package org.opentrafficsim.trafficcontrol.ccol;
   
   import java.awt.Container;
   import java.io.BufferedReader;
   import java.io.IOException;
   import java.io.InputStreamReader;
   import java.io.PrintWriter;
   import java.net.ServerSocket;
   import java.net.Socket;
  import java.util.Optional;
  import java.util.Set;
  
  import org.djunits.unit.DurationUnit;
  import org.djunits.value.vdouble.scalar.Duration;
  import org.djutils.event.Event;
  import org.djutils.event.EventType;
  import org.djutils.event.LocalEventProducer;
  import org.djutils.exceptions.Try;
  import org.opentrafficsim.base.logger.Logger;
  import org.opentrafficsim.core.dsol.OtsSimulator;
  import org.opentrafficsim.road.network.lane.object.detector.TrafficLightDetector;
  import org.opentrafficsim.road.network.lane.object.trafficlight.TrafficLight;
  import org.opentrafficsim.trafficcontrol.ActuatedTrafficController;
  import org.opentrafficsim.trafficcontrol.TrafficControlException;
  
  import nl.tudelft.simulation.dsol.SimRuntimeException;
  import nl.tudelft.simulation.dsol.experiment.Replication;
  
  /**
   * Communication link with a CCOL traffic control program.
   * <p>
   * Copyright (c) 2013-2024 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved. <br>
   * BSD-style license. See <a href="https://opentrafficsim.org/docs/license.html">OpenTrafficSim License</a>.
   * </p>
   * @author <a href="https://github.com/averbraeck">Alexander Verbraeck</a>
   * @author <a href="https://github.com/peter-knoppers">Peter Knoppers</a>
   * @author <a href="https://github.com/wjschakel">Wouter Schakel</a>
   */
  public class Ccol extends LocalEventProducer implements ActuatedTrafficController
  {
      /** Name of this CCOL traffic controller. */
      private final String id;
  
      /** The simulator. */
      private final OtsSimulator simulator;
  
      /** TCP port for incoming connection. */
      private static int port = 4321;
  
      /** The evaluation interval of a CCOL controller. */
      static final Duration EVALUATION_INTERVAL = new Duration(0.1, DurationUnit.SECOND);
  
      /** Socket used to listen for the incoming connection from the CCOL controller. */
      private ServerSocket serverSocket;
  
      /** Socket for communication with the CCOL controller. */
      private Socket clientSocket = null;
  
      /** Receives data from the CCOL process. */
      private BufferedReader ccolReader = null;
  
      /** Sends data to the CCOL process. */
      private PrintWriter ccolWriter = null;
  
      /** Thread that blocks until accept returns. */
      private Thread acceptThread;
  
      /**
       * Construct a new CCOL communication link.
       * @param id id of the traffic controller
       * @param controlProgram name of the CCOL program that this CCOL link must communicate with
       * @param trafficLights the traffic lights. The ids of the traffic lights must end with two digits that match the stream
       *            numbers as used in the traffic control program
       * @param sensors the traffic sensors. The ids of the traffic sensors must end with three digits; the first two of those
       *            must match the stream and sensor numbers used in the traffic control program
       * @param simulator the simulation engine
       * @throws TrafficControlException on failure to initialize the connection to the external CCOL program
       * @throws SimRuntimeException on failure to schedule the first evaluation event
       */
      public Ccol(final String id, final String controlProgram, final Set<TrafficLight> trafficLights,
              final Set<TrafficLightDetector> sensors, final OtsSimulator simulator)
              throws TrafficControlException, SimRuntimeException
      {
          this.id = id;
          this.simulator = simulator;
          try
          {
              // Set up a listening socket
              this.serverSocket = new ServerSocket(port);
              Runnable acceptTask = new Runnable()
              {
                  @Override
                  public void run()
                  {
                      try
                      {
                          setClientSocket(Ccol.this.serverSocket.accept());
                      }
                      catch (IOException exception)
                     {
                         exception.printStackTrace();
                     }
                 }
             };
             this.acceptThread = new Thread(acceptTask);
             this.acceptThread.start();
             // Start up the external CCOL program
             Runtime.getRuntime().exec(controlProgram + " localhost:" + this.serverSocket.getLocalPort());
         }
         catch (IOException e)
         {
             e.printStackTrace();
         }
         this.simulator.scheduleEventRel(Duration.ZERO, () -> Try.execute(() -> step(), "Exception during Ccol step."));
         this.simulator.addListener(this, Replication.END_REPLICATION_EVENT);
     }
 
     /**
      * Set the client socket (called from the accept thread).
      * @param socket the socket returned by accept
      */
     void setClientSocket(final Socket socket)
     {
         if (null != this.clientSocket)
         {
             Logger.ots().error("clientSocket already set");
             return;
         }
         this.clientSocket = socket;
         try
         {
             this.ccolReader = new BufferedReader(new InputStreamReader(this.clientSocket.getInputStream()));
             this.ccolWriter = new PrintWriter(this.clientSocket.getOutputStream());
         }
         catch (IOException exception)
         {
             exception.printStackTrace();
         }
         // Close the server socket to release resources and ensure that we cannot accept further connections
         try
         {
             this.serverSocket.close();
         }
         catch (IOException exception)
         {
             exception.printStackTrace();
         }
     }
 
     /**
      * Retrieve the client socket for shutdown.
      * @return the socket for communication with the CCOL client
      */
     Socket getClientSocket()
     {
         return this.clientSocket;
     }
 
     /**
      * Let the CCOL engine determine the new state of the traffic lights and update the traffic lights accordingly.
      * @throws TrafficControlException when the CCOL engine reports an error or communication with the CCOL engine fails
      * @throws SimRuntimeException when scheduling the next evaluation fails
      */
     @SuppressWarnings("unused")
     private void step() throws TrafficControlException, SimRuntimeException
     {
         // TODO time should be formatted as date, hour, etc.
         String message = String.format("STEP %s", this.simulator.getSimulatorTime());
         this.ccolWriter.print(message);
         try
         {
             String result = this.ccolReader.readLine();
             // TODO parse the result and update the state of traffic lights accordingly
             // Protocol must ensure that we know it when all updates have been received.
         }
         catch (IOException exception)
         {
             exception.printStackTrace();
         }
         // Schedule the next step.
         this.simulator.scheduleEventRel(EVALUATION_INTERVAL, () -> Try.execute(() -> step(), "Exception during Ccol step."));
     }
 
     @Override
     public void notify(final Event event)
     {
         EventType eventType = event.getType();
         if (eventType.equals(Replication.END_REPLICATION_EVENT))
         {
             if (null != this.serverSocket)
             {
                 try
                 {
                     this.serverSocket.close();
                 }
                 catch (IOException exception)
                 {
                     exception.printStackTrace();
                 }
                 this.serverSocket = null;
             }
             if (null != this.clientSocket)
             {
                 try
                 {
                     this.clientSocket.close();
                 }
                 catch (IOException exception)
                 {
                     exception.printStackTrace();
                 }
                 this.clientSocket = null;
             }
         }
         // Tracing etc. not implemented yet.
     }
 
     @Override
     public String getId()
     {
         return this.id;
     }
 
     @Override
     public String getFullId()
     {
         return this.id;
     }
 
     @Override
     public void updateDetector(final String detectorId, final boolean detectingGTU)
     {
         // FIXME: format of messages is TBD
         String message = String.format("DET %s %s", detectorId, detectingGTU);
         this.ccolWriter.print(message);
     }
 
     @Override
     public Optional<Container> getDisplayContainer()
     {
         return Optional.empty(); // For now, CCOL does not have a display panel
     }
 
 }