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

pragma solidity ^0.8.0;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        assembly {
            size := extcodesize(account)
        }
        return size > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        (bool success, ) = recipient.call{value: amount}("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain `call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        require(isContract(target), "Address: call to non-contract");

        (bool success, bytes memory returndata) = target.call{value: value}(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

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

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

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

    /**
     * @dev Tool to verifies that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason using the provided one.
     *
     * _Available since v4.3._
     */
    function verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal pure returns (bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

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

// 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;
    }
}

// SPDX-License-Identifier: MIT
pragma solidity 0.8.19;

import "./utils/Ownable.sol";
import "./MerkleDistributor.sol";

contract DistributorRegistry is Ownable {
    mapping(uint256 => address) public distributorsBySeason;
    mapping(address => bool) public distributors;

    /**
     * @dev Struct to represent claim data for batch processing.
     * @param rootNumber The Merkle root number associated with the claim.
     * @param index The index within the Merkle tree for this particular claim.
     * @param amount The amount of tokens to be claimed.
     * @param merkleProof The Merkle proof associated with the claim to validate it against the root.
     */
    struct MultiClaimData {
        uint256 seasonNumber;
        uint256 index;
        uint256 amount;
        bytes32[] merkleProof;
    }

    event DistributorAdded(uint256 indexed _seasonNumber, address _distributor);
    event DistributorRemoved(uint256 indexed _seasonNumber, address _distributor);

    constructor(address _admin) Ownable(_admin) {
        // solhint-disable-previous-line no-empty-blocks
    }

    function addDistributor(uint256 _seasonNumber, address _distributor) external onlyOwner {
        require(distributorsBySeason[_seasonNumber] == address(0), "Season number already set");
        distributorsBySeason[_seasonNumber] = _distributor;
        distributors[_distributor] = true;
        emit DistributorAdded(_seasonNumber, _distributor);
    }

    function removeDistributor(uint256 _seasonNumber) external onlyOwner {
        address distributor = distributorsBySeason[_seasonNumber];
        delete distributorsBySeason[_seasonNumber];
        delete distributors[distributor];
        emit DistributorRemoved(_seasonNumber, distributor);
    }

    function isDistributor(address _distributor) external view returns (bool) {
        return distributors[_distributor];
    }

    /**
     * @dev Supports batch claiming, instead of transferring to the recipient directly,
     * tokens are locked in the TokenLock contract.
     * @param _claimData An array containing details for each claim the caller wishes to make.
     */
    function multiClaim(MultiClaimData[] memory _claimData) external {
        for (uint256 i = 0; i < _claimData.length; ++i) {
            uint256 seasonNumber = _claimData[i].seasonNumber;
            uint256 index = _claimData[i].index;
            uint256 amount = _claimData[i].amount;
            bytes32[] memory merkleProof = _claimData[i].merkleProof;

            MerkleDistributor(distributorsBySeason[seasonNumber]).claimFromRegistry(
                index,
                amount,
                merkleProof,
                msg.sender
            );
        }
    }
}

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

pragma solidity ^0.8.0;

import "../Strings.sol";

/**
 * @dev Elliptic Curve Digital Signature Algorithm (ECDSA) operations.
 *
 * These functions can be used to verify that a message was signed by the holder
 * of the private keys of a given address.
 */
library ECDSA {
    enum RecoverError {
        NoError,
        InvalidSignature,
        InvalidSignatureLength,
        InvalidSignatureS,
        InvalidSignatureV
    }

    function _throwError(RecoverError error) private pure {
        if (error == RecoverError.NoError) {
            return; // no error: do nothing
        } else if (error == RecoverError.InvalidSignature) {
            revert("ECDSA: invalid signature");
        } else if (error == RecoverError.InvalidSignatureLength) {
            revert("ECDSA: invalid signature length");
        } else if (error == RecoverError.InvalidSignatureS) {
            revert("ECDSA: invalid signature 's' value");
        } else if (error == RecoverError.InvalidSignatureV) {
            revert("ECDSA: invalid signature 'v' value");
        }
    }

    /**
     * @dev Returns the address that signed a hashed message (`hash`) with
     * `signature` or error string. This address can then be used for verification purposes.
     *
     * The `ecrecover` EVM opcode allows for malleable (non-unique) signatures:
     * this function rejects them by requiring the `s` value to be in the lower
     * half order, and the `v` value to be either 27 or 28.
     *
     * IMPORTANT: `hash` _must_ be the result of a hash operation for the
     * verification to be secure: it is possible to craft signatures that
     * recover to arbitrary addresses for non-hashed data. A safe way to ensure
     * this is by receiving a hash of the original message (which may otherwise
     * be too long), and then calling {toEthSignedMessageHash} on it.
     *
     * Documentation for signature generation:
     * - with https://web3js.readthedocs.io/en/v1.3.4/web3-eth-accounts.html#sign[Web3.js]
     * - with https://docs.ethers.io/v5/api/signer/#Signer-signMessage[ethers]
     *
     * _Available since v4.3._
     */
    function tryRecover(bytes32 hash, bytes memory signature) internal pure returns (address, RecoverError) {
        // Check the signature length
        // - case 65: r,s,v signature (standard)
        // - case 64: r,vs signature (cf https://eips.ethereum.org/EIPS/eip-2098) _Available since v4.1._
        if (signature.length == 65) {
            bytes32 r;
            bytes32 s;
            uint8 v;
            // ecrecover takes the signature parameters, and the only way to get them
            // currently is to use assembly.
            assembly {
                r := mload(add(signature, 0x20))
                s := mload(add(signature, 0x40))
                v := byte(0, mload(add(signature, 0x60)))
            }
            return tryRecover(hash, v, r, s);
        } else if (signature.length == 64) {
            bytes32 r;
            bytes32 vs;
            // ecrecover takes the signature parameters, and the only way to get them
            // currently is to use assembly.
            assembly {
                r := mload(add(signature, 0x20))
                vs := mload(add(signature, 0x40))
            }
            return tryRecover(hash, r, vs);
        } else {
            return (address(0), RecoverError.InvalidSignatureLength);
        }
    }

    /**
     * @dev Returns the address that signed a hashed message (`hash`) with
     * `signature`. This address can then be used for verification purposes.
     *
     * The `ecrecover` EVM opcode allows for malleable (non-unique) signatures:
     * this function rejects them by requiring the `s` value to be in the lower
     * half order, and the `v` value to be either 27 or 28.
     *
     * IMPORTANT: `hash` _must_ be the result of a hash operation for the
     * verification to be secure: it is possible to craft signatures that
     * recover to arbitrary addresses for non-hashed data. A safe way to ensure
     * this is by receiving a hash of the original message (which may otherwise
     * be too long), and then calling {toEthSignedMessageHash} on it.
     */
    function recover(bytes32 hash, bytes memory signature) internal pure returns (address) {
        (address recovered, RecoverError error) = tryRecover(hash, signature);
        _throwError(error);
        return recovered;
    }

    /**
     * @dev Overload of {ECDSA-tryRecover} that receives the `r` and `vs` short-signature fields separately.
     *
     * See https://eips.ethereum.org/EIPS/eip-2098[EIP-2098 short signatures]
     *
     * _Available since v4.3._
     */
    function tryRecover(
        bytes32 hash,
        bytes32 r,
        bytes32 vs
    ) internal pure returns (address, RecoverError) {
        bytes32 s;
        uint8 v;
        assembly {
            s := and(vs, 0x7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff)
            v := add(shr(255, vs), 27)
        }
        return tryRecover(hash, v, r, s);
    }

    /**
     * @dev Overload of {ECDSA-recover} that receives the `r and `vs` short-signature fields separately.
     *
     * _Available since v4.2._
     */
    function recover(
        bytes32 hash,
        bytes32 r,
        bytes32 vs
    ) internal pure returns (address) {
        (address recovered, RecoverError error) = tryRecover(hash, r, vs);
        _throwError(error);
        return recovered;
    }

    /**
     * @dev Overload of {ECDSA-tryRecover} that receives the `v`,
     * `r` and `s` signature fields separately.
     *
     * _Available since v4.3._
     */
    function tryRecover(
        bytes32 hash,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) internal pure returns (address, RecoverError) {
        // EIP-2 still allows signature malleability for ecrecover(). Remove this possibility and make the signature
        // unique. Appendix F in the Ethereum Yellow paper (https://ethereum.github.io/yellowpaper/paper.pdf), defines
        // the valid range for s in (301): 0 < s < secp256k1n ÷ 2 + 1, and for v in (302): v ∈ {27, 28}. Most
        // signatures from current libraries generate a unique signature with an s-value in the lower half order.
        //
        // If your library generates malleable signatures, such as s-values in the upper range, calculate a new s-value
        // with 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141 - s1 and flip v from 27 to 28 or
        // vice versa. If your library also generates signatures with 0/1 for v instead 27/28, add 27 to v to accept
        // these malleable signatures as well.
        if (uint256(s) > 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0) {
            return (address(0), RecoverError.InvalidSignatureS);
        }
        if (v != 27 && v != 28) {
            return (address(0), RecoverError.InvalidSignatureV);
        }

        // If the signature is valid (and not malleable), return the signer address
        address signer = ecrecover(hash, v, r, s);
        if (signer == address(0)) {
            return (address(0), RecoverError.InvalidSignature);
        }

        return (signer, RecoverError.NoError);
    }

    /**
     * @dev Overload of {ECDSA-recover} that receives the `v`,
     * `r` and `s` signature fields separately.
     */
    function recover(
        bytes32 hash,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) internal pure returns (address) {
        (address recovered, RecoverError error) = tryRecover(hash, v, r, s);
        _throwError(error);
        return recovered;
    }

    /**
     * @dev Returns an Ethereum Signed Message, created from a `hash`. This
     * produces hash corresponding to the one signed with the
     * https://eth.wiki/json-rpc/API#eth_sign[`eth_sign`]
     * JSON-RPC method as part of EIP-191.
     *
     * See {recover}.
     */
    function toEthSignedMessageHash(bytes32 hash) internal pure returns (bytes32) {
        // 32 is the length in bytes of hash,
        // enforced by the type signature above
        return keccak256(abi.encodePacked("\x19Ethereum Signed Message:\n32", hash));
    }

    /**
     * @dev Returns an Ethereum Signed Message, created from `s`. This
     * produces hash corresponding to the one signed with the
     * https://eth.wiki/json-rpc/API#eth_sign[`eth_sign`]
     * JSON-RPC method as part of EIP-191.
     *
     * See {recover}.
     */
    function toEthSignedMessageHash(bytes memory s) internal pure returns (bytes32) {
        return keccak256(abi.encodePacked("\x19Ethereum Signed Message:\n", Strings.toString(s.length), s));
    }

    /**
     * @dev Returns an Ethereum Signed Typed Data, created from a
     * `domainSeparator` and a `structHash`. This produces hash corresponding
     * to the one signed with the
     * https://eips.ethereum.org/EIPS/eip-712[`eth_signTypedData`]
     * JSON-RPC method as part of EIP-712.
     *
     * See {recover}.
     */
    function toTypedDataHash(bytes32 domainSeparator, bytes32 structHash) internal pure returns (bytes32) {
        return keccak256(abi.encodePacked("\x19\x01", domainSeparator, structHash));
    }
}

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

pragma solidity ^0.8.0;

import "./IERC20.sol";
import "./extensions/IERC20Metadata.sol";
import "../../utils/Context.sol";

/**
 * @dev Implementation of the {IERC20} interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using {_mint}.
 * For a generic mechanism see {ERC20PresetMinterPauser}.
 *
 * TIP: For a detailed writeup see our guide
 * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * We have followed general OpenZeppelin Contracts guidelines: functions revert
 * instead returning `false` on failure. This behavior is nonetheless
 * conventional and does not conflict with the expectations of ERC20
 * applications.
 *
 * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See {IERC20-approve}.
 */
contract ERC20 is Context, IERC20, IERC20Metadata {
    mapping(address => uint256) private _balances;

    mapping(address => mapping(address => uint256)) private _allowances;

    uint256 private _totalSupply;

    string private _name;
    string private _symbol;

    /**
     * @dev Sets the values for {name} and {symbol}.
     *
     * The default value of {decimals} is 18. To select a different value for
     * {decimals} you should overload it.
     *
     * All two of these values are immutable: they can only be set once during
     * construction.
     */
    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
    }

    /**
     * @dev Returns the name of the token.
     */
    function name() public view virtual override returns (string memory) {
        return _name;
    }

    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public view virtual override returns (string memory) {
        return _symbol;
    }

    /**
     * @dev Returns the number of decimals used to get its user representation.
     * For example, if `decimals` equals `2`, a balance of `505` tokens should
     * be displayed to a user as `5.05` (`505 / 10 ** 2`).
     *
     * Tokens usually opt for a value of 18, imitating the relationship between
     * Ether and Wei. This is the value {ERC20} uses, unless this function is
     * overridden;
     *
     * NOTE: This information is only used for _display_ purposes: it in
     * no way affects any of the arithmetic of the contract, including
     * {IERC20-balanceOf} and {IERC20-transfer}.
     */
    function decimals() public view virtual override returns (uint8) {
        return 18;
    }

    /**
     * @dev See {IERC20-totalSupply}.
     */
    function totalSupply() public view virtual override returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address account) public view virtual override returns (uint256) {
        return _balances[account];
    }

    /**
     * @dev See {IERC20-transfer}.
     *
     * Requirements:
     *
     * - `recipient` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(_msgSender(), recipient, amount);
        return true;
    }

    /**
     * @dev See {IERC20-allowance}.
     */
    function allowance(address owner, address spender) public view virtual override returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See {IERC20-approve}.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        _approve(_msgSender(), spender, amount);
        return true;
    }

    /**
     * @dev See {IERC20-transferFrom}.
     *
     * Emits an {Approval} event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of {ERC20}.
     *
     * Requirements:
     *
     * - `sender` and `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     * - the caller must have allowance for ``sender``'s tokens of at least
     * `amount`.
     */
    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) public virtual override returns (bool) {
        _transfer(sender, recipient, amount);

        uint256 currentAllowance = _allowances[sender][_msgSender()];
        require(currentAllowance >= amount, "ERC20: transfer amount exceeds allowance");
        unchecked {
            _approve(sender, _msgSender(), currentAllowance - amount);
        }

        return true;
    }

    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender] + addedValue);
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
        uint256 currentAllowance = _allowances[_msgSender()][spender];
        require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
        unchecked {
            _approve(_msgSender(), spender, currentAllowance - subtractedValue);
        }

        return true;
    }

    /**
     * @dev Moves `amount` of tokens from `sender` to `recipient`.
     *
     * This internal function is equivalent to {transfer}, and can be used to
     * e.g. implement automatic token fees, slashing mechanisms, etc.
     *
     * Emits a {Transfer} event.
     *
     * Requirements:
     *
     * - `sender` cannot be the zero address.
     * - `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     */
    function _transfer(
        address sender,
        address recipient,
        uint256 amount
    ) internal virtual {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");

        _beforeTokenTransfer(sender, recipient, amount);

        uint256 senderBalance = _balances[sender];
        require(senderBalance >= amount, "ERC20: transfer amount exceeds balance");
        unchecked {
            _balances[sender] = senderBalance - amount;
        }
        _balances[recipient] += amount;

        emit Transfer(sender, recipient, amount);

        _afterTokenTransfer(sender, recipient, amount);
    }

    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
     * the total supply.
     *
     * Emits a {Transfer} event with `from` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     */
    function _mint(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: mint to the zero address");

        _beforeTokenTransfer(address(0), account, amount);

        _totalSupply += amount;
        _balances[account] += amount;
        emit Transfer(address(0), account, amount);

        _afterTokenTransfer(address(0), account, amount);
    }

    /**
     * @dev Destroys `amount` tokens from `account`, reducing the
     * total supply.
     *
     * Emits a {Transfer} event with `to` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens.
     */
    function _burn(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: burn from the zero address");

        _beforeTokenTransfer(account, address(0), amount);

        uint256 accountBalance = _balances[account];
        require(accountBalance >= amount, "ERC20: burn amount exceeds balance");
        unchecked {
            _balances[account] = accountBalance - amount;
        }
        _totalSupply -= amount;

        emit Transfer(account, address(0), amount);

        _afterTokenTransfer(account, address(0), amount);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
     *
     * This internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    function _approve(
        address owner,
        address spender,
        uint256 amount
    ) internal virtual {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    /**
     * @dev Hook that is called before any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * will be transferred to `to`.
     * - when `from` is zero, `amount` tokens will be minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {}

    /**
     * @dev Hook that is called after any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * has been transferred to `to`.
     * - when `from` is zero, `amount` tokens have been minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens have been burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _afterTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {}
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (interfaces/IERC1271.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC1271 standard signature validation method for
 * contracts as defined in https://eips.ethereum.org/EIPS/eip-1271[ERC-1271].
 *
 * _Available since v4.1._
 */
interface IERC1271 {
    /**
     * @dev Should return whether the signature provided is valid for the provided data
     * @param hash      Hash of the data to be signed
     * @param signature Signature byte array associated with _data
     */
    function isValidSignature(bytes32 hash, bytes memory signature) external view returns (bytes4 magicValue);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/IERC20Metadata.sol)

pragma solidity ^0.8.0;

import "../IERC20.sol";

/**
 * @dev Interface for the optional metadata functions from the ERC20 standard.
 *
 * _Available since v4.1._
 */
interface IERC20Metadata is IERC20 {
    /**
     * @dev Returns the name of the token.
     */
    function name() external view returns (string memory);

    /**
     * @dev Returns the symbol of the token.
     */
    function symbol() external view returns (string memory);

    /**
     * @dev Returns the decimals places of the token.
     */
    function decimals() external view returns (uint8);
}

// SPDX-License-Identifier: MIT
pragma solidity 0.8.19;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/utils/cryptography/MerkleProof.sol";
import {Pausable} from "@openzeppelin/contracts/security/Pausable.sol";

import "./NFI.sol";
import "./TokenLock.sol";

import "./utils/Ownable.sol";

/**
 * @title MerkleDistributor
 * @author NFTfi
 * @dev Modified version of Uniswap's MerkleDistributor
 * https://github.com/Uniswap/merkle-distributor/blob/master/contracts/MerkleDistributor.sol
 * Main difference: in claim instead of transferring the tokens to the user,
 * we transfer it to the tokenLock contract
 */
contract MerkleDistributor is Ownable, Pausable {
    NFI public immutable nfi;
    TokenLock public immutable tokenLock;
    address public immutable distributorRegistry;
    uint256 public immutable claimCutoffDate;

    bytes32 public merkleRoot;

    mapping(uint256 => uint256) private claimedBitMap;

    event Claimed(uint256 _index, uint256 _amount, bytes32[] _merkleProof, address indexed _account);

    /**
     * @dev Constructor initializes references for NFTfi token and TokenLock contract.
     * It also sets the owner of the contract.
     * @param _admin The initial owner of the contract, usually able to set Merkle roots.
     * @param _nfi Address of the NFTfi token contract.
     * @param _tokenLock Address of the TokenLock contract where tokens are transferred upon claims.
     */
    constructor(
        bytes32 _merkleRoot,
        address _admin,
        address _nfi,
        address _tokenLock,
        address _distributorRegistry,
        uint256 _claimCutoffDate
    ) Ownable(_admin) {
        merkleRoot = _merkleRoot;
        nfi = NFI(_nfi);
        tokenLock = TokenLock(_tokenLock);
        distributorRegistry = _distributorRegistry;
        claimCutoffDate = _claimCutoffDate;
    }

    function isClaimed(uint256 _index) public view returns (bool) {
        uint256 claimedWordIndex = _index / 256;
        uint256 claimedBitIndex = _index % 256;
        uint256 claimedWord = claimedBitMap[claimedWordIndex];
        uint256 mask = (1 << claimedBitIndex);
        return claimedWord & mask == mask;
    }

    function _setClaimed(uint256 _index) private {
        uint256 claimedWordIndex = _index / 256;
        uint256 claimedBitIndex = _index % 256;
        claimedBitMap[claimedWordIndex] = claimedBitMap[claimedWordIndex] | (1 << claimedBitIndex);
    }

    function claim(
        uint256 _index,
        uint256 _amount,
        bytes32[] memory _merkleProof
    ) external {
        _claim(_index, _amount, _merkleProof, msg.sender);
    }

    function claimFromRegistry(
        uint256 _index,
        uint256 _amount,
        bytes32[] memory _merkleProof,
        address _claimer
    ) external {
        require(msg.sender == distributorRegistry, "Only registry");
        _claim(_index, _amount, _merkleProof, _claimer);
    }

    function _claim(
        uint256 _index,
        uint256 _amount,
        bytes32[] memory _merkleProof,
        address _claimer
    ) internal whenNotPaused {
        require(block.timestamp < claimCutoffDate, "cutoff date elapsed");

        require(!isClaimed(_index), "distributor: already claimed");

        // Verify the merkle proof.
        bytes32 node = keccak256(abi.encodePacked(_index, _claimer, _amount));
        require(MerkleProof.verify(_merkleProof, merkleRoot, node), "distributor: invalid proof");

        // Mark it claimed and send the token.
        _setClaimed(_index);

        nfi.approve(address(tokenLock), _amount);
        tokenLock.lockTokensFromDistributor(_amount, _claimer);

        emit Claimed(_index, _amount, _merkleProof, _claimer);
    }

    /**
     * @dev Drain to admin address in an emergency
     * @param _amount of tokens to drain
     */
    function drain(uint256 _amount) public onlyOwner {
        nfi.transfer(owner(), _amount);
    }

    /**
     * @dev Triggers stopped state.
     *
     * Requirements:
     *
     * - Only the owner can call this method.
     * - The contract must not be paused.
     */
    function pause() external onlyOwner {
        _pause();
    }

    /**
     * @dev Returns to normal state.
     *
     * Requirements:
     *
     * - Only the owner can call this method.
     * - The contract must be paused.
     */
    function unpause() external onlyOwner {
        _unpause();
    }
}

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

pragma solidity ^0.8.0;

/**
 * @dev These functions deal with verification of Merkle Trees proofs.
 *
 * The proofs can be generated using the JavaScript library
 * https://github.com/miguelmota/merkletreejs[merkletreejs].
 * Note: the hashing algorithm should be keccak256 and pair sorting should be enabled.
 *
 * See `test/utils/cryptography/MerkleProof.test.js` for some examples.
 */
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 Returns the rebuilt hash obtained by traversing a Merklee 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++) {
            bytes32 proofElement = proof[i];
            if (computedHash <= proofElement) {
                // Hash(current computed hash + current element of the proof)
                computedHash = keccak256(abi.encodePacked(computedHash, proofElement));
            } else {
                // Hash(current element of the proof + current computed hash)
                computedHash = keccak256(abi.encodePacked(proofElement, computedHash));
            }
        }
        return computedHash;
    }
}

// SPDX-License-Identifier: MIT

pragma solidity 0.8.19;

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";

/**
 * @title NFI
 * @author NFTfi
 * @dev standard ERC20 token
 */
contract NFI is ERC20 {
    constructor(uint256 _initialSupply, address _owner) ERC20("NFTfi Token", "NFI") {
        _mint(_owner, _initialSupply);
    }
}

// SPDX-License-Identifier: BUSL-1.1

pragma solidity 0.8.19;

import "@openzeppelin/contracts/utils/Context.sol";

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

    address private _ownerCandidate;

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

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor(address _initialOwner) {
        _setOwner(_initialOwner);
    }

    /**
     * @dev Requests transferring ownership of the contract to a new account (`_newOwnerCandidate`).
     * Can only be called by the current owner.
     */
    function requestTransferOwnership(address _newOwnerCandidate) public virtual onlyOwner {
        require(_newOwnerCandidate != address(0), "Ownable: new owner is the zero address");
        _ownerCandidate = _newOwnerCandidate;
    }

    function acceptTransferOwnership() public virtual {
        require(_ownerCandidate == _msgSender(), "Ownable: not owner candidate");
        _setOwner(_ownerCandidate);
        delete _ownerCandidate;
    }

    function cancelTransferOwnership() public virtual onlyOwner {
        delete _ownerCandidate;
    }

    function rejectTransferOwnership() public virtual {
        require(_ownerCandidate == _msgSender(), "Ownable: not owner candidate");
        delete _ownerCandidate;
    }

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

    /**
     * @dev Sets the owner.
     */
    function _setOwner(address _newOwner) internal {
        address oldOwner = _owner;
        _owner = _newOwner;
        emit OwnershipTransferred(oldOwner, _newOwner);
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (security/Pausable.sol)

pragma solidity ^0.8.0;

import "../utils/Context.sol";

/**
 * @dev Contract module which allows children to implement an emergency stop
 * mechanism that can be triggered by an authorized account.
 *
 * This module is used through inheritance. It will make available the
 * modifiers `whenNotPaused` and `whenPaused`, which can be applied to
 * the functions of your contract. Note that they will not be pausable by
 * simply including this module, only once the modifiers are put in place.
 */
abstract contract Pausable is Context {
    /**
     * @dev Emitted when the pause is triggered by `account`.
     */
    event Paused(address account);

    /**
     * @dev Emitted when the pause is lifted by `account`.
     */
    event Unpaused(address account);

    bool private _paused;

    /**
     * @dev Initializes the contract in unpaused state.
     */
    constructor() {
        _paused = false;
    }

    /**
     * @dev Returns true if the contract is paused, and false otherwise.
     */
    function paused() public view virtual returns (bool) {
        return _paused;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is not paused.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    modifier whenNotPaused() {
        require(!paused(), "Pausable: paused");
        _;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is paused.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    modifier whenPaused() {
        require(paused(), "Pausable: not paused");
        _;
    }

    /**
     * @dev Triggers stopped state.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    function _pause() internal virtual whenNotPaused {
        _paused = true;
        emit Paused(_msgSender());
    }

    /**
     * @dev Returns to normal state.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    function _unpause() internal virtual whenPaused {
        _paused = false;
        emit Unpaused(_msgSender());
    }
}

// SPDX-License-Identifier: BUSL-1.1

pragma solidity 0.8.19;

import "@openzeppelin/contracts/utils/cryptography/SignatureChecker.sol";

/**
 * @title  ProtocolSigningUtils
 * @author NFTfi
 * @notice Helper library for NFTfi. This contract manages verifying signatures
 * from an NFTfi protocol address to enforce KYC requirements on-chain
 */
library ProtocolSigningUtils {
    /**
     * @dev Signature struct
     *
     * @param expiry The timestamp after which the signature is considered expired and invalid.
     * @param signer Signing protocol address
     * @param signature The actual ECDSA signature bytes of the signed data
     */
    struct ProtocolSignature {
        uint256 expiry;
        address signer;
        bytes signature;
    }

    /* ********* */
    /* FUNCTIONS */
    /* ********* */

    /**
     * @notice Verifies the validity of a protocol signature.
     * @dev This function checks whether the protocol signature is valid and hasn't expired.
     * It constructs a message from the input parameters and verifies its signature against
     * the expected signer.
     *
     * @param _user The address of the user initiating the withdrawal.
     * @param _amount The amount the user is withdrawing.
     * @param _requestTimestamp The timestamp when the withdrawal request was made.
     * @param _protocolSignature - The signature structure containing:
     * - signer: The address of the signer, in this case and address controlled by the protocol
     * - expiry: Date when the signature expires
     * - signature: The ECDSA signature of the protocol, obtained off-chain ahead of time, signing the following
     * combination of parameters:
     *   - user withdrawing from TokenLock
     *   - amount withdrawn
     *   - requestTimestamp time of the request for the withdrawal to check signature for each individual call
     *   - protocolSignature.signer
     *   - protocolSignature.expiry
     * @return bool True if the protocol signature is valid; otherwise, false.
     */
    function isValidProtocolSignature(
        address _user,
        uint256 _amount,
        uint256 _requestTimestamp,
        ProtocolSignature memory _protocolSignature
    ) internal view returns (bool) {
        require(block.timestamp <= _protocolSignature.expiry, "Protocol Signature expired");

        bytes32 message = keccak256(
            abi.encodePacked(_user, _amount, _requestTimestamp, _protocolSignature.signer, _protocolSignature.expiry)
        );

        return
            SignatureChecker.isValidSignatureNow(
                _protocolSignature.signer,
                ECDSA.toEthSignedMessageHash(message),
                _protocolSignature.signature
            );
    }
}

/**
 * @title  ProtocolSigningUtils
 * @author NFTfi
 * @notice Deployable contract for of the above library
 */
contract ProtocolSigningUtilsContract {
    /* ********* */
    /* FUNCTIONS */
    /* ********* */

    /**
     * @notice Verifies the validity of a protocol signature.
     * @dev This function checks whether the protocol signature is valid and hasn't expired.
     * It constructs a message from the input parameters and verifies its signature against
     * the expected signer.
     *
     * @param _user The address of the user initiating the withdrawal.
     * @param _amount The amount the user is withdrawing.
     * @param _requestTimestamp The timestamp when the withdrawal request was made.
     * @param _protocolSignature - The signature structure containing:
     * - signer: The address of the signer, in this case and address controlled by the protocol
     * - expiry: Date when the signature expires
     * - signature: The ECDSA signature of the protocol, obtained off-chain ahead of time, signing the following
     * combination of parameters:
     *   - user withdrawing from TokenLock
     *   - amount withdrawn
     *   - requestTimestamp time of the request for the withdrawal to check signature for each individual call
     *   - protocolSignature.signer
     *   - protocolSignature.expiry
     * @return bool True if the protocol signature is valid; otherwise, false.
     */
    function isValidProtocolSignature(
        address _user,
        uint256 _amount,
        uint256 _requestTimestamp,
        ProtocolSigningUtils.ProtocolSignature memory _protocolSignature
    ) external view returns (bool) {
        return ProtocolSigningUtils.isValidProtocolSignature(_user, _amount, _requestTimestamp, _protocolSignature);
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/utils/SafeERC20.sol)

pragma solidity ^0.8.0;

import "../IERC20.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));
        }
    }

    /**
     * @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");
        }
    }
}

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

pragma solidity ^0.8.0;

import "./ECDSA.sol";
import "../Address.sol";
import "../../interfaces/IERC1271.sol";

/**
 * @dev Signature verification helper: Provide a single mechanism to verify both private-key (EOA) ECDSA signature and
 * ERC1271 contract signatures. Using this instead of ECDSA.recover in your contract will make them compatible with
 * smart contract wallets such as Argent and Gnosis.
 *
 * Note: unlike ECDSA signatures, contract signature's are revocable, and the outcome of this function can thus change
 * through time. It could return true at block N and false at block N+1 (or the opposite).
 *
 * _Available since v4.1._
 */
library SignatureChecker {
    function isValidSignatureNow(
        address signer,
        bytes32 hash,
        bytes memory signature
    ) internal view returns (bool) {
        (address recovered, ECDSA.RecoverError error) = ECDSA.tryRecover(hash, signature);
        if (error == ECDSA.RecoverError.NoError && recovered == signer) {
            return true;
        }

        (bool success, bytes memory result) = signer.staticcall(
            abi.encodeWithSelector(IERC1271.isValidSignature.selector, hash, signature)
        );
        return (success && result.length == 32 && abi.decode(result, (bytes4)) == IERC1271.isValidSignature.selector);
    }
}

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

pragma solidity ^0.8.0;

/**
 * @dev String operations.
 */
library Strings {
    bytes16 private constant _HEX_SYMBOLS = "0123456789abcdef";

    /**
     * @dev Converts a `uint256` to its ASCII `string` decimal representation.
     */
    function toString(uint256 value) internal pure returns (string memory) {
        // Inspired by OraclizeAPI's implementation - MIT licence
        // https://github.com/oraclize/ethereum-api/blob/b42146b063c7d6ee1358846c198246239e9360e8/oraclizeAPI_0.4.25.sol

        if (value == 0) {
            return "0";
        }
        uint256 temp = value;
        uint256 digits;
        while (temp != 0) {
            digits++;
            temp /= 10;
        }
        bytes memory buffer = new bytes(digits);
        while (value != 0) {
            digits -= 1;
            buffer[digits] = bytes1(uint8(48 + uint256(value % 10)));
            value /= 10;
        }
        return string(buffer);
    }

    /**
     * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation.
     */
    function toHexString(uint256 value) internal pure returns (string memory) {
        if (value == 0) {
            return "0x00";
        }
        uint256 temp = value;
        uint256 length = 0;
        while (temp != 0) {
            length++;
            temp >>= 8;
        }
        return toHexString(value, length);
    }

    /**
     * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation with fixed length.
     */
    function toHexString(uint256 value, uint256 length) internal pure returns (string memory) {
        bytes memory buffer = new bytes(2 * length + 2);
        buffer[0] = "0";
        buffer[1] = "x";
        for (uint256 i = 2 * length + 1; i > 1; --i) {
            buffer[i] = _HEX_SYMBOLS[value & 0xf];
            value >>= 4;
        }
        require(value == 0, "Strings: hex length insufficient");
        return string(buffer);
    }
}

// SPDX-License-Identifier: BUSL-1.1

pragma solidity 0.8.19;

import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
import {Pausable} from "@openzeppelin/contracts/security/Pausable.sol";

import "./NFI.sol";
import "./DistributorRegistry.sol";
import "./TokenUtilityAccounting.sol";

import "./utils/Ownable.sol";
import "./utils/ProtocolSigningUtils.sol";

/**
 * @title TokenLock
 * @author NFTfi
 * @dev This contract allows users to lock tokens with a request-based withdrawal mechanism. Withdrawals
 * have cooldown periods and need a protocol signature if the tokens withdrawn come from the distributor
 * and not from an external source. It integrates with a `TokenUtilityAccounting` contract.
 */
contract TokenLock is Ownable, Pausable {
    using SafeERC20 for NFI;

    // Contract that calculates a token utility score with a (locked) time based multiplier.
    // Optional, can be left zero-address and added in the future.
    TokenUtilityAccounting public tokenUtilityAccounting;
    NFI public immutable nfiToken;

    DistributorRegistry public immutable distributorRegistry;

    address public protocolSignerAddress;

    // Cooldown time before a withdrawal can be executed after request in seconds
    uint256 public cooldown;

    mapping(address => uint256) public totalLockedTokens;
    mapping(address => uint256) public distributorLockedTokens;

    mapping(address => uint256) public withdrawalRequestAmounts;

    mapping(bytes32 => bool) private withdrawRequests;

    /**
     * @dev Emitted when tokens are locked in the contract.
     * @param _amount The amount of tokens locked.
     * @param _user Address of the user who locked the tokens.
     */
    event Locked(uint256 _amount, address indexed _user);

    /**
     * @dev Emitted when a user requests to withdraw their tokens.
     * @param _amount The amount of tokens the user wants to withdraw.
     * @param _user Address of the user requesting the withdrawal.
     * @param _timestamp When the withdrawal request was made. Unix timstamp in seconds.
     * Needs to be saved for withdrawal!
     * @param _needsProtocolSignature If the withdrawal requires a protocol signature.
     */
    event WithdrawalRequested(uint256 _amount, address indexed _user, uint256 _timestamp, bool _needsProtocolSignature);

    /**
     * @dev Emitted when a user's withdrawal request is deleted.
     * @param _amount The amount of tokens the user initially wanted to withdraw.
     * @param _user Address of the user whose request was deleted.
     * @param _timestamp When request was made (unix timstamp in seconds)
     */
    event WithdrawalRequestDeleted(uint256 _amount, address indexed _user, uint256 _timestamp);

    /**
     * @dev Emitted when a user withdraws their tokens.
     * @param _amount The amount of tokens withdrawn.
     * @param _user Address of the user making the withdrawal.
     */
    event Withdrawn(uint256 _amount, address indexed _user);

    /**
     * @dev Initializes the contract, setting initial admin, token, distributor, and cooldown values.
     * @param _admin Admin's address.
     * @param _nfi Address of the NFI token.
     * @param _distributorRegistry MerkleDistributor contract address.
     * @param _protocolSignerAddress protocol signature checking feature can be turned off by setting it to 0 address
     * @param _cooldown Cooldown time in seconds.
     */
    constructor(
        address _admin,
        address _nfi,
        address _distributorRegistry,
        address _tokenUtilityAccounting,
        address _protocolSignerAddress,
        uint256 _cooldown
    ) Ownable(_admin) {
        nfiToken = NFI(_nfi);
        distributorRegistry = DistributorRegistry(_distributorRegistry);
        tokenUtilityAccounting = TokenUtilityAccounting(_tokenUtilityAccounting);
        protocolSignerAddress = _protocolSignerAddress;
        cooldown = _cooldown;
    }

    /**
     * @dev Allows the distributor to lock tokens on behalf of a beneficiary (claimer).
     * @param _amount Amount of tokens to lock.
     * @param _beneficiary Address of the beneficiary.
     */
    function lockTokensFromDistributor(uint256 _amount, address _beneficiary) external {
        require(distributorRegistry.isDistributor(msg.sender), "Only registered distributor");
        _lockTokens(_amount, _beneficiary);
        distributorLockedTokens[_beneficiary] += _amount;
    }

    /**
     * @dev Allows a user to lock their externally owned tokens
     * @param _amount Amount of tokens to lock.
     */
    function lockTokens(uint256 _amount) external {
        _lockTokens(_amount, msg.sender);
    }

    /**
     * @dev Internal function to handle locking of tokens.
     * @param _amount Amount of tokens to lock.
     * @param _beneficiary Address for whom the tokens are being locked.
     */
    function _lockTokens(uint256 _amount, address _beneficiary) internal whenNotPaused {
        nfiToken.safeTransferFrom(msg.sender, address(this), _amount);
        totalLockedTokens[_beneficiary] += _amount;
        if (address(tokenUtilityAccounting) != address(0)) {
            tokenUtilityAccounting.lock(_beneficiary, _amount);
        }
        emit Locked(_amount, _beneficiary);
    }

    /**
     * @dev Allows a user to request a withdrawal of their tokens.
     * @param _amount Amount of tokens to request for withdrawal.
     */
    function requestWithdrawal(uint256 _amount) external whenNotPaused {
        require(
            _amount + withdrawalRequestAmounts[msg.sender] <= totalLockedTokens[msg.sender],
            "request amounts > total"
        );
        bytes32 requestHash = _calculateRequestHash(_amount, msg.sender, block.timestamp);
        require(!withdrawRequests[requestHash], "duplicate request");
        withdrawalRequestAmounts[msg.sender] += _amount;
        withdrawRequests[requestHash] = true;
        bool needsProtocolSignature = isProtocolSignatureNeeded(_amount, msg.sender);
        emit WithdrawalRequested(_amount, msg.sender, block.timestamp, needsProtocolSignature);
        if (address(tokenUtilityAccounting) != address(0)) {
            tokenUtilityAccounting.unlock(msg.sender, _amount);
        }
    }

    /**
     * @dev Allows a user to delete their withdrawal request.
     * @param _amount Amount of tokens that were requested for withdrawal.
     * @param _requestTimestamp Timestamp of the original withdrawal request.
     */
    function deleteWithdrawRequest(uint256 _amount, uint256 _requestTimestamp) external whenNotPaused {
        bytes32 requestHash = _calculateRequestHash(_amount, msg.sender, _requestTimestamp);
        require(withdrawRequests[requestHash], "no request");
        delete withdrawRequests[requestHash];
        withdrawalRequestAmounts[msg.sender] -= _amount;
        emit WithdrawalRequestDeleted(_amount, msg.sender, _requestTimestamp);
        if (address(tokenUtilityAccounting) != address(0)) {
            tokenUtilityAccounting.lock(msg.sender, _amount);
        }
    }

    /**
     * @dev Allows a user to withdraw their tokens after a cooldown,
     * with a protocol signature if we withdraw from the ditributor locked pot.
     * @param _amount Amount of tokens to withdraw.
     * @param _requestTimestamp Timestamp of the original withdrawal request.
     * @param _protocolSignatureExpiry The timestamp after which the signature is considered expired and invalid.
     * Not checked if we withdraw from the non-ditributor locked pot.
     * Can be left with 0 values in that case.
     * @param _protocolSignature The actual ECDSA signature bytes of the signed data
     * Not checked if we withdraw from the non-ditributor locked pot.
     * Can be left with 0 values in that case.
     */
    function withdraw(
        uint256 _amount,
        uint256 _requestTimestamp,
        uint256 _protocolSignatureExpiry,
        bytes calldata _protocolSignature
    ) external whenNotPaused {
        require(_amount <= totalLockedTokens[msg.sender], "withdraw amount > total");
        // cooldown checking feature can be turned off by setting it to 0
        if (cooldown > 0) {
            bytes32 requestHash = _calculateRequestHash(_amount, msg.sender, _requestTimestamp);
            require(withdrawRequests[requestHash], "no request");
            require(block.timestamp >= _requestTimestamp + cooldown, "cooldown not up");
            delete withdrawRequests[requestHash];
            withdrawalRequestAmounts[msg.sender] -= _amount;
        } else {
            if (address(tokenUtilityAccounting) != address(0)) {
                tokenUtilityAccounting.unlock(msg.sender, _amount);
            }
        }
        bool needsProtocolSignature = isProtocolSignatureNeeded(_amount, msg.sender);
        // protocol signature checking feature can be turned off by setting signer address to 0 address
        if (needsProtocolSignature && protocolSignerAddress != address(0)) {
            require(
                ProtocolSigningUtils.isValidProtocolSignature(
                    msg.sender,
                    _amount,
                    _requestTimestamp,
                    ProtocolSigningUtils.ProtocolSignature({
                        expiry: _protocolSignatureExpiry,
                        signer: protocolSignerAddress,
                        signature: _protocolSignature
                    })
                ),
                "Protocol signature invalid"
            );
            // if we needed Protocol Signature anyway, we deduct it primarily from the distributor locked pot
            if (distributorLockedTokens[msg.sender] > _amount) {
                distributorLockedTokens[msg.sender] -= _amount;
            } else {
                distributorLockedTokens[msg.sender] = 0;
            }
        }
        totalLockedTokens[msg.sender] -= _amount;
        nfiToken.safeTransfer(msg.sender, _amount);
        emit Withdrawn(_amount, msg.sender);
    }

    /**
     * @dev Allows the owner to set a new TokenUtilityAccounting contract.
     * @param _newTokenUtilityAccounting Address of the new TokenUtilityAccounting contract.
     */
    function setTokenUtilityAccounting(address _newTokenUtilityAccounting) external onlyOwner {
        tokenUtilityAccounting = TokenUtilityAccounting(_newTokenUtilityAccounting);
    }

    /**
     * @dev Sets up new cooldown period
     * cooldown checking feature can be turned off by setting it to 0
     * @param _cooldown - Cooldown time before a withdrawal can be executed after request in seconds
     */
    function setCooldown(uint256 _cooldown) external onlyOwner {
        cooldown = _cooldown;
    }

    /**
     * @dev Sets up new protocol signer address,
     * protocol signature checking feature can be turned off by setting it to 0 address
     * @param _protocolSignerAddress -
     */
    function setProtocolSignerAddress(address _protocolSignerAddress) external onlyOwner {
        protocolSignerAddress = _protocolSignerAddress;
    }

    /**
     * @dev Triggers stopped state.
     *
     * Requirements:
     *
     * - Only the owner can call this method.
     * - The contract must not be paused.
     */
    function pause() external onlyOwner {
        _pause();
    }

    /**
     * @dev Returns to normal state.
     *
     * Requirements:
     *
     * - Only the owner can call this method.
     * - The contract must be paused.
     */
    function unpause() external onlyOwner {
        _unpause();
    }

    /**
     * @dev Calculates the hash of a withdrawal request.
     * @param _amount Amount of tokens to withdraw.
     * @param _user Address of the user.
     * @param _timestamp Timestamp of the request.
     * @return Hash of the withdrawal request.
     */
    function _calculateRequestHash(
        uint256 _amount,
        address _user,
        uint256 _timestamp
    ) internal pure returns (bytes32) {
        return keccak256(abi.encodePacked(_amount, _user, _timestamp));
    }

    /**
     * @dev Determines if a protocol signature is needed for a withdrawal.
     * @param _amount Amount of tokens to withdraw.
     * @param _user Address of the user.
     * @return True if protocol signature is needed, false otherwise.
     */
    function isProtocolSignatureNeeded(uint256 _amount, address _user) public view returns (bool) {
        uint256 externalLockedTokens = totalLockedTokens[_user] - distributorLockedTokens[_user];
        return (externalLockedTokens < _amount);
    }
}

// SPDX-License-Identifier: BUSL-1.1

pragma solidity 0.8.19;

/**
 * @title TokenUtilityAccounting
 * @author NFTfi
 * @dev
 */
contract TokenUtilityAccounting {
    address public tokenLock;

    mapping(address => uint256) public weightedAvgLockTimes;
    mapping(address => uint256) public amounts;

    // these two only needed if we wanted to distribute a finite,
    // given amount of rewards proportionally for locking times and amounts acrued
    uint256 public totalWeightedAvgLockTime;
    uint256 public totalAmount;

    event Update(
        address indexed _user,
        uint256 _weightedAvgLockTime,
        uint256 _acruedUserAmount,
        uint256 _totalWeightedAvgLockTime,
        uint256 _totalAmount
    );

    constructor(address _tokenLock) {
        tokenLock = _tokenLock;
    }

    modifier onlyTokenLock() {
        require(msg.sender == tokenLock, "Only token lock");
        _;
    }

    function lock(address _user, uint256 _amount) external onlyTokenLock {
        _updateUserWeightedAvgLockTime(_user, _amount);
        _updateTotalWeightedAvgLockTime(_amount);
        amounts[_user] += _amount;
        totalAmount += _amount;
        emit Update(_user, weightedAvgLockTimes[_user], amounts[_user], totalWeightedAvgLockTime, totalAmount);
    }

    function unlock(address _user, uint256 _amount) external onlyTokenLock {
        amounts[_user] -= _amount;
        totalAmount -= _amount;
        emit Update(_user, weightedAvgLockTimes[_user], amounts[_user], totalWeightedAvgLockTime, totalAmount);
    }

    /**
     * @dev updates weighted avg lock time for a given user based on the added amount
     * @param _user -
     * @param _amount - amount added
     */
    function _updateUserWeightedAvgLockTime(address _user, uint256 _amount) internal {
        weightedAvgLockTimes[_user] = _calculateWeightedAvgLockTime(
            _amount,
            amounts[_user],
            weightedAvgLockTimes[_user]
        );
    }

    /**
     * @dev updates weighted avg lock time for the whole system based on the added amount
     * @param _amount - amount added
     */
    function _updateTotalWeightedAvgLockTime(uint256 _amount) internal {
        totalWeightedAvgLockTime = _calculateWeightedAvgLockTime(_amount, totalAmount, totalWeightedAvgLockTime);
    }

    /**
     * @dev calculates weightedAvgMultiplier virtual timestamp value with
     * a new data point of token _amount weight and the current time
     * This function is either called by _updateAvgMultiplierStart or has to be called after
     * an explicit stake() or a deleteWithdrawRequest(), or any other possible instances,
     * The function takes the existing average and it's weight (existing balance) then calculates
     * it with the new value and weight with a weighted avg calculation between the 2 datapoints.
     * @param _amount - amount added
     * @param _oldAmount - cumulative amount before
     * @param _oldWeightedAvgLockTime -
     */
    function _calculateWeightedAvgLockTime(
        uint256 _amount,
        uint256 _oldAmount,
        uint256 _oldWeightedAvgLockTime
    ) internal view returns (uint256) {
        if (_oldAmount == 0 || _oldWeightedAvgLockTime == 0) {
            // if we are at initial state with just 1 datapoint
            return block.timestamp;
        } else {
            uint256 totalWeight = _oldAmount + _amount;
            // weighted avg calculation between the old value and the new lock timestamp
            return (_oldAmount * _oldWeightedAvgLockTime + _amount * block.timestamp) / totalWeight;
        }
    }
}

{
  "compilationTarget": {
    "contracts/DistributorRegistry.sol": "DistributorRegistry"
  },
  "evmVersion": "paris",
  "libraries": {},
  "metadata": {
    "bytecodeHash": "none",
    "useLiteralContent": true
  },
  "optimizer": {
    "enabled": true,
    "runs": 200
  },
  "remappings": []
}