start building on the chainlink VRF

packages/foundry/contracts/Lottery.sol

@@ -21,30 +21,70 @@ pragma solidity ^0.8.19;
 
 import {PriceConverter} from "./PriceConverter.sol";
 import {AggregatorV3Interface} from "@chainlink/contracts/v0.8/shared/interfaces/AggregatorV3Interface.sol";
+import {VRFConsumerBaseV2Plus} from "@chainlink/contracts/v0.8/vrf/dev/VRFConsumerBaseV2Plus.sol";
+import {VRFV2PlusClient} from "@chainlink/contracts/v0.8/dev/vrf/libraries/VRFV2PlusClient.sol";
 
-contract Lottery {
+contract Lottery is VRFConsumerBaseV2Plus {
     using PriceConverter for uint256;
 
     /** Events */
-    event LotteryFunded(address indexed, uint256);
+    event LotteryFunded(address indexed sender, uint256 amountSent);
+    event RequestSent(uint256 requestId, uint32 numWords);
+    event RequestFulfilled(uint256 requestId, uint256[] randomWords);
 
     /** Errors */
     error NotEnoughEthFunded();
 
     /** Type declarations */
+    struct RequestStatus {
+        bool fulfilled; // whether the request has been successfully fulfilled
+        bool exists; // whether a requestId exists
+        uint256[] randomWords;
+    }
 
     /** Variables */
     address[] private s_participants;
-    mapping(address => uint256) private s_participantsToAmountFunded;
+
     AggregatorV3Interface private s_priceFeed;
 
+    mapping(address => uint256) private s_participantsToAmountFunded;
+    mapping(uint256 => RequestStatus)
+        public s_requests; /* requestId --> requestStatus */
+
+    // Your subscription ID.
+    uint256 public s_subscriptionId;
+
+    // Past request IDs.
+    uint256[] public requestIds;
+    uint256 public lastRequestId;
+
+    // The gas lane to use, which specifies the maximum gas price to bump to.
+    // For a list of available gas lanes on each network,
+    // see https://docs.chain.link/docs/vrf/v2-5/supported-networks
+    bytes32 public keyHash =
+        0x787d74caea10b2b357790d5b5247c2f63d1d91572a9846f780606e4d953677ae;
+
+    uint32 public callbackGasLimit = 100000;
+
+    // The default is 3, but you can set this higher.
+    uint16 public requestConfirmations = 3;
+
+    // For this example, retrieve 1 random values in one request.
+    // Cannot exceed VRFCoordinatorV2_5.MAX_NUM_WORDS.
+    uint32 public numWords = 1;
+
     /** Constants */
     uint256 private constant MIN_AMOUNT_TO_FUND = 50 * 1e18;
 
     /** Modifiers */
 
-    constructor(AggregatorV3Interface priceFeed) {
+    constructor(
+        AggregatorV3Interface priceFeed,
+        address vrfCoordinator,
+        uint256 subscriptionId
+    ) VRFConsumerBaseV2Plus(vrfCoordinator) {
         s_priceFeed = priceFeed;
+        s_subscriptionId = subscriptionId;
     }
 
     function getEtherInUsd(uint256 _ethValue) public view returns (uint256) {
@@ -62,6 +102,53 @@ contract Lottery {
         emit LotteryFunded(msg.sender, msg.value);
     }
 
+    function requestRandomWords()
+        external
+        onlyOwner
+        returns (uint256 requestId)
+    {
+        // Will revert if subscription is not set and funded.
+        requestId = s_vrfCoordinator.requestRandomWords(
+            VRFV2PlusClient.RandomWordsRequest({
+                keyHash: keyHash,
+                subId: s_subscriptionId,
+                requestConfirmations: requestConfirmations,
+                callbackGasLimit: callbackGasLimit,
+                numWords: numWords,
+                extraArgs: VRFV2PlusClient._argsToBytes(
+                    VRFV2PlusClient.ExtraArgsV1({nativePayment: false})
+                )
+            })
+        );
+        s_requests[requestId] = RequestStatus({
+            randomWords: new uint256[](0),
+            exists: true,
+            fulfilled: false
+        });
+        requestIds.push(requestId);
+        lastRequestId = requestId;
+        emit RequestSent(requestId, numWords);
+        return requestId;
+    }
+
+    function fulfillRandomWords(
+        uint256 _requestId,
+        uint256[] calldata _randomWords
+    ) internal override {
+        require(s_requests[_requestId].exists, "request not found");
+        s_requests[_requestId].fulfilled = true;
+        s_requests[_requestId].randomWords = _randomWords;
+        emit RequestFulfilled(_requestId, _randomWords);
+    }
+
+    function getRequestStatus(
+        uint256 _requestId
+    ) external view returns (bool fulfilled, uint256[] memory randomWords) {
+        require(s_requests[_requestId].exists, "request not found");
+        RequestStatus memory request = s_requests[_requestId];
+        return (request.fulfilled, request.randomWords);
+    }
+
     function pickWinner() private {}
 
     /** Getters */