content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   *
   *    http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.arrow.flight;
  
  /**
   * Client-side middleware for Flight.
   *
   * <p>Middleware are instantiated per-call and should store state in the middleware instance.
   */
  public interface FlightClientMiddleware {
    /** A callback used before request headers are sent. The headers may be manipulated. */
    void onBeforeSendingHeaders(CallHeaders outgoingHeaders);
  
    /** A callback called after response headers are received. The headers may be manipulated. */
    void onHeadersReceived(CallHeaders incomingHeaders);
  
    /** A callback called after the call completes. */
    void onCallCompleted(CallStatus status);
  
    /** A factory for client middleware instances. */
    interface Factory {
      /**
       * Create a new middleware instance for the given call.
       *
       * @throws FlightRuntimeException if the middleware wants to reject the call with the given
       *     status
       */
      FlightClientMiddleware onCallStarted(CallInfo info);
    }
  }
  