package org.opentrafficsim.road.gtu.lane.perception;
   
   import java.util.HashMap;
   import java.util.HashSet;
   import java.util.Map;
   import java.util.Set;
   import java.util.TreeMap;
   
   import org.djunits.unit.LengthUnit;
  import org.djunits.value.vdouble.scalar.Length;
  import org.djunits.value.vdouble.scalar.Time;
  import org.opentrafficsim.core.gtu.GTUDirectionality;
  import org.opentrafficsim.core.gtu.GTUException;
  import org.opentrafficsim.core.gtu.GTUType;
  import org.opentrafficsim.core.gtu.behavioralcharacteristics.ParameterException;
  import org.opentrafficsim.core.gtu.behavioralcharacteristics.ParameterTypes;
  import org.opentrafficsim.core.gtu.perception.AbstractPerception;
  import org.opentrafficsim.core.network.LateralDirectionality;
  import org.opentrafficsim.core.network.Link;
  import org.opentrafficsim.core.network.NetworkException;
  import org.opentrafficsim.core.network.Node;
  import org.opentrafficsim.core.network.route.Route;
  import org.opentrafficsim.road.gtu.lane.LaneBasedGTU;
  import org.opentrafficsim.road.gtu.strategical.route.LaneBasedStrategicalRoutePlanner;
  import org.opentrafficsim.road.network.lane.DirectedLanePosition;
  import org.opentrafficsim.road.network.lane.Lane;
  
  import nl.tudelft.simulation.language.Throw;
  
  /**
   * The perception module of a GTU based on lanes. It is responsible for perceiving (sensing) the environment of the GTU, which
   * includes the locations of other GTUs. Perception is done at a certain time, and the perceived information might have a
   * limited validity. In that sense, Perception is stateful. Information can be requested as often as needed, but will only be
   * recalculated when asked explicitly. This abstract class provides the building blocks for lane-based perception. <br>
   * Perception for lane-based GTUs involves information about GTUs in front of the owner GTU on the same lane (the 'leader' GTU),
   * parallel vehicles (important if we want to change lanes), distance to other vehicles on parallel lanes, as well in front as
   * to the back (important if we want to change lanes), and information about obstacles, traffic lights, speed signs, and ending
   * lanes.
   * <p>
   * Copyright (c) 2013-2016 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved. <br>
   * BSD-style license. See <a href="http://opentrafficsim.org/docs/license.html">OpenTrafficSim License</a>.
   * </p>
   * $LastChangedDate: 2015-07-24 02:58:59 +0200 (Fri, 24 Jul 2015) $, @version $Revision: 1147 $, by $Author: averbraeck $,
   * initial version Nov 15, 2015 <br>
   * @author <a href="http://www.tbm.tudelft.nl/averbraeck">Alexander Verbraeck</a>
   * @author <a href="http://www.tudelft.nl/pknoppers">Peter Knoppers</a>
   * @author <a href="http://www.transport.citg.tudelft.nl">Wouter Schakel</a>
   */
  public abstract class AbstractLanePerception extends AbstractPerception implements LanePerception
  {
  
      /** */
      private static final long serialVersionUID = 20151128L;
  
      /** Lane structure to perform the perception with. */
      private LaneStructure laneStructure = null;
  
      /** Most recent update time of lane structure. */
      private Time updateTime = null;
  
      /**
       * Create a new LanePerception module. Because the constructor is often called inside the constructor of a GTU, this
       * constructor does not ask for the pointer to the GTU, as it is often impossible to provide at the time of construction.
       * Use the setter of the GTU instead.
       * @param gtu GTU
       */
      public AbstractLanePerception(final LaneBasedGTU gtu)
      {
          super(gtu);
      }
  
      /** {@inheritDoc} */
      @Override
      public final LaneBasedGTU getGtu()
      {
          return (LaneBasedGTU) super.getGtu();
      }
  
      /** {@inheritDoc} */
      @Override
      public final LaneStructure getLaneStructure() throws ParameterException
      {
          if (this.laneStructure == null || this.updateTime.lt(getGtu().getSimulator().getSimulatorTime().getTime()))
          {
              // downstream structure length
              Length down = getGtu().getBehavioralCharacteristics().getParameter(ParameterTypes.PERCEPTION);
              // upstream structure length
              Length up = getGtu().getBehavioralCharacteristics().getParameter(ParameterTypes.LOOKBACK);
              // structure length downstream of split on link not on route
              Length downSplit = getGtu().getBehavioralCharacteristics().getParameter(ParameterTypes.LOOKAHEAD);
              // structure length upstream of merge on link not on route
              Length upMerge = Length.max(up, downSplit);
              // negative values for upstream
              up = up.neg();
              upMerge = upMerge.neg();
              // Create Lane Structure
              DirectedLanePosition dlp;
              try
              {
                 dlp = getGtu().getReferencePosition();
             }
             catch (GTUException exception)
             {
                 // Should not happen, we get the lane from the GTU
                 throw new RuntimeException("Could not get fraction on root lane.", exception);
             }
             Lane rootLane = dlp.getLane();
             GTUDirectionality direction = dlp.getGtuDirection();
             double fraction = dlp.getPosition().si / rootLane.getLength().si;
             LaneStructureRecord rootLSR =
                     new LaneStructureRecord(rootLane, direction, rootLane.getLength().multiplyBy(-fraction));
             this.laneStructure = new LaneStructure(rootLSR, downSplit);
             this.laneStructure.addLaneStructureRecord(rootLSR, RelativeLane.CURRENT);
             this.relativeLaneMap.clear();
             this.relativeLaneMap.put(rootLSR, RelativeLane.CURRENT);
             startBuild(rootLSR, fraction, getGtu().getGTUType(), down, downSplit, up, upMerge);
 
             // TODO possibly optimize by using a 'singleton' lane structure source, per GTUType
             // TODO possibly build and destroy at edges only
             this.updateTime = getGtu().getSimulator().getSimulatorTime().getTime();
         }
         return this.laneStructure;
     }
 
     /**
      * Local map where relative lanes are store per record, such that other records can be linked to the correct relative lane.
      */
     private final Map<LaneStructureRecord, RelativeLane> relativeLaneMap = new HashMap<>();
 
     /** Set of lanes that can be ignored as they are beyond build bounds. */
     private final Set<Lane> ignoreSet = new HashSet<>();
 
     /**
      * Starts the build from the current lane and creates an initial lateral set with correct start distances based on the
      * fraction.
      * 
      * <pre>
      *  ---------
      * |  /|\    |
      *  ---|-----
      * |  /|\    |
      *  ---|-----
      * |   o     | rootLSR
      *  ---|-----
      * |  \|/    |
      *  ---------
      *  
      * (---) fraction
      * </pre>
      * 
      * @param rootLSR record where the GTU is currently
      * @param fraction fractional position where the gtu is
      * @param gtuType GTU type
      * @param down maximum downstream distance to build structure
      * @param downSplit maximum downstream distance past split not following the route to build structure
      * @param up maximum upstream distance to build structure
      * @param upMerge maximum upstream distance upstream of downstream merges to build structure
      */
     private void startBuild(final LaneStructureRecord rootLSR, final double fraction, final GTUType gtuType, final Length down,
             final Length downSplit, final Length up, final Length upMerge)
     {
         // Build initial lateral set
         Set<LaneStructureRecord> recordSet = new HashSet<>();
         Set<Lane> laneSet = new HashSet<>();
         recordSet.add(rootLSR);
         laneSet.add(rootLSR.getLane());
         for (LateralDirectionality latDirection : new LateralDirectionality[] { LateralDirectionality.LEFT,
                 LateralDirectionality.RIGHT })
         {
             LaneStructureRecord current = rootLSR;
             RelativeLane relativeLane = RelativeLane.CURRENT;
             Set<Lane> adjacentLanes = current.getLane().accessibleAdjacentLanes(latDirection, gtuType);
             while (!adjacentLanes.isEmpty())
             {
                 Throw.when(adjacentLanes.size() > 1, RuntimeException.class,
                         "Multiple adjacent lanes encountered during construction of lane map.");
                 relativeLane = latDirection.isLeft() ? relativeLane.getLeft() : relativeLane.getRight();
                 Lane lane = adjacentLanes.iterator().next();
                 LaneStructureRecord adjacentRecord =
                         constructRecord(lane, current.getDirection(), lane.getLength().multiplyBy(-fraction), relativeLane);
                 if (latDirection.isLeft())
                 {
                     if (lane.accessibleAdjacentLanes(LateralDirectionality.RIGHT, gtuType).contains(current.getLane()))
                     {
                         adjacentRecord.setRight(current);
                     }
                     current.setLeft(adjacentRecord);
                 }
                 else
                 {
                     if (lane.accessibleAdjacentLanes(LateralDirectionality.LEFT, gtuType).contains(current.getLane()))
                     {
                         adjacentRecord.setLeft(current);
                     }
                     current.setRight(adjacentRecord);
                 }
                 recordSet.add(adjacentRecord);
                 laneSet.add(lane);
                 current = adjacentRecord;
                 adjacentLanes = current.getLane().accessibleAdjacentLanes(latDirection, gtuType);
             }
         }
         try
         {
             this.ignoreSet.clear();
             buildDownstreamRecursive(recordSet, gtuType, down, up, downSplit, upMerge);
             this.ignoreSet.clear();
             buildUpstreamRecursive(recordSet, gtuType, down, up, upMerge);
         }
         catch (GTUException | NetworkException exception)
         {
             throw new RuntimeException("Exception while building lane map.", exception);
         }
     }
 
     /**
      * Extends the lane structure with the downstream lanes of the current set. Per downstream link, a new set results, which
      * are extended laterally before performing the next downstream step. If the lateral extension finds new lanes, the
      * structure is extended upstream from those lanes over a limited distance.
      * 
      * <pre>
      *  --------- ---------
      * |       --|-)     --|-?A       ?: possible next steps
      *  --------- ---------
      * |       --|-)     --|-?A
      *  --------- =============       A, B: two separate downstream links
      * |       --|-)         --|-?B
      *  ----===== ------|------
      *     | C?(-|--   \|/   --|-?B   C: extend upstream if merge
      *      ----- -------------
      * </pre>
      * 
      * @param recordSet current lateral set of records
      * @param gtuType GTU type
      * @param down maximum downstream distance to build structure
      * @param up maximum upstream distance to build structure
      * @param downSplit maximum downstream distance past split not following the route to build structure
      * @param upMerge maximum upstream distance upstream of downstream merges to build structure
      * @throws GTUException if an inconsistency in the lane map is encountered
      * @throws NetworkException exception during movement over the network
      */
     private void buildDownstreamRecursive(final Set<LaneStructureRecord> recordSet, final GTUType gtuType, final Length down,
             final Length up, final Length downSplit, final Length upMerge) throws GTUException, NetworkException
     {
         // Loop lanes and put downstream lanes in sets per downstream link
         Map<Link, Set<Lane>> laneSets = new HashMap<>();
         Map<Link, TreeMap<RelativeLane, LaneStructureRecord>> recordSets = new HashMap<>();
         Map<Link, Length> maxStart = new HashMap<>();
         for (LaneStructureRecord laneRecord : recordSet)
         {
             if (!laneRecord.isCutOffEnd())
             {
                 for (Lane nextLane : laneRecord.getLane().nextLanes(gtuType).keySet())
                 {
                     Link nextLink = nextLane.getParentLink();
                     if (!laneSets.containsKey(nextLink))
                     {
                         laneSets.put(nextLink, new HashSet<>());
                         recordSets.put(nextLink, new TreeMap<>());
                         maxStart.put(nextLink, new Length(Double.MIN_VALUE, LengthUnit.SI));
                     }
                     laneSets.get(nextLink).add(nextLane);
                     RelativeLane relativeLane = this.relativeLaneMap.get(laneRecord);
                     Length start = laneRecord.getStartDistance().plus(laneRecord.getLane().getLength());
                     maxStart.put(nextLink, Length.max(maxStart.get(nextLink), start));
                     LaneStructureRecord nextRecord = constructRecord(nextLane,
                             laneRecord.getLane().nextLanes(gtuType).get(nextLane), start, relativeLane);
                     if (start.plus(nextLane.getLength()).ge(down))
                     {
                         nextRecord.setCutOffEnd(down.minus(start));
                     }
                     recordSets.get(nextLink).put(relativeLane, nextRecord);
                     laneRecord.addNext(nextRecord);
                     nextRecord.addPrev(laneRecord);
                 }
             }
             else
             {
                 for (Lane nextLane : laneRecord.getLane().nextLanes(gtuType).keySet())
                 {
                     this.ignoreSet.add(nextLane); // beyond 'down', do not add in lateral step
                 }
             }
         }
         // loop links to connect the lanes laterally and continue the build
         Link currentLink = recordSet.iterator().next().getLane().getParentLink();
         GTUDirectionality direction = recordSet.iterator().next().getDirection();
         for (Link link : laneSets.keySet())
         {
             connectLaterally(recordSets.get(link), gtuType);
             Set<LaneStructureRecord> set = new HashSet<>(recordSets.get(link).values()); // collection to set
             set = extendLateral(set, gtuType, down, up, upMerge, true);
             // reduce remaining downstream length if not on route, to at most 'downSplit'
             Node nextNode = direction.isPlus() ? currentLink.getEndNode() : currentLink.getStartNode();
             Length downLimit = down;
             Route route = getGtu().getStrategicalPlanner().getRoute();
             if (route != null && (!route.contains(nextNode) // if no route, do not limit
                     || !((LaneBasedStrategicalRoutePlanner) getGtu().getStrategicalPlanner())
                             .nextLinkDirection(nextNode, currentLink, gtuType).equals(link)))
             {
                 // as each lane has a separate start distance, use the maximum value from maxStart
                 downLimit = Length.min(downLimit, maxStart.get(link).plus(downSplit));
             }
             buildDownstreamRecursive(set, gtuType, downLimit, up, downSplit, upMerge);
         }
     }
 
     /**
      * Extends the lane structure with (multiple) left and right lanes of the current set. The extended lateral set is returned
      * for the downstream or upstream build to continue.
      * 
      * <pre>
      *  ---- ---------
      * | ?(-|-- /|\   |
      *  ---- ----|----   ?: extend upstream of merge if doMerge = true
      * | ?(-|-- /|\   |
      *  ---- ----|----  
      *      |         | } 
      *       ---------   } recordSet
      *      |         | }
      *       ----|---- 
      *      |   \|/   |
      *       ---------
      * </pre>
      * 
      * @param recordSet current lateral set of records
      * @param gtuType GTU type
      * @param down maximum downstream distance to build structure
      * @param up maximum upstream distance to build structure
      * @param upMerge maximum upstream distance upstream of downstream merges to build structure
      * @param downstreamBuild whether building downstream
      * @return laterally extended set
      * @throws GTUException if an inconsistency in the lane map is encountered
      * @throws NetworkException exception during movement over the network
      */
     private Set<LaneStructureRecord> extendLateral(final Set<LaneStructureRecord> recordSet, final GTUType gtuType,
             final Length down, final Length up, final Length upMerge, final boolean downstreamBuild)
             throws GTUException, NetworkException
     {
         Set<Lane> laneSet = new HashSet<>();
         for (LaneStructureRecord laneStructureRecord : recordSet)
         {
             laneSet.add(laneStructureRecord.getLane());
         }
         for (LateralDirectionality latDirection : new LateralDirectionality[] { LateralDirectionality.LEFT,
                 LateralDirectionality.RIGHT })
         {
             Set<LaneStructureRecord> expandSet = new HashSet<>();
             Length startDistance = null;
             Length endDistance = null;
             for (LaneStructureRecord laneRecord : recordSet)
             {
                 LaneStructureRecord current = laneRecord;
                 startDistance = current.getStartDistance();
                 endDistance = current.getStartDistance().plus(current.getLane().getLength());
                 RelativeLane relativeLane = this.relativeLaneMap.get(laneRecord);
                 Set<Lane> adjacentLanes = current.getLane().accessibleAdjacentLanes(latDirection, gtuType);
                 while (!adjacentLanes.isEmpty())
                 {
                     Throw.when(adjacentLanes.size() > 1, RuntimeException.class,
                             "Multiple adjacent lanes encountered during construction of lane map.");
                     Lane laneAdjacent = adjacentLanes.iterator().next();
                     Length adjacentStart = downstreamBuild ? startDistance : endDistance.minus(laneAdjacent.getLength());
                     // skip is lane already in set, no effective length in structure, or in ignore list
                     if (!laneSet.contains(laneAdjacent) && !adjacentStart.plus(laneAdjacent.getLength()).le(up)
                             && !adjacentStart.ge(down) && !this.ignoreSet.contains(laneAdjacent))
                     {
                         laneSet.add(laneAdjacent);
                         relativeLane = latDirection.isLeft() ? relativeLane.getLeft() : relativeLane.getRight();
                         LaneStructureRecord recordAdjacent =
                                 constructRecord(laneAdjacent, laneRecord.getDirection(), adjacentStart, relativeLane);
                         expandSet.add(recordAdjacent);
                         if (latDirection.isLeft())
                         {
                             if (laneAdjacent.accessibleAdjacentLanes(LateralDirectionality.RIGHT, gtuType)
                                     .contains(current.getLane()))
                             {
                                 recordAdjacent.setRight(current);
                             }
                             current.setLeft(recordAdjacent);
                         }
                         else
                         {
                             if (laneAdjacent.accessibleAdjacentLanes(LateralDirectionality.LEFT, gtuType)
                                     .contains(current.getLane()))
                             {
                                 recordAdjacent.setLeft(current);
                             }
                             current.setRight(recordAdjacent);
                         }
                         if (adjacentStart.plus(laneAdjacent.getLength()).ge(down))
                         {
                             recordAdjacent.setCutOffEnd(down.minus(adjacentStart));
                         }
                         if (adjacentStart.le(up))
                         {
                             recordAdjacent.setCutOffStart(up.minus(adjacentStart));
                         }
                         current = recordAdjacent;
                         adjacentLanes = current.getLane().accessibleAdjacentLanes(latDirection, gtuType);
                     }
                     else
                     {
                         break;
                     }
                 }
             }
             if (downstreamBuild & !expandSet.isEmpty())
             {
                 // limit search range and search upstream of merge
                 buildUpstreamRecursive(expandSet, gtuType, down, startDistance.plus(upMerge), upMerge);
             }
             recordSet.addAll(expandSet);
         }
         return recordSet;
     }
 
     /**
      * Extends the lane structure with the upstream lanes of the current set. Per upstream link, a new set results, which are
      * expanded laterally before performing the next upstream step.
      * @param recordSet current lateral set of records
      * @param gtuType GTU type
      * @param down maximum downstream distance to build structure
      * @param up maximum upstream distance to build structure
      * @param upMerge maximum upstream distance upstream of downstream merges to build structure
      * @throws GTUException if an inconsistency in the lane map is encountered
      * @throws NetworkException exception during movement over the network
      */
     private void buildUpstreamRecursive(final Set<LaneStructureRecord> recordSet, final GTUType gtuType, final Length down,
             final Length up, final Length upMerge) throws GTUException, NetworkException
     {
         // Loop lanes and put upstream lanes in sets per upstream link
         Map<Link, Set<Lane>> laneSets = new HashMap<>();
         Map<Link, TreeMap<RelativeLane, LaneStructureRecord>> recordSets = new HashMap<>();
         Map<Link, Length> minStart = new HashMap<>();
         for (LaneStructureRecord laneRecord : recordSet)
         {
             if (!laneRecord.isCutOffStart())
             {
                 for (Lane prevLane : laneRecord.getLane().prevLanes(gtuType).keySet())
                 {
                     Link prevLink = prevLane.getParentLink();
                     if (!laneSets.containsKey(prevLink))
                     {
                         laneSets.put(prevLink, new HashSet<>());
                         recordSets.put(prevLink, new TreeMap<>());
                         minStart.put(prevLink, new Length(Double.MAX_VALUE, LengthUnit.SI));
                     }
                     laneSets.get(prevLink).add(prevLane);
                     RelativeLane relativeLane = this.relativeLaneMap.get(laneRecord);
                     Length start = laneRecord.getStartDistance().minus(prevLane.getLength());
                     minStart.put(prevLink, Length.min(minStart.get(prevLink), start));
                     LaneStructureRecord prevRecord = constructRecord(prevLane,
                             laneRecord.getLane().prevLanes(gtuType).get(prevLane), start, relativeLane);
                     if (start.le(up))
                     {
                         prevRecord.setCutOffStart(up.minus(start));
                     }
                     recordSets.get(prevLink).put(relativeLane, prevRecord);
                     laneRecord.addPrev(prevRecord);
                     prevRecord.addNext(laneRecord);
                 }
             }
             else
             {
                 for (Lane prevLane : laneRecord.getLane().prevLanes(gtuType).keySet())
                 {
                     this.ignoreSet.add(prevLane); // beyond 'up', do not add in lateral step
                 }
             }
         }
         // loop links to connect the lanes laterally and continue the build
         for (Link link : laneSets.keySet())
         {
             connectLaterally(recordSets.get(link), gtuType);
             Set<LaneStructureRecord> set = new HashSet<>(recordSets.get(link).values()); // collection to set
             set = extendLateral(set, gtuType, down, up, upMerge, false);
             buildUpstreamRecursive(set, gtuType, down, up, upMerge);
         }
     }
 
     /**
      * Creates a lane structure record and adds it to relevant maps.
      * @param lane lane
      * @param direction direction
      * @param startDistance distance at start of record
      * @param relativeLane relative lane
      * @return created lane structure record
      */
     private LaneStructureRecord constructRecord(final Lane lane, final GTUDirectionality direction, final Length startDistance,
             final RelativeLane relativeLane)
     {
         LaneStructureRecord record = new LaneStructureRecord(lane, direction, startDistance);
         this.laneStructure.addLaneStructureRecord(record, relativeLane);
         this.relativeLaneMap.put(record, relativeLane);
         return record;
     }
 
     /**
      * Connects the lane structure records laterally if appropriate.
      * @param map Map<RelativeLane, LaneStructureRecord>; map
      * @param gtuType gtu type
      */
     private void connectLaterally(final Map<RelativeLane, LaneStructureRecord> map, final GTUType gtuType)
     {
         for (RelativeLane relativeLane : map.keySet())
         {
             if (map.containsKey(relativeLane.getRight()))
             {
                 Lane thisLane = map.get(relativeLane).getLane();
                 Lane rightLane = map.get(relativeLane.getRight()).getLane();
                 if (thisLane.accessibleAdjacentLanes(LateralDirectionality.RIGHT, gtuType).contains(rightLane))
                 {
                     map.get(relativeLane).setRight(map.get(relativeLane.getRight()));
                 }
                 if (rightLane.accessibleAdjacentLanes(LateralDirectionality.LEFT, gtuType).contains(thisLane))
                 {
                     map.get(relativeLane.getRight()).setLeft(map.get(relativeLane));
                 }
             }
         }
     }
 
 }