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100/// @notice Callback function used by Gelato VRF to return the random number.
101/// The randomness is derived by hashing the provided randomness with the request ID.
102/// @param randomness The random number generated by Gelato VRF.
103/// @param dataWithRound Additional data provided by Gelato VRF containing request details.
104function fulfillRandomness(
105    uint256 randomness,
106    bytes calldata dataWithRound
107) external {
108    require(msg.sender == _operator(), "only operator");
109
110    (, bytes memory data) = abi.decode(dataWithRound, (uint256, bytes));
111    (uint256 requestId, bytes memory extraData) = abi.decode(
112        data,
113        (uint256, bytes)
114    );
115
116    bytes32 requestHash = keccak256(dataWithRound);
117    bool isValidRequestHash = requestHash == requestedHash[requestId];
118
119    require(requestPending[requestId], "request fulfilled or missing");
120
121    if (isValidRequestHash) {
122        randomness = uint(
123            keccak256(
124                abi.encode(
125                    randomness,
126                    address(this),
127                    block.chainid,
128                    requestId
129                )
130            )
131        );
132
133        _fulfillRandomness(randomness, requestId, extraData);
134        requestPending[requestId] = false;
135    }
136}