VRFCoordinatorV2.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.4;

import {LinkTokenInterface} from "../shared/interfaces/LinkTokenInterface.sol";
import {BlockhashStoreInterface} from "./interfaces/BlockhashStoreInterface.sol";
import {AggregatorV3Interface} from "../interfaces/AggregatorV3Interface.sol";
import {VRFCoordinatorV2Interface} from "./interfaces/VRFCoordinatorV2Interface.sol";
import {TypeAndVersionInterface} from "../interfaces/TypeAndVersionInterface.sol";
import {IERC677Receiver} from "../shared/interfaces/IERC677Receiver.sol";
import {VRF} from "./VRF.sol";
import {ConfirmedOwner} from "../shared/access/ConfirmedOwner.sol";
import {VRFConsumerBaseV2} from "./VRFConsumerBaseV2.sol";
import {ChainSpecificUtil} from "../ChainSpecificUtil.sol";

contract VRFCoordinatorV2 is VRF, ConfirmedOwner, TypeAndVersionInterface, VRFCoordinatorV2Interface, IERC677Receiver {
  // solhint-disable-next-line chainlink-solidity/prefix-immutable-variables-with-i
  LinkTokenInterface public immutable LINK;
  // solhint-disable-next-line chainlink-solidity/prefix-immutable-variables-with-i
  AggregatorV3Interface public immutable LINK_ETH_FEED;
  // solhint-disable-next-line chainlink-solidity/prefix-immutable-variables-with-i
  BlockhashStoreInterface public immutable BLOCKHASH_STORE;

  // We need to maintain a list of consuming addresses.
  // This bound ensures we are able to loop over them as needed.
  // Should a user require more consumers, they can use multiple subscriptions.
  uint16 public constant MAX_CONSUMERS = 100;
  error TooManyConsumers();
  error InsufficientBalance();
  error InvalidConsumer(uint64 subId, address consumer);
  error InvalidSubscription();
  error OnlyCallableFromLink();
  error InvalidCalldata();
  error MustBeSubOwner(address owner);
  error PendingRequestExists();
  error MustBeRequestedOwner(address proposedOwner);
  error BalanceInvariantViolated(uint256 internalBalance, uint256 externalBalance); // Should never happen
  event FundsRecovered(address to, uint256 amount);
  // We use the subscription struct (1 word)
  // at fulfillment time.
  struct Subscription {
    // There are only 1e9*1e18 = 1e27 juels in existence, so the balance can fit in uint96 (2^96 ~ 7e28)
    uint96 balance; // Common link balance used for all consumer requests.
    uint64 reqCount; // For fee tiers
  }
  // We use the config for the mgmt APIs
  struct SubscriptionConfig {
    address owner; // Owner can fund/withdraw/cancel the sub.
    address requestedOwner; // For safely transferring sub ownership.
    // Maintains the list of keys in s_consumers.
    // We do this for 2 reasons:
    // 1. To be able to clean up all keys from s_consumers when canceling a subscription.
    // 2. To be able to return the list of all consumers in getSubscription.
    // Note that we need the s_consumers map to be able to directly check if a
    // consumer is valid without reading all the consumers from storage.
    address[] consumers;
  }
  // Note a nonce of 0 indicates an the consumer is not assigned to that subscription.
  mapping(address => mapping(uint64 => uint64)) /* consumer */ /* subId */ /* nonce */ private s_consumers;
  mapping(uint64 => SubscriptionConfig) /* subId */ /* subscriptionConfig */ private s_subscriptionConfigs;
  mapping(uint64 => Subscription) /* subId */ /* subscription */ private s_subscriptions;
  // We make the sub count public so that its possible to
  // get all the current subscriptions via getSubscription.
  uint64 private s_currentSubId;
  // s_totalBalance tracks the total link sent to/from
  // this contract through onTokenTransfer, cancelSubscription and oracleWithdraw.
  // A discrepancy with this contract's link balance indicates someone
  // sent tokens using transfer and so we may need to use recoverFunds.
  uint96 private s_totalBalance;
  event SubscriptionCreated(uint64 indexed subId, address owner);
  event SubscriptionFunded(uint64 indexed subId, uint256 oldBalance, uint256 newBalance);
  event SubscriptionConsumerAdded(uint64 indexed subId, address consumer);
  event SubscriptionConsumerRemoved(uint64 indexed subId, address consumer);
  event SubscriptionCanceled(uint64 indexed subId, address to, uint256 amount);
  event SubscriptionOwnerTransferRequested(uint64 indexed subId, address from, address to);
  event SubscriptionOwnerTransferred(uint64 indexed subId, address from, address to);

  // Set this maximum to 200 to give us a 56 block window to fulfill
  // the request before requiring the block hash feeder.
  uint16 public constant MAX_REQUEST_CONFIRMATIONS = 200;
  uint32 public constant MAX_NUM_WORDS = 500;
  // 5k is plenty for an EXTCODESIZE call (2600) + warm CALL (100)
  // and some arithmetic operations.
  uint256 private constant GAS_FOR_CALL_EXACT_CHECK = 5_000;
  error InvalidRequestConfirmations(uint16 have, uint16 min, uint16 max);
  error GasLimitTooBig(uint32 have, uint32 want);
  error NumWordsTooBig(uint32 have, uint32 want);
  error ProvingKeyAlreadyRegistered(bytes32 keyHash);
  error NoSuchProvingKey(bytes32 keyHash);
  error InvalidLinkWeiPrice(int256 linkWei);
  error InsufficientGasForConsumer(uint256 have, uint256 want);
  error NoCorrespondingRequest();
  error IncorrectCommitment();
  error BlockhashNotInStore(uint256 blockNum);
  error PaymentTooLarge();
  error Reentrant();
  struct RequestCommitment {
    uint64 blockNum;
    uint64 subId;
    uint32 callbackGasLimit;
    uint32 numWords;
    address sender;
  }
  mapping(bytes32 => address) /* keyHash */ /* oracle */ private s_provingKeys;
  bytes32[] private s_provingKeyHashes;
  mapping(address => uint96) /* oracle */ /* LINK balance */ private s_withdrawableTokens;
  mapping(uint256 => bytes32) /* requestID */ /* commitment */ private s_requestCommitments;
  event ProvingKeyRegistered(bytes32 keyHash, address indexed oracle);
  event ProvingKeyDeregistered(bytes32 keyHash, address indexed oracle);
  event RandomWordsRequested(
    bytes32 indexed keyHash,
    uint256 requestId,
    uint256 preSeed,
    uint64 indexed subId,
    uint16 minimumRequestConfirmations,
    uint32 callbackGasLimit,
    uint32 numWords,
    address indexed sender
  );
  event RandomWordsFulfilled(uint256 indexed requestId, uint256 outputSeed, uint96 payment, bool success);

  struct Config {
    uint16 minimumRequestConfirmations;
    uint32 maxGasLimit;
    // Reentrancy protection.
    bool reentrancyLock;
    // stalenessSeconds is how long before we consider the feed price to be stale
    // and fallback to fallbackWeiPerUnitLink.
    uint32 stalenessSeconds;
    // Gas to cover oracle payment after we calculate the payment.
    // We make it configurable in case those operations are repriced.
    uint32 gasAfterPaymentCalculation;
  }
  int256 private s_fallbackWeiPerUnitLink;
  Config private s_config;
  FeeConfig private s_feeConfig;
  struct FeeConfig {
    // Flat fee charged per fulfillment in millionths of link
    // So fee range is [0, 2^32/10^6].
    uint32 fulfillmentFlatFeeLinkPPMTier1;
    uint32 fulfillmentFlatFeeLinkPPMTier2;
    uint32 fulfillmentFlatFeeLinkPPMTier3;
    uint32 fulfillmentFlatFeeLinkPPMTier4;
    uint32 fulfillmentFlatFeeLinkPPMTier5;
    uint24 reqsForTier2;
    uint24 reqsForTier3;
    uint24 reqsForTier4;
    uint24 reqsForTier5;
  }
  event ConfigSet(
    uint16 minimumRequestConfirmations,
    uint32 maxGasLimit,
    uint32 stalenessSeconds,
    uint32 gasAfterPaymentCalculation,
    int256 fallbackWeiPerUnitLink,
    FeeConfig feeConfig
  );

  constructor(address link, address blockhashStore, address linkEthFeed) ConfirmedOwner(msg.sender) {
    LINK = LinkTokenInterface(link);
    LINK_ETH_FEED = AggregatorV3Interface(linkEthFeed);
    BLOCKHASH_STORE = BlockhashStoreInterface(blockhashStore);
  }

  /**
   * @notice Registers a proving key to an oracle.
   * @param oracle address of the oracle
   * @param publicProvingKey key that oracle can use to submit vrf fulfillments
   */
  function registerProvingKey(address oracle, uint256[2] calldata publicProvingKey) external onlyOwner {
    bytes32 kh = hashOfKey(publicProvingKey);
    if (s_provingKeys[kh] != address(0)) {
      revert ProvingKeyAlreadyRegistered(kh);
    }
    s_provingKeys[kh] = oracle;
    s_provingKeyHashes.push(kh);
    emit ProvingKeyRegistered(kh, oracle);
  }

  /**
   * @notice Deregisters a proving key to an oracle.
   * @param publicProvingKey key that oracle can use to submit vrf fulfillments
   */
  function deregisterProvingKey(uint256[2] calldata publicProvingKey) external onlyOwner {
    bytes32 kh = hashOfKey(publicProvingKey);
    address oracle = s_provingKeys[kh];
    if (oracle == address(0)) {
      revert NoSuchProvingKey(kh);
    }
    delete s_provingKeys[kh];
    for (uint256 i = 0; i < s_provingKeyHashes.length; i++) {
      if (s_provingKeyHashes[i] == kh) {
        bytes32 last = s_provingKeyHashes[s_provingKeyHashes.length - 1];
        // Copy last element and overwrite kh to be deleted with it
        s_provingKeyHashes[i] = last;
        s_provingKeyHashes.pop();
      }
    }
    emit ProvingKeyDeregistered(kh, oracle);
  }

  /**
   * @notice Returns the proving key hash key associated with this public key
   * @param publicKey the key to return the hash of
   */
  function hashOfKey(uint256[2] memory publicKey) public pure returns (bytes32) {
    return keccak256(abi.encode(publicKey));
  }

  /**
   * @notice Sets the configuration of the vrfv2 coordinator
   * @param minimumRequestConfirmations global min for request confirmations
   * @param maxGasLimit global max for request gas limit
   * @param stalenessSeconds if the eth/link feed is more stale then this, use the fallback price
   * @param gasAfterPaymentCalculation gas used in doing accounting after completing the gas measurement
   * @param fallbackWeiPerUnitLink fallback eth/link price in the case of a stale feed
   * @param feeConfig fee tier configuration
   */
  function setConfig(
    uint16 minimumRequestConfirmations,
    uint32 maxGasLimit,
    uint32 stalenessSeconds,
    uint32 gasAfterPaymentCalculation,
    int256 fallbackWeiPerUnitLink,
    FeeConfig memory feeConfig
  ) external onlyOwner {
    if (minimumRequestConfirmations > MAX_REQUEST_CONFIRMATIONS) {
      revert InvalidRequestConfirmations(
        minimumRequestConfirmations,
        minimumRequestConfirmations,
        MAX_REQUEST_CONFIRMATIONS
      );
    }
    if (fallbackWeiPerUnitLink <= 0) {
      revert InvalidLinkWeiPrice(fallbackWeiPerUnitLink);
    }
    s_config = Config({
      minimumRequestConfirmations: minimumRequestConfirmations,
      maxGasLimit: maxGasLimit,
      stalenessSeconds: stalenessSeconds,
      gasAfterPaymentCalculation: gasAfterPaymentCalculation,
      reentrancyLock: false
    });
    s_feeConfig = feeConfig;
    s_fallbackWeiPerUnitLink = fallbackWeiPerUnitLink;
    emit ConfigSet(
      minimumRequestConfirmations,
      maxGasLimit,
      stalenessSeconds,
      gasAfterPaymentCalculation,
      fallbackWeiPerUnitLink,
      s_feeConfig
    );
  }

  function getConfig()
    external
    view
    returns (
      uint16 minimumRequestConfirmations,
      uint32 maxGasLimit,
      uint32 stalenessSeconds,
      uint32 gasAfterPaymentCalculation
    )
  {
    return (
      s_config.minimumRequestConfirmations,
      s_config.maxGasLimit,
      s_config.stalenessSeconds,
      s_config.gasAfterPaymentCalculation
    );
  }

  function getFeeConfig()
    external
    view
    returns (
      uint32 fulfillmentFlatFeeLinkPPMTier1,
      uint32 fulfillmentFlatFeeLinkPPMTier2,
      uint32 fulfillmentFlatFeeLinkPPMTier3,
      uint32 fulfillmentFlatFeeLinkPPMTier4,
      uint32 fulfillmentFlatFeeLinkPPMTier5,
      uint24 reqsForTier2,
      uint24 reqsForTier3,
      uint24 reqsForTier4,
      uint24 reqsForTier5
    )
  {
    return (
      s_feeConfig.fulfillmentFlatFeeLinkPPMTier1,
      s_feeConfig.fulfillmentFlatFeeLinkPPMTier2,
      s_feeConfig.fulfillmentFlatFeeLinkPPMTier3,
      s_feeConfig.fulfillmentFlatFeeLinkPPMTier4,
      s_feeConfig.fulfillmentFlatFeeLinkPPMTier5,
      s_feeConfig.reqsForTier2,
      s_feeConfig.reqsForTier3,
      s_feeConfig.reqsForTier4,
      s_feeConfig.reqsForTier5
    );
  }

  function getTotalBalance() external view returns (uint256) {
    return s_totalBalance;
  }

  function getFallbackWeiPerUnitLink() external view returns (int256) {
    return s_fallbackWeiPerUnitLink;
  }

  /**
   * @notice Owner cancel subscription, sends remaining link directly to the subscription owner.
   * @param subId subscription id
   * @dev notably can be called even if there are pending requests, outstanding ones may fail onchain
   */
  function ownerCancelSubscription(uint64 subId) external onlyOwner {
    if (s_subscriptionConfigs[subId].owner == address(0)) {
      revert InvalidSubscription();
    }
    _cancelSubscriptionHelper(subId, s_subscriptionConfigs[subId].owner);
  }

  /**
   * @notice Recover link sent with transfer instead of transferAndCall.
   * @param to address to send link to
   */
  function recoverFunds(address to) external onlyOwner {
    uint256 externalBalance = LINK.balanceOf(address(this));
    uint256 internalBalance = uint256(s_totalBalance);
    if (internalBalance > externalBalance) {
      revert BalanceInvariantViolated(internalBalance, externalBalance);
    }
    if (internalBalance < externalBalance) {
      uint256 amount = externalBalance - internalBalance;
      LINK.transfer(to, amount);
      emit FundsRecovered(to, amount);
    }
    // If the balances are equal, nothing to be done.
  }

  /**
   * @inheritdoc VRFCoordinatorV2Interface
   */
  function getRequestConfig() external view override returns (uint16, uint32, bytes32[] memory) {
    return (s_config.minimumRequestConfirmations, s_config.maxGasLimit, s_provingKeyHashes);
  }

  /**
   * @inheritdoc VRFCoordinatorV2Interface
   */
  function requestRandomWords(
    bytes32 keyHash,
    uint64 subId,
    uint16 requestConfirmations,
    uint32 callbackGasLimit,
    uint32 numWords
  ) external override nonReentrant returns (uint256) {
    // Input validation using the subscription storage.
    if (s_subscriptionConfigs[subId].owner == address(0)) {
      revert InvalidSubscription();
    }
    // Its important to ensure that the consumer is in fact who they say they
    // are, otherwise they could use someone else's subscription balance.
    // A nonce of 0 indicates consumer is not allocated to the sub.
    uint64 currentNonce = s_consumers[msg.sender][subId];
    if (currentNonce == 0) {
      revert InvalidConsumer(subId, msg.sender);
    }
    // Input validation using the config storage word.
    if (
      requestConfirmations < s_config.minimumRequestConfirmations || requestConfirmations > MAX_REQUEST_CONFIRMATIONS
    ) {
      revert InvalidRequestConfirmations(
        requestConfirmations,
        s_config.minimumRequestConfirmations,
        MAX_REQUEST_CONFIRMATIONS
      );
    }
    // No lower bound on the requested gas limit. A user could request 0
    // and they would simply be billed for the proof verification and wouldn't be
    // able to do anything with the random value.
    if (callbackGasLimit > s_config.maxGasLimit) {
      revert GasLimitTooBig(callbackGasLimit, s_config.maxGasLimit);
    }
    if (numWords > MAX_NUM_WORDS) {
      revert NumWordsTooBig(numWords, MAX_NUM_WORDS);
    }
    // Note we do not check whether the keyHash is valid to save gas.
    // The consequence for users is that they can send requests
    // for invalid keyHashes which will simply not be fulfilled.
    uint64 nonce = currentNonce + 1;
    (uint256 requestId, uint256 preSeed) = _computeRequestId(keyHash, msg.sender, subId, nonce);

    s_requestCommitments[requestId] = keccak256(
      abi.encode(requestId, ChainSpecificUtil._getBlockNumber(), subId, callbackGasLimit, numWords, msg.sender)
    );
    emit RandomWordsRequested(
      keyHash,
      requestId,
      preSeed,
      subId,
      requestConfirmations,
      callbackGasLimit,
      numWords,
      msg.sender
    );
    s_consumers[msg.sender][subId] = nonce;

    return requestId;
  }

  /**
   * @notice Get request commitment
   * @param requestId id of request
   * @dev used to determine if a request is fulfilled or not
   */
  function getCommitment(uint256 requestId) external view returns (bytes32) {
    return s_requestCommitments[requestId];
  }

  function _computeRequestId(
    bytes32 keyHash,
    address sender,
    uint64 subId,
    uint64 nonce
  ) private pure returns (uint256, uint256) {
    uint256 preSeed = uint256(keccak256(abi.encode(keyHash, sender, subId, nonce)));
    return (uint256(keccak256(abi.encode(keyHash, preSeed))), preSeed);
  }

  /**
   * @dev calls target address with exactly gasAmount gas and data as calldata
   * or reverts if at least gasAmount gas is not available.
   */
  function _callWithExactGas(uint256 gasAmount, address target, bytes memory data) private returns (bool success) {
    assembly {
      let g := gas()
      // Compute g -= GAS_FOR_CALL_EXACT_CHECK and check for underflow
      // The gas actually passed to the callee is min(gasAmount, 63//64*gas available).
      // We want to ensure that we revert if gasAmount >  63//64*gas available
      // as we do not want to provide them with less, however that check itself costs
      // gas.  GAS_FOR_CALL_EXACT_CHECK ensures we have at least enough gas to be able
      // to revert if gasAmount >  63//64*gas available.
      if lt(g, GAS_FOR_CALL_EXACT_CHECK) {
        revert(0, 0)
      }
      g := sub(g, GAS_FOR_CALL_EXACT_CHECK)
      // if g - g//64 <= gasAmount, revert
      // (we subtract g//64 because of EIP-150)
      if iszero(gt(sub(g, div(g, 64)), gasAmount)) {
        revert(0, 0)
      }
      // solidity calls check that a contract actually exists at the destination, so we do the same
      if iszero(extcodesize(target)) {
        revert(0, 0)
      }
      // call and return whether we succeeded. ignore return data
      // call(gas,addr,value,argsOffset,argsLength,retOffset,retLength)
      success := call(gasAmount, target, 0, add(data, 0x20), mload(data), 0, 0)
    }
    return success;
  }

  function _getRandomnessFromProof(
    Proof memory proof,
    RequestCommitment memory rc
  ) private view returns (bytes32 keyHash, uint256 requestId, uint256 randomness) {
    keyHash = hashOfKey(proof.pk);
    // Only registered proving keys are permitted.
    address oracle = s_provingKeys[keyHash];
    if (oracle == address(0)) {
      revert NoSuchProvingKey(keyHash);
    }
    requestId = uint256(keccak256(abi.encode(keyHash, proof.seed)));
    bytes32 commitment = s_requestCommitments[requestId];
    if (commitment == 0) {
      revert NoCorrespondingRequest();
    }
    if (
      commitment != keccak256(abi.encode(requestId, rc.blockNum, rc.subId, rc.callbackGasLimit, rc.numWords, rc.sender))
    ) {
      revert IncorrectCommitment();
    }

    bytes32 blockHash = ChainSpecificUtil._getBlockhash(rc.blockNum);
    if (blockHash == bytes32(0)) {
      blockHash = BLOCKHASH_STORE.getBlockhash(rc.blockNum);
      if (blockHash == bytes32(0)) {
        revert BlockhashNotInStore(rc.blockNum);
      }
    }

    // The seed actually used by the VRF machinery, mixing in the blockhash
    uint256 actualSeed = uint256(keccak256(abi.encodePacked(proof.seed, blockHash)));
    randomness = VRF._randomValueFromVRFProof(proof, actualSeed); // Reverts on failure
  }

  /*
   * @notice Compute fee based on the request count
   * @param reqCount number of requests
   * @return feePPM fee in LINK PPM
   */
  function getFeeTier(uint64 reqCount) public view returns (uint32) {
    FeeConfig memory fc = s_feeConfig;
    if (0 <= reqCount && reqCount <= fc.reqsForTier2) {
      return fc.fulfillmentFlatFeeLinkPPMTier1;
    }
    if (fc.reqsForTier2 < reqCount && reqCount <= fc.reqsForTier3) {
      return fc.fulfillmentFlatFeeLinkPPMTier2;
    }
    if (fc.reqsForTier3 < reqCount && reqCount <= fc.reqsForTier4) {
      return fc.fulfillmentFlatFeeLinkPPMTier3;
    }
    if (fc.reqsForTier4 < reqCount && reqCount <= fc.reqsForTier5) {
      return fc.fulfillmentFlatFeeLinkPPMTier4;
    }
    return fc.fulfillmentFlatFeeLinkPPMTier5;
  }

  /*
   * @notice Fulfill a randomness request
   * @param proof contains the proof and randomness
   * @param rc request commitment pre-image, committed to at request time
   * @return payment amount billed to the subscription
   * @dev simulated offchain to determine if sufficient balance is present to fulfill the request
   */
  function fulfillRandomWords(Proof memory proof, RequestCommitment memory rc) external nonReentrant returns (uint96) {
    uint256 startGas = gasleft();
    (bytes32 keyHash, uint256 requestId, uint256 randomness) = _getRandomnessFromProof(proof, rc);

    uint256[] memory randomWords = new uint256[](rc.numWords);
    for (uint256 i = 0; i < rc.numWords; i++) {
      randomWords[i] = uint256(keccak256(abi.encode(randomness, i)));
    }

    delete s_requestCommitments[requestId];
    VRFConsumerBaseV2 v;
    bytes memory resp = abi.encodeWithSelector(v.rawFulfillRandomWords.selector, requestId, randomWords);
    // Call with explicitly the amount of callback gas requested
    // Important to not let them exhaust the gas budget and avoid oracle payment.
    // Do not allow any non-view/non-pure coordinator functions to be called
    // during the consumers callback code via reentrancyLock.
    // Note that _callWithExactGas will revert if we do not have sufficient gas
    // to give the callee their requested amount.
    s_config.reentrancyLock = true;
    bool success = _callWithExactGas(rc.callbackGasLimit, rc.sender, resp);
    s_config.reentrancyLock = false;

    // Increment the req count for fee tier selection.
    uint64 reqCount = s_subscriptions[rc.subId].reqCount;
    s_subscriptions[rc.subId].reqCount += 1;

    // We want to charge users exactly for how much gas they use in their callback.
    // The gasAfterPaymentCalculation is meant to cover these additional operations where we
    // decrement the subscription balance and increment the oracles withdrawable balance.
    // We also add the flat link fee to the payment amount.
    // Its specified in millionths of link, if s_config.fulfillmentFlatFeeLinkPPM = 1
    // 1 link / 1e6 = 1e18 juels / 1e6 = 1e12 juels.
    uint96 payment = _calculatePaymentAmount(
      startGas,
      s_config.gasAfterPaymentCalculation,
      getFeeTier(reqCount),
      tx.gasprice
    );
    if (s_subscriptions[rc.subId].balance < payment) {
      revert InsufficientBalance();
    }
    s_subscriptions[rc.subId].balance -= payment;
    s_withdrawableTokens[s_provingKeys[keyHash]] += payment;
    // Include payment in the event for tracking costs.
    emit RandomWordsFulfilled(requestId, randomness, payment, success);
    return payment;
  }

  // Get the amount of gas used for fulfillment
  function _calculatePaymentAmount(
    uint256 startGas,
    uint256 gasAfterPaymentCalculation,
    uint32 fulfillmentFlatFeeLinkPPM,
    uint256 weiPerUnitGas
  ) internal view returns (uint96) {
    int256 weiPerUnitLink;
    weiPerUnitLink = _getFeedData();
    if (weiPerUnitLink <= 0) {
      revert InvalidLinkWeiPrice(weiPerUnitLink);
    }
    // Will return non-zero on chains that have this enabled
    uint256 l1CostWei = ChainSpecificUtil._getCurrentTxL1GasFees(msg.data);
    // (1e18 juels/link) ((wei/gas * gas) + l1wei) / (wei/link) = juels
    uint256 paymentNoFee = (1e18 * (weiPerUnitGas * (gasAfterPaymentCalculation + startGas - gasleft()) + l1CostWei)) /
      uint256(weiPerUnitLink);
    uint256 fee = 1e12 * uint256(fulfillmentFlatFeeLinkPPM);
    if (paymentNoFee > (1e27 - fee)) {
      revert PaymentTooLarge(); // Payment + fee cannot be more than all of the link in existence.
    }
    return uint96(paymentNoFee + fee);
  }

  function _getFeedData() private view returns (int256) {
    uint32 stalenessSeconds = s_config.stalenessSeconds;
    bool staleFallback = stalenessSeconds > 0;
    uint256 timestamp;
    int256 weiPerUnitLink;
    (, weiPerUnitLink, , timestamp, ) = LINK_ETH_FEED.latestRoundData();
    // solhint-disable-next-line not-rely-on-time
    if (staleFallback && stalenessSeconds < block.timestamp - timestamp) {
      weiPerUnitLink = s_fallbackWeiPerUnitLink;
    }
    return weiPerUnitLink;
  }

  /*
   * @notice Oracle withdraw LINK earned through fulfilling requests
   * @param recipient where to send the funds
   * @param amount amount to withdraw
   */
  function oracleWithdraw(address recipient, uint96 amount) external nonReentrant {
    if (s_withdrawableTokens[msg.sender] < amount) {
      revert InsufficientBalance();
    }
    s_withdrawableTokens[msg.sender] -= amount;
    s_totalBalance -= amount;
    if (!LINK.transfer(recipient, amount)) {
      revert InsufficientBalance();
    }
  }

  function onTokenTransfer(address /* sender */, uint256 amount, bytes calldata data) external override nonReentrant {
    if (msg.sender != address(LINK)) {
      revert OnlyCallableFromLink();
    }
    if (data.length != 32) {
      revert InvalidCalldata();
    }
    uint64 subId = abi.decode(data, (uint64));
    if (s_subscriptionConfigs[subId].owner == address(0)) {
      revert InvalidSubscription();
    }
    // We do not check that the msg.sender is the subscription owner,
    // anyone can fund a subscription.
    uint256 oldBalance = s_subscriptions[subId].balance;
    s_subscriptions[subId].balance += uint96(amount);
    s_totalBalance += uint96(amount);
    emit SubscriptionFunded(subId, oldBalance, oldBalance + amount);
  }

  function getCurrentSubId() external view returns (uint64) {
    return s_currentSubId;
  }

  /**
   * @inheritdoc VRFCoordinatorV2Interface
   */
  function getSubscription(
    uint64 subId
  ) external view override returns (uint96 balance, uint64 reqCount, address owner, address[] memory consumers) {
    if (s_subscriptionConfigs[subId].owner == address(0)) {
      revert InvalidSubscription();
    }
    return (
      s_subscriptions[subId].balance,
      s_subscriptions[subId].reqCount,
      s_subscriptionConfigs[subId].owner,
      s_subscriptionConfigs[subId].consumers
    );
  }

  /**
   * @inheritdoc VRFCoordinatorV2Interface
   */
  function createSubscription() external override nonReentrant returns (uint64) {
    s_currentSubId++;
    uint64 currentSubId = s_currentSubId;
    address[] memory consumers = new address[](0);
    s_subscriptions[currentSubId] = Subscription({balance: 0, reqCount: 0});
    s_subscriptionConfigs[currentSubId] = SubscriptionConfig({
      owner: msg.sender,
      requestedOwner: address(0),
      consumers: consumers
    });

    emit SubscriptionCreated(currentSubId, msg.sender);
    return currentSubId;
  }

  /**
   * @inheritdoc VRFCoordinatorV2Interface
   */
  function requestSubscriptionOwnerTransfer(
    uint64 subId,
    address newOwner
  ) external override onlySubOwner(subId) nonReentrant {
    // Proposing to address(0) would never be claimable so don't need to check.
    if (s_subscriptionConfigs[subId].requestedOwner != newOwner) {
      s_subscriptionConfigs[subId].requestedOwner = newOwner;
      emit SubscriptionOwnerTransferRequested(subId, msg.sender, newOwner);
    }
  }

  /**
   * @inheritdoc VRFCoordinatorV2Interface
   */
  function acceptSubscriptionOwnerTransfer(uint64 subId) external override nonReentrant {
    if (s_subscriptionConfigs[subId].owner == address(0)) {
      revert InvalidSubscription();
    }
    if (s_subscriptionConfigs[subId].requestedOwner != msg.sender) {
      revert MustBeRequestedOwner(s_subscriptionConfigs[subId].requestedOwner);
    }
    address oldOwner = s_subscriptionConfigs[subId].owner;
    s_subscriptionConfigs[subId].owner = msg.sender;
    s_subscriptionConfigs[subId].requestedOwner = address(0);
    emit SubscriptionOwnerTransferred(subId, oldOwner, msg.sender);
  }

  /**
   * @inheritdoc VRFCoordinatorV2Interface
   */
  function removeConsumer(uint64 subId, address consumer) external override onlySubOwner(subId) nonReentrant {
    if (pendingRequestExists(subId)) {
      revert PendingRequestExists();
    }
    if (s_consumers[consumer][subId] == 0) {
      revert InvalidConsumer(subId, consumer);
    }
    // Note bounded by MAX_CONSUMERS
    address[] memory consumers = s_subscriptionConfigs[subId].consumers;
    uint256 lastConsumerIndex = consumers.length - 1;
    for (uint256 i = 0; i < consumers.length; i++) {
      if (consumers[i] == consumer) {
        address last = consumers[lastConsumerIndex];
        // Storage write to preserve last element
        s_subscriptionConfigs[subId].consumers[i] = last;
        // Storage remove last element
        s_subscriptionConfigs[subId].consumers.pop();
        break;
      }
    }
    delete s_consumers[consumer][subId];
    emit SubscriptionConsumerRemoved(subId, consumer);
  }

  /**
   * @inheritdoc VRFCoordinatorV2Interface
   */
  function addConsumer(uint64 subId, address consumer) external override onlySubOwner(subId) nonReentrant {
    // Already maxed, cannot add any more consumers.
    if (s_subscriptionConfigs[subId].consumers.length == MAX_CONSUMERS) {
      revert TooManyConsumers();
    }
    if (s_consumers[consumer][subId] != 0) {
      // Idempotence - do nothing if already added.
      // Ensures uniqueness in s_subscriptions[subId].consumers.
      return;
    }
    // Initialize the nonce to 1, indicating the consumer is allocated.
    s_consumers[consumer][subId] = 1;
    s_subscriptionConfigs[subId].consumers.push(consumer);

    emit SubscriptionConsumerAdded(subId, consumer);
  }

  /**
   * @inheritdoc VRFCoordinatorV2Interface
   */
  function cancelSubscription(uint64 subId, address to) external override onlySubOwner(subId) nonReentrant {
    if (pendingRequestExists(subId)) {
      revert PendingRequestExists();
    }
    _cancelSubscriptionHelper(subId, to);
  }

  function _cancelSubscriptionHelper(uint64 subId, address to) private nonReentrant {
    SubscriptionConfig memory subConfig = s_subscriptionConfigs[subId];
    Subscription memory sub = s_subscriptions[subId];
    uint96 balance = sub.balance;
    // Note bounded by MAX_CONSUMERS;
    // If no consumers, does nothing.
    for (uint256 i = 0; i < subConfig.consumers.length; i++) {
      delete s_consumers[subConfig.consumers[i]][subId];
    }
    delete s_subscriptionConfigs[subId];
    delete s_subscriptions[subId];
    s_totalBalance -= balance;
    if (!LINK.transfer(to, uint256(balance))) {
      revert InsufficientBalance();
    }
    emit SubscriptionCanceled(subId, to, balance);
  }

  /**
   * @inheritdoc VRFCoordinatorV2Interface
   * @dev Looping is bounded to MAX_CONSUMERS*(number of keyhashes).
   * @dev Used to disable subscription canceling while outstanding request are present.
   */
  function pendingRequestExists(uint64 subId) public view override returns (bool) {
    SubscriptionConfig memory subConfig = s_subscriptionConfigs[subId];
    for (uint256 i = 0; i < subConfig.consumers.length; i++) {
      for (uint256 j = 0; j < s_provingKeyHashes.length; j++) {
        (uint256 reqId, ) = _computeRequestId(
          s_provingKeyHashes[j],
          subConfig.consumers[i],
          subId,
          s_consumers[subConfig.consumers[i]][subId]
        );
        if (s_requestCommitments[reqId] != 0) {
          return true;
        }
      }
    }
    return false;
  }

  modifier onlySubOwner(uint64 subId) {
    address owner = s_subscriptionConfigs[subId].owner;
    if (owner == address(0)) {
      revert InvalidSubscription();
    }
    if (msg.sender != owner) {
      revert MustBeSubOwner(owner);
    }
    _;
  }

  modifier nonReentrant() {
    if (s_config.reentrancyLock) {
      revert Reentrant();
    }
    _;
  }

  /**
   * @notice The type and version of this contract
   * @return Type and version string
   */
  function typeAndVersion() external pure virtual override returns (string memory) {
    return "VRFCoordinatorV2 1.0.0";
  }
}