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.auth;
  
  import io.grpc.CallOptions;
  import io.grpc.Channel;
  import io.grpc.ClientCall;
  import io.grpc.ClientInterceptor;
  import io.grpc.ForwardingClientCall.SimpleForwardingClientCall;
  import io.grpc.Metadata;
  import io.grpc.MethodDescriptor;
  
  /** GRPC client intercepter that handles authentication with the server. */
  public class ClientAuthInterceptor implements ClientInterceptor {
    private volatile ClientAuthHandler authHandler = null;
  
    public void setAuthHandler(ClientAuthHandler authHandler) {
      this.authHandler = authHandler;
    }
  
    public ClientAuthInterceptor() {}
  
    public boolean hasAuthHandler() {
      return authHandler != null;
    }
  
    @Override
    public <ReqT, RespT> ClientCall<ReqT, RespT> interceptCall(
        MethodDescriptor<ReqT, RespT> methodDescriptor, CallOptions callOptions, Channel next) {
      ClientCall<ReqT, RespT> call = next.newCall(methodDescriptor, callOptions);
  
      // once we have an auth header, add that to the calls.
      if (authHandler != null) {
        call = new HeaderAttachingClientCall<>(call);
      }
  
      return call;
    }
  
    private final class HeaderAttachingClientCall<ReqT, RespT>
        extends SimpleForwardingClientCall<ReqT, RespT> {
  
      private HeaderAttachingClientCall(ClientCall<ReqT, RespT> call) {
        super(call);
      }
  
      @Override
      public void start(Listener<RespT> responseListener, Metadata headers) {
        final Metadata authHeaders = new Metadata();
        authHeaders.put(AuthConstants.TOKEN_KEY, authHandler.getCallToken());
        headers.merge(authHeaders);
        super.start(responseListener, headers);
      }
    }
  }
  