/*
 * 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;

/**
 * Interface for Server side authentication handlers.
 */
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 an 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;
    }
  };
}
