// SPDX-License-Identifier: MIT

pragma solidity 0.8.9;



// Part: IBasicRewards

interface IBasicRewards {
    function stakeFor(address, uint256) external returns (bool);

    function balanceOf(address) external view returns (uint256);

    function withdrawAll(bool) external;

    function getReward() external returns (bool);
}

// Part: ICurveFactoryPool

interface ICurveFactoryPool {
    function get_dy(
        int128 i,
        int128 j,
        uint256 dx
    ) external view returns (uint256);

    function get_balances() external view returns (uint256[2] memory);

    function add_liquidity(
        uint256[2] memory _amounts,
        uint256 _min_mint_amount,
        address _receiver
    ) external returns (uint256);

    function exchange(
        int128 i,
        int128 j,
        uint256 _dx,
        uint256 _min_dy,
        address _receiver
    ) external returns (uint256);
}

// Part: ICurveV2Pool

interface ICurveV2Pool {
    function get_dy(
        uint256 i,
        uint256 j,
        uint256 dx
    ) external view returns (uint256);

    function exchange_underlying(
        uint256 i,
        uint256 j,
        uint256 dx,
        uint256 min_dy
    ) external payable returns (uint256);
}

// Part: OpenZeppelin/openzeppelin-contracts@4.1.0/Address

/**
 * @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;
        // solhint-disable-next-line no-inline-assembly
        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");

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (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");

        // solhint-disable-next-line avoid-low-level-calls
        (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");

        // solhint-disable-next-line avoid-low-level-calls
        (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");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private 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

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// Part: OpenZeppelin/openzeppelin-contracts@4.1.0/IERC20

/**
 * @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);
}

// Part: OpenZeppelin/openzeppelin-contracts@4.1.0/MerkleProof

/**
 * @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) {
        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));
            }
        }

        // Check if the computed hash (root) is equal to the provided root
        return computedHash == root;
    }
}

// Part: OpenZeppelin/openzeppelin-contracts@4.1.0/ReentrancyGuard

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

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

    uint256 private _status;

    constructor () {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and make it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        // On the first call to nonReentrant, _notEntered will be true
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

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

        _;

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

// Part: OpenZeppelin/openzeppelin-contracts@4.1.0/SafeERC20

/**
 * @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'
        // solhint-disable-next-line max-line-length
        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
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

// Part: UnionBase

// Common variables and functions
contract UnionBase {
    address public constant CVXCRV_STAKING_CONTRACT =
        0x3Fe65692bfCD0e6CF84cB1E7d24108E434A7587e;
    address public constant CURVE_CRV_ETH_POOL =
        0x8301AE4fc9c624d1D396cbDAa1ed877821D7C511;
    address public constant CURVE_CVX_ETH_POOL =
        0xB576491F1E6e5E62f1d8F26062Ee822B40B0E0d4;
    address public constant CURVE_CVXCRV_CRV_POOL =
        0x9D0464996170c6B9e75eED71c68B99dDEDf279e8;

    address public constant CRV_TOKEN =
        0xD533a949740bb3306d119CC777fa900bA034cd52;
    address public constant CVXCRV_TOKEN =
        0x62B9c7356A2Dc64a1969e19C23e4f579F9810Aa7;
    address public constant CVX_TOKEN =
        0x4e3FBD56CD56c3e72c1403e103b45Db9da5B9D2B;

    uint256 public constant CRVETH_ETH_INDEX = 0;
    uint256 public constant CRVETH_CRV_INDEX = 1;
    int128 public constant CVXCRV_CRV_INDEX = 0;
    int128 public constant CVXCRV_CVXCRV_INDEX = 1;
    uint256 public constant CVXETH_ETH_INDEX = 0;
    uint256 public constant CVXETH_CVX_INDEX = 1;

    IBasicRewards cvxCrvStaking = IBasicRewards(CVXCRV_STAKING_CONTRACT);
    ICurveV2Pool cvxEthSwap = ICurveV2Pool(CURVE_CVX_ETH_POOL);
    ICurveV2Pool crvEthSwap = ICurveV2Pool(CURVE_CRV_ETH_POOL);
    ICurveFactoryPool crvCvxCrvSwap = ICurveFactoryPool(CURVE_CVXCRV_CRV_POOL);

    /// @notice Swap CRV for cvxCRV on Curve
    /// @param amount - amount to swap
    /// @param recipient - where swapped tokens will be sent to
    /// @return amount of CRV obtained after the swap
    function _swapCrvToCvxCrv(uint256 amount, address recipient)
        internal
        returns (uint256)
    {
        return
            crvCvxCrvSwap.exchange(
                CVXCRV_CRV_INDEX,
                CVXCRV_CVXCRV_INDEX,
                amount,
                0,
                recipient
            );
    }

    /// @notice Swap CRV for cvxCRV on Curve
    /// @param amount - amount to swap
    /// @param recipient - where swapped tokens will be sent to
    /// @return amount of CRV obtained after the swap
    function _swapCvxCrvToCrv(uint256 amount, address recipient)
        internal
        returns (uint256)
    {
        return
            crvCvxCrvSwap.exchange(
                CVXCRV_CVXCRV_INDEX,
                CVXCRV_CRV_INDEX,
                amount,
                0,
                recipient
            );
    }

    /// @notice Swap CRV for native ETH on Curve
    /// @param amount - amount to swap
    /// @return amount of ETH obtained after the swap
    function _swapCrvToEth(uint256 amount) internal returns (uint256) {
        return
            crvEthSwap.exchange_underlying{value: 0}(
                CRVETH_CRV_INDEX,
                CRVETH_ETH_INDEX,
                amount,
                0
            );
    }

    /// @notice Swap native ETH for CRV on Curve
    /// @param amount - amount to swap
    /// @return amount of CRV obtained after the swap
    function _swapEthToCrv(uint256 amount) internal returns (uint256) {
        return
            crvEthSwap.exchange_underlying{value: amount}(
                CRVETH_ETH_INDEX,
                CRVETH_CRV_INDEX,
                amount,
                0
            );
    }

    /// @notice Swap native ETH for CVX on Curve
    /// @param amount - amount to swap
    /// @return amount of CRV obtained after the swap
    function _swapEthToCvx(uint256 amount) internal returns (uint256) {
        return
            cvxEthSwap.exchange_underlying{value: amount}(
                CVXETH_ETH_INDEX,
                CVXETH_CVX_INDEX,
                amount,
                0
            );
    }
}

// File: MerkleDistributor.sol

// Allows anyone to claim a token if they exist in a merkle root.
contract MerkleDistributor is ReentrancyGuard, UnionBase {
    using SafeERC20 for IERC20;

    // Possible options when claiming
    enum Option {
        Claim,
        ClaimAsETH,
        ClaimAsCRV,
        ClaimAsCVX,
        ClaimAndStake
    }

    address public immutable token;
    bytes32 public merkleRoot;
    uint32 public week;
    bool public frozen;

    address public admin;
    address public depositor;

    // This is a packed array of booleans.
    mapping(uint256 => mapping(uint256 => uint256)) private claimedBitMap;

    // This event is triggered whenever a call to #claim succeeds.
    event Claimed(
        uint256 index,
        uint256 indexed amount,
        address indexed account,
        uint256 week,
        Option indexed option
    );
    // This event is triggered whenever the merkle root gets updated.
    event MerkleRootUpdated(bytes32 indexed merkleRoot, uint32 indexed week);
    // This event is triggered whenever the admin is updated.
    event AdminUpdated(address indexed oldAdmin, address indexed newAdmin);

    constructor(
        address token_,
        address depositor_,
        bytes32 merkleRoot_
    ) {
        token = token_;
        admin = msg.sender;
        depositor = depositor_;
        merkleRoot = merkleRoot_;
        week = 0;
        frozen = true;
    }

    /// @notice Check if the index has been marked as claimed.
    /// @param index - the index to check
    /// @return true if index has been marked as claimed.
    function isClaimed(uint256 index) public view returns (bool) {
        uint256 claimedWordIndex = index / 256;
        uint256 claimedBitIndex = index % 256;
        uint256 claimedWord = claimedBitMap[week][claimedWordIndex];
        uint256 mask = (1 << claimedBitIndex);
        return claimedWord & mask == mask;
    }

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

    /// @notice Set approvals for the tokens used when swapping
    function setApprovals() external onlyAdmin {
        IERC20(CRV_TOKEN).safeApprove(CURVE_CRV_ETH_POOL, 0);
        IERC20(CRV_TOKEN).safeApprove(CURVE_CRV_ETH_POOL, 2**256 - 1);

        IERC20(CVXCRV_TOKEN).safeApprove(CVXCRV_STAKING_CONTRACT, 0);
        IERC20(CVXCRV_TOKEN).safeApprove(CVXCRV_STAKING_CONTRACT, 2**256 - 1);

        IERC20(CVXCRV_TOKEN).safeApprove(CURVE_CVXCRV_CRV_POOL, 0);
        IERC20(CVXCRV_TOKEN).safeApprove(CURVE_CVXCRV_CRV_POOL, 2**256 - 1);
    }

    /// @notice Transfers ownership of the contract
    /// @param newAdmin - address of the new admin of the contract
    function updateAdmin(address newAdmin) external onlyAdmin {
        require(newAdmin != address(0));
        address oldAdmin = admin;
        admin = newAdmin;
        emit AdminUpdated(oldAdmin, newAdmin);
    }

    /// @notice Claim the given amount of the token to the given address.
    /// Reverts if the inputs are invalid.
    /// @param index - claimer index
    /// @param account - claimer account
    /// @param amount - claim amount
    /// @param merkleProof - merkle proof for the claim
    /// @param option - claiming option
    function claim(
        uint256 index,
        address account,
        uint256 amount,
        bytes32[] calldata merkleProof,
        Option option
    ) external nonReentrant {
        require(!frozen, "Claiming is frozen.");
        require(!isClaimed(index), "Drop already claimed.");

        // Verify the merkle proof.
        bytes32 node = keccak256(abi.encodePacked(index, account, amount));
        require(
            MerkleProof.verify(merkleProof, merkleRoot, node),
            "Invalid proof."
        );

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

        if (option == Option.ClaimAsCRV) {
            _swapCvxCrvToCrv(amount, account);
        } else if (option == Option.ClaimAsETH) {
            uint256 _crvBalance = _swapCvxCrvToCrv(amount, address(this));
            uint256 _ethAmount = _swapCrvToEth(_crvBalance);
            (bool success, ) = account.call{value: _ethAmount}("");
            require(success, "ETH transfer failed");
        } else if (option == Option.ClaimAsCVX) {
            uint256 _crvBalance = _swapCvxCrvToCrv(amount, address(this));
            uint256 _ethAmount = _swapCrvToEth(_crvBalance);
            uint256 _cvxAmount = _swapEthToCvx(_ethAmount);
            IERC20(CVX_TOKEN).safeTransfer(account, _cvxAmount);
        } else if (option == Option.ClaimAndStake) {
            require(cvxCrvStaking.stakeFor(account, amount), "Staking failed");
        } else {
            IERC20(token).safeTransfer(account, amount);
        }

        emit Claimed(index, amount, account, week, option);
    }

    /// @notice Freezes the claim function to allow the merkleRoot to be changed
    /// @dev Can be called by the owner or the depositor zap contract
    function freeze() public {
        require(
            (msg.sender == admin) || (msg.sender == depositor),
            "Admin or depositor only"
        );
        frozen = true;
    }

    /// @notice Unfreezes the claim function.
    function unfreeze() public onlyAdmin {
        frozen = false;
    }

    /// @notice Update the merkle root and increment the week.
    /// @param _merkleRoot - the new root to push
    function updateMerkleRoot(bytes32 _merkleRoot) public onlyAdmin {
        require(frozen, "Contract not frozen.");

        // Increment the week (simulates the clearing of the claimedBitMap)
        week = week + 1;
        // Set the new merkle root
        merkleRoot = _merkleRoot;

        emit MerkleRootUpdated(merkleRoot, week);
    }

    receive() external payable {}

    modifier onlyAdmin() {
        require(msg.sender == admin, "Admin only");
        _;
    }
}