// SPDX-License-Identifier: MIT
pragma solidity ^0.8.19;

import {IFunctionsClient} from "./interfaces/IFunctionsClient.sol";
import {IFunctionsRouter} from "./interfaces/IFunctionsRouter.sol";

import {FunctionsRequest} from "./libraries/FunctionsRequest.sol";

/// @title The Chainlink Functions client contract
/// @notice Contract developers can inherit this contract in order to make Chainlink Functions requests
abstract contract FunctionsClient is IFunctionsClient {
  using FunctionsRequest for FunctionsRequest.Request;

  IFunctionsRouter internal immutable i_router;

  event RequestSent(bytes32 indexed id);
  event RequestFulfilled(bytes32 indexed id);

  error OnlyRouterCanFulfill();

  constructor(
    address router
  ) {
    i_router = IFunctionsRouter(router);
  }

  /// @notice Sends a Chainlink Functions request
  /// @param data The CBOR encoded bytes data for a Functions request
  /// @param subscriptionId The subscription ID that will be charged to service the request
  /// @param callbackGasLimit the amount of gas that will be available for the fulfillment callback
  /// @return requestId The generated request ID for this request
  function _sendRequest(
    bytes memory data,
    uint64 subscriptionId,
    uint32 callbackGasLimit,
    bytes32 donId
  ) internal returns (bytes32) {
    bytes32 requestId =
      i_router.sendRequest(subscriptionId, data, FunctionsRequest.REQUEST_DATA_VERSION, callbackGasLimit, donId);
    emit RequestSent(requestId);
    return requestId;
  }

  /// @notice User defined function to handle a response from the DON
  /// @param requestId The request ID, returned by sendRequest()
  /// @param response Aggregated response from the execution of the user's source code
  /// @param err Aggregated error from the execution of the user code or from the execution pipeline
  /// @dev Either response or error parameter will be set, but never both
  function fulfillRequest(bytes32 requestId, bytes memory response, bytes memory err) internal virtual;

  /// @inheritdoc IFunctionsClient
  function handleOracleFulfillment(bytes32 requestId, bytes memory response, bytes memory err) external override {
    if (msg.sender != address(i_router)) {
      revert OnlyRouterCanFulfill();
    }
    fulfillRequest(requestId, response, err);
    emit RequestFulfilled(requestId);
  }
}