// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (utils/Address.sol)

pragma solidity ^0.8.1;

/**
 * @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
     *
     * Furthermore, `isContract` will also return true if the target contract within
     * the same transaction is already scheduled for destruction by `SELFDESTRUCT`,
     * which only has an effect at the end of a transaction.
     * ====
     *
     * [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://consensys.net/diligence/blog/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 functionCallWithValue(target, data, 0, "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");
        (bool success, bytes memory returndata) = target.call{value: value}(data);
        return verifyCallResultFromTarget(target, 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) {
        (bool success, bytes memory returndata) = target.staticcall(data);
        return verifyCallResultFromTarget(target, 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) {
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return verifyCallResultFromTarget(target, success, returndata, errorMessage);
    }

    /**
     * @dev Tool to verify that a low level call to smart-contract was successful, and revert (either by bubbling
     * the revert reason or using the provided one) in case of unsuccessful call or if target was not a contract.
     *
     * _Available since v4.8._
     */
    function verifyCallResultFromTarget(
        address target,
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        if (success) {
            if (returndata.length == 0) {
                // only check isContract if the call was successful and the return data is empty
                // otherwise we already know that it was a contract
                require(isContract(target), "Address: call to non-contract");
            }
            return returndata;
        } else {
            _revert(returndata, errorMessage);
        }
    }

    /**
     * @dev Tool to verify that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason or 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 {
            _revert(returndata, errorMessage);
        }
    }

    function _revert(bytes memory returndata, string memory errorMessage) private pure {
        // 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
            /// @solidity memory-safe-assembly
            assembly {
                let returndata_size := mload(returndata)
                revert(add(32, returndata), returndata_size)
            }
        } else {
            revert(errorMessage);
        }
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Context.sol)

pragma solidity ^0.8.0;

/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

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

pragma solidity 0.8.16;
//SPDX-License-Identifier: MIT

library Errors {

    // Common Errors
    error AddressZero();
    error NullAmount();
    error CallerNotAllowed();
    error IncorrectRewardToken();
    error SameAddress();
    error InequalArraySizes();
    error EmptyArray();
    error EmptyParameters();
    error AlreadyInitialized();
    error InvalidParameter();
    error CannotRecoverToken();
    error ForbiddenCall();

    error CannotBeOwner();
    error CallerNotPendingOwner();

    error Killed();
    error AlreadyKilled();
    error NotKilled();
    error KillDelayExpired();
    error KillDelayNotExpired();


    // Merkle Errors
    error MerkleRootNotUpdated();
    error AlreadyClaimed();
    error InvalidProof();
    error EmptyMerkleRoot();
    error IncorrectRewardAmount();
    error MerkleRootFrozen();
    error NotFrozen();
    error AlreadyFrozen();


    // Quest Errors
    error CallerNotQuestBoard();
    error IncorrectQuestID();
    error IncorrectPeriod();
    error TokenNotWhitelisted();
    error QuestAlreadyListed();
    error QuestNotListed();
    error PeriodAlreadyUpdated();
    error PeriodNotClosed();
    error PeriodStillActive();
    error PeriodNotListed();
    error EmptyQuest();
    error EmptyPeriod();
    error ExpiredQuest();
    error QuestNotStarted();

    error NotInitialized();
    error NoDistributorSet();
    error DisitributorFail();
    error InvalidGauge();
    error InvalidQuestID();
    error InvalidPeriod();
    error ObjectiveTooLow();
    error NewObjectiveTooLow();
    error RewardPerVoteTooLow();
    error MinValueOverMaxValue();
    error IncorrectDuration();
    error IncorrectAddDuration();
    error IncorrectTotalRewardAmount();
    error IncorrectAddedRewardAmount();
    error IncorrectFeeAmount();
    error InvalidQuestType();
    error QuestTypesIncompatible();
    error CalletNotQuestCreator();
    error LowerRewardPerVote();
    error LowerObjective();
    error CreatorNotAllowed();
    error AlreadyListed();
    error NotListed();
    error MaxListSize();
    error BoardIsNotAllowedDistributor();


    //Math
    error NumberExceed48Bits();

}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.6.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @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);

    /**
     * @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);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/IERC20Permit.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 Permit extension allowing approvals to be made via signatures, as defined in
 * https://eips.ethereum.org/EIPS/eip-2612[EIP-2612].
 *
 * Adds the {permit} method, which can be used to change an account's ERC20 allowance (see {IERC20-allowance}) by
 * presenting a message signed by the account. By not relying on {IERC20-approve}, the token holder account doesn't
 * need to send a transaction, and thus is not required to hold Ether at all.
 */
interface IERC20Permit {
    /**
     * @dev Sets `value` as the allowance of `spender` over ``owner``'s tokens,
     * given ``owner``'s signed approval.
     *
     * IMPORTANT: The same issues {IERC20-approve} has related to transaction
     * ordering also apply here.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `deadline` must be a timestamp in the future.
     * - `v`, `r` and `s` must be a valid `secp256k1` signature from `owner`
     * over the EIP712-formatted function arguments.
     * - the signature must use ``owner``'s current nonce (see {nonces}).
     *
     * For more information on the signature format, see the
     * https://eips.ethereum.org/EIPS/eip-2612#specification[relevant EIP
     * section].
     */
    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external;

    /**
     * @dev Returns the current nonce for `owner`. This value must be
     * included whenever a signature is generated for {permit}.
     *
     * Every successful call to {permit} increases ``owner``'s nonce by one. This
     * prevents a signature from being used multiple times.
     */
    function nonces(address owner) external view returns (uint256);

    /**
     * @dev Returns the domain separator used in the encoding of the signature for {permit}, as defined by {EIP712}.
     */
    // solhint-disable-next-line func-name-mixedcase
    function DOMAIN_SEPARATOR() external view returns (bytes32);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (utils/cryptography/MerkleProof.sol)

pragma solidity ^0.8.0;

/**
 * @dev These functions deal with verification of Merkle Tree proofs.
 *
 * The tree and the proofs can be generated using our
 * https://github.com/OpenZeppelin/merkle-tree[JavaScript library].
 * You will find a quickstart guide in the readme.
 *
 * WARNING: You should avoid using leaf values that are 64 bytes long prior to
 * hashing, or use a hash function other than keccak256 for hashing leaves.
 * This is because the concatenation of a sorted pair of internal nodes in
 * the merkle tree could be reinterpreted as a leaf value.
 * OpenZeppelin's JavaScript library generates merkle trees that are safe
 * against this attack out of the box.
 */
library MerkleProof {
    /**
     * @dev Returns true if a `leaf` can be proved to be a part of a Merkle tree
     * defined by `root`. For this, a `proof` must be provided, containing
     * sibling hashes on the branch from the leaf to the root of the tree. Each
     * pair of leaves and each pair of pre-images are assumed to be sorted.
     */
    function verify(bytes32[] memory proof, bytes32 root, bytes32 leaf) internal pure returns (bool) {
        return processProof(proof, leaf) == root;
    }

    /**
     * @dev Calldata version of {verify}
     *
     * _Available since v4.7._
     */
    function verifyCalldata(bytes32[] calldata proof, bytes32 root, bytes32 leaf) internal pure returns (bool) {
        return processProofCalldata(proof, leaf) == root;
    }

    /**
     * @dev Returns the rebuilt hash obtained by traversing a Merkle tree up
     * from `leaf` using `proof`. A `proof` is valid if and only if the rebuilt
     * hash matches the root of the tree. When processing the proof, the pairs
     * of leafs & pre-images are assumed to be sorted.
     *
     * _Available since v4.4._
     */
    function processProof(bytes32[] memory proof, bytes32 leaf) internal pure returns (bytes32) {
        bytes32 computedHash = leaf;
        for (uint256 i = 0; i < proof.length; i++) {
            computedHash = _hashPair(computedHash, proof[i]);
        }
        return computedHash;
    }

    /**
     * @dev Calldata version of {processProof}
     *
     * _Available since v4.7._
     */
    function processProofCalldata(bytes32[] calldata proof, bytes32 leaf) internal pure returns (bytes32) {
        bytes32 computedHash = leaf;
        for (uint256 i = 0; i < proof.length; i++) {
            computedHash = _hashPair(computedHash, proof[i]);
        }
        return computedHash;
    }

    /**
     * @dev Returns true if the `leaves` can be simultaneously proven to be a part of a merkle tree defined by
     * `root`, according to `proof` and `proofFlags` as described in {processMultiProof}.
     *
     * CAUTION: Not all merkle trees admit multiproofs. See {processMultiProof} for details.
     *
     * _Available since v4.7._
     */
    function multiProofVerify(
        bytes32[] memory proof,
        bool[] memory proofFlags,
        bytes32 root,
        bytes32[] memory leaves
    ) internal pure returns (bool) {
        return processMultiProof(proof, proofFlags, leaves) == root;
    }

    /**
     * @dev Calldata version of {multiProofVerify}
     *
     * CAUTION: Not all merkle trees admit multiproofs. See {processMultiProof} for details.
     *
     * _Available since v4.7._
     */
    function multiProofVerifyCalldata(
        bytes32[] calldata proof,
        bool[] calldata proofFlags,
        bytes32 root,
        bytes32[] memory leaves
    ) internal pure returns (bool) {
        return processMultiProofCalldata(proof, proofFlags, leaves) == root;
    }

    /**
     * @dev Returns the root of a tree reconstructed from `leaves` and sibling nodes in `proof`. The reconstruction
     * proceeds by incrementally reconstructing all inner nodes by combining a leaf/inner node with either another
     * leaf/inner node or a proof sibling node, depending on whether each `proofFlags` item is true or false
     * respectively.
     *
     * CAUTION: Not all merkle trees admit multiproofs. To use multiproofs, it is sufficient to ensure that: 1) the tree
     * is complete (but not necessarily perfect), 2) the leaves to be proven are in the opposite order they are in the
     * tree (i.e., as seen from right to left starting at the deepest layer and continuing at the next layer).
     *
     * _Available since v4.7._
     */
    function processMultiProof(
        bytes32[] memory proof,
        bool[] memory proofFlags,
        bytes32[] memory leaves
    ) internal pure returns (bytes32 merkleRoot) {
        // This function rebuilds the root hash by traversing the tree up from the leaves. The root is rebuilt by
        // consuming and producing values on a queue. The queue starts with the `leaves` array, then goes onto the
        // `hashes` array. At the end of the process, the last hash in the `hashes` array should contain the root of
        // the merkle tree.
        uint256 leavesLen = leaves.length;
        uint256 totalHashes = proofFlags.length;

        // Check proof validity.
        require(leavesLen + proof.length - 1 == totalHashes, "MerkleProof: invalid multiproof");

        // The xxxPos values are "pointers" to the next value to consume in each array. All accesses are done using
        // `xxx[xxxPos++]`, which return the current value and increment the pointer, thus mimicking a queue's "pop".
        bytes32[] memory hashes = new bytes32[](totalHashes);
        uint256 leafPos = 0;
        uint256 hashPos = 0;
        uint256 proofPos = 0;
        // At each step, we compute the next hash using two values:
        // - a value from the "main queue". If not all leaves have been consumed, we get the next leaf, otherwise we
        //   get the next hash.
        // - depending on the flag, either another value from the "main queue" (merging branches) or an element from the
        //   `proof` array.
        for (uint256 i = 0; i < totalHashes; i++) {
            bytes32 a = leafPos < leavesLen ? leaves[leafPos++] : hashes[hashPos++];
            bytes32 b = proofFlags[i]
                ? (leafPos < leavesLen ? leaves[leafPos++] : hashes[hashPos++])
                : proof[proofPos++];
            hashes[i] = _hashPair(a, b);
        }

        if (totalHashes > 0) {
            unchecked {
                return hashes[totalHashes - 1];
            }
        } else if (leavesLen > 0) {
            return leaves[0];
        } else {
            return proof[0];
        }
    }

    /**
     * @dev Calldata version of {processMultiProof}.
     *
     * CAUTION: Not all merkle trees admit multiproofs. See {processMultiProof} for details.
     *
     * _Available since v4.7._
     */
    function processMultiProofCalldata(
        bytes32[] calldata proof,
        bool[] calldata proofFlags,
        bytes32[] memory leaves
    ) internal pure returns (bytes32 merkleRoot) {
        // This function rebuilds the root hash by traversing the tree up from the leaves. The root is rebuilt by
        // consuming and producing values on a queue. The queue starts with the `leaves` array, then goes onto the
        // `hashes` array. At the end of the process, the last hash in the `hashes` array should contain the root of
        // the merkle tree.
        uint256 leavesLen = leaves.length;
        uint256 totalHashes = proofFlags.length;

        // Check proof validity.
        require(leavesLen + proof.length - 1 == totalHashes, "MerkleProof: invalid multiproof");

        // The xxxPos values are "pointers" to the next value to consume in each array. All accesses are done using
        // `xxx[xxxPos++]`, which return the current value and increment the pointer, thus mimicking a queue's "pop".
        bytes32[] memory hashes = new bytes32[](totalHashes);
        uint256 leafPos = 0;
        uint256 hashPos = 0;
        uint256 proofPos = 0;
        // At each step, we compute the next hash using two values:
        // - a value from the "main queue". If not all leaves have been consumed, we get the next leaf, otherwise we
        //   get the next hash.
        // - depending on the flag, either another value from the "main queue" (merging branches) or an element from the
        //   `proof` array.
        for (uint256 i = 0; i < totalHashes; i++) {
            bytes32 a = leafPos < leavesLen ? leaves[leafPos++] : hashes[hashPos++];
            bytes32 b = proofFlags[i]
                ? (leafPos < leavesLen ? leaves[leafPos++] : hashes[hashPos++])
                : proof[proofPos++];
            hashes[i] = _hashPair(a, b);
        }

        if (totalHashes > 0) {
            unchecked {
                return hashes[totalHashes - 1];
            }
        } else if (leavesLen > 0) {
            return leaves[0];
        } else {
            return proof[0];
        }
    }

    function _hashPair(bytes32 a, bytes32 b) private pure returns (bytes32) {
        return a < b ? _efficientHash(a, b) : _efficientHash(b, a);
    }

    function _efficientHash(bytes32 a, bytes32 b) private pure returns (bytes32 value) {
        /// @solidity memory-safe-assembly
        assembly {
            mstore(0x00, a)
            mstore(0x20, b)
            value := keccak256(0x00, 0x40)
        }
    }
}

//██████╗  █████╗ ██╗      █████╗ ██████╗ ██╗███╗   ██╗
//██╔══██╗██╔══██╗██║     ██╔══██╗██╔══██╗██║████╗  ██║
//██████╔╝███████║██║     ███████║██║  ██║██║██╔██╗ ██║
//██╔═══╝ ██╔══██║██║     ██╔══██║██║  ██║██║██║╚██╗██║
//██║     ██║  ██║███████╗██║  ██║██████╔╝██║██║ ╚████║
//╚═╝     ╚═╝  ╚═╝╚══════╝╚═╝  ╚═╝╚═════╝ ╚═╝╚═╝  ╚═══╝
 

//SPDX-License-Identifier: BUSL-1.1
pragma solidity 0.8.16;

import "./oz/interfaces/IERC20.sol";
import "./oz/libraries/SafeERC20.sol";
import "./oz/utils/MerkleProof.sol";
import "./utils/Owner.sol";
import "./oz/utils/ReentrancyGuard.sol";
import "./libraries/Errors.sol";

/** @title Quest Multi Merkle Distributor  */
/// @author Paladin
/*
    Contract holds ERC20 rewards from Quests
    Can handle multiple MerkleRoots
*/

contract MultiMerkleDistributor is Owner, ReentrancyGuard {
    using SafeERC20 for IERC20;

    /** @notice Seconds in a Week */
    uint256 private constant WEEK = 604800;

    /** @notice Mapping listing the reward token associated to each Quest ID */
    // QuestID => reward token
    mapping(uint256 => address) public questRewardToken;

    /** @notice Mapping of tokens this contract is or was distributing */
    // token address => boolean
    mapping(address => bool) public rewardTokens;

    // Periods: timestamp => start of a week, used as a voting period 
    // in the Curve GaugeController though the timestamp / WEEK *  WEEK logic.
    // Handled through the QuestManager contract.
    // Those can be fetched through this contract when they are closed, or through the QuestManager contract.

    /** @notice List of Closed QuestPeriods by Quest ID */
    // QuestID => array of periods
    mapping(uint256 => uint256[]) public questClosedPeriods;

    /** @notice Merkle Root for each period of a Quest (indexed by Quest ID) */
    // QuestID => period => merkleRoot
    mapping(uint256 => mapping(uint256 => bytes32)) public questMerkleRootPerPeriod;

    /** @notice Amount of rewards for each period of a Quest (indexed by Quest ID) */
    // QuestID => period => totalRewardsAmount
    mapping(uint256 => mapping(uint256 => uint256)) public questRewardsPerPeriod;

    /** @notice BitMap of claims for each period of a Quest */
    // QuestID => period => claimedBitMap
    // This is a packed array of booleans.
    mapping(uint256 => mapping(uint256 => mapping(uint256 => uint256))) private questPeriodClaimedBitMap;

    /** @notice Address of the QuestBoard contract */
    address public immutable questBoard;


    // Events

    /** @notice Event emitted when a user Claims */
    event Claimed(
        uint256 indexed questID,
        uint256 indexed period,
        uint256 index,
        uint256 amount,
        address rewardToken,
        address indexed account
    );
    /** @notice Event emitted when a New Quest is added */
    event NewQuest(uint256 indexed questID, address rewardToken);
    /** @notice Event emitted when a Period of a Quest is updated (when the Merkle Root is added) */
    event QuestPeriodUpdated(uint256 indexed questID, uint256 indexed period, bytes32 merkleRoot);


    // Modifier

    /** @notice Check the caller is either the admin or the QuestBoard contract */
    modifier onlyAllowed(){
        if(msg.sender != questBoard && msg.sender != owner()) revert Errors.CallerNotAllowed();
        _;
    }


    // Constructor

    constructor(address _questBoard){
        if(_questBoard == address(0)) revert Errors.AddressZero();

        questBoard = _questBoard;
    }

    // Functions
   
    /**
    * @notice Checks if the rewards were claimed for a user on a given period
    * @dev Checks if the rewards were claimed for a user (based on the index) on a given period
    * @param questID ID of the Quest
    * @param period Amount of underlying to borrow
    * @param index Index of the claim
    * @return bool : true if already claimed
    */
    function isClaimed(uint256 questID, uint256 period, uint256 index) public view returns (bool) {
        uint256 claimedWordIndex = index >> 8;
        uint256 claimedBitIndex = index & 0xff;
        uint256 claimedWord = questPeriodClaimedBitMap[questID][period][claimedWordIndex];
        uint256 mask = (1 << claimedBitIndex);
        return claimedWord & mask != 0;
    }
   
    /**
    * @dev Sets the rewards as claimed for the index on the given period
    * @param questID ID of the Quest
    * @param period Timestamp of the period
    * @param index Index of the claim
    */
    function _setClaimed(uint256 questID, uint256 period, uint256 index) private {
        uint256 claimedWordIndex = index >> 8;
        uint256 claimedBitIndex = index & 0xff;
        questPeriodClaimedBitMap[questID][period][claimedWordIndex] |= (1 << claimedBitIndex);
    }

    //Basic Claim   
    /**
    * @notice Claims the reward for a user for a given period of a Quest
    * @dev Claims the reward for a user for a given period of a Quest if the correct proof was given
    * @param questID ID of the Quest
    * @param period Timestamp of the period
    * @param index Index in the Merkle Tree
    * @param account Address of the user claiming the rewards
    * @param amount Amount of rewards to claim
    * @param merkleProof Proof to claim the rewards
    */
    function claim(uint256 questID, uint256 period, uint256 index, address account, uint256 amount, bytes32[] calldata merkleProof) public nonReentrant {
        if(account == address(0)) revert Errors.AddressZero();
        if(questMerkleRootPerPeriod[questID][period] == 0) revert Errors.MerkleRootNotUpdated();
        if(isClaimed(questID, period, index)) revert Errors.AlreadyClaimed();

        // Check that the given parameters match the given Proof
        bytes32 node = keccak256(abi.encodePacked(questID, period, index, account, amount));
        if(!MerkleProof.verify(merkleProof, questMerkleRootPerPeriod[questID][period], node)) revert Errors.InvalidProof();

        // Set the rewards as claimed for that period
        // And transfer the rewards to the user
        address rewardToken = questRewardToken[questID];
        _setClaimed(questID, period, index);
        questRewardsPerPeriod[questID][period] -= amount;
        IERC20(rewardToken).safeTransfer(account, amount);

        emit Claimed(questID, period, index, amount, rewardToken, account);
    }


    //Struct ClaimParams
    struct ClaimParams {
        uint256 questID;
        uint256 period;
        uint256 index;
        uint256 amount;
        bytes32[] merkleProof;
    }


    //Multi Claim   
    /**
    * @notice Claims multiple rewards for a given list
    * @dev Calls the claim() method for each entry in the claims array
    * @param account Address of the user claiming the rewards
    * @param claims List of ClaimParams struct data to claim
    */
    function multiClaim(address account, ClaimParams[] calldata claims) external {
        uint256 length = claims.length;
        
        if(length == 0) revert Errors.EmptyParameters();

        for(uint256 i; i < length;){
            claim(claims[i].questID, claims[i].period, claims[i].index, account, claims[i].amount, claims[i].merkleProof);

            unchecked{ ++i; }
        }
    }


    //FullQuest Claim (form of Multi Claim but for only one Quest => only one ERC20 transfer)
    //Only works for the given periods (in ClaimParams) for the Quest. Any omitted period will be skipped   
    /**
    * @notice Claims the reward for all the given periods of a Quest, and transfer all the rewards at once
    * @dev Sums up all the rewards for given periods of a Quest, and executes only one transfer
    * @param account Address of the user claiming the rewards
    * @param questID ID of the Quest
    * @param claims List of ClaimParams struct data to claim
    */
    function claimQuest(address account, uint256 questID, ClaimParams[] calldata claims) external nonReentrant {
        if(account == address(0)) revert Errors.AddressZero();
        uint256 length = claims.length;

        if(length == 0) revert Errors.EmptyParameters();

        // Total amount claimable, to transfer at once
        uint256 totalClaimAmount;
        address rewardToken = questRewardToken[questID];

        for(uint256 i; i < length;){
            if(claims[i].questID != questID) revert Errors.IncorrectQuestID();
            if(questMerkleRootPerPeriod[questID][claims[i].period] == 0) revert Errors.MerkleRootNotUpdated();
            if(isClaimed(questID, claims[i].period, claims[i].index)) revert Errors.AlreadyClaimed();

            // For each period given, if the proof matches the given parameters, 
            // set as claimed and add to the to total to transfer
            bytes32 node = keccak256(abi.encodePacked(questID, claims[i].period, claims[i].index, account, claims[i].amount));
            if(!MerkleProof.verify(claims[i].merkleProof, questMerkleRootPerPeriod[questID][claims[i].period], node)) revert Errors.InvalidProof();

            _setClaimed(questID, claims[i].period, claims[i].index);
            questRewardsPerPeriod[questID][claims[i].period] -= claims[i].amount;
            totalClaimAmount += claims[i].amount;

            emit Claimed(questID, claims[i].period, claims[i].index, claims[i].amount, rewardToken, account);

            unchecked{ ++i; }
        }

        // Transfer the total claimed amount
        IERC20(rewardToken).safeTransfer(account, totalClaimAmount);
    }

   
    /**
    * @notice Returns all current Closed periods for the given Quest ID
    * @dev Returns all current Closed periods for the given Quest ID
    * @param questID ID of the Quest
    * @return uint256[] : List of closed periods
    */
    function getClosedPeriodsByQuests(uint256 questID) external view returns (uint256[] memory) {
        return questClosedPeriods[questID];
    }



    // Manager functions
   
    /**
    * @notice Adds a new Quest to the listing
    * @dev Adds a new Quest ID and the associated reward token
    * @param questID ID of the Quest
    * @param token Address of the ERC20 reward token
    * @return bool : success
    */
    function addQuest(uint256 questID, address token) external returns(bool) {
        if(msg.sender != questBoard) revert Errors.CallerNotAllowed();
        if(questRewardToken[questID] != address(0)) revert Errors.QuestAlreadyListed();
        if(token == address(0)) revert Errors.TokenNotWhitelisted();

        // Add a new Quest using the QuestID, and list the reward token for that Quest
        questRewardToken[questID] = token;

        if(!rewardTokens[token]) rewardTokens[token] = true;

        emit NewQuest(questID, token);

        return true;
    }

    /**
    * @notice Adds a new period & the rewards of this period for a Quest
    * @dev Adds a new period & the rewards of this period for a Quest
    * @param questID ID of the Quest
    * @param period Timestamp of the period
    * @param totalRewardAmount Total amount of rewards to distribute for the period
    * @return bool : success
    */
    function addQuestPeriod(uint256 questID, uint256 period, uint256 totalRewardAmount) external returns(bool) {
        period = (period / WEEK) * WEEK;
        if(msg.sender != questBoard) revert Errors.CallerNotAllowed();
        if(questRewardToken[questID] == address(0)) revert Errors.QuestNotListed();
        if(questRewardsPerPeriod[questID][period] != 0) revert Errors.PeriodAlreadyUpdated();
        if(period == 0) revert Errors.IncorrectPeriod();
        if(totalRewardAmount == 0) revert Errors.NullAmount();

        questRewardsPerPeriod[questID][period] = totalRewardAmount;

        return true;
    }


    function fixQuestPeriod(uint256 questID, uint256 period, uint256 newTotalRewardAmount) external returns(bool) {
        if(msg.sender != questBoard) revert Errors.CallerNotAllowed();
        period = (period / WEEK) * WEEK;
        if(questRewardToken[questID] == address(0)) revert Errors.QuestNotListed();
        if(period == 0) revert Errors.IncorrectPeriod();
        if(questRewardsPerPeriod[questID][period] == 0) revert Errors.PeriodNotListed();

        uint256 previousTotalRewardAmount = questRewardsPerPeriod[questID][period];

        questRewardsPerPeriod[questID][period] = newTotalRewardAmount;

        if(previousTotalRewardAmount > newTotalRewardAmount){
            // Send back the extra amount of reward token that was incorrectly sent
            // In the case of missing reward token, the Board will send them to this contract

            uint256 extraAmount = previousTotalRewardAmount - newTotalRewardAmount;
            IERC20(questRewardToken[questID]).safeTransfer(questBoard, extraAmount);
        }

        return true;
    }
   
    /**
    * @notice Updates the period of a Quest by adding the Merkle Root
    * @dev Add the Merkle Root for the eriod of the given Quest
    * @param questID ID of the Quest
    * @param period timestamp of the period
    * @param totalAmount sum of all rewards for the Merkle Tree
    * @param merkleRoot MerkleRoot to add
    * @return bool: success
    */
    function updateQuestPeriod(uint256 questID, uint256 period, uint256 totalAmount, bytes32 merkleRoot) external onlyAllowed returns(bool) {
        period = (period / WEEK) * WEEK;
        if(questRewardToken[questID] == address(0)) revert Errors.QuestNotListed();
        if(period == 0) revert Errors.IncorrectPeriod();
        if(questRewardsPerPeriod[questID][period] == 0) revert Errors.PeriodNotListed();
        if(questMerkleRootPerPeriod[questID][period] != 0) revert Errors.PeriodAlreadyUpdated();
        if(merkleRoot == 0) revert Errors.EmptyMerkleRoot();

        // Add a new Closed Period for the Quest
        questClosedPeriods[questID].push(period);

        if(totalAmount != questRewardsPerPeriod[questID][period]) revert Errors.IncorrectRewardAmount();

        // Add the new MerkleRoot for that Closed Period
        questMerkleRootPerPeriod[questID][period] = merkleRoot;

        emit QuestPeriodUpdated(questID, period, merkleRoot);

        return true;
    }


    //  Admin functions
   
    /**
    * @notice Recovers ERC2O tokens sent by mistake to the contract
    * @dev Recovers ERC2O tokens sent by mistake to the contract
    * @param token Address tof the EC2O token
    * @return bool: success
    */
    function recoverERC20(address token) external onlyOwner nonReentrant returns(bool) {
        if(rewardTokens[token]) revert Errors.CannotRecoverToken();
        uint256 amount = IERC20(token).balanceOf(address(this));
        if(amount == 0) revert Errors.NullAmount();
        IERC20(token).safeTransfer(owner(), amount);

        return true;
    }

    // 
    /**
    * @notice Allows to update the MerkleRoot for a given period of a Quest if the current Root is incorrect
    * @dev Updates the MerkleRoot for the period of the Quest
    * @param questID ID of the Quest
    * @param period Timestamp of the period
    * @param merkleRoot New MerkleRoot to add
    * @return bool : success
    */
    function emergencyUpdateQuestPeriod(uint256 questID, uint256 period, uint256 addedRewardAmount, bytes32 merkleRoot) external onlyOwner returns(bool) {
        // In case the given MerkleRoot was incorrect:
        // Process:
        // 1 - block claims for the Quest period by using this method to set an incorrect MerkleRoot, where no proof matches the root
        // 2 - prepare a new Merkle Tree, taking in account user previous claims on that period, and missing/overpaid rewards
        //      a - for all new claims to be added, set them after the last index of the previous Merkle Tree
        //      b - for users that did not claim, keep the same index, and adjust the amount to claim if needed
        //      c - for indexes that were claimed, place an empty node in the Merkle Tree (with an amount at 0 & the address 0xdead as the account)
        // 3 - update the Quest period with the correct MerkleRoot
        // (no need to change the Bitmap, as the new MerkleTree will account for the indexes already claimed)

        period = (period / WEEK) * WEEK;
        if(questRewardToken[questID] == address(0)) revert Errors.QuestNotListed();
        if(period == 0) revert Errors.IncorrectPeriod();
        if(questMerkleRootPerPeriod[questID][period] == 0) revert Errors.PeriodNotClosed();
        if(merkleRoot == 0) revert Errors.EmptyMerkleRoot();

        questMerkleRootPerPeriod[questID][period] = merkleRoot;

        questRewardsPerPeriod[questID][period] += addedRewardAmount;

        emit QuestPeriodUpdated(questID, period, merkleRoot);

        return true;
    }

}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (access/Ownable.sol)

pragma solidity ^0.8.0;

import "./Context.sol";

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

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

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _transferOwnership(_msgSender());
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        _checkOwner();
        _;
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if the sender is not the owner.
     */
    function _checkOwner() internal view virtual {
        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);
    }
}

// SPDX-License-Identifier: MIT
pragma solidity 0.8.16;

import "../oz/utils/Ownable.sol";
import "../libraries/Errors.sol";

/** @title 2-step Ownership  */
/// @author Paladin
/*
    Extends OZ Ownable contract to add 2-step ownership transfer
*/

contract Owner is Ownable {

    address public pendingOwner;

    event NewPendingOwner(address indexed previousPendingOwner, address indexed newPendingOwner);

    function transferOwnership(address newOwner) public override virtual onlyOwner {
        if(newOwner == address(0)) revert Errors.AddressZero();
        if(newOwner == owner()) revert Errors.CannotBeOwner();
        address oldPendingOwner = pendingOwner;

        pendingOwner = newOwner;

        emit NewPendingOwner(oldPendingOwner, newOwner);
    }

    function acceptOwnership() public virtual {
        if(msg.sender != pendingOwner) revert Errors.CallerNotPendingOwner();
        address newOwner = pendingOwner;
        _transferOwnership(pendingOwner);
        pendingOwner = address(0);

        emit NewPendingOwner(newOwner, address(0));
    }

}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (security/ReentrancyGuard.sol)

pragma solidity ^0.8.0;

/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 */
abstract contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor() {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and making it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        _nonReentrantBefore();
        _;
        _nonReentrantAfter();
    }

    function _nonReentrantBefore() private {
        // On the first call to nonReentrant, _status will be _NOT_ENTERED
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;
    }

    function _nonReentrantAfter() private {
        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Returns true if the reentrancy guard is currently set to "entered", which indicates there is a
     * `nonReentrant` function in the call stack.
     */
    function _reentrancyGuardEntered() internal view returns (bool) {
        return _status == _ENTERED;
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (token/ERC20/utils/SafeERC20.sol)

pragma solidity ^0.8.0;

import "../interfaces/IERC20.sol";
import "../extensions/IERC20Permit.sol";
import "../utils/Address.sol";

/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using 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));
        }
    }

    function safePermit(
        IERC20Permit token,
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) internal {
        uint256 nonceBefore = token.nonces(owner);
        token.permit(owner, spender, value, deadline, v, r, s);
        uint256 nonceAfter = token.nonces(owner);
        require(nonceAfter == nonceBefore + 1, "SafeERC20: permit did not succeed");
    }

    /**
     * @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");
        }
    }
}

{
  "compilationTarget": {
    "contracts/MultiMerkleDistributor.sol": "MultiMerkleDistributor"
  },
  "evmVersion": "london",
  "libraries": {},
  "metadata": {
    "bytecodeHash": "ipfs"
  },
  "optimizer": {
    "enabled": true,
    "runs": 200
  },
  "remappings": []
}