package org.opentrafficsim.road.gtu.lane.tactical;
   
   import java.util.ArrayList;
   import java.util.Collection;
   import java.util.HashSet;
   import java.util.List;
   import java.util.Set;
   
   import nl.tudelft.simulation.language.d3.DirectedPoint;
  
  import org.djunits.unit.AccelerationUnit;
  import org.djunits.unit.TimeUnit;
  import org.djunits.value.vdouble.scalar.Acceleration;
  import org.djunits.value.vdouble.scalar.Length;
  import org.djunits.value.vdouble.scalar.Time;
  import org.opentrafficsim.core.gtu.GTU;
  import org.opentrafficsim.core.gtu.GTUDirectionality;
  import org.opentrafficsim.core.gtu.GTUException;
  import org.opentrafficsim.core.gtu.TurnIndicatorStatus;
  import org.opentrafficsim.core.gtu.plan.operational.OperationalPlan;
  import org.opentrafficsim.core.gtu.plan.operational.OperationalPlan.Segment;
  import org.opentrafficsim.core.gtu.plan.operational.OperationalPlanException;
  import org.opentrafficsim.core.network.LateralDirectionality;
  import org.opentrafficsim.core.network.NetworkException;
  import org.opentrafficsim.road.gtu.lane.LaneBasedGTU;
  import org.opentrafficsim.road.gtu.lane.driver.LaneBasedBehavioralCharacteristics;
  import org.opentrafficsim.road.gtu.lane.perception.LanePerception;
  import org.opentrafficsim.road.gtu.lane.tactical.directedlanechange.DirectedAltruistic;
  import org.opentrafficsim.road.gtu.lane.tactical.directedlanechange.DirectedEgoistic;
  import org.opentrafficsim.road.gtu.lane.tactical.directedlanechange.DirectedLaneChangeModel;
  import org.opentrafficsim.road.gtu.lane.tactical.directedlanechange.DirectedLaneMovementStep;
  import org.opentrafficsim.road.gtu.lane.tactical.following.AccelerationStep;
  import org.opentrafficsim.road.gtu.lane.tactical.following.GTUFollowingModelOld;
  import org.opentrafficsim.road.gtu.lane.tactical.following.HeadwayGTU;
  import org.opentrafficsim.road.network.lane.Lane;
  
  /**
   * Lane-based tactical planner that implements car following behavior and rule-based lane change. This tactical planner
   * retrieves the car following model from the strategical planner and will generate an operational plan for the GTU.
   * <p>
   * A lane change occurs when:
   * <ol>
   * <li>The route indicates that the current lane does not lead to the destination; main choices are the time when the GTU
   * switches to the "right" lane, and what should happen when the split gets closer and the lane change has failed. Observations
   * indicate that vehicles if necessary stop in their current lane until they can go to the desired lane. A lane drop is
   * automatically part of this implementation, because the lane with a lane drop will not lead to the GTU's destination.</li>
   * <li>The desired speed of the vehicle is a particular delta-speed higher than its predecessor, the headway to the predecessor
   * in the current lane has exceeded a certain value, it is allowed to change to the target lane, the target lane lies on the
   * GTU's route, and the gap in the target lane is acceptable (including the evaluation of the perceived speed of a following GTU
   * in the target lane).</li>
   * <li>The current lane is not the optimum lane given the traffic rules (for example, to keep right), the headway to the
   * predecessor on the target lane is greater than a certain value, the speed of the predecessor on the target lane is greater
   * than or equal to our speed, the target lane is on the route, it is allowed to switch to the target lane, and the gap at the
   * target lane is acceptable (including the perceived speed of any vehicle in front or behind on the target lane).</li>
   * </ol>
   * <p>
   * This lane-based tactical planner makes decisions based on headway (GTU following model). It can ask the strategic planner for
   * assistance on the route to take when the network splits.
   * <p>
   * Copyright (c) 2013-2015 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 25, 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>
   */
  public class LaneBasedGTUFollowingChange0TacticalPlanner extends AbstractLaneBasedTacticalPlanner
  {
      /** */
      private static final long serialVersionUID = 20160129L;
  
      /** Earliest next lane change time. */
      private Time.Abs earliestNexLaneChangeTime = Time.Abs.ZERO;
  
      /** Lane we changed to at instantaneous lane change. */
      private Lane referenceLane = null;
  
      /** Position on the reference lane. */
      private Length.Rel referencePos = null;
  
      /** When a failure in planning occurs, should we destroy the GTU to avoid halting of the model? */
      private boolean destroyGtuOnFailure = false;
  
      /**
       * Instantiated a tactical planner with just GTU following behavior and no lane changes.
       */
      public LaneBasedGTUFollowingChange0TacticalPlanner()
      {
          super();
      }
  
      /** {@inheritDoc} */
      @Override
      public OperationalPlan generateOperationalPlan(final GTU gtu, final Time.Abs startTime,
          final DirectedPoint locationAtStartTime) throws OperationalPlanException, NetworkException, GTUException
      {
          try
          {
             // ask Perception for the local situation
             LaneBasedGTU laneBasedGTU = (LaneBasedGTU) gtu;
             LanePerception perception = laneBasedGTU.getPerception();
             LaneBasedBehavioralCharacteristics drivingCharacteristics = laneBasedGTU.getBehavioralCharacteristics();
 
             // start with the turn indicator off -- this can change during the method
             laneBasedGTU.setTurnIndicatorStatus(TurnIndicatorStatus.NONE);
 
             // if the GTU's maximum speed is zero (block), generate a stand still plan for one second
             if (laneBasedGTU.getMaximumVelocity().si < OperationalPlan.DRIFTING_SPEED_SI)
             {
                 return new OperationalPlan(gtu, locationAtStartTime, startTime, new Time.Rel(1.0, TimeUnit.SECOND));
             }
 
             // perceive the forward headway, accessible lanes and speed limit.
             perception.updateForwardHeadwayGTU();
             perception.updateAccessibleAdjacentLanesLeft();
             perception.updateAccessibleAdjacentLanesRight();
             perception.updateSpeedLimit();
 
             // find out where we are going
             Length.Rel forwardHeadway = drivingCharacteristics.getForwardHeadwayDistance();
             LanePathInfo lanePathInfo = buildLanePathInfo(laneBasedGTU, forwardHeadway);
             NextSplitInfo nextSplitInfo = determineNextSplit(laneBasedGTU, forwardHeadway);
             Set<Lane> correctLanes = laneBasedGTU.getLanes().keySet();
             correctLanes.retainAll(nextSplitInfo.getCorrectCurrentLanes());
 
             // Step 1: Do we want to change lanes because of the current lane not leading to our destination?
             if (lanePathInfo.getPath().getLength().lt(forwardHeadway))
             {
                 if (correctLanes.isEmpty())
                 {
                     LateralDirectionality direction = determineLeftRight(laneBasedGTU, nextSplitInfo);
                     if (direction != null)
                     {
                         gtu.setTurnIndicatorStatus(direction.isLeft() ? TurnIndicatorStatus.LEFT : TurnIndicatorStatus.RIGHT);
                         if (canChange(laneBasedGTU, perception, lanePathInfo, direction))
                         {
                             DirectedPoint newLocation = changeLane(laneBasedGTU, direction);
                             lanePathInfo =
                                 buildLanePathInfo(laneBasedGTU, this.referenceLane, this.referencePos,
                                     forwardHeadway);
                             return currentLanePlan(laneBasedGTU, startTime, newLocation, lanePathInfo);
                         }
                     }
                 }
             }
 
             // Condition, if we have just changed lane, let's not change immediately again.
             // TODO make direction dependent!
             if (gtu.getSimulator().getSimulatorTime().getTime().lt(this.earliestNexLaneChangeTime))
             {
                 return currentLanePlan(laneBasedGTU, startTime, locationAtStartTime, lanePathInfo);
             }
 
             // Step 2. Do we want to change lanes to the left because of our predecessor on the current lane?
             // does the lane left of us [TODO: driving direction] bring us to our destination as well?
             Set<Lane> leftLanes = perception.getAccessibleAdjacentLanesLeft().get(lanePathInfo.getReferenceLane());
             if (nextSplitInfo.isSplit())
             {
                 leftLanes.retainAll(nextSplitInfo.getCorrectCurrentLanes());
             }
             if (!leftLanes.isEmpty() && laneBasedGTU.getVelocity().si > 4.0) // XXX we are driving...
             {
                 perception.updateBackwardHeadwayGTU();
                 perception.updateParallelGTUsLeft();
                 perception.updateLaneTrafficLeft();
                 if (perception.getParallelGTUsLeft().isEmpty())
                 {
                     Collection<HeadwayGTU> sameLaneTraffic = new HashSet<>();
                     if (perception.getForwardHeadwayGTU() != null
                         && perception.getForwardHeadwayGTU().getGtuId() != null)
                     {
                         sameLaneTraffic.add(perception.getForwardHeadwayGTU());
                     }
                     if (perception.getBackwardHeadwayGTU() != null
                         && perception.getBackwardHeadwayGTU().getGtuId() != null)
                     {
                         sameLaneTraffic.add(perception.getBackwardHeadwayGTU());
                     }
                     DirectedLaneChangeModel dlcm = new DirectedAltruistic();
                     DirectedLaneMovementStep dlms =
                         dlcm.computeLaneChangeAndAcceleration(laneBasedGTU, LateralDirectionality.LEFT,
                             sameLaneTraffic, perception.getNeighboringGTUsLeft(), laneBasedGTU
                                 .getBehavioralCharacteristics().getForwardHeadwayDistance(), perception.getSpeedLimit(),
                             new Acceleration(1.0, AccelerationUnit.SI), new Acceleration(0.5, AccelerationUnit.SI),
                             new Time.Rel(0.5, TimeUnit.SECOND));
                     if (dlms.getLaneChange() != null)
                     {
                         gtu.setTurnIndicatorStatus(TurnIndicatorStatus.LEFT);
                         if (canChange(laneBasedGTU, perception, lanePathInfo, LateralDirectionality.LEFT))
                         {
                             DirectedPoint newLocation = changeLane(laneBasedGTU, LateralDirectionality.LEFT);
                             lanePathInfo =
                                 buildLanePathInfo(laneBasedGTU, this.referenceLane, this.referencePos,
                                     forwardHeadway);
                             return currentLanePlan(laneBasedGTU, startTime, newLocation, lanePathInfo);
                         }
                     }
                 }
             }
 
             // Step 3. Do we want to change lanes to the right because of TODO traffic rules?
             Set<Lane> rightLanes = perception.getAccessibleAdjacentLanesRight().get(lanePathInfo.getReferenceLane());
             if (nextSplitInfo.isSplit())
             {
                 rightLanes.retainAll(nextSplitInfo.getCorrectCurrentLanes());
             }
             if (!rightLanes.isEmpty() && laneBasedGTU.getVelocity().si > 4.0) // XXX we are driving...
             {
                 perception.updateBackwardHeadwayGTU();
                 perception.updateParallelGTUsRight();
                 perception.updateLaneTrafficRight();
                 if (perception.getParallelGTUsRight().isEmpty())
                 {
                     Collection<HeadwayGTU> sameLaneTraffic = new HashSet<>();
                     if (perception.getForwardHeadwayGTU() != null
                         && perception.getForwardHeadwayGTU().getGtuId() != null)
                     {
                         sameLaneTraffic.add(perception.getForwardHeadwayGTU());
                     }
                     if (perception.getBackwardHeadwayGTU() != null
                         && perception.getBackwardHeadwayGTU().getGtuId() != null)
                     {
                         sameLaneTraffic.add(perception.getBackwardHeadwayGTU());
                     }
                     DirectedLaneChangeModel dlcm = new DirectedAltruistic();
                     DirectedLaneMovementStep dlms =
                         dlcm.computeLaneChangeAndAcceleration(laneBasedGTU, LateralDirectionality.RIGHT,
                             sameLaneTraffic, perception.getNeighboringGTUsRight(), laneBasedGTU
                                 .getBehavioralCharacteristics().getForwardHeadwayDistance(), perception.getSpeedLimit(),
                             new Acceleration(1.0, AccelerationUnit.SI), new Acceleration(0.5, AccelerationUnit.SI),
                             new Time.Rel(0.5, TimeUnit.SECOND));
                     if (dlms.getLaneChange() != null)
                     {
                         gtu.setTurnIndicatorStatus(TurnIndicatorStatus.RIGHT);
                         if (canChange(laneBasedGTU, perception, lanePathInfo, LateralDirectionality.RIGHT))
                         {
                             DirectedPoint newLocation = changeLane(laneBasedGTU, LateralDirectionality.RIGHT);
                             lanePathInfo =
                                 buildLanePathInfo(laneBasedGTU, this.referenceLane, this.referencePos,
                                     forwardHeadway);
                             return currentLanePlan(laneBasedGTU, startTime, newLocation, lanePathInfo);
                         }
                     }
                 }
             }
 
             return currentLanePlan(laneBasedGTU, startTime, locationAtStartTime, lanePathInfo);
         }
         catch (GTUException | NetworkException | OperationalPlanException exception)
         {
             if (isDestroyGtuOnFailure())
             {
                 System.err.println("LaneBasedGTUFollowingChange0TacticalPlanner.generateOperationalPlan() failed for "
                     + gtu + " because of " + exception.getMessage() + " -- GTU destroyed");
                 gtu.destroy();
                 return new OperationalPlan(gtu, locationAtStartTime, startTime, new Time.Rel(1.0, TimeUnit.SECOND));
             }
             throw exception;
         }
     }
 
     /**
      * Make a plan for the current lane.
      * @param laneBasedGTU the gtu to generate the plan for
      * @param startTime the time from which the new operational plan has to be operational
      * @param locationAtStartTime the location of the GTU at the start time of the new plan
      * @param lanePathInfo the lane path for the current lane.
      * @return An operation plan for staying in the current lane.
      * @throws OperationalPlanException when there is a problem planning a path in the network
      * @throws GTUException when there is a problem with the state of the GTU when planning a path
      */
     private OperationalPlan currentLanePlan(final LaneBasedGTU laneBasedGTU, final Time.Abs startTime,
         final DirectedPoint locationAtStartTime, final LanePathInfo lanePathInfo) throws OperationalPlanException,
         GTUException
     {
         LanePerception perception = laneBasedGTU.getPerception();
         GTUFollowingModelOld gfm = laneBasedGTU.getBehavioralCharacteristics().getGTUFollowingModel();
 
         // No lane change. Continue on current lane.
         AccelerationStep accelerationStep;
         if (perception.getForwardHeadwayGTU().getGtuId() == null)
         {
             accelerationStep =
                 gfm.computeAccelerationStepWithNoLeader(laneBasedGTU,
                     lanePathInfo.getPath().getLength().minus(laneBasedGTU.getLength().multiplyBy(2.0)),
                     perception.getSpeedLimit());
         }
         else
         {
             accelerationStep =
                 gfm.computeAccelerationStep(laneBasedGTU, perception.getForwardHeadwayGTU().getGtuSpeed(), perception
                     .getForwardHeadwayGTU().getDistance(),
                     lanePathInfo.getPath().getLength().minus(laneBasedGTU.getLength().multiplyBy(2.0)), perception
                         .getSpeedLimit());
         }
 
         // see if we have to continue standing still. In that case, generate a stand still plan
         if (accelerationStep.getAcceleration().si < 1E-6
             && laneBasedGTU.getVelocity().si < OperationalPlan.DRIFTING_SPEED_SI)
         {
             return new OperationalPlan(laneBasedGTU, locationAtStartTime, startTime, accelerationStep.getDuration());
         }
 
         // build a list of lanes forward, with a maximum headway.
         List<Segment> operationalPlanSegmentList = new ArrayList<>();
         if (accelerationStep.getAcceleration().si == 0.0)
         {
             Segment segment = new OperationalPlan.SpeedSegment(accelerationStep.getDuration());
             operationalPlanSegmentList.add(segment);
         }
         else
         {
             Segment segment =
                 new OperationalPlan.AccelerationSegment(accelerationStep.getDuration(),
                     accelerationStep.getAcceleration());
             operationalPlanSegmentList.add(segment);
         }
         OperationalPlan op =
             new OperationalPlan(laneBasedGTU, lanePathInfo.getPath(), startTime, laneBasedGTU.getVelocity(),
                 operationalPlanSegmentList);
         return op;
     }
 
     /**
      * We are not on a lane that leads to our destination. Determine whether the lateral direction to go is left or right.
      * @param laneBasedGTU the gtu
      * @param nextSplitInfo the information about the next split
      * @return the lateral direction to go, or null if this cannot be determined
      */
     private LateralDirectionality
         determineLeftRight(final LaneBasedGTU laneBasedGTU, final NextSplitInfo nextSplitInfo)
     {
         // are the lanes in nextSplitInfo.getCorrectCurrentLanes() left or right of the current lane(s) of the GTU?
         for (Lane correctLane : nextSplitInfo.getCorrectCurrentLanes())
         {
             for (Lane currentLane : laneBasedGTU.getLanes().keySet())
             {
                 if (correctLane.getParentLink().equals(currentLane.getParentLink()))
                 {
                     double deltaOffset =
                         correctLane.getDesignLineOffsetAtBegin().si - currentLane.getDesignLineOffsetAtBegin().si;
                     if (laneBasedGTU.getLanes().get(currentLane).equals(GTUDirectionality.DIR_PLUS))
                     {
                         return deltaOffset > 0 ? LateralDirectionality.LEFT : LateralDirectionality.RIGHT;
                     }
                     else
                     {
                         return deltaOffset < 0 ? LateralDirectionality.LEFT : LateralDirectionality.RIGHT;
                     }
                 }
             }
         }
         return null;
     }
 
     /**
      * See if a lane change in the given direction if possible.
      * @param gtu the GTU that has to make the lane change
      * @param perception the perception, where forward headway, accessible lanes and speed limit have been assessed
      * @param lanePathInfo the information for the path on the current lane
      * @param direction the lateral direction, either LEFT or RIGHT
      * @return whether a lane change is possible.
      * @throws NetworkException when there is a network inconsistency in updating the perception
      * @throws GTUException when there is an issue retrieving GTU information for the perception update
      */
     private boolean canChange(final LaneBasedGTU gtu, final LanePerception perception, final LanePathInfo lanePathInfo,
         final LateralDirectionality direction) throws GTUException, NetworkException
     {
         Collection<HeadwayGTU> otherLaneTraffic;
         perception.updateForwardHeadwayGTU();
         perception.updateBackwardHeadwayGTU();
         if (direction.isLeft())
         {
             perception.updateParallelGTUsLeft();
             perception.updateLaneTrafficLeft();
             otherLaneTraffic = perception.getNeighboringGTUsLeft();
         }
         else
         {
             perception.updateParallelGTUsRight();
             perception.updateLaneTrafficRight();
             otherLaneTraffic = perception.getNeighboringGTUsRight();
         }
         if (!perception.parallelGTUs(direction).isEmpty())
         {
             return false;
         }
 
         Collection<HeadwayGTU> sameLaneTraffic = new HashSet<>();
         if (perception.getForwardHeadwayGTU() != null && perception.getForwardHeadwayGTU().getGtuId() != null)
         {
             sameLaneTraffic.add(perception.getForwardHeadwayGTU());
         }
         if (perception.getBackwardHeadwayGTU() != null && perception.getBackwardHeadwayGTU().getGtuId() != null)
         {
             sameLaneTraffic.add(perception.getBackwardHeadwayGTU());
         }
 
         // TODO make type of plan (Egoistic, Altruistic) parameter of the class
         DirectedLaneChangeModel dlcm = new DirectedEgoistic();
         // TODO make the elasticities 2.0 and 0.1 parameters of the class
         DirectedLaneMovementStep dlms =
             dlcm.computeLaneChangeAndAcceleration(gtu, direction, sameLaneTraffic, otherLaneTraffic, gtu
                 .getBehavioralCharacteristics().getForwardHeadwayDistance(), perception.getSpeedLimit(), new Acceleration(
                 2.0, AccelerationUnit.SI), new Acceleration(0.1, AccelerationUnit.SI), new Time.Rel(0.5,
                 TimeUnit.SECOND));
         if (dlms.getLaneChange() == null)
         {
             return false;
         }
 
         return true;
     }
 
     /**
      * Change lanes instantaneously.
      * @param gtu the gtu
      * @param direction the direction
      * @return the new location of the reference point of the GTU
      * @throws GTUException in case the enterlane fails
      */
     private DirectedPoint changeLane(final LaneBasedGTU gtu, final LateralDirectionality direction) throws GTUException
     {
         DirectedPoint p = null;
         Set<Lane> lanes = new HashSet<>(gtu.getLanes().keySet());
         for (Lane lane : lanes)
         {
             Set<Lane> adjacentLanes = lane.accessibleAdjacentLanes(direction, gtu.getGTUType());
             double fraction = gtu.fractionalPosition(lane, gtu.getReference());
             for (Lane adjacentLane : adjacentLanes)
             {
                 gtu.enterLane(adjacentLane, adjacentLane.getLength().multiplyBy(fraction), gtu.getLanes().get(lane));
                 if (fraction >= 0.0 && fraction <= 1.0)
                 {
                     p = adjacentLane.getCenterLine().getLocationFractionExtended(fraction);
                     this.referenceLane = adjacentLane;
                     this.referencePos = adjacentLane.getLength().multiplyBy(fraction);
                 }
                 System.out.println("gtu " + gtu.getId() + " entered lane " + adjacentLane + " at pos "
                     + adjacentLane.getLength().multiplyBy(fraction));
             }
             gtu.leaveLane(lane);
         }
 
         if (p == null)
         {
             System.err.println("Warning: " + gtu + " not with its reference point on any lane. Came from " + lanes
                 + ", now at " + gtu.getLanes().keySet());
             Lane l = gtu.getLanes().keySet().iterator().next();
             double fraction = gtu.fractionalPosition(l, gtu.getReference());
             p = l.getCenterLine().getLocationFractionExtended(fraction);
             this.referenceLane = l;
             this.referencePos = l.getLength().multiplyBy(fraction);
         }
 
         // stay at least 15 seconds in the current lane
         this.earliestNexLaneChangeTime =
             gtu.getSimulator().getSimulatorTime().getTime().plus(new Time.Rel(15, TimeUnit.SECOND));
 
         // make sure out turn indicator is on!
         gtu.setTurnIndicatorStatus(direction.isLeft() ? TurnIndicatorStatus.LEFT : TurnIndicatorStatus.RIGHT);
         
         return p;
     }
 
     /**
      * @return destroyGtuOnFailure, indicating when a failure in planning occurs, whether we should destroy the GTU to avoid
      *         halting of the model
      */
     public final boolean isDestroyGtuOnFailure()
     {
         return this.destroyGtuOnFailure;
     }
 
     /**
      * When a failure in planning occurs, should we destroy the GTU to avoid halting of the model?
      * @param destroyGtuOnFailure set destroyGtuOnFailure to true or false
      */
     public final void setDestroyGtuOnFailure(final boolean destroyGtuOnFailure)
     {
         this.destroyGtuOnFailure = destroyGtuOnFailure;
     }
 
 }