/*
    * 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
    *
    *      https://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.commons.net.daytime;
  
  import java.io.IOException;
  import java.io.PrintWriter;
  import java.net.InetAddress;
  import java.net.Socket;
  import java.time.Clock;
  import java.time.ZonedDateTime;
  import java.time.format.DateTimeFormatter;
  import java.util.Locale;
  import java.util.Objects;
  import java.util.concurrent.BlockingQueue;
  import java.util.concurrent.LinkedBlockingQueue;
  import java.util.concurrent.TimeUnit;
  
  import org.apache.commons.net.MockTcpServer;
  
  /**
   * The MockDaytimeTCPServer class is a simple TCP implementation of a server for the Daytime Protocol described in
   * <a href="https://datatracker.ietf.org/doc/html/rfc867">RFC 867</a>.
   * <p>
   * Listens for TCP socket connections on the daytime protocol port and writes the local day time to socket {@code outputStream} as {@link String} in format
   * {@code EEEE, MMMM d, uuuu, HH:mm:ss-z}. See the <a href="https://datatracker.ietf.org/doc/html/rfc867"> RFC-867 spec </a> for more details.
   * </p>
   * <p>
   * This implementation uses {@link MockDaytimeTCPServer#enqueue(Clock)} and {@link BlockingQueue<Clock>} to queue next {@link Clock} that will be used to obtain
   * and write daytime data into {@code clientSocket}.
   * </p>
   * <p>
   * NOTE: this is for <strong>debugging and testing purposes only</strong> and not meant to be run as a reliable server.
   * </p>
   *
   * @see MockTcpServer
   * @see DaytimeTCPClientTest DaytimeTCPClientTest (for example usage in tests)
   */
  public final class MockDaytimeTCPServer extends MockTcpServer {
  
      private static final DateTimeFormatter DAYTIME_DATA_FORMAT = DateTimeFormatter.ofPattern("EEEE, MMMM d, uuuu, HH:mm:ss-z", Locale.ENGLISH);
  
      private final BlockingQueue<Clock> responseQueue = new LinkedBlockingQueue<>();
  
      /**
       * Creates new {@link MockDaytimeTCPServer} that will bind to {@link InetAddress#getLocalHost()}
       * on random port.
       *
       * @throws IOException if an I/O error occurs when opening the socket.
       */
      public MockDaytimeTCPServer() throws IOException {
      }
  
      /**
       * Creates new {@link MockDaytimeTCPServer} that will bind to {@link InetAddress#getLocalHost()}
       * on specified port.
       *
       * @param port the port number the server will bind to, or 0 to use a port number that is automatically allocated
       * @throws IOException if an I/O error occurs when opening the socket.
       */
      public MockDaytimeTCPServer(final int port) throws IOException {
          super(port);
      }
  
      /**
       * Creates new {@link MockDaytimeTCPServer} that will bind to specified {@link InetAddress} and on specified port.
       *
       * @param port the port number the server will bind to, or 0 to use a port number that is automatically allocated
       * @param serverAddress the InetAddress the server will bind to
       * @throws IOException if an I/O error occurs when opening the socket.
       */
      public MockDaytimeTCPServer(final int port, final InetAddress serverAddress) throws IOException {
          super(port, serverAddress);
      }
  
      /**
       * Queues clock that will be used in next accepted {@link Socket}
       * to return Daytime data, as defined in <a href="https://datatracker.ietf.org/doc/html/rfc867">RFC 867</a> spec
       *
       * @param clock that will be used
       * @return the queued {@code clock}
       */
      public Clock enqueue(final Clock clock) {
          responseQueue.add(clock);
          return clock;
     }
 
     @Override
     protected void processClientSocket(final Socket clientSocket) throws Exception {
         try (PrintWriter pw = new PrintWriter(clientSocket.getOutputStream())) {
             final Clock nextClock = Objects.requireNonNull(responseQueue.poll(5, TimeUnit.SECONDS), "Could not obtain next clock for DaytimeTCPMockServer");
             final ZonedDateTime dateTime = ZonedDateTime.now(nextClock);
             pw.write(dateTime.format(DAYTIME_DATA_FORMAT));
             pw.flush();
         }
     }
 
 }