package org.opentrafficsim.road.gtu.perception.mental.channel;
   
   import java.util.Iterator;
   import java.util.NoSuchElementException;
   import java.util.Set;
   import java.util.function.Function;
   import java.util.function.Predicate;
   
   import org.djunits.value.vdouble.scalar.Length;
  import org.opentrafficsim.base.DistancedObject;
  import org.opentrafficsim.base.OtsRuntimeException;
  import org.opentrafficsim.base.parameters.ParameterTypeDouble;
  import org.opentrafficsim.base.parameters.ParameterTypeLength;
  import org.opentrafficsim.base.parameters.constraint.NumericConstraint;
  import org.opentrafficsim.road.gtu.LaneBasedGtu;
  import org.opentrafficsim.road.gtu.perception.LanePerception;
  import org.opentrafficsim.road.gtu.perception.RelativeLane;
  import org.opentrafficsim.road.gtu.perception.categories.neighbors.NeighborsPerception;
  import org.opentrafficsim.road.gtu.perception.mental.AbstractTask;
  
  /**
   * Task demand for signal (front: brake lights, left: right indicator, right: left indicator). This applies to the first leader
   * with signal, and is defined as {@code TD_signal * (1 - s/x0)}, where {@code TD_signal} is a constant, {@code s} is the
   * distance to the leader with signal and {@code x0} is the look-ahead distance.
   * <p>
   * Copyright (c) 2024-2026 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 Wouter Schakel
   */
  public class ChannelTaskSignal extends AbstractTask implements ChannelTask
  {
  
      /** Signal task demand. */
      public static final ParameterTypeDouble TDSIGNAL =
              new ParameterTypeDouble("td_signal", "Signal task demand", 0.2, NumericConstraint.POSITIVEZERO);
  
      /** Distance discount range. */
      public static final ParameterTypeLength X0_D = ChannelMental.X0_D;
  
      /** Standard set of left, right and front signal task. */
      private static final Set<ChannelTask> SET =
              Set.of(new ChannelTaskSignal(LEFT), new ChannelTaskSignal(RIGHT), new ChannelTaskSignal(FRONT));
  
      /** Standard supplier that supplies instances for left, right and front signal task. */
      public static final Function<LanePerception, Set<ChannelTask>> SUPPLIER = (p) -> SET;
  
      /** Channel. */
      private final Object channel;
  
      /** Predicate to test the signal on a GTU. */
      private final Predicate<LaneBasedGtu> predicate;
  
      /** Relative lane that applies. */
      private final RelativeLane lane;
  
      /**
       * Constructor.
       * @param channel channel.
       */
      public ChannelTaskSignal(final Object channel)
      {
          super("signal");
          this.channel = channel;
          if (channel.equals(FRONT))
          {
              this.predicate = (t) -> t.isBrakingLightsOn();
              this.lane = RelativeLane.CURRENT;
          }
          else if (channel.equals(LEFT))
          {
              this.predicate = (t) -> t.getTurnIndicatorStatus().isRightOrBoth();
              this.lane = RelativeLane.LEFT;
          }
          else if (channel.equals(RIGHT))
          {
              this.predicate = (t) -> t.getTurnIndicatorStatus().isLeftOrBoth();
              this.lane = RelativeLane.RIGHT;
          }
          else
          {
              throw new IllegalArgumentException("Channel " + channel + " is not supported by signal channel.");
          }
      }
  
      @Override
      public String getId()
      {
          return String.format("signal (%s)", this.channel);
      }
  
      @Override
      public Object getChannel()
      {
          return this.channel;
      }
  
      @Override
      public double calculateTaskDemand(final LanePerception perception)
     {
         NeighborsPerception neighbors = perception.getPerceptionCategoryOptional(NeighborsPerception.class)
                 .orElseThrow(() -> new NoSuchElementException("NeighborsPerception not present."));
         Iterator<DistancedObject<LaneBasedGtu>> leaders = neighbors.getLeaders(this.lane).underlyingWithDistance();
         while (leaders.hasNext())
         {
             DistancedObject<LaneBasedGtu> leader = leaders.next();
             if (this.predicate.test(leader.object()))
             {
                 Length x0 = perception.getGtu().getParameters().getOptionalParameter(X0_D)
                         .orElseThrow(() -> new OtsRuntimeException("Parameter x0_d not present."));
                 double tdSignal = perception.getGtu().getParameters().getOptionalParameter(TDSIGNAL)
                         .orElseThrow(() -> new OtsRuntimeException("Parameter td_signal not available."));
                 return tdSignal * (1.0 - leader.distance().si / x0.si);
             }
         }
         return 0.0;
     }
 
 }