// SPDX-License-Identifier: MIT
pragma solidity ^0.8.6;

/**
 * @title Chainlink Functions billing subscription registry interface.
 */
interface FunctionsBillingRegistryInterface {
  struct RequestBilling {
    // a unique subscription ID allocated by billing system,
    uint64 subscriptionId;
    // the client contract that initiated the request to the DON
    // to use the subscription it must be added as a consumer on the subscription
    address client;
    // customer specified gas limit for the fulfillment callback
    uint32 gasLimit;
    // the expected gas price used to execute the transaction
    uint256 gasPrice;
  }

  /**
   * @notice Get configuration relevant for making requests
   * @return uint32 global max for request gas limit
   * @return address[] list of registered DONs
   */
  function getRequestConfig() external view returns (uint32, address[] memory);

  /**
   * @notice Determine the charged fee that will be paid to the Registry owner
   * @param data Encoded Chainlink Functions request data, use FunctionsClient API to encode a request
   * @param billing The request's billing configuration
   * @return fee Cost in Juels (1e18) of LINK
   */
  function getRequiredFee(bytes calldata data, FunctionsBillingRegistryInterface.RequestBilling memory billing)
    external
    view
    returns (uint96);

  /**
   * @notice Estimate the total cost to make a request: gas re-imbursement, plus DON fee, plus Registry fee
   * @param gasLimit Encoded Chainlink Functions request data, use FunctionsClient API to encode a request
   * @param gasPrice The request's billing configuration
   * @param donFee Fee charged by the DON that is paid to Oracle Node
   * @param registryFee Fee charged by the DON that is paid to Oracle Node
   * @return costEstimate Cost in Juels (1e18) of LINK
   */
  function estimateCost(
    uint32 gasLimit,
    uint256 gasPrice,
    uint96 donFee,
    uint96 registryFee
  ) external view returns (uint96);

  /**
   * @notice Initiate the billing process for an Functions request
   * @param data Encoded Chainlink Functions request data, use FunctionsClient API to encode a request
   * @param billing Billing configuration for the request
   * @return requestId - A unique identifier of the request. Can be used to match a request to a response in fulfillRequest.
   * @dev Only callable by a node that has been approved on the Registry
   */
  function startBilling(bytes calldata data, RequestBilling calldata billing) external returns (bytes32);

  /**
   * @notice Finalize billing process for an Functions request by sending a callback to the Client contract and then charging the subscription
   * @param requestId identifier for the request that was generated by the Registry in the beginBilling commitment
   * @param response response data from DON consensus
   * @param err error from DON consensus
   * @param transmitter the Oracle who sent the report
   * @param signers the Oracles who had a part in generating the report
   * @param signerCount the number of signers on the report
   * @param reportValidationGas the amount of gas used for the report validation. Cost is split by all fulfillments on the report.
   * @param initialGas the initial amount of gas that should be used as a baseline to charge the single fulfillment for execution cost
   * @return success whether the callback was successsful
   * @dev Only callable by a node that has been approved on the Registry
   * @dev simulated offchain to determine if sufficient balance is present to fulfill the request
   */
  function fulfillAndBill(
    bytes32 requestId,
    bytes calldata response,
    bytes calldata err,
    address transmitter,
    address[31] memory signers, // 31 comes from OCR2Abstract.sol's maxNumOracles constant
    uint8 signerCount,
    uint256 reportValidationGas,
    uint256 initialGas
  ) external returns (bool success);

  /**
   * @notice Gets subscription owner.
   * @param subscriptionId - ID of the subscription
   * @return owner - owner of the subscription.
   */
  function getSubscriptionOwner(uint64 subscriptionId) external view returns (address owner);
}