the user has provided.
  /// `rewardDebt` The amount of REWARD_TOKEN entitled to the user.
  struct UserInfo {
    uint256 amount;
    int256 rewardDebt;
  }

  /// @notice Info of each MCV2 pool.
  /// `allocPoint` The amount of allocation points assigned to the pool.
  /// Also known as the amount of REWARD_TOKEN to distribute per block.
  struct PoolInfo {
    uint256 accRewardTokenPerShare;
    uint256 lastRewardTime;
    uint256 allocPoint;
  }

  /// @notice Address of REWARD_TOKEN contract.
  IERC20 public immutable REWARD_TOKEN;

  /// @notice Info of each MCV2 pool.
  PoolInfo[] public poolInfo;

  /// @notice Address of the LP token for each MCV2 pool.
  IERC20[] public lpToken;

  //stores existence of lp tokens to avoid duplicate entries
  mapping(IERC20 => bool) lpTokenExists;

  /// @notice Address of each `IRewarder` contract in MCV2.
  IRewarder[] public rewarder;

  /// @notice Info of each user that stakes LP tokens.
  mapping(uint256 => mapping(address => UserInfo)) public userInfo;

  /// @dev Total allocation points. Must be the sum of all allocation points in all pools.
  uint256 public totalAllocPoint;

  uint256 public rewardTokenPerSecond;

  uint256 private constant ACC_REWARD_TOKEN_PRECISION = 1e12;

  uint256 private epochRewardAmount;

  address public rewardsManager;

  event Deposit(
    address indexed user,
    uint256 indexed pid,
    uint256 amount,
    address indexed to
  );
  event Withdraw(
    address indexed user,
    uint256 indexed pid,
    uint256 amount,
    address indexed to
  );
  event EmergencyWithdraw(
    address indexed user,
    uint256 indexed pid,
    uint256 amount,
    address indexed to
  );
  event Harvest(address indexed user, uint256 indexed pid, uint256 amount);
  event LogPoolAddition(
    uint256 indexed pid,
    uint256 allocPoint,
    IERC20 indexed lpToken,
    IRewarder indexed rewarder
  );
  event LogSetPool(
    uint256 indexed pid,
    uint256 allocPoint,
    IRewarder indexed rewarder,
    bool overwrite
  );
  event LogUpdatePool(
    uint256 indexed pid,
    uint256 lastRewardTime,
    uint256 lpSupply,
    uint256 accRewardTokenPerShare
  );
  event LogRewardTokenPerSecond(uint256 rewardTokenPerSecond);

  constructor(IERC20 rewardToken_) public {
    REWARD_TOKEN = rewardToken_;
  }

  /// @notice Returns the number of MCV2 pools.
  function poolLength() public view returns (uint256 pools) {
    pools = poolInfo.length;
  }

  /// @notice Add a new LP to the pool. Can only be called by the owner.
  /// @param allocPoint AP of the new pool.
  /// @param _lpToken Address of the LP ERC-20 token.
  /// @param _rewarder Address of the rewarder delegate.
  function add(
    uint256 allocPoint,
    IERC20 _lpToken,
    IRewarder _rewarder
  ) public onlyOwner {
    require(lpTokenExists[_lpToken] == false, 'LP token already added');
    totalAllocPoint = totalAllocPoint.add(allocPoint);
    lpToken.push(_lpToken);
    rewarder.push(_rewarder);

    poolInfo.push(
      PoolInfo({
        allocPoint: allocPoint,
        lastRewardTime: block.timestamp,
        accRewardTokenPerShare: 0
      })
    );
    lpTokenExists[_lpToken] = true;
    emit LogPoolAddition(
      lpToken.length.sub(1),
      allocPoint,
      _lpToken,
      _rewarder
    );
  }

  /// @notice Update the given pool's REWARD_TOKEN allocation point and `IRewarder` contract. Can only be called by the owner.
  /// @param _pid The index of the pool. See `poolInfo`.
  /// @param _allocPoint New AP of the pool.
  /// @param _rewarder Address of the rewarder delegate.
  /// @param overwrite True if _rewarder should be `set`. Otherwise `_rewarder` is ignored.
  function set(
    uint256 _pid,
    uint256 _allocPoint,
    IRewarder _rewarder,
    bool overwrite
  ) public onlyOwner {
    totalAllocPoint = totalAllocPoint.sub(poolInfo[_pid].allocPoint).add(
      _allocPoint
    );
    poolInfo[_pid].allocPoint = _allocPoint;
    if (overwrite) {
      rewarder[_pid] = _rewarder;
    }
    emit LogSetPool(
      _pid,
      _allocPoint,
      overwrite ? _rewarder : rewarder[_pid],
      overwrite
    );
  }

  /// @notice Sets the rewardToken per second to be distributed. Can only be called by the owner.
  /// @param rewardTokenPerSecond_ The amount of RewardToken to be distributed per second
  function setRewardTokenPerSecond(uint256 rewardTokenPerSecond_)
    external
    onlyOwnerOrRewardsManager
  {
    rewardTokenPerSecond = rewardTokenPerSecond_;
    emit LogRewardTokenPerSecond(rewardTokenPerSecond);
  }

  /// @notice View function to see pending REWARD_TOKEN on frontend.
  /// @param _pid The index of the pool. See `poolInfo`.
  /// @param _user Address of user.
  /// @return pending REWARD_TOKEN reward for a given user.
  function pendingRewardToken(uint256 _pid, address _user)
    external
    view
    returns (uint256 pending)
  {
    PoolInfo memory pool = poolInfo[_pid];
    UserInfo storage user = userInfo[_pid][_user];
    uint256 accRewardTokenPerShare = pool.accRewardTokenPerShare;
    uint256 lpSupply = lpToken[_pid].balanceOf(address(this));
    if (block.timestamp > pool.lastRewardTime && lpSupply != 0) {
      uint256 time = block.timestamp.sub(pool.lastRewardTime);
      uint256 rewardTokenReward = time
        .mul(rewardTokenPerSecond)
        .mul(pool.allocPoint)
        .div(totalAllocPoint);
      accRewardTokenPerShare = accRewardTokenPerShare.add(
        rewardTokenReward.mul(ACC_REWARD_TOKEN_PRECISION).div(lpSupply)
      );
    }
    pending = int256(
      user.amount.mul(accRewardTokenPerShare).div(ACC_REWARD_TOKEN_PRECISION)
    ).sub(user.rewardDebt).toUInt256();
  }

  /// @notice Update reward variables for all pools. Be careful of gas spending!
  /// @param pids Pool IDs of all to be updated. Make sure to update all active pools.
  function massUpdatePools(uint256[] calldata pids) external {
    uint256 len = pids.length;
    for (uint256 i = 0; i < len; ++i) {
      updatePool(pids[i]);
    }
  }

  /// @notice Update reward variables of the given pool.
  /// @param pid The index of the pool. See `poolInfo`.
  /// @return pool Returns the pool that was updated.
  function updatePool(uint256 pid) public returns (PoolInfo memory pool) {
    pool = poolInfo[pid];
    if (block.timestamp > pool.lastRewardTime) {
      uint256 lpSupply = lpToken[pid].balanceOf(address(this));
      if (lpSupply > 0) {
        uint256 time = block.timestamp.sub(pool.lastRewardTime);
        uint256 rewardTokenReward = time
          .mul(rewardTokenPerSecond)
          .mul(pool.allocPoint)
          .div(totalAllocPoint);
        pool.accRewardTokenPerShare = pool.accRewardTokenPerShare.add(
          (rewardTokenReward.mul(ACC_REWARD_TOKEN_PRECISION).div(lpSupply))
        );
      }
      pool.lastRewardTime = block.timestamp;
      poolInfo[pid] = pool;
      emit LogUpdatePool(
        pid,
        pool.lastRewardTime,
        lpSupply,
        pool.accRewardTokenPerShare
      );
    }
  }

  /// @notice Deposit LP tokens to MCV2 for REWARD_TOKEN allocation.
  /// @param pid The index of the pool. See `poolInfo`.
  /// @param amount LP token amount to deposit.
  /// @param to The receiver of `amount` deposit benefit.
  function deposit(
    uint256 pid,
    uint256 amount,
    address to
  ) public {
    PoolInfo memory pool = updatePool(pid);
    UserInfo storage user = userInfo[pid][to];

    // Effects
    user.amount = user.amount.add(amount);
    user.rewardDebt = user.rewardDebt.add(
      int256(
        amount.mul(pool.accRewardTokenPerShare).div(ACC_REWARD_TOKEN_PRECISION)
      )
    );

    // Interactions
    IRewarder _rewarder = rewarder[pid];
    if (address(_rewarder) != address(0)) {
      _rewarder.onRewardTokenReward(pid, to, to, 0, user.amount);
    }

    lpToken[pid].safeTransferFrom(msg.sender, address(this), amount);

    emit Deposit(msg.sender, pid, amount, to);
  }

  /// @notice Withdraw LP tokens from MCV2.
  /// @param pid The index of the pool. See `poolInfo`.
  /// @param amount LP token amount to withdraw.
  /// @param to Receiver of the LP tokens.
  function withdraw(
    uint256 pid,
    uint256 amount,
    address to
  ) public {
    PoolInfo memory pool = updatePool(pid);
    UserInfo storage user = userInfo[pid][msg.sender];

    // Effects
    user.rewardDebt = user.rewardDebt.sub(
      int256(
        amount.mul(pool.accRewardTokenPerShare).div(ACC_REWARD_TOKEN_PRECISION)
      )
    );
    user.amount = user.amount.sub(amount);

    // Interactions
    IRewarder _rewarder = rewarder[pid];
    if (address(_rewarder) != address(0)) {
      _rewarder.onRewardTokenReward(pid, msg.sender, to, 0, user.amount);
    }

    lpToken[pid].safeTransfer(to, amount);

    emit Withdraw(msg.sender, pid, amount, to);
  }

  /// @notice Harvest proceeds for transaction sender to `to`.
  /// @param pid The index of the pool. See `poolInfo`.
  /// @param to Receiver of REWARD_TOKEN rewards.
  function harvest(uint256 pid, address to) public {
    PoolInfo memory pool = updatePool(pid);
    UserInfo storage user = userInfo[pid][msg.sender];
    int256 accumulatedRewardToken = int256(
      user.amount.mul(pool.accRewardTokenPerShare).div(
        ACC_REWARD_TOKEN_PRECISION
      )
    );
    uint256 _pendingRewardToken = accumulatedRewardToken
      .sub(user.rewardDebt)
      .toUInt256();

    // Effects
    user.rewardDebt = accumulatedRewardToken;

    // Interactions
    if (_pendingRewardToken != 0) {
      REWARD_TOKEN.safeTransfer(to, _pendingRewardToken);
    }

    IRewarder _rewarder = rewarder[pid];
    if (address(_rewarder) != address(0)) {
      _rewarder.onRewardTokenReward(
        pid,
        msg.sender,
        to,
        _pendingRewardToken,
        user.amount
      );
    }

    emit Harvest(msg.sender, pid, _pendingRewardToken);
  }

  /// @notice Withdraw LP tokens from MCV2 and harvest proceeds for transaction sender to `to`.
  /// @param pid The index of the pool. See `poolInfo`.
  /// @param amount LP token amount to withdraw.
  /// @param to Receiver of the LP tokens and REWARD_TOKEN rewards.
  function withdrawAndHarvest(
    uint256 pid,
    uint256 amount,
    address to
  ) public {
    PoolInfo memory pool = updatePool(pid);
    UserInfo storage user = userInfo[pid][msg.sender];
    int256 accumulatedRewardToken = int256(
      user.amount.mul(pool.accRewardTokenPerShare).div(
        ACC_REWARD_TOKEN_PRECISION
      )
    );
    uint256 _pendingRewardToken = accumulatedRewardToken
      .sub(user.rewardDebt)
      .toUInt256();

    // Effects
    user.rewardDebt = accumulatedRewardToken.sub(
      int256(
        amount.mul(pool.accRewardTokenPerShare).div(ACC_REWARD_TOKEN_PRECISION)
      )
    );
    user.amount = user.amount.sub(amount);

    // Interactions
    REWARD_TOKEN.safeTransfer(to, _pendingRewardToken);

    IRewarder _rewarder = rewarder[pid];
    if (address(_rewarder) != address(0)) {
      _rewarder.onRewardTokenReward(
        pid,
        msg.sender,
        to,
        _pendingRewardToken,
        user.amount
      );
    }

    lpToken[pid].safeTransfer(to, amount);

    emit Withdraw(msg.sender, pid, amount, to);
    emit Harvest(msg.sender, pid, _pendingRewardToken);
  }

  /// @notice Withdraw without caring about rewards. EMERGENCY ONLY.
  /// @param pid The index of the pool. See `poolInfo`.
  /// @param to Receiver of the LP tokens.
  function emergencyWithdraw(uint256 pid, address to) public {
    UserInfo storage user = userInfo[pid][msg.sender];
    uint256 amount = user.amount;
    user.amount = 0;
    user.rewardDebt = 0;

    IRewarder _rewarder = rewarder[pid];
    if (address(_rewarder) != address(0)) {
      _rewarder.onRewardTokenReward(pid, msg.sender, to, 0, 0);
    }

    // Note: transfer can fail or succeed if `amount` is zero.
    lpToken[pid].safeTransfer(to, amount);
    emit EmergencyWithdraw(msg.sender, pid, amount, to);
  }

  function setRewardsManager(address _rewardsManager) public onlyOwner {
    rewardsManager = _rewardsManager;
  }

  modifier onlyOwnerOrRewardsManager() {
    require(rewardsManager != address(0), 'Rewards Manager not set');
    require(
      owner() == msg.sender || msg.sender == rewardsManager,
      'Caller is not owner or rewards manager'
    );
    _;
  }
}

// File: @openzeppelin/contracts/access/Ownable.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "../utils/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.
 *
 * 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: @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



// SPDX-License-Identifier: MIT

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/token/ERC20/SafeERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

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");
        }
    }
}

// File: @openzeppelin/contracts/utils/ReentrancyGuard.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @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].
 */
abstract 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;
    }
}

// File: contracts/lib/SignedSafeMath.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;

library SignedSafeMath {
    int256 constant private _INT256_MIN = -2**255;

    /**
     * @dev Returns the multiplication of two signed integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(int256 a, int256 b) internal pure returns (int256) {
        // 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;
        }

        require(!(a == -1 && b == _INT256_MIN), "SignedSafeMath: multiplication overflow");

        int256 c = a * b;
        require(c / a == b, "SignedSafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the integer division of two signed 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(int256 a, int256 b) internal pure returns (int256) {
        require(b != 0, "SignedSafeMath: division by zero");
        require(!(b == -1 && a == _INT256_MIN), "SignedSafeMath: division overflow");

        int256 c = a / b;

        return c;
    }

    /**
     * @dev Returns the subtraction of two signed integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(int256 a, int256 b) internal pure returns (int256) {
        int256 c = a - b;
        require((b >= 0 && c <= a) || (b < 0 && c > a), "SignedSafeMath: subtraction overflow");

        return c;
    }

    /**
     * @dev Returns the addition of two signed integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(int256 a, int256 b) internal pure returns (int256) {
        int256 c = a + b;
        require((b >= 0 && c >= a) || (b < 0 && c < a), "SignedSafeMath: addition overflow");

        return c;
    }

    function toUInt256(int256 a) internal pure returns (uint256) {
        require(a >= 0, "Integer < 0");
        return uint256(a);
    }
}

// File: contracts/interfaces/IRewarder.sol



//SPDX-License-Identifier: Unlicense
pragma solidity ^0.6.12;

import {IERC20} from '@openzeppelin/contracts/token/ERC20/IERC20.sol';

interface IRewarder {
    function onRewardTokenReward(uint256 pid, address user, address recipient, uint256 rewardTokenAmount, uint256 newLpAmount) external;
    function pendingTokens(uint256 pid, address user, uint256 rewardTokenAmount) external view returns (IERC20[] memory, uint256[] memory);
}

// File: @openzeppelin/contracts/utils/Context.sol



// SPDX-License-Identifier: MIT

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/utils/Address.sol



// SPDX-License-Identifier: MIT

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);
            }
        }
    }
}