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 java.util.Iterator;
  import java.util.Optional;
  import org.apache.arrow.flight.FlightServer;
  import org.apache.arrow.flight.auth2.CallHeaderAuthenticator;
  
  /**
   * Interface for Server side authentication handlers.
   *
   * @deprecated As of 14.0.0. This implements a stateful "login" flow that does not play well with
   *     distributed or stateless systems. It will not be removed, but should not be used. Instead,
   *     see {@link FlightServer.Builder#headerAuthenticator(CallHeaderAuthenticator)} and {@link
   *     CallHeaderAuthenticator}.
   */
  @Deprecated
  public interface ServerAuthHandler {
  
    /**
     * Validate the client token provided on each call.
     *
     * @return An empty optional if the client is not authenticated; the peer identity otherwise (may
     *     be the empty string).
     */
    Optional<String> isValid(byte[] token);
  
    /**
     * Handle the initial handshake with the client.
     *
     * @param outgoing A writer to send messages to the client.
     * @param incoming An iterator of messages from the client.
     * @return true if client is authenticated, false otherwise.
     */
    boolean authenticate(ServerAuthSender outgoing, Iterator<byte[]> incoming);
  
    /**
     * Interface for a server implementations to send back authentication messages back to the client.
     */
    interface ServerAuthSender {
  
      void send(byte[] payload);
  
      void onError(Throwable cause);
    }
  
    /** An auth handler that does nothing. */
    ServerAuthHandler NO_OP =
        new ServerAuthHandler() {
  
          @Override
          public Optional<String> isValid(byte[] token) {
            return Optional.of("");
          }
  
          @Override
          public boolean authenticate(ServerAuthSender outgoing, Iterator<byte[]> incoming) {
            return true;
          }
        };
  }
  