// File: @chainlink/contracts/src/v0.7/Operator.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.7.0;

import "./AuthorizedReceiver.sol";
import "./LinkTokenReceiver.sol";
import "./ConfirmedOwner.sol";
import "./interfaces/LinkTokenInterface.sol";
import "./interfaces/OperatorInterface.sol";
import "./interfaces/OwnableInterface.sol";
import "./interfaces/WithdrawalInterface.sol";
import "./vendor/Address.sol";
import "./vendor/SafeMathChainlink.sol";

/**
 * @title The Chainlink Operator contract
 * @notice Node operators can deploy this contract to fulfill requests sent to them
 */
contract Operator is AuthorizedReceiver, ConfirmedOwner, LinkTokenReceiver, OperatorInterface, WithdrawalInterface {
  using Address for address;
  using SafeMathChainlink for uint256;

  struct Commitment {
    bytes31 paramsHash;
    uint8 dataVersion;
  }

  uint256 public constant getExpiryTime = 5 minutes;
  uint256 private constant MAXIMUM_DATA_VERSION = 256;
  uint256 private constant MINIMUM_CONSUMER_GAS_LIMIT = 400000;
  uint256 private constant SELECTOR_LENGTH = 4;
  uint256 private constant EXPECTED_REQUEST_WORDS = 2;
  uint256 private constant MINIMUM_REQUEST_LENGTH = SELECTOR_LENGTH + (32 * EXPECTED_REQUEST_WORDS);
  // We initialize fields to 1 instead of 0 so that the first invocation
  // does not cost more gas.
  uint256 private constant ONE_FOR_CONSISTENT_GAS_COST = 1;
  // oracleRequest is intended for version 1, enabling single word responses
  bytes4 private constant ORACLE_REQUEST_SELECTOR = this.oracleRequest.selector;
  // operatorRequest is intended for version 2, enabling multi-word responses
  bytes4 private constant OPERATOR_REQUEST_SELECTOR = this.operatorRequest.selector;

  LinkTokenInterface internal immutable linkToken;
  mapping(bytes32 => Commitment) private s_commitments;
  mapping(address => bool) private s_owned;
  // Tokens sent for requests that have not been fulfilled yet
  uint256 private s_tokensInEscrow = ONE_FOR_CONSISTENT_GAS_COST;

  event OracleRequest(
    bytes32 indexed specId,
    address requester,
    bytes32 requestId,
    uint256 payment,
    address callbackAddr,
    bytes4 callbackFunctionId,
    uint256 cancelExpiration,
    uint256 dataVersion,
    bytes data
  );

  event CancelOracleRequest(bytes32 indexed requestId);

  event OracleResponse(bytes32 indexed requestId);

  event OwnableContractAccepted(address indexed acceptedContract);

  event TargetsUpdatedAuthorizedSenders(address[] targets, address[] senders, address changedBy);

  /**
   * @notice Deploy with the address of the LINK token
   * @dev Sets the LinkToken address for the imported LinkTokenInterface
   * @param link The address of the LINK token
   * @param owner The address of the owner
   */
  constructor(address link, address owner) ConfirmedOwner(owner) {
    linkToken = LinkTokenInterface(link); // external but already deployed and unalterable
  }

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

  /**
   * @notice Creates the Chainlink request. This is a backwards compatible API
   * with the Oracle.sol contract, but the behavior changes because
   * callbackAddress is assumed to be the same as the request sender.
   * @param callbackAddress The consumer of the request
   * @param payment The amount of payment given (specified in wei)
   * @param specId The Job Specification ID
   * @param callbackAddress The address the oracle data will be sent to
   * @param callbackFunctionId The callback function ID for the response
   * @param nonce The nonce sent by the requester
   * @param dataVersion The specified data version
   * @param data The extra request parameters
   */
  function oracleRequest(
    address sender,
    uint256 payment,
    bytes32 specId,
    address callbackAddress,
    bytes4 callbackFunctionId,
    uint256 nonce,
    uint256 dataVersion,
    bytes calldata data
  ) external override validateFromLINK {
    (bytes32 requestId, uint256 expiration) = _verifyAndProcessOracleRequest(
      sender,
      payment,
      callbackAddress,
      callbackFunctionId,
      nonce,
      dataVersion
    );
    emit OracleRequest(specId, sender, requestId, payment, sender, callbackFunctionId, expiration, dataVersion, data);
  }

  /**
   * @notice Creates the Chainlink request
   * @dev Stores the hash of the params as the on-chain commitment for the request.
   * Emits OracleRequest event for the Chainlink node to detect.
   * @param sender The sender of the request
   * @param payment The amount of payment given (specified in wei)
   * @param specId The Job Specification ID
   * @param callbackFunctionId The callback function ID for the response
   * @param nonce The nonce sent by the requester
   * @param dataVersion The specified data version
   * @param data The extra request parameters
   */
  function operatorRequest(
    address sender,
    uint256 payment,
    bytes32 specId,
    bytes4 callbackFunctionId,
    uint256 nonce,
    uint256 dataVersion,
    bytes calldata data
  ) external override validateFromLINK {
    (bytes32 requestId, uint256 expiration) = _verifyAndProcessOracleRequest(
      sender,
      payment,
      sender,
      callbackFunctionId,
      nonce,
      dataVersion
    );
    emit OracleRequest(specId, sender, requestId, payment, sender, callbackFunctionId, expiration, dataVersion, data);
  }

  /**
   * @notice Called by the Chainlink node to fulfill requests
   * @dev Given params must hash back to the commitment stored from `oracleRequest`.
   * Will call the callback address' callback function without bubbling up error
   * checking in a `require` so that the node can get paid.
   * @param requestId The fulfillment request ID that must match the requester's
   * @param payment The payment amount that will be released for the oracle (specified in wei)
   * @param callbackAddress The callback address to call for fulfillment
   * @param callbackFunctionId The callback function ID to use for fulfillment
   * @param expiration The expiration that the node should respond by before the requester can cancel
   * @param data The data to return to the consuming contract
   * @return Status if the external call was successful
   */
  function fulfillOracleRequest(
    bytes32 requestId,
    uint256 payment,
    address callbackAddress,
    bytes4 callbackFunctionId,
    uint256 expiration,
    bytes32 data
  )
    external
    override
    validateAuthorizedSender
    validateRequestId(requestId)
    validateCallbackAddress(callbackAddress)
    returns (bool)
  {
    _verifyOracleRequestAndProcessPayment(requestId, payment, callbackAddress, callbackFunctionId, expiration, 1);
    emit OracleResponse(requestId);
    require(gasleft() >= MINIMUM_CONSUMER_GAS_LIMIT, "Must provide consumer enough gas");
    // All updates to the oracle's fulfillment should come before calling the
    // callback(addr+functionId) as it is untrusted.
    // See: https://solidity.readthedocs.io/en/develop/security-considerations.html#use-the-checks-effects-interactions-pattern
    (bool success, ) = callbackAddress.call(abi.encodeWithSelector(callbackFunctionId, requestId, data)); // solhint-disable-line avoid-low-level-calls
    return success;
  }

  /**
   * @notice Called by the Chainlink node to fulfill requests with multi-word support
   * @dev Given params must hash back to the commitment stored from `oracleRequest`.
   * Will call the callback address' callback function without bubbling up error
   * checking in a `require` so that the node can get paid.
   * @param requestId The fulfillment request ID that must match the requester's
   * @param payment The payment amount that will be released for the oracle (specified in wei)
   * @param callbackAddress The callback address to call for fulfillment
   * @param callbackFunctionId The callback function ID to use for fulfillment
   * @param expiration The expiration that the node should respond by before the requester can cancel
   * @param data The data to return to the consuming contract
   * @return Status if the external call was successful
   */
  function fulfillOracleRequest2(
    bytes32 requestId,
    uint256 payment,
    address callbackAddress,
    bytes4 callbackFunctionId,
    uint256 expiration,
    bytes calldata data
  )
    external
    override
    validateAuthorizedSender
    validateRequestId(requestId)
    validateCallbackAddress(callbackAddress)
    validateMultiWordResponseId(requestId, data)
    returns (bool)
  {
    _verifyOracleRequestAndProcessPayment(requestId, payment, callbackAddress, callbackFunctionId, expiration, 2);
    emit OracleResponse(requestId);
    require(gasleft() >= MINIMUM_CONSUMER_GAS_LIMIT, "Must provide consumer enough gas");
    // All updates to the oracle's fulfillment should come before calling the
    // callback(addr+functionId) as it is untrusted.
    // See: https://solidity.readthedocs.io/en/develop/security-considerations.html#use-the-checks-effects-interactions-pattern
    (bool success, ) = callbackAddress.call(abi.encodePacked(callbackFunctionId, data)); // solhint-disable-line avoid-low-level-calls
    return success;
  }

  /**
   * @notice Transfer the ownership of ownable contracts. This is primarilly
   * intended for Authorized Forwarders but could possibly be extended to work
   * with future contracts.
   * @param ownable list of addresses to transfer
   * @param newOwner address to transfer ownership to
   */
  function transferOwnableContracts(address[] calldata ownable, address newOwner) external onlyOwner {
    for (uint256 i = 0; i < ownable.length; i++) {
      s_owned[ownable[i]] = false;
      OwnableInterface(ownable[i]).transferOwnership(newOwner);
    }
  }

  /**
   * @notice Accept the ownership of an ownable contract. This is primarilly
   * intended for Authorized Forwarders but could possibly be extended to work
   * with future contracts.
   * @dev Must be the pending owner on the contract
   * @param ownable list of addresses of Ownable contracts to accept
   */
  function acceptOwnableContracts(address[] calldata ownable) public validateAuthorizedSenderSetter {
    for (uint256 i = 0; i < ownable.length; i++) {
      s_owned[ownable[i]] = true;
      emit OwnableContractAccepted(ownable[i]);
      OwnableInterface(ownable[i]).acceptOwnership();
    }
  }

  /**
   * @notice Sets the fulfillment permission for
   * @param targets The addresses to set permissions on
   * @param senders The addresses that are allowed to send updates
   */
  function setAuthorizedSendersOn(address[] calldata targets, address[] calldata senders)
    public
    validateAuthorizedSenderSetter
  {
    TargetsUpdatedAuthorizedSenders(targets, senders, msg.sender);

    for (uint256 i = 0; i < targets.length; i++) {
      AuthorizedReceiverInterface(targets[i]).setAuthorizedSenders(senders);
    }
  }

  /**
   * @notice Accepts ownership of ownable contracts and then immediately sets
   * the authorized sender list on each of the newly owned contracts. This is
   * primarilly intended for Authorized Forwarders but could possibly be
   * extended to work with future contracts.
   * @param targets The addresses to set permissions on
   * @param senders The addresses that are allowed to send updates
   */
  function acceptAuthorizedReceivers(address[] calldata targets, address[] calldata senders)
    external
    validateAuthorizedSenderSetter
  {
    acceptOwnableContracts(targets);
    setAuthorizedSendersOn(targets, senders);
  }

  /**
   * @notice Allows the node operator to withdraw earned LINK to a given address
   * @dev The owner of the contract can be another wallet and does not have to be a Chainlink node
   * @param recipient The address to send the LINK token to
   * @param amount The amount to send (specified in wei)
   */
  function withdraw(address recipient, uint256 amount)
    external
    override(OracleInterface, WithdrawalInterface)
    onlyOwner
    validateAvailableFunds(amount)
  {
    assert(linkToken.transfer(recipient, amount));
  }

  /**
   * @notice Displays the amount of LINK that is available for the node operator to withdraw
   * @dev We use `ONE_FOR_CONSISTENT_GAS_COST` in place of 0 in storage
   * @return The amount of withdrawable LINK on the contract
   */
  function withdrawable() external view override(OracleInterface, WithdrawalInterface) returns (uint256) {
    return _fundsAvailable();
  }

  /**
   * @notice Forward a call to another contract
   * @dev Only callable by the owner
   * @param to address
   * @param data to forward
   */
  function ownerForward(address to, bytes calldata data) external onlyOwner validateNotToLINK(to) {
    require(to.isContract(), "Must forward to a contract");
    (bool status, ) = to.call(data);
    require(status, "Forwarded call failed");
  }

  /**
   * @notice Interact with other LinkTokenReceiver contracts by calling transferAndCall
   * @param to The address to transfer to.
   * @param value The amount to be transferred.
   * @param data The extra data to be passed to the receiving contract.
   * @return success bool
   */
  function ownerTransferAndCall(
    address to,
    uint256 value,
    bytes calldata data
  ) external override onlyOwner validateAvailableFunds(value) returns (bool success) {
    return linkToken.transferAndCall(to, value, data);
  }

  /**
   * @notice Distribute funds to multiple addresses using ETH send
   * to this payable function.
   * @dev Array length must be equal, ETH sent must equal the sum of amounts.
   * A malicious receiver could cause the distribution to revert, in which case
   * it is expected that the address is removed from the list.
   * @param receivers list of addresses
   * @param amounts list of amounts
   */
  function distributeFunds(address payable[] calldata receivers, uint256[] calldata amounts) external payable {
    require(receivers.length > 0 && receivers.length == amounts.length, "Invalid array length(s)");
    uint256 valueRemaining = msg.value;
    for (uint256 i = 0; i < receivers.length; i++) {
      uint256 sendAmount = amounts[i];
      valueRemaining = valueRemaining.sub(sendAmount);
      receivers[i].transfer(sendAmount);
    }
    require(valueRemaining == 0, "Too much ETH sent");
  }

  /**
   * @notice Allows recipient to cancel requests sent to this oracle contract.
   * Will transfer the LINK sent for the request back to the recipient address.
   * @dev Given params must hash to a commitment stored on the contract in order
   * for the request to be valid. Emits CancelOracleRequest event.
   * @param requestId The request ID
   * @param payment The amount of payment given (specified in wei)
   * @param callbackFunc The requester's specified callback function selector
   * @param expiration The time of the expiration for the request
   */
  function cancelOracleRequest(
    bytes32 requestId,
    uint256 payment,
    bytes4 callbackFunc,
    uint256 expiration
  ) external override {
    bytes31 paramsHash = _buildParamsHash(payment, msg.sender, callbackFunc, expiration);
    require(s_commitments[requestId].paramsHash == paramsHash, "Params do not match request ID");
    // solhint-disable-next-line not-rely-on-time
    require(expiration <= block.timestamp, "Request is not expired");

    delete s_commitments[requestId];
    emit CancelOracleRequest(requestId);

    linkToken.transfer(msg.sender, payment);
  }

  /**
   * @notice Allows requester to cancel requests sent to this oracle contract.
   * Will transfer the LINK sent for the request back to the recipient address.
   * @dev Given params must hash to a commitment stored on the contract in order
   * for the request to be valid. Emits CancelOracleRequest event.
   * @param nonce The nonce used to generate the request ID
   * @param payment The amount of payment given (specified in wei)
   * @param callbackFunc The requester's specified callback function selector
   * @param expiration The time of the expiration for the request
   */
  function cancelOracleRequestByRequester(
    uint256 nonce,
    uint256 payment,
    bytes4 callbackFunc,
    uint256 expiration
  ) external {
    bytes32 requestId = keccak256(abi.encodePacked(msg.sender, nonce));
    bytes31 paramsHash = _buildParamsHash(payment, msg.sender, callbackFunc, expiration);
    require(s_commitments[requestId].paramsHash == paramsHash, "Params do not match request ID");
    // solhint-disable-next-line not-rely-on-time
    require(expiration <= block.timestamp, "Request is not expired");

    delete s_commitments[requestId];
    emit CancelOracleRequest(requestId);

    linkToken.transfer(msg.sender, payment);
  }

  /**
   * @notice Returns the address of the LINK token
   * @dev This is the public implementation for chainlinkTokenAddress, which is
   * an internal method of the ChainlinkClient contract
   */
  function getChainlinkToken() public view override returns (address) {
    return address(linkToken);
  }

  /**
   * @notice Require that the token transfer action is valid
   * @dev OPERATOR_REQUEST_SELECTOR = multiword, ORACLE_REQUEST_SELECTOR = singleword
   */
  function _validateTokenTransferAction(bytes4 funcSelector, bytes memory data) internal pure override {
    require(data.length >= MINIMUM_REQUEST_LENGTH, "Invalid request length");
    require(
      funcSelector == OPERATOR_REQUEST_SELECTOR || funcSelector == ORACLE_REQUEST_SELECTOR,
      "Must use whitelisted functions"
    );
  }

  /**
   * @notice Verify the Oracle Request and record necessary information
   * @param sender The sender of the request
   * @param payment The amount of payment given (specified in wei)
   * @param callbackAddress The callback address for the response
   * @param callbackFunctionId The callback function ID for the response
   * @param nonce The nonce sent by the requester
   */
  function _verifyAndProcessOracleRequest(
    address sender,
    uint256 payment,
    address callbackAddress,
    bytes4 callbackFunctionId,
    uint256 nonce,
    uint256 dataVersion
  ) private validateNotToLINK(callbackAddress) returns (bytes32 requestId, uint256 expiration) {
    requestId = keccak256(abi.encodePacked(sender, nonce));
    require(s_commitments[requestId].paramsHash == 0, "Must use a unique ID");
    // solhint-disable-next-line not-rely-on-time
    expiration = block.timestamp.add(getExpiryTime);
    bytes31 paramsHash = _buildParamsHash(payment, callbackAddress, callbackFunctionId, expiration);
    s_commitments[requestId] = Commitment(paramsHash, _safeCastToUint8(dataVersion));
    s_tokensInEscrow = s_tokensInEscrow.add(payment);
    return (requestId, expiration);
  }

  /**
   * @notice Verify the Oracle request and unlock escrowed payment
   * @param requestId The fulfillment request ID that must match the requester's
   * @param payment The payment amount that will be released for the oracle (specified in wei)
   * @param callbackAddress The callback address to call for fulfillment
   * @param callbackFunctionId The callback function ID to use for fulfillment
   * @param expiration The expiration that the node should respond by before the requester can cancel
   */
  function _verifyOracleRequestAndProcessPayment(
    bytes32 requestId,
    uint256 payment,
    address callbackAddress,
    bytes4 callbackFunctionId,
    uint256 expiration,
    uint256 dataVersion
  ) internal {
    bytes31 paramsHash = _buildParamsHash(payment, callbackAddress, callbackFunctionId, expiration);
    require(s_commitments[requestId].paramsHash == paramsHash, "Params do not match request ID");
    require(s_commitments[requestId].dataVersion <= _safeCastToUint8(dataVersion), "Data versions must match");
    s_tokensInEscrow = s_tokensInEscrow.sub(payment);
    delete s_commitments[requestId];
  }

  /**
   * @notice Build the bytes31 hash from the payment, callback and expiration.
   * @param payment The payment amount that will be released for the oracle (specified in wei)
   * @param callbackAddress The callback address to call for fulfillment
   * @param callbackFunctionId The callback function ID to use for fulfillment
   * @param expiration The expiration that the node should respond by before the requester can cancel
   * @return hash bytes31
   */
  function _buildParamsHash(
    uint256 payment,
    address callbackAddress,
    bytes4 callbackFunctionId,
    uint256 expiration
  ) internal pure returns (bytes31) {
    return bytes31(keccak256(abi.encodePacked(payment, callbackAddress, callbackFunctionId, expiration)));
  }

  /**
   * @notice Safely cast uint256 to uint8
   * @param number uint256
   * @return uint8 number
   */
  function _safeCastToUint8(uint256 number) internal pure returns (uint8) {
    require(number < MAXIMUM_DATA_VERSION, "number too big to cast");
    return uint8(number);
  }

  /**
   * @notice Returns the LINK available in this contract, not locked in escrow
   * @return uint256 LINK tokens available
   */
  function _fundsAvailable() private view returns (uint256) {
    uint256 inEscrow = s_tokensInEscrow.sub(ONE_FOR_CONSISTENT_GAS_COST);
    return linkToken.balanceOf(address(this)).sub(inEscrow);
  }

  /**
   * @notice concrete implementation of AuthorizedReceiver
   * @return bool of whether sender is authorized
   */
  function _canSetAuthorizedSenders() internal view override returns (bool) {
    return isAuthorizedSender(msg.sender) || owner() == msg.sender;
  }

  // MODIFIERS

  /**
   * @dev Reverts if the first 32 bytes of the bytes array is not equal to requestId
   * @param requestId bytes32
   * @param data bytes
   */
  modifier validateMultiWordResponseId(bytes32 requestId, bytes calldata data) {
    require(data.length >= 32, "Response must be > 32 bytes");
    bytes32 firstDataWord;
    assembly {
      // extract the first word from data
      // functionSelector = 4
      // wordLength = 32
      // dataArgumentOffset = 7 * wordLength
      // funcSelector + dataArgumentOffset == 0xe4
      firstDataWord := calldataload(0xe4)
    }
    require(requestId == firstDataWord, "First word must be requestId");
    _;
  }

  /**
   * @dev Reverts if amount requested is greater than withdrawable balance
   * @param amount The given amount to compare to `s_withdrawableTokens`
   */
  modifier validateAvailableFunds(uint256 amount) {
    require(_fundsAvailable() >= amount, "Amount requested is greater than withdrawable balance");
    _;
  }

  /**
   * @dev Reverts if request ID does not exist
   * @param requestId The given request ID to check in stored `commitments`
   */
  modifier validateRequestId(bytes32 requestId) {
    require(s_commitments[requestId].paramsHash != 0, "Must have a valid requestId");
    _;
  }

  /**
   * @dev Reverts if the callback address is the LINK token
   * @param to The callback address
   */
  modifier validateNotToLINK(address to) {
    require(to != address(linkToken), "Cannot call to LINK");
    _;
  }

  /**
   * @dev Reverts if the target address is owned by the operator
   */
  modifier validateCallbackAddress(address callbackAddress) {
    require(!s_owned[callbackAddress], "Cannot call owned contract");
    _;
  }
}

// File: @chainlink/contracts/src/v0.7/AuthorizedReceiver.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.7.0;

import "./interfaces/AuthorizedReceiverInterface.sol";

abstract contract AuthorizedReceiver is AuthorizedReceiverInterface {
  mapping(address => bool) private s_authorizedSenders;
  address[] private s_authorizedSenderList;

  event AuthorizedSendersChanged(address[] senders, address changedBy);

  /**
   * @notice Sets the fulfillment permission for a given node. Use `true` to allow, `false` to disallow.
   * @param senders The addresses of the authorized Chainlink node
   */
  function setAuthorizedSenders(address[] calldata senders) external override validateAuthorizedSenderSetter {
    require(senders.length > 0, "Must have at least 1 authorized sender");
    // Set previous authorized senders to false
    uint256 authorizedSendersLength = s_authorizedSenderList.length;
    for (uint256 i = 0; i < authorizedSendersLength; i++) {
      s_authorizedSenders[s_authorizedSenderList[i]] = false;
    }
    // Set new to true
    for (uint256 i = 0; i < senders.length; i++) {
      s_authorizedSenders[senders[i]] = true;
    }
    // Replace list
    s_authorizedSenderList = senders;
    emit AuthorizedSendersChanged(senders, msg.sender);
  }

  /**
   * @notice Retrieve a list of authorized senders
   * @return array of addresses
   */
  function getAuthorizedSenders() external view override returns (address[] memory) {
    return s_authorizedSenderList;
  }

  /**
   * @notice Use this to check if a node is authorized for fulfilling requests
   * @param sender The address of the Chainlink node
   * @return The authorization status of the node
   */
  function isAuthorizedSender(address sender) public view override returns (bool) {
    return s_authorizedSenders[sender];
  }

  /**
   * @notice customizable guard of who can update the authorized sender list
   * @return bool whether sender can update authorized sender list
   */
  function _canSetAuthorizedSenders() internal virtual returns (bool);

  /**
   * @notice validates the sender is an authorized sender
   */
  function _validateIsAuthorizedSender() internal view {
    require(isAuthorizedSender(msg.sender), "Not authorized sender");
  }

  /**
   * @notice prevents non-authorized addresses from calling this method
   */
  modifier validateAuthorizedSender() {
    _validateIsAuthorizedSender();
    _;
  }

  /**
   * @notice prevents non-authorized addresses from calling this method
   */
  modifier validateAuthorizedSenderSetter() {
    require(_canSetAuthorizedSenders(), "Cannot set authorized senders");
    _;
  }
}

// File: @chainlink/contracts/src/v0.7/LinkTokenReceiver.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.7.0;

abstract contract LinkTokenReceiver {
  /**
   * @notice Called when LINK is sent to the contract via `transferAndCall`
   * @dev The data payload's first 2 words will be overwritten by the `sender` and `amount`
   * values to ensure correctness. Calls oracleRequest.
   * @param sender Address of the sender
   * @param amount Amount of LINK sent (specified in wei)
   * @param data Payload of the transaction
   */
  function onTokenTransfer(
    address sender,
    uint256 amount,
    bytes memory data
  ) public validateFromLINK permittedFunctionsForLINK(data) {
    assembly {
      // solhint-disable-next-line avoid-low-level-calls
      mstore(add(data, 36), sender) // ensure correct sender is passed
      // solhint-disable-next-line avoid-low-level-calls
      mstore(add(data, 68), amount) // ensure correct amount is passed
    }
    // solhint-disable-next-line avoid-low-level-calls
    (bool success, ) = address(this).delegatecall(data); // calls oracleRequest
    require(success, "Unable to create request");
  }

  function getChainlinkToken() public view virtual returns (address);

  /**
   * @notice Validate the function called on token transfer
   */
  function _validateTokenTransferAction(bytes4 funcSelector, bytes memory data) internal virtual;

  /**
   * @dev Reverts if not sent from the LINK token
   */
  modifier validateFromLINK() {
    require(msg.sender == getChainlinkToken(), "Must use LINK token");
    _;
  }

  /**
   * @dev Reverts if the given data does not begin with the `oracleRequest` function selector
   * @param data The data payload of the request
   */
  modifier permittedFunctionsForLINK(bytes memory data) {
    bytes4 funcSelector;
    assembly {
      // solhint-disable-next-line avoid-low-level-calls
      funcSelector := mload(add(data, 32))
    }
    _validateTokenTransferAction(funcSelector, data);
    _;
  }
}

// File: @chainlink/contracts/src/v0.7/ConfirmedOwner.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.7.0;

import "./ConfirmedOwnerWithProposal.sol";

/**
 * @title The ConfirmedOwner contract
 * @notice A contract with helpers for basic contract ownership.
 */
contract ConfirmedOwner is ConfirmedOwnerWithProposal {
  constructor(address newOwner) ConfirmedOwnerWithProposal(newOwner, address(0)) {}
}

// File: @chainlink/contracts/src/v0.7/interfaces/LinkTokenInterface.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.7.0;

interface LinkTokenInterface {
  function allowance(address owner, address spender) external view returns (uint256 remaining);

  function approve(address spender, uint256 value) external returns (bool success);

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

  function decimals() external view returns (uint8 decimalPlaces);

  function decreaseApproval(address spender, uint256 addedValue) external returns (bool success);

  function increaseApproval(address spender, uint256 subtractedValue) external;

  function name() external view returns (string memory tokenName);

  function symbol() external view returns (string memory tokenSymbol);

  function totalSupply() external view returns (uint256 totalTokensIssued);

  function transfer(address to, uint256 value) external returns (bool success);

  function transferAndCall(
    address to,
    uint256 value,
    bytes calldata data
  ) external returns (bool success);

  function transferFrom(
    address from,
    address to,
    uint256 value
  ) external returns (bool success);
}

// File: @chainlink/contracts/src/v0.7/interfaces/OperatorInterface.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.7.0;

import "./ChainlinkRequestInterface.sol";
import "./OracleInterface.sol";

interface OperatorInterface is ChainlinkRequestInterface, OracleInterface {
  function operatorRequest(
    address sender,
    uint256 payment,
    bytes32 specId,
    bytes4 callbackFunctionId,
    uint256 nonce,
    uint256 dataVersion,
    bytes calldata data
  ) external;

  function fulfillOracleRequest2(
    bytes32 requestId,
    uint256 payment,
    address callbackAddress,
    bytes4 callbackFunctionId,
    uint256 expiration,
    bytes calldata data
  ) external returns (bool);

  function ownerTransferAndCall(
    address to,
    uint256 value,
    bytes calldata data
  ) external returns (bool success);
}

// File: @chainlink/contracts/src/v0.7/interfaces/OwnableInterface.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.7.0;

interface OwnableInterface {
  function owner() external returns (address);

  function transferOwnership(address recipient) external;

  function acceptOwnership() external;
}

// File: @chainlink/contracts/src/v0.7/interfaces/WithdrawalInterface.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.7.0;

interface WithdrawalInterface {
  /**
   * @notice transfer LINK held by the contract belonging to msg.sender to
   * another address
   * @param recipient is the address to send the LINK to
   * @param amount is the amount of LINK to send
   */
  function withdraw(address recipient, uint256 amount) external;

  /**
   * @notice query the available amount of LINK to withdraw by msg.sender
   */
  function withdrawable() external view returns (uint256);
}

// File: @chainlink/contracts/src/v0.7/vendor/Address.sol



// SPDX-License-Identifier: MIT
// From https://github.com/OpenZeppelin/openzeppelin-contracts v3.4.0(fa64a1ced0b70ab89073d5d0b6e01b0778f7e7d6)

pragma solidity >=0.6.2 <0.8.0;

/**
 * @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);
      }
    }
  }
}

// File: @chainlink/contracts/src/v0.7/vendor/SafeMathChainlink.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.7.0;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMathChainlink {
  /**
   * @dev Returns the addition of two unsigned integers, reverting on
   * overflow.
   *
   * Counterpart to Solidity's `+` operator.
   *
   * Requirements:
   * - Addition cannot overflow.
   */
  function add(uint256 a, uint256 b) internal pure returns (uint256) {
    uint256 c = a + b;
    require(c >= a, "SafeMath: addition overflow");

    return c;
  }

  /**
   * @dev Returns the subtraction of two unsigned integers, reverting on
   * overflow (when the result is negative).
   *
   * Counterpart to Solidity's `-` operator.
   *
   * Requirements:
   * - Subtraction cannot overflow.
   */
  function sub(uint256 a, uint256 b) internal pure returns (uint256) {
    require(b <= a, "SafeMath: subtraction overflow");
    uint256 c = a - b;

    return c;
  }

  /**
   * @dev Returns the multiplication of two unsigned integers, reverting on
   * overflow.
   *
   * Counterpart to Solidity's `*` operator.
   *
   * Requirements:
   * - Multiplication cannot overflow.
   */
  function mul(uint256 a, uint256 b) internal pure returns (uint256) {
    // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
    // benefit is lost if 'b' is also tested.
    // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
    if (a == 0) {
      return 0;
    }

    uint256 c = a * b;
    require(c / a == b, "SafeMath: multiplication overflow");

    return c;
  }

  /**
   * @dev Returns the integer division of two unsigned integers. Reverts on
   * division by zero. The result is rounded towards zero.
   *
   * Counterpart to Solidity's `/` operator. Note: this function uses a
   * `revert` opcode (which leaves remaining gas untouched) while Solidity
   * uses an invalid opcode to revert (consuming all remaining gas).
   *
   * Requirements:
   * - The divisor cannot be zero.
   */
  function div(uint256 a, uint256 b) internal pure returns (uint256) {
    // Solidity only automatically asserts when dividing by 0
    require(b > 0, "SafeMath: division by zero");
    uint256 c = a / b;
    // assert(a == b * c + a % b); // There is no case in which this doesn't hold

    return c;
  }

  /**
   * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
   * Reverts when dividing by zero.
   *
   * Counterpart to Solidity's `%` operator. This function uses a `revert`
   * opcode (which leaves remaining gas untouched) while Solidity uses an
   * invalid opcode to revert (consuming all remaining gas).
   *
   * Requirements:
   * - The divisor cannot be zero.
   */
  function mod(uint256 a, uint256 b) internal pure returns (uint256) {
    require(b != 0, "SafeMath: modulo by zero");
    return a % b;
  }
}

// File: @chainlink/contracts/src/v0.7/interfaces/AuthorizedReceiverInterface.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.7.0;

interface AuthorizedReceiverInterface {
  function isAuthorizedSender(address sender) external view returns (bool);

  function getAuthorizedSenders() external returns (address[] memory);

  function setAuthorizedSenders(address[] calldata senders) external;
}

// File: @chainlink/contracts/src/v0.7/ConfirmedOwnerWithProposal.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.7.0;

import "./interfaces/OwnableInterface.sol";

/**
 * @title The ConfirmedOwner contract
 * @notice A contract with helpers for basic contract ownership.
 */
contract ConfirmedOwnerWithProposal is OwnableInterface {
  address private s_owner;
  address private s_pendingOwner;

  event OwnershipTransferRequested(address indexed from, address indexed to);
  event OwnershipTransferred(address indexed from, address indexed to);

  constructor(address newOwner, address pendingOwner) {
    require(newOwner != address(0), "Cannot set owner to zero");

    s_owner = newOwner;
    if (pendingOwner != address(0)) {
      _transferOwnership(pendingOwner);
    }
  }

  /**
   * @notice Allows an owner to begin transferring ownership to a new address,
   * pending.
   */
  function transferOwnership(address to) public override onlyOwner {
    _transferOwnership(to);
  }

  /**
   * @notice Allows an ownership transfer to be completed by the recipient.
   */
  function acceptOwnership() external override {
    require(msg.sender == s_pendingOwner, "Must be proposed owner");

    address oldOwner = s_owner;
    s_owner = msg.sender;
    s_pendingOwner = address(0);

    emit OwnershipTransferred(oldOwner, msg.sender);
  }

  /**
   * @notice Get the current owner
   */
  function owner() public view override returns (address) {
    return s_owner;
  }

  /**
   * @notice validate, transfer ownership, and emit relevant events
   */
  function _transferOwnership(address to) private {
    require(to != msg.sender, "Cannot transfer to self");

    s_pendingOwner = to;

    emit OwnershipTransferRequested(s_owner, to);
  }

  /**
   * @notice validate access
   */
  function _validateOwnership() internal view {
    require(msg.sender == s_owner, "Only callable by owner");
  }

  /**
   * @notice Reverts if called by anyone other than the contract owner.
   */
  modifier onlyOwner() {
    _validateOwnership();
    _;
  }
}

// File: @chainlink/contracts/src/v0.7/interfaces/ChainlinkRequestInterface.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.7.0;

interface ChainlinkRequestInterface {
  function oracleRequest(
    address sender,
    uint256 requestPrice,
    bytes32 serviceAgreementID,
    address callbackAddress,
    bytes4 callbackFunctionId,
    uint256 nonce,
    uint256 dataVersion,
    bytes calldata data
  ) external;

  function cancelOracleRequest(
    bytes32 requestId,
    uint256 payment,
    bytes4 callbackFunctionId,
    uint256 expiration
  ) external;
}

// File: @chainlink/contracts/src/v0.7/interfaces/OracleInterface.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.7.0;

interface OracleInterface {
  function fulfillOracleRequest(
    bytes32 requestId,
    uint256 payment,
    address callbackAddress,
    bytes4 callbackFunctionId,
    uint256 expiration,
    bytes32 data
  ) external returns (bool);

  function withdraw(address recipient, uint256 amount) external;

  function withdrawable() external view returns (uint256);
}