Contract Source Code:

// SPDX-License-Identifier: UNLICENSED
// File: @openzeppelin/contracts/security/ReentrancyGuard.sol


// OpenZeppelin Contracts (last updated v4.9.0) (security/ReentrancyGuard.sol)

pragma solidity ^0.8.0;

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

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

    uint256 private _status;

    constructor() {
        _status = _NOT_ENTERED;
    }

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

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

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

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

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

// File: gravity/claims.sol


pragma solidity ^0.8.0;


interface IMintableToken {
    function mint(address to, uint256 amount) external;
}

contract TokenClaim is ReentrancyGuard {
    IMintableToken public token;

    struct Claim {
        uint256 expiry;
        mapping(address => uint256) allocations;
        mapping(address => bool) claimed;
        uint256 totalAllocated;
        address[] allocatedAddresses;
    }

    mapping(bytes32 => Claim) public claims;  // Mapping still uses bytes32 for efficiency
    mapping(address => mapping(bytes32 => uint256)) public userClaims;
    string[] public claimIds;

    address public admin;

    event ClaimCreated(string indexed claimId, uint256 expiry);
    event TokensAllocated(string indexed claimId, address indexed account, uint256 amount);
    event TokensClaimed(string indexed claimId, address indexed account, uint256 amount);
    event ClaimExpiryExtended(string indexed claimId, uint256 newExpiry);

    modifier onlyAdmin() {
        require(msg.sender == admin, "Caller is not admin");
        _;
    }

    modifier claimExists(string memory claimId) {
        require(claims[_getClaimHash(claimId)].expiry != 0, "Claim does not exist");
        _;
    }

    modifier onlyBeforeStart(string memory claimId) {
        require(block.timestamp < claims[_getClaimHash(claimId)].expiry, "Claim already started");
        _;
    }

    constructor(address tokenAddress, address owner) {
        token = IMintableToken(tokenAddress);
        admin = owner;
    }

    function createClaim(string memory claimId, uint256 expiry) external onlyAdmin {
        require(expiry > block.timestamp, "Expiry must be in the future");
        bytes32 claimHash = _getClaimHash(claimId);
        if (claims[claimHash].expiry == 0) {
            claims[claimHash].expiry = expiry;
            claimIds.push(claimId);
            emit ClaimCreated(claimId, expiry);
        } else {
            require(block.timestamp < claims[claimHash].expiry, "Claim has already started");
            claims[claimHash].expiry = expiry;
        }
    }

    function allocateTokens(
        string memory claimId,
        address[] calldata addresses,
        uint256[] calldata amounts
    ) external onlyAdmin claimExists(claimId) onlyBeforeStart(claimId) {
        require(addresses.length == amounts.length, "Addresses and amounts length mismatch");

        bytes32 claimHash = _getClaimHash(claimId);
        Claim storage claim = claims[claimHash];
        for (uint256 i = 0; i < addresses.length; i++) {
            require(!claim.claimed[addresses[i]], "Tokens already claimed by address");
            if (claim.allocations[addresses[i]] == 0) {
                claim.allocatedAddresses.push(addresses[i]);
            }
            claim.allocations[addresses[i]] += amounts[i];
            claim.totalAllocated += amounts[i];
            emit TokensAllocated(claimId, addresses[i], amounts[i]);
        }
    }

    function claimTokens(string memory claimId) external claimExists(claimId) nonReentrant {
        bytes32 claimHash = _getClaimHash(claimId);
        Claim storage claim = claims[claimHash];

        require(block.timestamp < claim.expiry, "Claim period has expired");
        require(!claim.claimed[msg.sender], "Tokens already claimed");
        uint256 amount = claim.allocations[msg.sender];
        require(amount > 0, "No tokens allocated");

        claim.claimed[msg.sender] = true;
        claim.allocations[msg.sender] = 0;
        claim.totalAllocated -= amount;

        token.mint(msg.sender, amount);

        emit TokensClaimed(claimId, msg.sender, amount);
    }

    function getAllocation(string memory claimId, address account) external view claimExists(claimId) returns (uint256) {
        return claims[_getClaimHash(claimId)].allocations[account];
    }

    function hasClaimed(string memory claimId, address account) external view claimExists(claimId) returns (bool) {
        return claims[_getClaimHash(claimId)].claimed[account];
    }

    function extendClaimExpiry(string memory claimId, uint256 additionalTime) external onlyAdmin claimExists(claimId) {
        bytes32 claimHash = _getClaimHash(claimId);
        Claim storage claim = claims[claimHash];
        require(claim.expiry > block.timestamp, "Claim has already expired");
        claim.expiry += additionalTime;
        emit ClaimExpiryExtended(claimId, claim.expiry);
    }

    // Internal function to hash the string claimId to use as a mapping key
    function _getClaimHash(string memory claimId) internal pure returns (bytes32) {
        return keccak256(abi.encodePacked(claimId));
    }
}