package org.opentrafficsim.road.gtu.lane.perception;
   
   import java.util.LinkedHashSet;
   import java.util.List;
   import java.util.Set;
   
   import org.djunits.value.vdouble.scalar.Length;
   import org.opentrafficsim.core.gtu.RelativePosition;
   import org.opentrafficsim.core.network.route.Route;
  import org.opentrafficsim.road.gtu.lane.LaneBasedGtu;
  import org.opentrafficsim.road.gtu.lane.perception.headway.Headway;
  import org.opentrafficsim.road.gtu.lane.perception.structure.LaneRecordInterface;
  import org.opentrafficsim.road.network.lane.object.LaneBasedObject;
  
  /**
   * Iterable that searches downstream or upstream for a certain type of lane based object.
   * <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://tudelft.nl/staff/p.knoppers-1">Peter Knoppers</a>
   * @author <a href="https://github.com/wjschakel">Wouter Schakel</a>
   * @param <H> headway type
   * @param <L> lane based object type
   */
  public abstract class LaneBasedObjectIterable<H extends Headway, L extends LaneBasedObject>
          extends AbstractPerceptionIterable<H, L, Boolean>
  {
  
      /** Margin for start and end of lane. */
      private static final Length MARGIN = Length.instantiateSI(1e-9);
  
      /** Class of lane based objects to return. */
      private final Class<L> clazz;
  
      /**
       * Constructor.
       * @param perceivingGtu LaneBasedGtu; perceiving GTU
       * @param clazz Class&lt;L&gt;; class of lane based objects to return
       * @param root LaneRecord&lt;?&gt;; root record
       * @param initialPosition Length; initial position
       * @param downstream boolean; downstream
       * @param maxDistance Length; max distance to search
       * @param relativePosition RelativePosition; relative position
       * @param route Route; route of the GTU, may be {@code null}
       */
      public LaneBasedObjectIterable(final LaneBasedGtu perceivingGtu, final Class<L> clazz, final LaneRecordInterface<?> root,
              final Length initialPosition, final boolean downstream, final Length maxDistance,
              final RelativePosition relativePosition, final Route route)
      {
          super(perceivingGtu, root, initialPosition, downstream, maxDistance, relativePosition, route);
          this.clazz = clazz;
      }
  
      /** {@inheritDoc} */
      @SuppressWarnings("unchecked")
      @Override
      protected Entry getNext(final LaneRecordInterface<?> record, final Length position, final Boolean counter)
      {
          List<LaneBasedObject> list;
          if (isDownstream())
          {
              if (!record.isDownstreamBranch())
              {
                  return null;
              }
              Length pos = position.eq0() && counter == null ? MARGIN.neg() : position;
              list = record.getLane().getObjectAhead(pos);
          }
          else
          {
              Length pos = position.eq(record.getLane().getLength()) && counter == null
                      ? record.getLane().getLength().plus(MARGIN) : position;
              list = record.getLane().getObjectBehind(pos);
          }
          while (list != null)
          {
              Set<L> set = new LinkedHashSet<>();
              Length pos = list.get(0).getLongitudinalPosition();
              for (LaneBasedObject object : list)
              {
                  if (this.clazz.isAssignableFrom(object.getClass()))
                  {
                      // is assignable, so safe cast
                      set.add((L) object);
                  }
              }
              if (!set.isEmpty())
              {
                  if (set.size() == 1)
                  {
                      return new Entry(set.iterator().next(), true, pos);
                  }
                  return new Entry(set, true, pos);
              }
              if (isDownstream())
              {
                  list = record.getLane().getObjectAhead(pos);
             }
             else
             {
                 list = record.getLane().getObjectBehind(pos);
             }
         }
         return null;
     }
 
     /** {@inheritDoc} */
     @Override
     protected final Length getDistance(final L object, final LaneRecordInterface<?> record, final Length position)
     {
         return isDownstream() ? record.getDistanceToPosition(position).minus(getDx())
                 : record.getDistanceToPosition(position).neg().plus(getDx());
     }
 
     /** {@inheritDoc} */
     @Override
     public String toString()
     {
         return "LaneBasedObjectIterable [class=" + this.clazz + ", downstream=" + isDownstream() + "]";
     }
 
 }