// 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/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/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/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/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);
            }
        }
    }
}

// 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/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/interfaces/uniswap/IUniswapV2Pair.sol



/*
 * Copyright (C) 2020-2021 The Wolfpack
 * This file is part of wolves.finance - https://github.com/wolvesofwallstreet/wolves.finance
 *
 * This file is derived from Uniswap, available under the GNU General Public
 * License 3.0. https://uniswap.org/
 *
 * SPDX-License-Identifier: Apache-2.0 AND GPL-3.0-or-later
 * See the file LICENSES/README.md for more information.
 */

pragma solidity >=0.6.0;

interface IUniswapV2Pair {
  event Approval(address indexed owner, address indexed spender, uint256 value);
  event Transfer(address indexed from, address indexed to, uint256 value);

  function name() external pure returns (string memory);

  function symbol() external pure returns (string memory);

  function decimals() external pure returns (uint8);

  function totalSupply() external view returns (uint256);

  function balanceOf(address owner) external view returns (uint256);

  function allowance(address owner, address spender)
    external
    view
    returns (uint256);

  function approve(address spender, uint256 value) external returns (bool);

  function transfer(address to, uint256 value) external returns (bool);

  function transferFrom(
    address from,
    address to,
    uint256 value
  ) external returns (bool);

  // solhint-disable-next-line func-name-mixedcase
  function DOMAIN_SEPARATOR() external view returns (bytes32);

  // solhint-disable-next-line func-name-mixedcase
  function PERMIT_TYPEHASH() external pure returns (bytes32);

  function nonces(address owner) external view returns (uint256);

  function permit(
    address owner,
    address spender,
    uint256 value,
    uint256 deadline,
    uint8 v,
    bytes32 r,
    bytes32 s
  ) external;

  event Mint(address indexed sender, uint256 amount0, uint256 amount1);
  event Burn(
    address indexed sender,
    uint256 amount0,
    uint256 amount1,
    address indexed to
  );
  event Swap(
    address indexed sender,
    uint256 amount0In,
    uint256 amount1In,
    uint256 amount0Out,
    uint256 amount1Out,
    address indexed to
  );
  event Sync(uint112 reserve0, uint112 reserve1);

  // solhint-disable-next-line func-name-mixedcase
  function MINIMUM_LIQUIDITY() external pure returns (uint256);

  function factory() external view returns (address);

  function token0() external view returns (address);

  function token1() external view returns (address);

  function getReserves()
    external
    view
    returns (
      uint112 reserve0,
      uint112 reserve1,
      uint32 blockTimestampLast
    );

  function price0CumulativeLast() external view returns (uint256);

  function price1CumulativeLast() external view returns (uint256);

  function kLast() external view returns (uint256);

  function mint(address to) external returns (uint256 liquidity);

  function burn(address to) external returns (uint256 amount0, uint256 amount1);

  function swap(
    uint256 amount0Out,
    uint256 amount1Out,
    address to,
    bytes calldata data
  ) external;

  function skim(address to) external;

  function sync() external;

  function initialize(address, address) external;
}

// File: contracts/src/investment/UniV2StakeFarm.sol



/*
 * Copyright (C) 2020-2021 The Wolfpack
 * This file is part of wolves.finance - https://github.com/wolvesofwallstreet/wolves.finance
 *
 * SPDX-License-Identifier: Apache-2.0
 * See the file LICENSES/README.md for more information.
 */

pragma solidity >=0.6.0 <0.8.0;

import '@openzeppelin/contracts/token/ERC20/IERC20.sol';
import '@openzeppelin/contracts/token/ERC20/SafeERC20.sol';
import '@openzeppelin/contracts/math/SafeMath.sol';
import '@openzeppelin/contracts/access/Ownable.sol';
import '@openzeppelin/contracts/utils/ReentrancyGuard.sol';

import './interfaces/IController.sol';
import './interfaces/IFarm.sol';
import './interfaces/IStakeFarm.sol';
import '../../interfaces/uniswap/IUniswapV2Pair.sol';

contract UniV2StakeFarm is IFarm, IStakeFarm, Ownable, ReentrancyGuard {
  using SafeMath for uint256;
  using SafeERC20 for IERC20;

  /* ========== STATE VARIABLES ========== */

  IUniswapV2Pair public stakingToken;
  uint256 public override periodFinish = 0;
  uint256 public rewardRate = 0;
  uint256 public rewardsDuration = 7 days;
  uint256 public lastUpdateTime;
  uint256 public rewardPerTokenStored;
  uint256 private availableRewards;

  mapping(address => uint256) public userRewardPerTokenPaid;
  mapping(address => uint256) public rewards;
  // TODO: Remove next 2 lines after dapp launch (special reward condition)
  mapping(address => uint256) private firstStakeTime;
  uint256 private constant ETH_LIMIT = 2e17;

  uint256 private _totalSupply;
  mapping(address => uint256) private _balances;

  // Unique name of this farm instance, used in controller
  string private _farmName;
  // Uniswap route to get price for token 0 in pair
  IUniswapV2Pair public immutable route;
  // The address of the controller
  IController public controller;
  // The direction of the uniswap pairs
  uint8 public pairDirection;

  /* ========== CONSTRUCTOR ========== */

  constructor(
    address _owner,
    string memory _name,
    address _stakingToken,
    address _rewardToken,
    address _controller,
    address _route
  ) {
    _farmName = _name;
    stakingToken = IUniswapV2Pair(_stakingToken);
    controller = IController(_controller);
    route = IUniswapV2Pair(_route);

    address routeLink;

    /**
     * @dev Calculate the sort order of the keys once to save gas in further steps
     *
     * Our token sort order is:
     * - stakeToken: token0[routeLink], token1[rewardToken]
     * - route:      token0[routeLink], token1[stableCoin]
     *
     * If the sort order differs, we set one bit for each of both
     */
    if (stakingToken.token0() == _rewardToken) {
      pairDirection = 1;
      routeLink = stakingToken.token1();
    } else routeLink = stakingToken.token0();

    if (
      address(_route) != address(0) &&
      IUniswapV2Pair(_route).token1() == routeLink
    ) pairDirection |= 2;
    transferOwnership(_owner);
  }

  /* ========== VIEWS ========== */

  function farmName() external view override returns (string memory) {
    return _farmName;
  }

  function totalSupply() external view returns (uint256) {
    return _totalSupply;
  }

  function balanceOf(address account) external view returns (uint256) {
    return _balances[account];
  }

  function lastTimeRewardApplicable() public view returns (uint256) {
    // solhint-disable-next-line not-rely-on-time
    return block.timestamp < periodFinish ? block.timestamp : periodFinish;
  }

  function rewardPerToken() public view returns (uint256) {
    if (_totalSupply == 0) {
      return rewardPerTokenStored;
    }
    return
      rewardPerTokenStored.add(
        lastTimeRewardApplicable()
          .sub(lastUpdateTime)
          .mul(rewardRate)
          .mul(1e18)
          .div(_totalSupply)
      );
  }

  function earned(address account) public view returns (uint256) {
    return
      _balances[account]
        .mul(rewardPerToken().sub(userRewardPerTokenPaid[account]))
        .div(1e18)
        .add(rewards[account]);
  }

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

  function getUIData(address _user) external view returns (uint256[9] memory) {
    (uint112 reserve0, uint112 reserve1, uint256 price) = _getTokenUiData();
    uint256[9] memory result =
      [
        // Pool
        stakingToken.totalSupply(),
        (uint256(reserve0)),
        (uint256(reserve1)),
        price,
        // Stake
        _totalSupply,
        _balances[_user],
        rewardsDuration,
        rewardRate.mul(rewardsDuration),
        earned(_user)
      ];
    return result;
  }

  /* ========== MUTATIVE FUNCTIONS ========== */

  function stake(uint256 amount)
    external
    override
    nonReentrant
    updateReward(msg.sender)
  {
    require(amount > 0, 'Cannot stake 0');

    /*(uint256 fee) = */
    controller.onDeposit(amount);

    _totalSupply = _totalSupply.add(amount);
    _balances[msg.sender] = _balances[msg.sender].add(amount);
    IERC20(address(stakingToken)).safeTransferFrom(
      msg.sender,
      address(this),
      amount
    );

    // TODO: Remove after launch
    if (
      firstStakeTime[msg.sender] == 0 &&
      _ethAmount(_balances[msg.sender]) >= ETH_LIMIT
      // solhint-disable-next-line not-rely-on-time
    ) firstStakeTime[msg.sender] = block.timestamp;

    emit Staked(msg.sender, amount);
  }

  function unstake(uint256 amount)
    public
    override
    nonReentrant
    updateReward(msg.sender)
  {
    require(amount > 0, 'Cannot withdraw 0');

    /*(uint256 fee) = */
    controller.onWithdraw(amount);

    _totalSupply = _totalSupply.sub(amount);
    _balances[msg.sender] = _balances[msg.sender].sub(amount);
    IERC20(address(stakingToken)).safeTransfer(msg.sender, amount);

    // TODO: Remove after launch
    if (
      firstStakeTime[msg.sender] > 0 &&
      (_balances[msg.sender] == 0 ||
        _ethAmount(_balances[msg.sender]) < ETH_LIMIT)
    ) firstStakeTime[msg.sender] = 0;

    emit Unstaked(msg.sender, amount);
  }

  function transfer(address recipient, uint256 amount)
    external
    override
    updateReward(msg.sender)
    updateReward(recipient)
  {
    require(recipient != address(0), 'invalid address');
    require(amount > 0, 'zero amount');

    _balances[msg.sender] = _balances[msg.sender].sub(amount);
    _balances[recipient] = _balances[recipient].add(amount);
    emit Transfered(msg.sender, recipient, amount);
  }

  function getReward() public override nonReentrant updateReward(msg.sender) {
    uint256 reward = rewards[msg.sender];
    if (reward > 0) {
      rewards[msg.sender] = 0;
      availableRewards = availableRewards.sub(reward);
      controller.payOutRewards(msg.sender, reward);
      emit RewardPaid(msg.sender, reward);
    }
  }

  function exit() external override {
    unstake(_balances[msg.sender]);
    getReward();
  }

  /* ========== RESTRICTED FUNCTIONS ========== */

  function setController(address newController)
    external
    override
    onlyController
  {
    controller = IController(newController);
    emit ControllerChanged(newController);
  }

  function notifyRewardAmount(uint256 reward)
    external
    override
    onlyController
    updateReward(address(0))
  {
    // solhint-disable-next-line not-rely-on-time
    if (block.timestamp >= periodFinish) {
      rewardRate = reward.div(rewardsDuration);
    } else {
      // solhint-disable-next-line not-rely-on-time
      uint256 remaining = periodFinish.sub(block.timestamp);
      uint256 leftover = remaining.mul(rewardRate);
      rewardRate = reward.add(leftover).div(rewardsDuration);
    }
    availableRewards = availableRewards.add(reward);

    // Ensure the provided reward amount is not more than the balance in the
    // contract.
    //
    // This keeps the reward rate in the right range, preventing overflows due
    // to very high values of rewardRate in the earned and rewardsPerToken
    // functions.
    //
    // Reward + leftover must be less than 2^256 / 10^18 to avoid overflow.
    //
    require(
      rewardRate <= availableRewards.div(rewardsDuration),
      'Provided reward too high'
    );

    // solhint-disable-next-line not-rely-on-time
    lastUpdateTime = block.timestamp;
    // solhint-disable-next-line not-rely-on-time
    periodFinish = block.timestamp.add(rewardsDuration);

    emit RewardAdded(reward);
  }

  // We don't have any rebalancing here
  // solhint-disable-next-line no-empty-blocks
  function rebalance() external override onlyController {}

  // Added to support recovering LP Rewards from other systems to be distributed to holders
  function recoverERC20(address tokenAddress, uint256 tokenAmount)
    external
    onlyOwner
  {
    // Cannot recover the staking token or the rewards token
    require(
      tokenAddress != address(stakingToken),
      'pool tokens not recoverable'
    );
    IERC20(tokenAddress).safeTransfer(owner(), tokenAmount);
    emit Recovered(tokenAddress, tokenAmount);
  }

  function setRewardsDuration(uint256 _rewardsDuration)
    external
    override
    onlyOwner
  {
    require(
      // solhint-disable-next-line not-rely-on-time
      periodFinish == 0 || block.timestamp > periodFinish,
      'reward period not finished'
    );
    rewardsDuration = _rewardsDuration;
    emit RewardsDurationUpdated(rewardsDuration);
  }

  /* ========== PRIVATE ========== */

  function _ethAmount(uint256 amountToken) private view returns (uint256) {
    (uint112 reserve0, uint112 reserve1, ) = stakingToken.getReserves();

    // RouteLink is token1, swap
    if ((pairDirection & 1) != 0) reserve0 = reserve1;

    return (uint256(reserve0).mul(amountToken)).div(stakingToken.totalSupply());
  }

  /**
   * @dev Returns the reserves in order: ETH -> Token, ETH/stable
   */
  function _getTokenUiData()
    internal
    view
    returns (
      uint112,
      uint112,
      uint256
    )
  {
    (uint112 reserve0, uint112 reserve1, ) = stakingToken.getReserves();
    (uint112 reserve0R, uint112 reserve1R, ) =
      address(route) != address(0) ? route.getReserves() : (1, 1, 0);

    uint112 swap;

    // RouteLink is token1, swap
    if ((pairDirection & 1) != 0) {
      swap = reserve0;
      reserve0 = reserve1;
      reserve1 = swap;
    }

    // RouteLink is token1, swap
    if ((pairDirection & 2) != 0) {
      swap = reserve0R;
      reserve0R = reserve1R;
      reserve1R = swap;
    }

    return (reserve0, reserve1, uint256(reserve0R).mul(1e18).div(reserve1R));
  }

  /* ========== MODIFIERS ========== */

  modifier onlyController {
    require(_msgSender() == address(controller), 'not controller');
    _;
  }

  modifier updateReward(address account) {
    rewardPerTokenStored = rewardPerToken();
    lastUpdateTime = lastTimeRewardApplicable();
    if (account != address(0)) {
      rewards[account] = earned(account);
      userRewardPerTokenPaid[account] = rewardPerTokenStored;
    }
    _;
  }

  /* ========== EVENTS ========== */

  event RewardAdded(uint256 reward);
  event Staked(address indexed user, uint256 amount);
  event Unstaked(address indexed user, uint256 amount);
  event Transfered(address indexed from, address indexed to, uint256 amount);
  event RewardPaid(address indexed user, uint256 reward);
  event RewardsDurationUpdated(uint256 newDuration);
  event Recovered(address token, uint256 amount);
  event ControllerChanged(address newController);
}

// File: contracts/src/investment/interfaces/IController.sol



/*
 * Copyright (C) 2020-2021 The Wolfpack
 * This file is part of wolves.finance - https://github.com/wolvesofwallstreet/wolves.finance
 *
 * SPDX-License-Identifier: Apache-2.0
 * See the file LICENSES/README.md for more information.
 */

pragma solidity >=0.6.0 <0.8.0;

interface IController {
  /**
   * @dev Revert on failure, return deposit fee in 1e-18/fee notation on success
   */
  function onDeposit(uint256 amount) external view returns (uint256 fee);

  /**
   * @dev Revert on failure, return withdrawal fee in 1e-18/fee notation on success
   */
  function onWithdraw(uint256 amount) external view returns (uint256 fee);

  /**
   * @dev Distribute rewards to sender and fee to internal contracts
   */
  function payOutRewards(address recipient, uint256 amount) external;
}

// File: contracts/src/investment/interfaces/IFarm.sol



/*
 * Copyright (C) 2020-2021 The Wolfpack
 * This file is part of wolves.finance - https://github.com/wolvesofwallstreet/wolves.finance
 *
 * SPDX-License-Identifier: Apache-2.0
 * See the file LICENSES/README.md for more information.
 */

pragma solidity >=0.6.0 <0.8.0;

interface IFarm {
  /**
   * @dev Return a unique farm name
   */
  function farmName() external view returns (string memory);

  /**
   * @dev Return when reward period is finished (UTC timestamp)
   */
  function periodFinish() external view returns (uint256);

  /**
   * @dev Sets a new controller, can only called by current controller
   */
  function setController(address newController) external;

  /**
   * @dev This function must be called initially and close at the time the
   * reward period ends
   */
  function notifyRewardAmount(uint256 reward) external;

  /**
   * @dev Set the duration of farm rewards, to continue rewards,
   * notifyRewardAmount() has to called for the next period
   */
  function setRewardsDuration(uint256 _rewardsDuration) external;

  /**
   * @dev Rebalance strategies (if implemented)
   */
  function rebalance() external;
}

// File: contracts/src/investment/interfaces/IStakeFarm.sol



/*
 * Copyright (C) 2020-2021 The Wolfpack
 * This file is part of wolves.finance - https://github.com/wolvesofwallstreet/wolves.finance
 *
 * SPDX-License-Identifier: Apache-2.0
 * See the file LICENSES/README.md for more information.
 */

pragma solidity >=0.6.0 <0.8.0;

/**
 * @title IStakeFarm
 *
 * @dev IStakeFarm is the business logic interface to staking farms.
 */

interface IStakeFarm {
  /**
   * @dev Stake amount of ERC20 tokens and earn rewards
   */
  function stake(uint256 amount) external;

  /**
   * @dev Unstake amount of previous staked tokens, rewards will not be claimed
   */
  function unstake(uint256 amount) external;

  /**
   * @dev Claim rewards harvested during stake time
   */
  function getReward() external;

  /**
   * @dev Unstake and getRewards in a single step
   */
  function exit() external;

  /**
   * @dev Transfer amount of stake from msg.sender to recipient.
   */
  function transfer(address recipient, uint256 amount) external;
}