/**
 *Submitted for verification at BscScan.com on 2021-10-30
*/

// SPDX-License-Identifier: MIT

pragma solidity ^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/utils/Address.sol@v4.3.2


pragma solidity ^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;
		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");

		(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");

		(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");

		(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");

		(bool success, bytes memory returndata) = target.delegatecall(data);
		return verifyCallResult(success, returndata, errorMessage);
	}

	/**
	 * @dev Tool to verifies that a low level call was successful, and revert if it wasn't, either by bubbling the
	 * revert reason using the provided one.
	 *
	 * _Available since v4.3._
	 */
	function verifyCallResult(
		bool success,
		bytes memory returndata,
		string memory errorMessage
	) internal 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

				assembly {
					let returndata_size := mload(returndata)
					revert(add(32, returndata), returndata_size)
				}
			} else {
				revert(errorMessage);
			}
		}
	}
}


// File @openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol@v4.3.2


pragma solidity ^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 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'
		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) + value;
		_callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
	}

	function safeDecreaseAllowance(
		IERC20 token,
		address spender,
		uint256 value
	) internal {
		unchecked {
			uint256 oldAllowance = token.allowance(address(this), spender);
			require(oldAllowance >= value, "SafeERC20: decreased allowance below zero");
			uint256 newAllowance = oldAllowance - value;
			_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
			require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
		}
	}
}


// File @openzeppelin/contracts/utils/Context.sol@v4.3.2


pragma solidity ^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 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) {
		return msg.sender;
	}

	function _msgData() internal view virtual returns (bytes calldata) {
		return msg.data;
	}
}


// File @openzeppelin/contracts/access/Ownable.sol@v4.3.2


pragma solidity ^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() {
		_setOwner(_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 {
		_setOwner(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");
		_setOwner(newOwner);
	}

	function _setOwner(address newOwner) private {
		address oldOwner = _owner;
		_owner = newOwner;
		emit OwnershipTransferred(oldOwner, newOwner);
	}
}


// File @openzeppelin/contracts/proxy/utils/Initializable.sol@v4.3.2


pragma solidity ^0.8.0;

/**
 * @dev This is a base contract to aid in writing upgradeable contracts, or any kind of contract that will be deployed
 * behind a proxy. Since a proxied contract can't have a constructor, it's common to move constructor logic to an
 * external initializer function, usually called `initialize`. It then becomes necessary to protect this initializer
 * function so it can only be called once. The {initializer} modifier provided by this contract will have this effect.
 *
 * TIP: To avoid leaving the proxy in an uninitialized state, the initializer function should be called as early as
 * possible by providing the encoded function call as the `_data` argument to {ERC1967Proxy-constructor}.
 *
 * CAUTION: When used with inheritance, manual care must be taken to not invoke a parent initializer twice, or to ensure
 * that all initializers are idempotent. This is not verified automatically as constructors are by Solidity.
 */
abstract contract Initializable {
	/**
	 * @dev Indicates that the contract has been initialized.
	 */
	bool private _initialized;

	/**
	 * @dev Indicates that the contract is in the process of being initialized.
	 */
	bool private _initializing;

	/**
	 * @dev Modifier to protect an initializer function from being invoked twice.
	 */
	modifier initializer() {
		require(_initializing || !_initialized, "Initializable: contract is already initialized");

		bool isTopLevelCall = !_initializing;
		if (isTopLevelCall) {
			_initializing = true;
			_initialized = true;
		}

		_;

		if (isTopLevelCall) {
			_initializing = false;
		}
	}
}


// File @openzeppelin/contracts/security/ReentrancyGuard.sol@v4.3.2


pragma solidity ^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() {
		_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/ERC20RewardStakingV4.sol
pragma solidity ^0.8.4;


contract ERC20RewardStakingV4 is ReentrancyGuard, Ownable, Initializable {
	using SafeERC20 for IERC20;

	// Info of each user.
	struct UserInfo {
		uint256 amount;     // How many LP tokens the user has provided.
		uint256 rewardDebt; // Reward debt. See explanation below.
	}

	// Info of each pool.
	struct PoolInfo {
		IERC20 lpToken;           // Address of LP token contract.
		uint256 allocPoint;       // How many allocation points assigned to this pool. Rewards to distribute per block.
		uint256 lastRewardBlock;  // Last block number that Rewards distribution occurs.
		uint256 accRewardTokenPerShare; // Accumulated Rewards per share, times 1e30. See below.
	}

	// The stake token
	IERC20 public STAKE_TOKEN;
	// The reward token
	IERC20 public REWARD_TOKEN;

	// Reward tokens created per block.
	uint256 public rewardPerBlock;

	// Keep track of number of tokens staked in case the contract earns reflect fees
	uint256 public totalStaked = 0;
	// Keep track of number of reward tokens paid to find remaining reward balance
	uint256 public totalRewardsPaid = 0;
	// Keep track of number of reward tokens paid to find remaining reward balance
	uint256 public totalRewardsAllocated = 0;

	// Info of each pool.
	PoolInfo public poolInfo;
	// Info of each user that stakes LP tokens.
	mapping (address => UserInfo) public userInfo;
	// Total allocation poitns. Must be the sum of all allocation points in all pools.
	uint256 private totalAllocPoint = 0;
	// The block number when Reward mining starts.
	uint256 public startBlock;
	// The block number when mining ends.
	uint256 public bonusEndBlock;

	event Deposit(address indexed user, uint256 amount);
	event DepositRewards(uint256 amount);
	event Withdraw(address indexed user, uint256 amount);
	event EmergencyWithdraw(address indexed user, uint256 amount);
	event SkimStakeTokenFees(address indexed user, uint256 amount);
	event LogUpdatePool(uint256 bonusEndBlock, uint256 rewardPerBlock);
	event EmergencyRewardWithdraw(address indexed user, uint256 amount);
	event EmergencySweepWithdraw(address indexed user, IERC20 indexed token, uint256 amount);

	function initialize(
		IERC20 _stakeToken,
		IERC20 _rewardToken,
		uint256 _rewardPerBlock,
		uint256 _startBlock,
		uint256 _bonusEndBlock
	) external initializer
	{
		STAKE_TOKEN = _stakeToken;
		REWARD_TOKEN = _rewardToken;
		rewardPerBlock = _rewardPerBlock;
		startBlock = _startBlock;
		bonusEndBlock = _bonusEndBlock;

		// staking pool
		poolInfo = PoolInfo({
			lpToken: _stakeToken,
			allocPoint: 1000,
			lastRewardBlock: startBlock,
			accRewardTokenPerShare: 0
		});

		totalAllocPoint = 1000;
	}

	// Return reward multiplier over the given _from to _to block.
	function getMultiplier(uint256 _from, uint256 _to) public view returns (uint256) {
		if (_to <= bonusEndBlock) {
			return _to - _from;
		} else if (_from >= bonusEndBlock) {
			return 0;
		} else {
			return bonusEndBlock - _from;
		}
	}

	/// @param  _bonusEndBlock The block when rewards will end
	function setBonusEndBlock(uint256 _bonusEndBlock) external onlyOwner {
		require(_bonusEndBlock > block.number, 'new bonus end block must be greater than current');
		bonusEndBlock = _bonusEndBlock;
		emit LogUpdatePool(bonusEndBlock, rewardPerBlock);
	}

	// View function to see pending Reward on frontend.
	function pendingReward(address _user) external view returns (uint256) {
		UserInfo storage user = userInfo[_user];
		uint256 accRewardTokenPerShare = poolInfo.accRewardTokenPerShare;
		if (block.number > poolInfo.lastRewardBlock && totalStaked != 0) {
			uint256 multiplier = getMultiplier(poolInfo.lastRewardBlock, block.number);
			uint256 tokenReward = multiplier * rewardPerBlock * poolInfo.allocPoint / totalAllocPoint;
			accRewardTokenPerShare = accRewardTokenPerShare + (tokenReward * 1e30 / totalStaked);
		}
		return user.amount * accRewardTokenPerShare / 1e30 - user.rewardDebt;
	}

	// Update reward variables of the given pool to be up-to-date.
	function updatePool() public {
		if (block.number <= poolInfo.lastRewardBlock) {
			return;
		}
		if (totalStaked == 0) {
			poolInfo.lastRewardBlock = block.number;
			return;
		}
		uint256 multiplier = getMultiplier(poolInfo.lastRewardBlock, block.number);
		uint256 tokenReward = multiplier * rewardPerBlock * poolInfo.allocPoint / totalAllocPoint;
		totalRewardsAllocated += tokenReward;
		poolInfo.accRewardTokenPerShare = poolInfo.accRewardTokenPerShare + (tokenReward * 1e30 / totalStaked);
		poolInfo.lastRewardBlock = block.number;
	}


	/// Deposit staking token into the contract to earn rewards.
	/// @dev Since this contract needs to be supplied with rewards we are
	///  sending the balance of the contract if the pending rewards are higher
	/// @param _amount The amount of staking tokens to deposit
	function deposit(uint256 _amount) external nonReentrant {
		UserInfo storage user = userInfo[msg.sender];
		updatePool();
		if (user.amount > 0) {
			uint256 pending = user.amount * poolInfo.accRewardTokenPerShare / 1e30 - user.rewardDebt;
			if(pending > 0) {
				// If rewardBalance is low then revert to avoid losing the user's rewards
				require(rewardBalance() >= pending, "insufficient reward balance");
				safeTransferRewardInternal(address(msg.sender), pending);
			}
		}

		uint256 finalDepositAmount = 0;
		if (_amount > 0) {
			uint256 preStakeBalance = STAKE_TOKEN.balanceOf(address(this));
			poolInfo.lpToken.safeTransferFrom(address(msg.sender), address(this), _amount);
			finalDepositAmount = STAKE_TOKEN.balanceOf(address(this)) - preStakeBalance;
			user.amount = user.amount + finalDepositAmount;
			totalStaked = totalStaked + finalDepositAmount;
		}
		user.rewardDebt = user.amount * poolInfo.accRewardTokenPerShare / 1e30;

		emit Deposit(msg.sender, finalDepositAmount);
	}

	/// Withdraw rewards and/or staked tokens. Pass a 0 amount to withdraw only rewards
	/// @param _amount The amount of staking tokens to withdraw
	function withdraw(uint256 _amount) external nonReentrant {
		UserInfo storage user = userInfo[msg.sender];
		require(user.amount >= _amount, "withdraw: not good");
		updatePool();
		uint256 pending = user.amount * poolInfo.accRewardTokenPerShare / 1e30 - user.rewardDebt;
		if(pending > 0) {
			// If rewardBalance is low then revert to avoid losing the user's rewards
			require(rewardBalance() >= pending, "insufficient reward balance");
			safeTransferRewardInternal(address(msg.sender), pending);
		}

		if(_amount > 0) {
			user.amount = user.amount - _amount;
			poolInfo.lpToken.safeTransfer(address(msg.sender), _amount);
			totalStaked = totalStaked - _amount;
		}

		user.rewardDebt = user.amount * poolInfo.accRewardTokenPerShare / 1e30;

		emit Withdraw(msg.sender, _amount);
	}

	/// Obtain the reward balance of this contract
	/// @return wei balace of conract
	function rewardBalance() public view returns (uint256) {
		uint256 balance = REWARD_TOKEN.balanceOf(address(this));
		if (STAKE_TOKEN == REWARD_TOKEN) {
			return balance - totalStaked;
		}
		return balance;
	}

	/// Get the balance of rewards that have not been harvested
	/// @return wei balance of rewards left to be paid
	function getUnharvestedRewards() public view returns (uint256) {
		return totalRewardsAllocated - totalRewardsPaid;
	}

	// Deposit Rewards into contract
	function depositRewards(uint256 _amount) external {
		require(_amount > 0, 'Deposit value must be greater than 0.');
		REWARD_TOKEN.safeTransferFrom(address(msg.sender), address(this), _amount);
		emit DepositRewards(_amount);
	}

	/// @param _to address to send reward token to
	/// @param _amount value of reward token to transfer
	function safeTransferRewardInternal(address _to, uint256 _amount) internal {
		totalRewardsPaid += _amount;
		REWARD_TOKEN.safeTransfer(_to, _amount);
	}

	/// @dev Obtain the stake balance of this contract
	function totalStakeTokenBalance() public view returns (uint256) {
		if (STAKE_TOKEN == REWARD_TOKEN)
			return totalStaked;
		return STAKE_TOKEN.balanceOf(address(this));
	}

	/// @dev Obtain the stake token fees (if any) earned by reflect token
	/// @notice If STAKE_TOKEN == REWARD_TOKEN there are no fees to skim
	function getStakeTokenFeeBalance() public view returns (uint256) {
		return totalStakeTokenBalance() - totalStaked;
	}

	/* Admin Functions */

	/// @param _rewardPerBlock The amount of reward tokens to be given per block
	function setRewardPerBlock(uint256 _rewardPerBlock) external onlyOwner {
		rewardPerBlock = _rewardPerBlock;
		emit LogUpdatePool(bonusEndBlock, rewardPerBlock);
	}

		/// @dev Remove excess stake tokens earned by reflect fees
	function skimStakeTokenFees(address _to) external onlyOwner {
		uint256 stakeTokenFeeBalance = getStakeTokenFeeBalance();
		STAKE_TOKEN.safeTransfer(_to, stakeTokenFeeBalance);
		emit SkimStakeTokenFees(_to, stakeTokenFeeBalance);
	}

	/* Emergency Functions */

	// Withdraw without caring about rewards. EMERGENCY ONLY.
	function emergencyWithdraw() external nonReentrant {
		UserInfo storage user = userInfo[msg.sender];
		poolInfo.lpToken.safeTransfer(address(msg.sender), user.amount);
		totalStaked = totalStaked - user.amount;
		user.amount = 0;
		user.rewardDebt = 0;
		emit EmergencyWithdraw(msg.sender, user.amount);
	}

	// Withdraw reward. EMERGENCY ONLY.
	function emergencyRewardWithdraw(uint256 _amount) external onlyOwner {
		require(_amount <= rewardBalance(), 'not enough rewards');
		// Withdraw rewards
		REWARD_TOKEN.safeTransfer(msg.sender, _amount);
		emit EmergencyRewardWithdraw(msg.sender, _amount);
	}

	/// @notice A public function to sweep accidental ERC20 transfers to this contract.
	///   Tokens are sent to owner
	/// @param token The address of the ERC20 token to sweep
	function sweepToken(IERC20 token) external onlyOwner {
		require(address(token) != address(STAKE_TOKEN), "can not sweep stake token");
		require(address(token) != address(REWARD_TOKEN), "can not sweep reward token");
		uint256 balance = token.balanceOf(address(this));
		token.safeTransfer(msg.sender, balance);
		emit EmergencySweepWithdraw(msg.sender, token, balance);
	}

}

{
  "compilationTarget": {
    "ERC20RewardStakingV4.sol": "ERC20RewardStakingV4"
  },
  "evmVersion": "london",
  "libraries": {},
  "metadata": {
    "bytecodeHash": "ipfs"
  },
  "optimizer": {
    "enabled": false,
    "runs": 200
  },
  "remappings": []
}