pragma solidity 0.8.13;

//
// OpenZeppelin Contracts v4.4.1 (utils/Context.sol)
/**
 * @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;
  }
}

//
// OpenZeppelin Contracts v4.4.1 (access/Ownable.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() {
    _transferOwnership(_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 {
    _transferOwnership(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");
    _transferOwnership(newOwner);
  }

  /**
   * @dev Transfers ownership of the contract to a new account (`newOwner`).
   * Internal function without access restriction.
   */
  function _transferOwnership(address newOwner) internal virtual {
    address oldOwner = _owner;
    _owner = newOwner;
    emit OwnershipTransferred(oldOwner, newOwner);
  }
}

//
// OpenZeppelin Contracts v4.4.1 (security/ReentrancyGuard.sol)
/**
 * @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 making 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;
  }
}

//
// OpenZeppelin Contracts (last updated v4.5.0) (token/ERC20/IERC20.sol)
/**
 * @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 `to`.
   *
   * Returns a boolean value indicating whether the operation succeeded.
   *
   * Emits a {Transfer} event.
   */
  function transfer(address to, 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 `from` to `to` 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 from,
    address to,
    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);
}

//
// OpenZeppelin Contracts (last updated v4.5.0) (utils/Address.sol)
/**
 * @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
   * ====
   *
   * [IMPORTANT]
   * ====
   * You shouldn't rely on `isContract` to protect against flash loan attacks!
   *
   * Preventing calls from contracts is highly discouraged. It breaks composability, breaks support for smart wallets
   * like Gnosis Safe, and does not provide security since it can be circumvented by calling from a contract
   * constructor.
   * ====
   */
  function isContract(address account) internal view returns (bool) {
    // This method relies on extcodesize/address.code.length, which returns 0
    // for contracts in construction, since the code is only stored at the end
    // of the constructor execution.

    return account.code.length > 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);
      }
    }
  }
}

//
// OpenZeppelin Contracts v4.4.1 (token/ERC20/utils/SafeERC20.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 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"
      );
    }
  }
}

//
// OpenZeppelin Contracts v4.4.1 (utils/math/SafeMath.sol)
// CAUTION
// This version of SafeMath should only be used with Solidity 0.8 or later,
// because it relies on the compiler's built in overflow checks.
/**
 * @dev Wrappers over Solidity's arithmetic operations.
 *
 * NOTE: `SafeMath` is generally not needed starting with Solidity 0.8, since the compiler
 * now has built in overflow checking.
 */
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) {
    unchecked {
      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) {
    unchecked {
      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) {
    unchecked {
      // 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) {
    unchecked {
      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) {
    unchecked {
      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) {
    return a + b;
  }

  /**
   * @dev Returns the subtraction of two unsigned integers, reverting on
   * overflow (when the result is negative).
   *
   * Counterpart to Solidity's `-` operator.
   *
   * Requirements:
   *
   * - Subtraction cannot overflow.
   */
  function sub(uint256 a, uint256 b) internal pure returns (uint256) {
    return 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) {
    return a * b;
  }

  /**
   * @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.
   *
   * Requirements:
   *
   * - The divisor cannot be zero.
   */
  function div(uint256 a, uint256 b) internal pure returns (uint256) {
    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) {
    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) {
    unchecked {
      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.
   *
   * 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) {
    unchecked {
      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) {
    unchecked {
      require(b > 0, errorMessage);
      return a % b;
    }
  }
}

//
// OpenZeppelin Contracts v4.4.1 (interfaces/IERC20.sol)
interface IZenGarden {
  struct UserInfo {
    uint256 amount;
    uint256 rewardDebt;
  }

  struct PoolInfo {
    IERC20 erc20Token;
    uint256 allocPoint;
    uint256 lastRewardBlock;
    uint256 accumulatedHNRPerShare;
    uint256 maxStakingAmountPerUser;
  }

  event PaymentReceived(address from, uint256 amount);

  event Deposit(address indexed user, uint256 indexed pid, uint256 amount);

  event Withdraw(address indexed user, uint256 indexed pid, uint256 amount);

  event EmergencyWithdraw(
    address indexed user,
    uint256 indexed pid,
    uint256 amount
  );
}

//
contract ZenGarden is Ownable, ReentrancyGuard, IZenGarden {
  using SafeMath for uint256;
  using SafeERC20 for IERC20;

  IERC20 public HNR;
  PoolInfo[] public poolInfo;

  uint256 public HNRPerBlock;
  uint256 public maxHNRAvailableForFarming;
  uint256 public totalAllocation;
  uint256 public startBlock;
  uint256 public endBlock;

  mapping(address => bool) isErc20TokenWhitelisted;
  mapping(uint256 => mapping(address => UserInfo)) public userInfo;

  constructor(
    IERC20 _HNR,
    uint256 _maxHNRAvailableForFarming,
    uint256 blocksPerDay,
    uint256 numberOfDays
  ) {
    require(
      address(_HNR) != address(0),
      "constructor: _HNR must not be zero address"
    );
    require(
      _maxHNRAvailableForFarming > 0,
      "constructor: _maxHNRAvailableForFarming must be greater than zero"
    );

    HNR = _HNR;
    maxHNRAvailableForFarming = _maxHNRAvailableForFarming;
    // start at the moment of the deploy + slight delay to ensure fairness
    startBlock = block.number + uint256(5000);
    endBlock = startBlock.add(blocksPerDay.mul(numberOfDays));

    uint256 numberOfBlocksForFarming = endBlock.sub(startBlock);
    HNRPerBlock = maxHNRAvailableForFarming.div(numberOfBlocksForFarming);
  }

  receive() external payable virtual {
    emit PaymentReceived(_msgSender(), msg.value);
  }

  fallback() external payable {
    payable(owner()).transfer(msg.value);
  }

  function blockNumber() external view returns (uint256) {
    return block.number;
  }

  function numberOfPools() external view returns (uint256) {
    return poolInfo.length;
  }

  function add(
    uint256 _allocPoint,
    IERC20 _erc20Token,
    uint256 _maxStakingAmountPerUser,
    bool _withUpdate
  ) public onlyOwner {
    require(block.number < endBlock, "add: must be before end");
    address erc20TokenAddress = address(_erc20Token);
    require(
      erc20TokenAddress != address(0),
      "add: _erc20Token must not be zero address"
    );
    require(
      isErc20TokenWhitelisted[erc20TokenAddress] == false,
      "add: already whitelisted"
    );
    require(
      _maxStakingAmountPerUser > 0,
      "add: _maxStakingAmountPerUser must be greater than zero"
    );

    if (_withUpdate) {
      massUpdatePools();
    }

    uint256 lastRewardBlock = block.number > startBlock
      ? block.number
      : startBlock;
    totalAllocation = totalAllocation.add(_allocPoint);
    poolInfo.push(
      PoolInfo({
        erc20Token: _erc20Token,
        allocPoint: _allocPoint,
        lastRewardBlock: lastRewardBlock,
        accumulatedHNRPerShare: 0,
        maxStakingAmountPerUser: _maxStakingAmountPerUser
      })
    );

    isErc20TokenWhitelisted[erc20TokenAddress] = true;
  }

  function set(
    uint256 _pid,
    uint256 _allocPoint,
    uint256 _maxStakingAmountPerUser,
    bool _withUpdate
  ) public onlyOwner {
    require(block.number < endBlock, "set: must be before end");
    require(_pid < poolInfo.length, "set: invalid _pid");
    require(
      _maxStakingAmountPerUser > 0,
      "set: _maxStakingAmountPerUser must be greater than zero"
    );

    if (_withUpdate) {
      massUpdatePools();
    }

    totalAllocation = totalAllocation.sub(poolInfo[_pid].allocPoint).add(
      _allocPoint
    );

    poolInfo[_pid].allocPoint = _allocPoint;
    poolInfo[_pid].maxStakingAmountPerUser = _maxStakingAmountPerUser;
  }

  function pendingHNR(uint256 _pid, address _user)
    external
    view
    returns (uint256)
  {
    require(_pid < poolInfo.length, "pendingHNR: invalid _pid");

    PoolInfo storage pool = poolInfo[_pid];
    UserInfo storage user = userInfo[_pid][_user];

    uint256 accHNRPerShare = pool.accumulatedHNRPerShare;
    uint256 lpSupply = pool.erc20Token.balanceOf(address(this));

    if (block.number > pool.lastRewardBlock && lpSupply != 0) {
      uint256 maxEndBlock = block.number <= endBlock ? block.number : endBlock;
      uint256 multiplier = getMultiplier(pool.lastRewardBlock, maxEndBlock);
      uint256 hnrReward = multiplier.mul(HNRPerBlock).mul(pool.allocPoint).div(
        totalAllocation
      );
      accHNRPerShare = accHNRPerShare.add(hnrReward.mul(1e18).div(lpSupply));
    }

    return user.amount.mul(accHNRPerShare).div(1e18).sub(user.rewardDebt);
  }

  function massUpdatePools() public {
    uint256 length = poolInfo.length;
    for (uint256 pid = 0; pid < length; pid = uncheckedIncrement(pid)) {
      updatePool(pid);
    }
  }

  function uncheckedIncrement(uint256 index) internal pure returns (uint256) {
    unchecked {
      return index + 1;
    }
  }

  function updatePool(uint256 _pid) public {
    require(_pid < poolInfo.length, "updatePool: invalid _pid");

    PoolInfo storage pool = poolInfo[_pid];
    if (block.number <= pool.lastRewardBlock) {
      return;
    }

    uint256 erc20Supply = pool.erc20Token.balanceOf(address(this));
    if (erc20Supply == 0) {
      pool.lastRewardBlock = block.number;
      return;
    }

    uint256 maxEndBlock = block.number <= endBlock ? block.number : endBlock;
    uint256 multiplier = getMultiplier(pool.lastRewardBlock, maxEndBlock);

    if (multiplier == 0) {
      return;
    }

    uint256 hnrReward = multiplier.mul(HNRPerBlock).mul(pool.allocPoint).div(
      totalAllocation
    );

    pool.accumulatedHNRPerShare = pool.accumulatedHNRPerShare.add(
      hnrReward.mul(1e18).div(erc20Supply)
    );
    pool.lastRewardBlock = maxEndBlock;
  }

  function deposit(uint256 _pid, uint256 _amount) external nonReentrant {
    PoolInfo storage pool = poolInfo[_pid];
    UserInfo storage user = userInfo[_pid][msg.sender];

    require(
      user.amount.add(_amount) <= pool.maxStakingAmountPerUser,
      "deposit: can not exceed max staking amount per user"
    );

    updatePool(_pid);

    if (user.amount > 0) {
      uint256 pending = user
        .amount
        .mul(pool.accumulatedHNRPerShare)
        .div(1e18)
        .sub(user.rewardDebt);
      if (pending > 0) {
        safeHNRTransfer(msg.sender, pending);
      }
    }

    if (_amount > 0) {
      pool.erc20Token.safeTransferFrom(
        address(msg.sender),
        address(this),
        _amount
      );
      user.amount = user.amount.add(_amount);
    }

    user.rewardDebt = user.amount.mul(pool.accumulatedHNRPerShare).div(1e18);
    emit Deposit(msg.sender, _pid, _amount);
  }

  function withdraw(uint256 _pid, uint256 _amount) external nonReentrant {
    PoolInfo storage pool = poolInfo[_pid];
    UserInfo storage user = userInfo[_pid][msg.sender];

    require(user.amount >= _amount, "withdraw: _amount not good");

    updatePool(_pid);

    uint256 pending = user
      .amount
      .mul(pool.accumulatedHNRPerShare)
      .div(1e18)
      .sub(user.rewardDebt);
    if (pending > 0) {
      safeHNRTransfer(msg.sender, pending);
    }

    if (_amount > 0) {
      user.amount = user.amount.sub(_amount);
      pool.erc20Token.safeTransfer(address(msg.sender), _amount);
    }

    user.rewardDebt = user.amount.mul(pool.accumulatedHNRPerShare).div(1e18);
    emit Withdraw(msg.sender, _pid, _amount);
  }

  function emergencyWithdraw(uint256 _pid) external nonReentrant {
    require(_pid < poolInfo.length, "updatePool: invalid _pid");

    PoolInfo storage pool = poolInfo[_pid];
    UserInfo storage user = userInfo[_pid][msg.sender];

    uint256 amount = user.amount;
    user.amount = 0;
    user.rewardDebt = 0;

    pool.erc20Token.safeTransfer(address(msg.sender), amount);
    emit EmergencyWithdraw(msg.sender, _pid, amount);
  }

  function safeHNRTransfer(address _to, uint256 _amount) private {
    uint256 hnrBalance = HNR.balanceOf(address(this));
    HNR.transfer(_to, _amount > hnrBalance ? hnrBalance : _amount);
  }

  function getMultiplier(uint256 _from, uint256 _to)
    private
    pure
    returns (uint256)
  {
    return _to.sub(_from);
  }

  function updateRewardPerBlockAndEndBlock(
    uint256 newRewardPerBlock,
    uint256 newEndBlock
  ) external onlyOwner {
    if (block.number >= startBlock) {
      massUpdatePools();
    }
    require(
      newEndBlock > block.number,
      "Owner: New endBlock must be after current block"
    );
    require(
      newEndBlock > startBlock,
      "Owner: New endBlock must be after start block"
    );

    endBlock = newEndBlock;
    HNRPerBlock = newRewardPerBlock;
  }

  function adminRewardWithdraw(uint256 amount) external onlyOwner {
    HNR.safeTransfer(msg.sender, amount);
  }
}