// File: contracts/SparkSender.sol



// SPDX-License-Identifier: MIT
pragma solidity =0.8.7;


/// @title Contains 512-bit math functions
/// @notice Facilitates multiplication and division that can have overflow of an intermediate value without any loss of precision
/// @dev Handles "phantom overflow" i.e., allows multiplication and division where an intermediate value overflows 256 bits
library FullMath {
  /// @notice Calculates floor(a×b÷denominator) with full precision. Throws if result overflows a uint256 or denominator == 0
  /// @param a The multiplicand
  /// @param b The multiplier
  /// @param denominator The divisor
  /// @return result The 256-bit result
  /// @dev Credit to Remco Bloemen under MIT license https://xn--2-umb.com/21/muldiv
  function mulDiv(
    uint256 a,
    uint256 b,
    uint256 denominator
  ) internal pure returns (uint256 result) {
    // 512-bit multiply [prod1 prod0] = a * b
    // Compute the product mod 2**256 and mod 2**256 - 1
    // then use the Chinese Remainder Theorem to reconstruct
    // the 512 bit result. The result is stored in two 256
    // variables such that product = prod1 * 2**256 + prod0
    uint256 prod0; // Least significant 256 bits of the product
    uint256 prod1; // Most significant 256 bits of the product
    assembly {
      let mm := mulmod(a, b, not(0))
      prod0 := mul(a, b)
      prod1 := sub(sub(mm, prod0), lt(mm, prod0))
    }

    // Handle non-overflow cases, 256 by 256 division
    if (prod1 == 0) {
      require(denominator > 0);
      assembly {
        result := div(prod0, denominator)
      }
      return result;
    }

    // Make sure the result is less than 2**256.
    // Also prevents denominator == 0
    require(denominator > prod1);

    ///////////////////////////////////////////////
    // 512 by 256 division.
    ///////////////////////////////////////////////

    // Make division exact by subtracting the remainder from [prod1 prod0]
    // Compute remainder using mulmod
    uint256 remainder;
    assembly {
      remainder := mulmod(a, b, denominator)
    }
    // Subtract 256 bit number from 512 bit number
    assembly {
      prod1 := sub(prod1, gt(remainder, prod0))
      prod0 := sub(prod0, remainder)
    }

    // Factor powers of two out of denominator
    // Compute largest power of two divisor of denominator.
    // Always >= 1.
    unchecked {
      uint256 twos = (type(uint256).max - denominator + 1) & denominator;
      // Divide denominator by power of two
      assembly {
        denominator := div(denominator, twos)
      }

      // Divide [prod1 prod0] by the factors of two
      assembly {
        prod0 := div(prod0, twos)
      }
      // Shift in bits from prod1 into prod0. For this we need
      // to flip `twos` such that it is 2**256 / twos.
      // If twos is zero, then it becomes one
      assembly {
        twos := add(div(sub(0, twos), twos), 1)
      }
      prod0 |= prod1 * twos;

      // Invert denominator mod 2**256
      // Now that denominator is an odd number, it has an inverse
      // modulo 2**256 such that denominator * inv = 1 mod 2**256.
      // Compute the inverse by starting with a seed that is correct
      // correct for four bits. That is, denominator * inv = 1 mod 2**4
      uint256 inv = (3 * denominator) ^ 2;
      // Now use Newton-Raphson iteration to improve the precision.
      // Thanks to Hensel's lifting lemma, this also works in modular
      // arithmetic, doubling the correct bits in each step.
      inv *= 2 - denominator * inv; // inverse mod 2**8
      inv *= 2 - denominator * inv; // inverse mod 2**16
      inv *= 2 - denominator * inv; // inverse mod 2**32
      inv *= 2 - denominator * inv; // inverse mod 2**64
      inv *= 2 - denominator * inv; // inverse mod 2**128
      inv *= 2 - denominator * inv; // inverse mod 2**256

      // Because the division is now exact we can divide by multiplying
      // with the modular inverse of denominator. This will give us the
      // correct result modulo 2**256. Since the precoditions guarantee
      // that the outcome is less than 2**256, this is the final result.
      // We don't need to compute the high bits of the result and prod1
      // is no longer required.
      result = prod0 * inv;
      return result;
    }
  }
}


// OpenZeppelin Contracts v4.4.1 (utils/StorageSlot.sol)

/**
 * @dev Library for reading and writing primitive types to specific storage slots.
 *
 * Storage slots are often used to avoid storage conflict when dealing with upgradeable contracts.
 * This library helps with reading and writing to such slots without the need for inline assembly.
 *
 * The functions in this library return Slot structs that contain a `value` member that can be used to read or write.
 *
 * Example usage to set ERC1967 implementation slot:
 * ```
 * contract ERC1967 {
 *     bytes32 internal constant _IMPLEMENTATION_SLOT = 0x360894a13ba1a3210667c828492db98dca3e2076cc3735a920a3ca505d382bbc;
 *
 *     function _getImplementation() internal view returns (address) {
 *         return StorageSlot.getAddressSlot(_IMPLEMENTATION_SLOT).value;
 *     }
 *
 *     function _setImplementation(address newImplementation) internal {
 *         require(Address.isContract(newImplementation), "ERC1967: new implementation is not a contract");
 *         StorageSlot.getAddressSlot(_IMPLEMENTATION_SLOT).value = newImplementation;
 *     }
 * }
 * ```
 *
 * _Available since v4.1 for `address`, `bool`, `bytes32`, and `uint256`._
 */
library StorageSlotUpgradeable {
    struct AddressSlot {
        address value;
    }

    struct BooleanSlot {
        bool value;
    }

    struct Bytes32Slot {
        bytes32 value;
    }

    struct Uint256Slot {
        uint256 value;
    }

    /**
     * @dev Returns an `AddressSlot` with member `value` located at `slot`.
     */
    function getAddressSlot(bytes32 slot) internal pure returns (AddressSlot storage r) {
        assembly {
            r.slot := slot
        }
    }

    /**
     * @dev Returns an `BooleanSlot` with member `value` located at `slot`.
     */
    function getBooleanSlot(bytes32 slot) internal pure returns (BooleanSlot storage r) {
        assembly {
            r.slot := slot
        }
    }

    /**
     * @dev Returns an `Bytes32Slot` with member `value` located at `slot`.
     */
    function getBytes32Slot(bytes32 slot) internal pure returns (Bytes32Slot storage r) {
        assembly {
            r.slot := slot
        }
    }

    /**
     * @dev Returns an `Uint256Slot` with member `value` located at `slot`.
     */
    function getUint256Slot(bytes32 slot) internal pure returns (Uint256Slot storage r) {
        assembly {
            r.slot := slot
        }
    }
}


// OpenZeppelin Contracts v4.4.1 (proxy/beacon/IBeacon.sol)


/**
 * @dev This is the interface that {BeaconProxy} expects of its beacon.
 */
interface IBeaconUpgradeable {
    /**
     * @dev Must return an address that can be used as a delegate call target.
     *
     * {BeaconProxy} will check that this address is a contract.
     */
    function implementation() external view returns (address);
}

// OpenZeppelin Contracts (last updated v4.5.0) (interfaces/draft-IERC1822.sol)


/**
 * @dev ERC1822: Universal Upgradeable Proxy Standard (UUPS) documents a method for upgradeability through a simplified
 * proxy whose upgrades are fully controlled by the current implementation.
 */
interface IERC1822ProxiableUpgradeable {
    /**
     * @dev Returns the storage slot that the proxiable contract assumes is being used to store the implementation
     * address.
     *
     * IMPORTANT: A proxy pointing at a proxiable contract should not be considered proxiable itself, because this risks
     * bricking a proxy that upgrades to it, by delegating to itself until out of gas. Thus it is critical that this
     * function revert if invoked through a proxy.
     */
    function proxiableUUID() external view returns (bytes32);
}


// OpenZeppelin Contracts (last updated v4.5.0) (utils/Address.sol)

/**
 * @dev Collection of functions related to the address type
 */
library AddressUpgradeable {
    /**
     * @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 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 (last updated v4.5.0) (proxy/utils/Initializable.sol)

/**
 * @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 proxied contracts do not make use of 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.
 *
 * [CAUTION]
 * ====
 * Avoid leaving a contract uninitialized.
 *
 * An uninitialized contract can be taken over by an attacker. This applies to both a proxy and its implementation
 * contract, which may impact the proxy. To initialize the implementation contract, you can either invoke the
 * initializer manually, or you can include a constructor to automatically mark it as initialized when it is deployed:
 *
 * [.hljs-theme-light.nopadding]
 * ```
 * /// @custom:oz-upgrades-unsafe-allow constructor
 * constructor() initializer {}
 * ```
 * ====
 */
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() {
        // If the contract is initializing we ignore whether _initialized is set in order to support multiple
        // inheritance patterns, but we only do this in the context of a constructor, because in other contexts the
        // contract may have been reentered.
        require(_initializing ? _isConstructor() : !_initialized, "Initializable: contract is already initialized");

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

        _;

        if (isTopLevelCall) {
            _initializing = false;
        }
    }

    /**
     * @dev Modifier to protect an initialization function so that it can only be invoked by functions with the
     * {initializer} modifier, directly or indirectly.
     */
    modifier onlyInitializing() {
        require(_initializing, "Initializable: contract is not initializing");
        _;
    }

    function _isConstructor() private view returns (bool) {
        return !AddressUpgradeable.isContract(address(this));
    }
}


// OpenZeppelin Contracts (last updated v4.5.0) (proxy/ERC1967/ERC1967Upgrade.sol)

/**
 * @dev This abstract contract provides getters and event emitting update functions for
 * https://eips.ethereum.org/EIPS/eip-1967[EIP1967] slots.
 *
 * _Available since v4.1._
 *
 * @custom:oz-upgrades-unsafe-allow delegatecall
 */
abstract contract ERC1967UpgradeUpgradeable is Initializable {
    function __ERC1967Upgrade_init() internal onlyInitializing {
    }

    function __ERC1967Upgrade_init_unchained() internal onlyInitializing {
    }
    // This is the keccak-256 hash of "eip1967.proxy.rollback" subtracted by 1
    bytes32 private constant _ROLLBACK_SLOT = 0x4910fdfa16fed3260ed0e7147f7cc6da11a60208b5b9406d12a635614ffd9143;

    /**
     * @dev Storage slot with the address of the current implementation.
     * This is the keccak-256 hash of "eip1967.proxy.implementation" subtracted by 1, and is
     * validated in the constructor.
     */
    bytes32 internal constant _IMPLEMENTATION_SLOT = 0x360894a13ba1a3210667c828492db98dca3e2076cc3735a920a3ca505d382bbc;

    /**
     * @dev Emitted when the implementation is upgraded.
     */
    event Upgraded(address indexed implementation);

    /**
     * @dev Returns the current implementation address.
     */
    function _getImplementation() internal view returns (address) {
        return StorageSlotUpgradeable.getAddressSlot(_IMPLEMENTATION_SLOT).value;
    }

    /**
     * @dev Stores a new address in the EIP1967 implementation slot.
     */
    function _setImplementation(address newImplementation) private {
        require(AddressUpgradeable.isContract(newImplementation), "ERC1967: new implementation is not a contract");
        StorageSlotUpgradeable.getAddressSlot(_IMPLEMENTATION_SLOT).value = newImplementation;
    }

    /**
     * @dev Perform implementation upgrade
     *
     * Emits an {Upgraded} event.
     */
    function _upgradeTo(address newImplementation) internal {
        _setImplementation(newImplementation);
        emit Upgraded(newImplementation);
    }

    /**
     * @dev Perform implementation upgrade with additional setup call.
     *
     * Emits an {Upgraded} event.
     */
    function _upgradeToAndCall(
        address newImplementation,
        bytes memory data,
        bool forceCall
    ) internal {
        _upgradeTo(newImplementation);
        if (data.length > 0 || forceCall) {
            _functionDelegateCall(newImplementation, data);
        }
    }

    /**
     * @dev Perform implementation upgrade with security checks for UUPS proxies, and additional setup call.
     *
     * Emits an {Upgraded} event.
     */
    function _upgradeToAndCallUUPS(
        address newImplementation,
        bytes memory data,
        bool forceCall
    ) internal {
        // Upgrades from old implementations will perform a rollback test. This test requires the new
        // implementation to upgrade back to the old, non-ERC1822 compliant, implementation. Removing
        // this special case will break upgrade paths from old UUPS implementation to new ones.
        if (StorageSlotUpgradeable.getBooleanSlot(_ROLLBACK_SLOT).value) {
            _setImplementation(newImplementation);
        } else {
            try IERC1822ProxiableUpgradeable(newImplementation).proxiableUUID() returns (bytes32 slot) {
                require(slot == _IMPLEMENTATION_SLOT, "ERC1967Upgrade: unsupported proxiableUUID");
            } catch {
                revert("ERC1967Upgrade: new implementation is not UUPS");
            }
            _upgradeToAndCall(newImplementation, data, forceCall);
        }
    }

    /**
     * @dev Storage slot with the admin of the contract.
     * This is the keccak-256 hash of "eip1967.proxy.admin" subtracted by 1, and is
     * validated in the constructor.
     */
    bytes32 internal constant _ADMIN_SLOT = 0xb53127684a568b3173ae13b9f8a6016e243e63b6e8ee1178d6a717850b5d6103;

    /**
     * @dev Emitted when the admin account has changed.
     */
    event AdminChanged(address previousAdmin, address newAdmin);

    /**
     * @dev Returns the current admin.
     */
    function _getAdmin() internal view returns (address) {
        return StorageSlotUpgradeable.getAddressSlot(_ADMIN_SLOT).value;
    }

    /**
     * @dev Stores a new address in the EIP1967 admin slot.
     */
    function _setAdmin(address newAdmin) private {
        require(newAdmin != address(0), "ERC1967: new admin is the zero address");
        StorageSlotUpgradeable.getAddressSlot(_ADMIN_SLOT).value = newAdmin;
    }

    /**
     * @dev Changes the admin of the proxy.
     *
     * Emits an {AdminChanged} event.
     */
    function _changeAdmin(address newAdmin) internal {
        emit AdminChanged(_getAdmin(), newAdmin);
        _setAdmin(newAdmin);
    }

    /**
     * @dev The storage slot of the UpgradeableBeacon contract which defines the implementation for this proxy.
     * This is bytes32(uint256(keccak256('eip1967.proxy.beacon')) - 1)) and is validated in the constructor.
     */
    bytes32 internal constant _BEACON_SLOT = 0xa3f0ad74e5423aebfd80d3ef4346578335a9a72aeaee59ff6cb3582b35133d50;

    /**
     * @dev Emitted when the beacon is upgraded.
     */
    event BeaconUpgraded(address indexed beacon);

    /**
     * @dev Returns the current beacon.
     */
    function _getBeacon() internal view returns (address) {
        return StorageSlotUpgradeable.getAddressSlot(_BEACON_SLOT).value;
    }

    /**
     * @dev Stores a new beacon in the EIP1967 beacon slot.
     */
    function _setBeacon(address newBeacon) private {
        require(AddressUpgradeable.isContract(newBeacon), "ERC1967: new beacon is not a contract");
        require(
            AddressUpgradeable.isContract(IBeaconUpgradeable(newBeacon).implementation()),
            "ERC1967: beacon implementation is not a contract"
        );
        StorageSlotUpgradeable.getAddressSlot(_BEACON_SLOT).value = newBeacon;
    }

    /**
     * @dev Perform beacon upgrade with additional setup call. Note: This upgrades the address of the beacon, it does
     * not upgrade the implementation contained in the beacon (see {UpgradeableBeacon-_setImplementation} for that).
     *
     * Emits a {BeaconUpgraded} event.
     */
    function _upgradeBeaconToAndCall(
        address newBeacon,
        bytes memory data,
        bool forceCall
    ) internal {
        _setBeacon(newBeacon);
        emit BeaconUpgraded(newBeacon);
        if (data.length > 0 || forceCall) {
            _functionDelegateCall(IBeaconUpgradeable(newBeacon).implementation(), data);
        }
    }

    /**
     * @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) private returns (bytes memory) {
        require(AddressUpgradeable.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 AddressUpgradeable.verifyCallResult(success, returndata, "Address: low-level delegate call failed");
    }

    /**
     * @dev This empty reserved space is put in place to allow future versions to add new
     * variables without shifting down storage in the inheritance chain.
     * See https://docs.openzeppelin.com/contracts/4.x/upgradeable#storage_gaps
     */
    uint256[50] private __gap;
}


// OpenZeppelin Contracts (last updated v4.5.0) (proxy/utils/UUPSUpgradeable.sol)

/**
 * @dev An upgradeability mechanism designed for UUPS proxies. The functions included here can perform an upgrade of an
 * {ERC1967Proxy}, when this contract is set as the implementation behind such a proxy.
 *
 * A security mechanism ensures that an upgrade does not turn off upgradeability accidentally, although this risk is
 * reinstated if the upgrade retains upgradeability but removes the security mechanism, e.g. by replacing
 * `UUPSUpgradeable` with a custom implementation of upgrades.
 *
 * The {_authorizeUpgrade} function must be overridden to include access restriction to the upgrade mechanism.
 *
 * _Available since v4.1._
 */
abstract contract UUPSUpgradeable is Initializable, IERC1822ProxiableUpgradeable, ERC1967UpgradeUpgradeable {
    function __UUPSUpgradeable_init() internal onlyInitializing {
    }

    function __UUPSUpgradeable_init_unchained() internal onlyInitializing {
    }
    /// @custom:oz-upgrades-unsafe-allow state-variable-immutable state-variable-assignment
    address private immutable __self = address(this);

    /**
     * @dev Check that the execution is being performed through a delegatecall call and that the execution context is
     * a proxy contract with an implementation (as defined in ERC1967) pointing to self. This should only be the case
     * for UUPS and transparent proxies that are using the current contract as their implementation. Execution of a
     * function through ERC1167 minimal proxies (clones) would not normally pass this test, but is not guaranteed to
     * fail.
     */
    modifier onlyProxy() {
        require(address(this) != __self, "Function must be called through delegatecall");
        require(_getImplementation() == __self, "Function must be called through active proxy");
        _;
    }

    /**
     * @dev Check that the execution is not being performed through a delegate call. This allows a function to be
     * callable on the implementing contract but not through proxies.
     */
    modifier notDelegated() {
        require(address(this) == __self, "UUPSUpgradeable: must not be called through delegatecall");
        _;
    }

    /**
     * @dev Implementation of the ERC1822 {proxiableUUID} function. This returns the storage slot used by the
     * implementation. It is used to validate that the this implementation remains valid after an upgrade.
     *
     * IMPORTANT: A proxy pointing at a proxiable contract should not be considered proxiable itself, because this risks
     * bricking a proxy that upgrades to it, by delegating to itself until out of gas. Thus it is critical that this
     * function revert if invoked through a proxy. This is guaranteed by the `notDelegated` modifier.
     */
    function proxiableUUID() external view virtual override notDelegated returns (bytes32) {
        return _IMPLEMENTATION_SLOT;
    }

    /**
     * @dev Upgrade the implementation of the proxy to `newImplementation`.
     *
     * Calls {_authorizeUpgrade}.
     *
     * Emits an {Upgraded} event.
     */
    function upgradeTo(address newImplementation) external virtual onlyProxy {
        _authorizeUpgrade(newImplementation);
        _upgradeToAndCallUUPS(newImplementation, new bytes(0), false);
    }

    /**
     * @dev Upgrade the implementation of the proxy to `newImplementation`, and subsequently execute the function call
     * encoded in `data`.
     *
     * Calls {_authorizeUpgrade}.
     *
     * Emits an {Upgraded} event.
     */
    function upgradeToAndCall(address newImplementation, bytes memory data) external payable virtual onlyProxy {
        _authorizeUpgrade(newImplementation);
        _upgradeToAndCallUUPS(newImplementation, data, true);
    }

    /**
     * @dev Function that should revert when `msg.sender` is not authorized to upgrade the contract. Called by
     * {upgradeTo} and {upgradeToAndCall}.
     *
     * Normally, this function will use an xref:access.adoc[access control] modifier such as {Ownable-onlyOwner}.
     *
     * ```solidity
     * function _authorizeUpgrade(address) internal override onlyOwner {}
     * ```
     */
    function _authorizeUpgrade(address newImplementation) internal virtual;

    /**
     * @dev This empty reserved space is put in place to allow future versions to add new
     * variables without shifting down storage in the inheritance chain.
     * See https://docs.openzeppelin.com/contracts/4.x/upgradeable#storage_gaps
     */
    uint256[50] private __gap;
}


// 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 ReentrancyGuardUpgradeable is Initializable {
    // 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;

    function __ReentrancyGuard_init() internal onlyInitializing {
        __ReentrancyGuard_init_unchained();
    }

    function __ReentrancyGuard_init_unchained() internal onlyInitializing {
        _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;
    }

    /**
     * @dev This empty reserved space is put in place to allow future versions to add new
     * variables without shifting down storage in the inheritance chain.
     * See https://docs.openzeppelin.com/contracts/4.x/upgradeable#storage_gaps
     */
    uint256[49] private __gap;
}


// 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 ContextUpgradeable is Initializable {
    function __Context_init() internal onlyInitializing {
    }

    function __Context_init_unchained() internal onlyInitializing {
    }
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

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

    /**
     * @dev This empty reserved space is put in place to allow future versions to add new
     * variables without shifting down storage in the inheritance chain.
     * See https://docs.openzeppelin.com/contracts/4.x/upgradeable#storage_gaps
     */
    uint256[50] private __gap;
}


// 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 OwnableUpgradeable is Initializable, ContextUpgradeable {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    function __Ownable_init() internal onlyInitializing {
        __Ownable_init_unchained();
    }

    function __Ownable_init_unchained() internal onlyInitializing {
        _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);
    }

    /**
     * @dev This empty reserved space is put in place to allow future versions to add new
     * variables without shifting down storage in the inheritance chain.
     * See https://docs.openzeppelin.com/contracts/4.x/upgradeable#storage_gaps
     */
    uint256[49] private __gap;
}


// OpenZeppelin Contracts (last updated v4.5.0) (token/ERC20/IERC20.sol)

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20Upgradeable {
    /**
     * @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 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 SafeERC20Upgradeable {
    using AddressUpgradeable for address;

    function safeTransfer(
        IERC20Upgradeable token,
        address to,
        uint256 value
    ) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(
        IERC20Upgradeable 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(
        IERC20Upgradeable 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(
        IERC20Upgradeable 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(
        IERC20Upgradeable 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(IERC20Upgradeable 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");
        }
    }
}

contract SparkMultiSender is OwnableUpgradeable, ReentrancyGuardUpgradeable, UUPSUpgradeable {

    using SafeERC20Upgradeable for IERC20Upgradeable;

    event MultiSendedTokens(uint256 total, address tokenAddress);
    event MultiSendedEther(uint256 total);
    event EmergencyWithdraw(address token, uint256 balance);

    struct Tokens {
        address recipient;
        uint256 amount;
    }

    constructor () {

    }

    function initialize(address _feeTokenSRKb, address _feeTokenSFUEL) external initializer {
        __Ownable_init();

        _setArrayLimit(200);

        if(_feeTokenSRKb != address(0)) {
            _setFeeToken(_feeTokenSRKb, true, 0.01 ether);
            _setFeeTokenSRKb(_feeTokenSRKb);
        }

        if(_feeTokenSFUEL != address(0)) {
            _setFeeToken(_feeTokenSFUEL, true, 0.01 ether);
            _setFeeTokenSFUEL(_feeTokenSFUEL);
        }

        _setFeeBNB(0.01 ether);

        _setPause(true);
    }

    ////////////// VIEW FUNCTIONS //////////////

    function getTxCount(address _user) external view returns (uint256) {
        return _getTxCount(_user);
    }

    function getArrayLimit() external view returns (uint256) {
        return _getArrayLimit();
    }

    function getFee() external view returns (uint256, uint256, uint256) {
        (, uint256 _feeSRKb) = _getFeeToken(_getFeeTokenSRKb());
        (, uint256 _feeSFUEL) = _getFeeToken(_getFeeTokenSFUEL());
        return (_feeSRKb, _feeSFUEL, _getFeeBNB());
    }

    function getFeeTokenSRKb() external view returns (address) {
        return _getFeeTokenSRKb();
    }

    function getFeeTokenSFUEL() external view returns (address) {
        return _getFeeTokenSFUEL();
    }

    function isPaused() external view returns (bool) {
        return _getPause();
    }

    function getSubscription(address _user) external view returns (uint256) {
        return _getWhitelist(_user);
    }

    function isSubscribed(address _user) external view returns (bool) {
        return _getWhitelist(_user) >= block.timestamp;
    }
    
    ////////////// INTERNAL FUNCTIONS //////////////

    function _getTxCount(address _user) internal view returns (uint256) {
        return StorageSlotUpgradeable.getUint256Slot(keccak256(abi.encodePacked("txCount", _user))).value;
    }

    function _setTxCount(address _user, uint256 _txCount) internal {
        StorageSlotUpgradeable.getUint256Slot(keccak256(abi.encodePacked("txCount", _user))).value = _txCount;
    }

    function _getArrayLimit() internal view returns (uint256) {
        return StorageSlotUpgradeable.getUint256Slot(keccak256(abi.encodePacked("arrayLimit"))).value;
    }

    function _setArrayLimit(uint256 _arrayLimit) internal {
        StorageSlotUpgradeable.getUint256Slot(keccak256(abi.encodePacked("arrayLimit"))).value = _arrayLimit;
    }

    /*
    // NOTE: This is not optimized, refer to _getFeeToken() and _settFeeToken() for optimized version
    function _getFeeSRKb() internal view returns (uint256) {
        return StorageSlotUpgradeable.getUint256Slot(keccak256(abi.encodePacked("fee"))).value;
    }

    function _setFeeSRKb(uint256 _fee) internal {
        StorageSlotUpgradeable.getUint256Slot(keccak256(abi.encodePacked("fee"))).value = _fee;
    }

    function _getFeeSFUEL() internal view returns (uint256) {
        return StorageSlotUpgradeable.getUint256Slot(keccak256(abi.encodePacked("feeSFUEL"))).value;
    }

    function _setFeeSFUEL(uint256 _fee) internal {
        StorageSlotUpgradeable.getUint256Slot(keccak256(abi.encodePacked("feeSFUEL"))).value = _fee;
    }
    */

    function _getFeeBNB() internal view returns (uint256) {
        return StorageSlotUpgradeable.getUint256Slot(keccak256(abi.encodePacked("feeBNB"))).value;
    }

    function _setFeeBNB(uint256 _fee) internal {
        StorageSlotUpgradeable.getUint256Slot(keccak256(abi.encodePacked("feeBNB"))).value = _fee;
    }

    function _getFeeToken(address _feeToken) internal view returns(bool _isActive, uint256 _fee) {
        return (StorageSlotUpgradeable.getBooleanSlot(keccak256(abi.encodePacked("feeToken", _feeToken, "isActive"))).value,
                StorageSlotUpgradeable.getUint256Slot(keccak256(abi.encodePacked("feeToken", _feeToken, "fee"))).value);
    }

    function _setFeeToken(address _feeToken, bool _isActive, uint256 _fee) internal {
        StorageSlotUpgradeable.getBooleanSlot(keccak256(abi.encodePacked("feeToken", _feeToken, "isActive"))).value = _isActive;
        StorageSlotUpgradeable.getUint256Slot(keccak256(abi.encodePacked("feeToken", _feeToken, "fee"))).value = _fee;
    }

    function _migrateOldFeeTokens() internal {
        uint256 _feeSRKb = StorageSlotUpgradeable.getUint256Slot(keccak256(abi.encodePacked("fee"))).value;
        uint256 _feeSFUEL = StorageSlotUpgradeable.getUint256Slot(keccak256(abi.encodePacked("feeSFUEL"))).value;

        if (_getFeeTokenSRKb() != address(0)) _setFeeToken(_getFeeTokenSRKb(), true, _feeSRKb);
        if (_getFeeTokenSFUEL() != address(0)) _setFeeToken(_getFeeTokenSFUEL(), true, _feeSFUEL);
    }

    function _getFeeTokenSRKb() internal view returns (address) {
        return StorageSlotUpgradeable.getAddressSlot(keccak256(abi.encodePacked("feeToken"))).value;
    }

    function _setFeeTokenSRKb(address _feeToken) internal { 
        StorageSlotUpgradeable.getAddressSlot(keccak256(abi.encodePacked("feeToken"))).value = _feeToken;
    }

    function _getFeeTokenSFUEL() internal view returns (address) {
        return StorageSlotUpgradeable.getAddressSlot(keccak256(abi.encodePacked("feeTokenSFUEL"))).value;
    }

    function _setFeeTokenSFUEL(address _feeToken) internal { 
        StorageSlotUpgradeable.getAddressSlot(keccak256(abi.encodePacked("feeTokenSFUEL"))).value = _feeToken;
    }

    function _getPause() internal view returns (bool) {
        return StorageSlotUpgradeable.getBooleanSlot(keccak256(abi.encodePacked("systemPause"))).value;
    }

    function _setPause(bool _pause) internal {
        StorageSlotUpgradeable.getBooleanSlot(keccak256(abi.encodePacked("systemPause"))).value = _pause;
    }

    function _getWhitelist(address _user) internal view returns (uint256) {
        return StorageSlotUpgradeable.getUint256Slot(keccak256(abi.encodePacked("whitelist", _user))).value;
    }

    function _setWhitelist(address _user, uint256 _expiry) internal {
        StorageSlotUpgradeable.getUint256Slot(keccak256(abi.encodePacked("whitelist", _user))).value = _expiry;
    }

    ////////////// ADMIN FUNCTIONS //////////////

    function pause() external onlyOwner {
        require(!_getPause(), "System already paused");
        _setPause(true);
    }

    function unpause() external onlyOwner {
        require(_getPause(), "System already unpaused");
        _setPause(false);
    }

    function setArrayLimit(uint256 _arrayLimit) external onlyOwner {
        _setArrayLimit(_arrayLimit);
    }

    function setFeeSRKb(uint256 _fee) external onlyOwner {
        _setFeeToken(_getFeeTokenSRKb(), true, _fee);
    }

    function setFeeSFUEL(uint256 _fee) external onlyOwner {
        _setFeeToken(_getFeeTokenSFUEL(), true, _fee);
    }

    function setFeeBNB(uint256 _fee) external onlyOwner {
        _setFeeBNB(_fee);
    }

    function setFeeTokenSRKb(address _token) external onlyOwner {
        (, uint256 _fee) = _getFeeToken(_getFeeTokenSRKb());
        _setFeeToken(_getFeeTokenSRKb(), false, 0);
        _setFeeToken(_token, true, _fee);
        _setFeeTokenSRKb(_token);
    }

    function setFeeTokenSFUEL(address _token) external onlyOwner {
        (, uint256 _fee) = _getFeeToken(_getFeeTokenSFUEL());
        _setFeeToken(_getFeeTokenSFUEL(), false, 0);
        _setFeeToken(_token, true, _fee);
        _setFeeTokenSFUEL(_token);
    }

    function migrateOldFeeTokens() external onlyOwner {
        _migrateOldFeeTokens();
    }

    function emergencyWithdraw(address _token) external onlyOwner {
        uint256 balance = IERC20Upgradeable(_token).balanceOf(address(this));
        IERC20Upgradeable(_token).safeTransfer(msg.sender, balance);

        emit EmergencyWithdraw(_token, balance);
    }

    function emergencyWithdrawETH() external onlyOwner {
        uint256 balance = address(this).balance;
        payable(msg.sender).transfer(balance);

        emit EmergencyWithdraw(address(0), balance);
    }

    function setSubscription(address _user, uint256 _expiry) external onlyOwner {
        _setWhitelist(_user, _expiry);
    }

    ////////////// EXTERNAL FUNCTIONS //////////////

    function multisendToken(address _tokenAddress, Tokens[] memory _receivers, address _feeToken) external nonReentrant {
        if (_getWhitelist(msg.sender) < block.timestamp) {
            require(_feeToken == _getFeeTokenSRKb() || _feeToken == _getFeeTokenSFUEL(), "Invalid fee token");

            (bool isActive, uint256 fee) = _getFeeToken(_feeToken);
            require(isActive, "Fee token is not active");

            require(IERC20Upgradeable(_feeToken).allowance(msg.sender, address(this)) >= fee, "Not enough allowanace");
            require(IERC20Upgradeable(_feeToken).balanceOf(msg.sender) >= fee, "Not enough balance");

            IERC20Upgradeable(_feeToken).safeTransferFrom(msg.sender, address(this), fee);
        }

        _multisendToken(_tokenAddress, _receivers);
    }

    function multisendToken(address _tokenAddress, Tokens[] memory _receivers) external payable nonReentrant {
        if (_getWhitelist(msg.sender) < block.timestamp) {
            require(msg.value >= _getFeeBNB(), "Not enough BNB");
            if (msg.value > _getFeeBNB()) payable(msg.sender).transfer(msg.value - _getFeeBNB()); // Refund excess BNB
        }
        else if (msg.value > 0){
            payable(msg.sender).transfer(msg.value); // Refund all BNB if any
        }

        _multisendToken(_tokenAddress, _receivers);
    }

    function _multisendToken(address _tokenAddress, Tokens[] memory _receivers) internal {
        require(!_getPause(), "System is paused");
        uint256 total = 0;
        require(_receivers.length <= _getArrayLimit(), "Array limit exceeded");

        for (uint256 i = 0; i < _receivers.length; i++) {
            IERC20Upgradeable(_tokenAddress).safeTransferFrom(msg.sender, _receivers[i].recipient, _receivers[i].amount);
            total += _receivers[i].amount;
        }

        _setTxCount(msg.sender, _getTxCount(msg.sender) + 1);
        emit MultiSendedTokens(total, _tokenAddress);
    }

    function multisendEther(Tokens[] memory _receivers, address _feeToken) external payable nonReentrant {
        if (_getWhitelist(msg.sender) < block.timestamp) {
            require(_feeToken == _getFeeTokenSRKb() || _feeToken == _getFeeTokenSFUEL(), "Invalid fee token");

            (bool isActive, uint256 fee) = _getFeeToken(_feeToken);
            require(isActive, "Fee token is not active");

            require(IERC20Upgradeable(_feeToken).allowance(msg.sender, address(this)) >= fee, "Not enough allowanace");
            require(IERC20Upgradeable(_feeToken).balanceOf(msg.sender) >= fee, "Not enough balance");

            IERC20Upgradeable(_feeToken).safeTransferFrom(msg.sender, address(this), fee);
        }

        uint256 totalETH;

        for (uint x = 0 ; x < _receivers.length; x++) {
            totalETH += _receivers[x].amount;
        }

        require(msg.value >= totalETH, "Not enough BNB");
        if (msg.value > totalETH) payable(msg.sender).transfer(msg.value - totalETH); // Refund excess BNB

        _multisendEther(_receivers);
    }

    function multisendEther(Tokens[] memory _receivers) external payable nonReentrant {
        uint256 totalETH;
        uint256 requiredETH;

        for (uint x = 0 ; x < _receivers.length; x++) {
            totalETH += _receivers[x].amount;
        }

        if (_getWhitelist(msg.sender) < block.timestamp) {
            requiredETH = (totalETH + _getFeeBNB());
        }
        else{
            requiredETH = totalETH;
        }

        require(msg.value >= requiredETH, "Not enough BNB");
        if (msg.value > requiredETH) payable(msg.sender).transfer(msg.value - requiredETH); // Refund excess BNB

        _multisendEther(_receivers);
    }

    function _multisendEther(Tokens[] memory _receivers) internal {
        require(!_getPause(), "System is paused");
        uint256 total = 0;
        require(_receivers.length <= _getArrayLimit(), "Array limit exceeded");

        for (uint256 i = 0; i < _receivers.length; i++) {
            payable(_receivers[i].recipient).transfer(_receivers[i].amount);
            total += _receivers[i].amount;
        }

        _setTxCount(msg.sender, _getTxCount(msg.sender) + 1);
        emit MultiSendedEther(total);
    }


    // solhint-disable-next-line no-empty-blocks
    function _authorizeUpgrade(address) internal override onlyOwner {}
}