package org.opentrafficsim.sim0mq.publisher;
   
   import java.util.Set;
   
   import org.djutils.exceptions.Throw;
   import org.djutils.metadata.MetaData;
   import org.djutils.metadata.ObjectDescriptor;
   import org.djutils.serialization.SerializationException;
   import org.opentrafficsim.core.gtu.Gtu;
  import org.opentrafficsim.core.network.Link;
  import org.opentrafficsim.core.network.Network;
  import org.sim0mq.Sim0MQException;
  
  /**
   * Transceiver for the ids of the GTUs on a link.
   * <p>
   * Copyright (c) 2020-2024 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 LinkGtuIdTransceiver extends AbstractTransceiver
  {
      /** The network. */
      private final Network network;
  
      /**
       * Construct a GtuIdTransceiver.
       * @param network the OTS network
       */
      public LinkGtuIdTransceiver(final Network network)
      {
          super("Link GTU id transceiver",
                  new MetaData("Link id", "Link id",
                          new ObjectDescriptor[] {new ObjectDescriptor("Link id", "Link id", String.class)}),
                  new MetaData("String array with all Link ids", "String array with all Link ids",
                          new ObjectDescriptor[] {new ObjectDescriptor("String array",
                                  "String array filled with all currently valid Link ids", String[].class)}));
          Throw.whenNull(network, "Network may not be null");
          this.network = network;
      }
  
      @Override
      public final Object[] get(final Object[] address, final ReturnWrapper returnWrapper)
              throws Sim0MQException, SerializationException
      {
          String bad = verifyMetaData(getAddressFields(), address);
          if (bad != null)
          {
              returnWrapper.nack("Bad address; need id of a link");
              return null;
          }
          Link link = this.network.getLink((String) address[0]);
          if (null == link)
          {
              returnWrapper.nack("Network does not contain a link with id " + address[0]);
              return null;
          }
          Set<Gtu> gtus = link.getGTUs();
          Object[] result = new Object[gtus.size()];
          int nextIndex = 0;
          for (Gtu gtu : gtus)
          {
              result[nextIndex++] = gtu.getId();
          }
          return result;
      }
  
      @Override
      public String toString()
      {
          return "LinkGtuIdTransceiver [network=" + this.network + ", super=" + super.toString() + "]";
      }
  
  }