package org.opentrafficsim.road.gtu.lane.tactical.util;
   
   import java.io.Serializable;
   import java.util.ArrayList;
   import java.util.HashMap;
   import java.util.List;
   import java.util.SortedMap;
   import java.util.TreeMap;
   import java.util.UUID;
  
  import org.djunits.unit.AccelerationUnit;
  import org.djunits.unit.DurationUnit;
  import org.djunits.unit.LengthUnit;
  import org.djunits.value.vdouble.scalar.Acceleration;
  import org.djunits.value.vdouble.scalar.Duration;
  import org.djunits.value.vdouble.scalar.Length;
  import org.djunits.value.vdouble.scalar.Speed;
  import org.djunits.value.vdouble.scalar.Time;
  import org.djutils.exceptions.Throw;
  import org.opentrafficsim.base.parameters.ParameterException;
  import org.opentrafficsim.base.parameters.ParameterTypeAcceleration;
  import org.opentrafficsim.base.parameters.ParameterTypeDouble;
  import org.opentrafficsim.base.parameters.ParameterTypeDuration;
  import org.opentrafficsim.base.parameters.ParameterTypeLength;
  import org.opentrafficsim.base.parameters.ParameterTypes;
  import org.opentrafficsim.base.parameters.Parameters;
  import org.opentrafficsim.base.parameters.constraint.ConstraintInterface;
  import org.opentrafficsim.core.gtu.GTUException;
  import org.opentrafficsim.core.gtu.GTUType;
  import org.opentrafficsim.core.gtu.TurnIndicatorIntent;
  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.lane.perception.PerceptionCollectable;
  import org.opentrafficsim.road.gtu.lane.perception.PerceptionIterable;
  import org.opentrafficsim.road.gtu.lane.perception.headway.AbstractHeadwayGTU;
  import org.opentrafficsim.road.gtu.lane.perception.headway.HeadwayConflict;
  import org.opentrafficsim.road.gtu.lane.perception.headway.HeadwayGTU;
  import org.opentrafficsim.road.gtu.lane.perception.headway.HeadwayGTUSimple;
  import org.opentrafficsim.road.gtu.lane.perception.headway.HeadwayStopLine;
  import org.opentrafficsim.road.gtu.lane.tactical.Blockable;
  import org.opentrafficsim.road.gtu.lane.tactical.following.CarFollowingModel;
  import org.opentrafficsim.road.gtu.lane.tactical.pt.BusSchedule;
  import org.opentrafficsim.road.network.lane.CrossSectionLink;
  import org.opentrafficsim.road.network.lane.conflict.BusStopConflictRule;
  import org.opentrafficsim.road.network.lane.conflict.Conflict;
  import org.opentrafficsim.road.network.lane.conflict.ConflictRule;
  import org.opentrafficsim.road.network.lane.conflict.ConflictType;
  import org.opentrafficsim.road.network.speed.SpeedLimitInfo;
  
  /**
   * This class implements default behavior for intersection conflicts for use in tactical planners.
   * <p>
   * Copyright (c) 2013-2019 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/current/license.html">OpenTrafficSim License</a>.
   * <p>
   * @version $Revision$, $LastChangedDate$, by $Author$, initial version Jun 3, 2016 <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>
   */
  // TODO do not ignore vehicles upstream of conflict if they have green
  // TODO conflict over multiple lanes (longitudinal in own direction)
  // TODO a) yielding while having priority happens only when leaders is standing still on conflict (then its useless...)
  // b) two vehicles can remain upstream of merge if vehicle stands on merge but leaves some space to move
  // probably 1 is yielding, and 1 is courtesy yielding as the other stands still
  // c) they might start moving together and collide further down (no response to negative headway on merge)
  public final class ConflictUtil
  {
  
      /** Minimum time gap between events. */
      public static final ParameterTypeDuration MIN_GAP = new ParameterTypeDuration("minGap", "Minimum gap for conflicts.",
              new Duration(0.000001, DurationUnit.SECOND), ConstraintInterface.POSITIVE);
  
      /** Comfortable deceleration. */
      public static final ParameterTypeAcceleration B = ParameterTypes.B;
  
      /** Critical deceleration. */
      public static final ParameterTypeAcceleration BCRIT = ParameterTypes.BCRIT;
  
      /** Stopping distance. */
      public static final ParameterTypeLength S0 = ParameterTypes.S0;
  
      /** Stopping distance at conflicts. */
      public static final ParameterTypeLength S0_CONF = new ParameterTypeLength("s0 conf", "Stopping distance at conflicts.",
              new Length(1.5, LengthUnit.METER), ConstraintInterface.POSITIVE);
  
      /** Multiplication factor on time for conservative assessment. */
      public static final ParameterTypeDouble TIME_FACTOR =
              new ParameterTypeDouble("timeFactor", "Safety factor on estimated time.", 1.25, ConstraintInterface.ATLEASTONE);
  
      /** Area before stop line where one is considered arrived at the intersection. */
      public static final ParameterTypeLength STOP_AREA =
              new ParameterTypeLength("stopArea", "Area before stop line where one is considered arrived at the intersection.",
                      new Length(4, LengthUnit.METER), ConstraintInterface.POSITIVE);
  
      /** Parameter of how much time before departure a bus indicates its departure to get priority. */
      public static final ParameterTypeDuration TI = new ParameterTypeDuration("ti", "Indicator time before departure.",
              Duration.createSI(3.0), ConstraintInterface.POSITIVE);
 
     /** Time step for free acceleration anticipation. */
     private static final Duration TIME_STEP = new Duration(0.5, DurationUnit.SI);
 
     /** Cross standing vehicles on crossings. We allow this to prevent dead-locks. A better model should render this useless. */
     private static boolean CROSSSTANDING = true;
 
     /**
      * Do not instantiate.
      */
     private ConflictUtil()
     {
         //
     }
 
     /**
      * Approach conflicts by applying appropriate acceleration (or deceleration). The model may yield for a vehicle even while
      * having priority. Such a 'yield plan' is remembered in <tt>YieldPlans</tt>. By forwarding the same <tt>YieldPlans</tt> for
      * a GTU consistency of such plans is provided. If any conflict is not accepted to pass, stopping before a more upstream
      * conflict is applied if there not sufficient stopping length in between conflicts.
      * @param parameters Parameters; parameters
      * @param conflicts PerceptionCollectable&lt;HeadwayConflict,Conflict&gt;; set of conflicts to approach
      * @param leaders PerceptionCollectable&lt;HeadwayGTU,LaneBasedGTU&gt;; leading vehicles
      * @param carFollowingModel CarFollowingModel; car-following model
      * @param vehicleLength Length; length of vehicle
      * @param vehicleWidth Length; width of vehicle
      * @param speed Speed; current speed
      * @param acceleration Acceleration; current acceleration
      * @param speedLimitInfo SpeedLimitInfo; speed limit info
      * @param conflictPlans ConflictPlans; set of plans for conflict
      * @param gtu LaneBasedGTU; gtu
      * @return acceleration appropriate for approaching the conflicts
      * @throws GTUException in case of an unsupported conflict rule
      * @throws ParameterException if a parameter is not defined or out of bounds
      */
     @SuppressWarnings("checkstyle:parameternumber")
     public static Acceleration approachConflicts(final Parameters parameters,
             final PerceptionCollectable<HeadwayConflict, Conflict> conflicts,
             final PerceptionCollectable<HeadwayGTU, LaneBasedGTU> leaders, final CarFollowingModel carFollowingModel,
             final Length vehicleLength, final Length vehicleWidth, final Speed speed, final Acceleration acceleration,
             final SpeedLimitInfo speedLimitInfo, final ConflictPlans conflictPlans, final LaneBasedGTU gtu)
             throws GTUException, ParameterException
     {
 
         conflictPlans.cleanPlans();
 
         Acceleration a = Acceleration.POS_MAXVALUE;
         Length stoppingDistance = Length.createSI(
                 parameters.getParameter(S0).si + vehicleLength.si + .5 * speed.si * speed.si / parameters.getParameter(B).si);
         if (!conflicts.isEmpty() && conflicts.first().getDistance().gt(stoppingDistance))
         {
             conflictPlans.setBlocking(false);
             return a;
         }
 
         List<Length> prevStarts = new ArrayList<>();
         List<Length> prevEnds = new ArrayList<>();
         List<Class<? extends ConflictRule>> conflictRuleTypes = new ArrayList<>();
         boolean blocking = false;
 
         for (HeadwayConflict conflict : conflicts)
         {
 
             // adjust acceleration for situations where stopping might not be required
             if (conflict.isCrossing())
             {
                 // avoid collision if crossing is occupied
                 a = Acceleration.min(a, avoidCrossingCollision(parameters, conflict, carFollowingModel, speed, speedLimitInfo));
             }
             else
             {
                 // follow leading GTUs on merge or split
                 a = Acceleration.min(a, followConflictingLeaderOnMergeOrSplit(conflict, parameters, carFollowingModel, speed,
                         speedLimitInfo, vehicleWidth));
             }
             if (conflict.getDistance().lt0())
             {
                 if (conflict.getConflictType().isCrossing() && !conflict.getConflictPriority().isPriority())
                 {
                     // note that we are blocking a conflict
                     blocking = true;
                 }
                 // ignore conflicts we are on (i.e. negative distance to start of conflict)
                 continue;
             }
 
             // indicator if bus
             if (gtu.getStrategicalPlanner().getRoute() instanceof BusSchedule && gtu.getGTUType().isOfType(GTUType.BUS)
                     && conflict.getConflictRuleType().equals(BusStopConflictRule.class))
             {
                 BusSchedule busSchedule = (BusSchedule) gtu.getStrategicalPlanner().getRoute();
                 Time actualDeparture = busSchedule.getActualDepartureConflict(conflict.getId());
                 if (actualDeparture != null
                         && actualDeparture.si < gtu.getSimulator().getSimulatorTime().si + parameters.getParameter(TI).si)
                 {
                     // TODO depending on left/right-hand traffic
                     conflictPlans.setIndicatorIntent(TurnIndicatorIntent.LEFT, conflict.getDistance());
                 }
             }
 
             // determine if we need to stop
             boolean stop;
             switch (conflict.getConflictPriority())
             {
                 case PRIORITY:
                 {
                     stop = stopForPriorityConflict(conflict, leaders, speed, vehicleLength, parameters, conflictPlans);
                     break;
                 }
                 case YIELD: // TODO depending on rules, we may need to stop and not just yield
                 case TURN_ON_RED:
                 {
                     stop = stopForGiveWayConflict(conflict, leaders, speed, acceleration, vehicleLength, parameters,
                             speedLimitInfo, carFollowingModel, blocking ? BCRIT : B);
                     break;
                 }
                 case STOP:
                 {
                     stop = stopForStopConflict(conflict, leaders, speed, acceleration, vehicleLength, parameters,
                             speedLimitInfo, carFollowingModel, blocking ? BCRIT : B);
                     break;
                 }
                 case ALL_STOP:
                 {
                     stop = stopForAllStopConflict(conflict, conflictPlans);
                     break;
                 }
                 case SPLIT:
                 {
                     stop = false; // skipped anyway
                     break;
                 }
                 default:
                 {
                     throw new GTUException("Unsupported conflict rule encountered while approaching conflicts.");
                 }
             }
 
             // stop if required, account for upstream conflicts to keep clear
             if (!conflict.getConflictType().equals(ConflictType.SPLIT))
             {
 
                 if (stop)
                 {
                     prevStarts.add(conflict.getDistance());
                     conflictRuleTypes.add(conflict.getConflictRuleType());
                     // stop for first conflict looking upstream of this blocked conflict that allows sufficient space
                     int j = 0; // most upstream conflict if not in between conflicts
                     for (int i = prevEnds.size() - 1; i >= 0; i--) // downstream to upstream
                     {
                         // note, at this point prevStarts contains one more conflict than prevEnds
                         if (prevStarts.get(i + 1).minus(prevEnds.get(i)).gt(passableDistance(vehicleLength, parameters)))
                         {
                             j = i + 1;
                             break;
                         }
                     }
                     if (blocking && j == 0)
                     {
                         // we are blocking a conflict, let's not stop more upstream than the conflict that forces our stop
                         j = prevStarts.size() - 1;
                     }
 
                     // TODO
                     // if this lowers our acceleration, we need to check if we are able to pass upstream conflicts still in time
 
                     // stop for j'th conflict, if deceleration is too strong, for next one
                     parameters.setParameterResettable(S0, parameters.getParameter(S0_CONF));
                     Acceleration aCF = new Acceleration(-Double.MAX_VALUE, AccelerationUnit.SI);
                     while (aCF.si < -6.0 && j < prevStarts.size())
                     {
                         if (prevStarts.get(j).lt(parameters.getParameter(S0_CONF)))
                         {
                             // TODO what to do when we happen to be in the stopping distance? Stopping might be reasonable,
                             // while car-following might give strong deceleration due to s < s0.
                             aCF = Acceleration.max(aCF, new Acceleration(-6.0, AccelerationUnit.SI));
                         }
                         else
                         {
                             Acceleration aStop = CarFollowingUtil.stop(carFollowingModel, parameters, speed, speedLimitInfo,
                                     prevStarts.get(j));
                             if (conflictRuleTypes.get(j).equals(BusStopConflictRule.class)
                                     && aStop.lt(parameters.getParameter(ParameterTypes.BCRIT).neg()))
                             {
                                 // as it may suddenly switch state, i.e. ignore like a yellow traffic light
                                 aStop = Acceleration.POS_MAXVALUE;
                             }
                             aCF = Acceleration.max(aCF, aStop);
                         }
                         j++;
                     }
                     parameters.resetParameter(S0);
                     a = Acceleration.min(a, aCF);
                     break;
                 }
 
                 // keep conflict clear (when stopping for another conflict), if there are conflicting vehicles
                 if (!conflict.getUpstreamConflictingGTUs().isEmpty())
                 {
                     prevStarts.add(conflict.getDistance());
                     conflictRuleTypes.add(conflict.getConflictRuleType());
                     prevEnds.add(conflict.getDistance().plus(conflict.getLength()));
                 }
             }
 
         }
         conflictPlans.setBlocking(blocking);
 
         if (a.si < -6.0 && speed.si > 5 / 3.6)
         {
             System.err.println("Deceleration from conflict util stronger than 6m/s^2.");
             // return IGNORE;
         }
         return a;
     }
 
     /**
      * Determines acceleration for following conflicting vehicles <i>on</i> a merge or split conflict.
      * @param conflict HeadwayConflict; merge or split conflict
      * @param parameters Parameters; parameters
      * @param carFollowingModel CarFollowingModel; car-following model
      * @param speed Speed; current speed
      * @param speedLimitInfo SpeedLimitInfo; speed limit info
      * @param vehicleWidth Length; own width
      * @return acceleration for following conflicting vehicles <i>on</i> a merge or split conflict
      * @throws ParameterException if a parameter is not given or out of bounds
      */
     private static Acceleration followConflictingLeaderOnMergeOrSplit(final HeadwayConflict conflict,
             final Parameters parameters, final CarFollowingModel carFollowingModel, final Speed speed,
             final SpeedLimitInfo speedLimitInfo, final Length vehicleWidth) throws ParameterException
     {
         // ignore if no conflicting GTU's, or if first is downstream of conflict
         PerceptionIterable<HeadwayGTU> downstreamGTUs = conflict.getDownstreamConflictingGTUs();
         if (downstreamGTUs.isEmpty() || downstreamGTUs.first().isAhead())
         {
             return Acceleration.POS_MAXVALUE;
         }
         // get the most upstream GTU to consider
         HeadwayGTU c = null;
         Length virtualHeadway = null;
         if (conflict.getDistance().gt0())
         {
             c = downstreamGTUs.first();
             virtualHeadway = conflict.getDistance().plus(c.getOverlapRear());
         }
         else
         {
             for (HeadwayGTU con : downstreamGTUs)
             {
                 if (con.isAhead())
                 {
                     // conflict GTU completely downstream of conflict (i.e. regular car-following, ignore here)
                     return Acceleration.POS_MAXVALUE;
                 }
                 // conflict GTU (partially) on the conflict
                 // {@formatter:off}
                 // ______________________________________________ 
                 //   ___      virtual headway   |  ___  |
                 //  |___|(-----------------------)|___|(vehicle from south, on lane from south)
                 // _____________________________|_______|________
                 //                              /       / 
                 //                             /       /
                 // {@formatter:on}
                 virtualHeadway = conflict.getDistance().plus(con.getOverlapRear());
                 if (virtualHeadway.gt0())
                 {
                     if (conflict.isSplit())
                     {
                         double conflictWidth = conflict.getWidthAtFraction(
                                 (-conflict.getDistance().si + virtualHeadway.si) / conflict.getConflictingLength().si).si;
                         double gtuWidth = con.getWidth().si + vehicleWidth.si;
                         if (conflictWidth > gtuWidth)
                         {
                             continue;
                         }
                     }
                     // found first downstream GTU on conflict
                     c = con;
                     break;
                 }
             }
         }
         if (c == null)
         {
             // conflict GTU downstream of start of conflict, but upstream of us
             return Acceleration.POS_MAXVALUE;
         }
         // follow leader
         SortedMap<Length, Speed> leaders = new TreeMap<>();
         leaders.put(virtualHeadway, c.getSpeed());
         Acceleration a = CarFollowingUtil.followSingleLeader(carFollowingModel, parameters, speed, speedLimitInfo,
                 virtualHeadway, c.getSpeed());
         // if conflicting GTU is partially upstream of the conflict and at (near) stand-still, stop for the conflict rather than
         // following the tail of the conflicting GTU
         if (conflict.isMerge() && virtualHeadway.lt(conflict.getDistance()))
         {
             // {@formatter:off}
             /*
              * ______________________________________________
              *    ___    stop for conflict  |       | 
              *   |___|(--------------------)|   ___ |
              * _____________________________|__/  /_|________ 
              *                              / /__/  /
              *                             /       /
              */
             // {@formatter:on}
             parameters.setParameterResettable(S0, parameters.getParameter(S0_CONF));
             Acceleration aStop =
                     CarFollowingUtil.stop(carFollowingModel, parameters, speed, speedLimitInfo, conflict.getDistance());
             parameters.resetParameter(S0);
             a = Acceleration.max(a, aStop); // max, which ever allows the largest acceleration
         }
         return a;
     }
 
     /**
      * Determines an acceleration required to avoid a collision with GTUs <i>on</i> a crossing conflict.
      * @param parameters Parameters; parameters
      * @param conflict HeadwayConflict; conflict
      * @param carFollowingModel CarFollowingModel; car-following model
      * @param speed Speed; current speed
      * @param speedLimitInfo SpeedLimitInfo; speed limit info
      * @return acceleration required to avoid a collision
      * @throws ParameterException if parameter is not defined
      */
     private static Acceleration avoidCrossingCollision(final Parameters parameters, final HeadwayConflict conflict,
             final CarFollowingModel carFollowingModel, final Speed speed, final SpeedLimitInfo speedLimitInfo)
             throws ParameterException
     {
 
         // TODO only within visibility
         List<HeadwayGTU> conflictingGTUs = new ArrayList<>();
         for (HeadwayGTU gtu : conflict.getUpstreamConflictingGTUs())
         {
             if (isOnRoute(conflict.getConflictingLink(), gtu))
             {
                 // first upstream vehicle on route to this conflict
                 conflictingGTUs.add(gtu);
                 break;
             }
         }
         for (HeadwayGTU gtu : conflict.getDownstreamConflictingGTUs())
         {
             if (gtu.isParallel())
             {
                 conflictingGTUs.add(gtu);
             }
             else
             {
                 // vehicles beyond conflict are not a thread
                 break;
             }
         }
 
         if (conflictingGTUs.isEmpty())
         {
             return Acceleration.POS_MAXVALUE;
         }
 
         Acceleration a = Acceleration.POS_MAXVALUE;
         for (HeadwayGTU conflictingGTU : conflictingGTUs)
         {
             AnticipationInfo tteC;
             Length distance;
             if (conflictingGTU.isParallel())
             {
                 tteC = new AnticipationInfo(Duration.ZERO, conflictingGTU.getSpeed());
                 distance = conflictingGTU.getOverlapRear().abs().plus(conflictingGTU.getOverlap())
                         .plus(conflictingGTU.getOverlapFront().abs());
             }
             else
             {
                 tteC = AnticipationInfo.anticipateMovement(conflictingGTU.getDistance(), conflictingGTU.getSpeed(),
                         Acceleration.ZERO);
                 distance = conflictingGTU.getDistance().plus(conflict.getLength()).plus(conflictingGTU.getLength());
             }
             AnticipationInfo ttcC = AnticipationInfo.anticipateMovement(distance, conflictingGTU.getSpeed(), Acceleration.ZERO);
             AnticipationInfo tteO = AnticipationInfo.anticipateMovementFreeAcceleration(conflict.getDistance(), speed,
                     parameters, carFollowingModel, speedLimitInfo, TIME_STEP);
             // enter before cleared
             // TODO safety factor?
             if (tteC.getDuration().lt(tteO.getDuration()) && tteO.getDuration().lt(ttcC.getDuration()))
             {
                 if (!conflictingGTU.getSpeed().eq0() || !CROSSSTANDING)
                 {
                     // solve parabolic speed profile s = v*t + .5*a*t*t, a =
                     double acc = 2 * (conflict.getDistance().si - speed.si * ttcC.getDuration().si)
                             / (ttcC.getDuration().si * ttcC.getDuration().si);
                     // time till zero speed > time to avoid conflict?
                     if (speed.si / -acc > ttcC.getDuration().si)
                     {
                         a = Acceleration.min(a, new Acceleration(acc, AccelerationUnit.SI));
                     }
                     else
                     {
                         // will reach zero speed ourselves
                         a = Acceleration.min(a, CarFollowingUtil.stop(carFollowingModel, parameters, speed, speedLimitInfo,
                                 conflict.getDistance()));
                     }
                 }
                 // conflicting vehicle stand-still, ignore even at conflict
             }
         }
         return a;
     }
 
     /**
      * Approach a priority conflict. Stopping is applied to give way to conflicting traffic in case congestion is present on the
      * own lane. This is courtesy yielding.
      * @param conflict HeadwayConflict; conflict to approach
      * @param leaders PerceptionCollectable&lt;HeadwayGTU,LaneBasedGTU&gt;; leading vehicles in own lane
      * @param speed Speed; current speed
      * @param vehicleLength Length; vehicle length
      * @param parameters Parameters; parameters
      * @param yieldPlans ConflictPlans; set of plans for yielding with priority
      * @return whether to stop for this conflict
      * @throws ParameterException if parameter B is not defined
      */
     public static boolean stopForPriorityConflict(final HeadwayConflict conflict,
             final PerceptionCollectable<HeadwayGTU, LaneBasedGTU> leaders, final Speed speed, final Length vehicleLength,
             final Parameters parameters, final ConflictPlans yieldPlans) throws ParameterException
     {
 
         if (leaders.isEmpty() || conflict.getUpstreamConflictingGTUs().isEmpty())
         {
             // no leader, or no conflicting vehicle
             return false;
         }
 
         // Stop as long as some leader is standing still, and leader is not leaving sufficient space yet
         // use start of conflict on merge, end of conflict on crossing
         Length typeCorrection = conflict.isCrossing() ? conflict.getLength() : Length.ZERO;
         // distance leader has to cover before we can pass the conflict
         Length distance = conflict.getDistance().minus(leaders.first().getDistance())
                 .plus(passableDistance(vehicleLength, parameters)).plus(typeCorrection);
         if (distance.gt0())
         {
             // for ourselves
             Length required = conflict.getDistance().plus(typeCorrection).plus(passableDistance(vehicleLength, parameters));
             for (HeadwayGTU leader : leaders)
             {
                 if (leader.getSpeed().eq0())
                 {
                     // first stand-still leader is not fully upstream of the conflict (in that case, ignore), and does not
                     // allow sufficient space for all vehicles in between
                     return leader.getDistance().ge(conflict.getDistance()) && required.ge(leader.getDistance());
                 }
                 required = required // add required distance for leaders
                         .plus(passableDistance(leader.getLength(), leader.getParameters()));
             }
         }
         return false;
 
     }
 
     /**
      * Approach a give-way conflict.
      * @param conflict HeadwayConflict; conflict
      * @param leaders PerceptionCollectable&lt;HeadwayGTU,LaneBasedGTU&gt;; leaders
      * @param speed Speed; current speed
      * @param acceleration Acceleration; current acceleration
      * @param vehicleLength Length; vehicle length
      * @param parameters Parameters; parameters
      * @param speedLimitInfo SpeedLimitInfo; speed limit info
      * @param carFollowingModel CarFollowingModel; car-following model
      * @param bType ParameterTypeAcceleration; parameter type for considered deceleration
      * @return whether to stop for this conflict
      * @throws ParameterException if a parameter is not defined
      */
     @SuppressWarnings("checkstyle:parameternumber")
     public static boolean stopForGiveWayConflict(final HeadwayConflict conflict,
             final PerceptionCollectable<HeadwayGTU, LaneBasedGTU> leaders, final Speed speed, final Acceleration acceleration,
             final Length vehicleLength, final Parameters parameters, final SpeedLimitInfo speedLimitInfo,
             final CarFollowingModel carFollowingModel, final ParameterTypeAcceleration bType) throws ParameterException
     {
 
         // TODO conflicting vehicle on crossing conflict, but will leave sooner then we enter, so no problem?
         // TODO more generally, also upstream conflicting vehicles at crossings may leave the conflict before we enter
         if (conflict.getConflictType().equals(ConflictType.CROSSING) && !conflict.getDownstreamConflictingGTUs().isEmpty()
                 && conflict.getDownstreamConflictingGTUs().first().isParallel())
         {
             // vehicle on the conflict
             return true;
         }
 
         // Get data independent of conflicting vehicle
         // parameters
         Acceleration b = parameters.getParameter(bType).neg();
         double f = parameters.getParameter(TIME_FACTOR);
         Duration gap = parameters.getParameter(MIN_GAP);
         // time till conflict is cleared
         Length distance = conflict.getDistance().plus(vehicleLength);
         if (conflict.isCrossing())
         {
             // merge is cleared at start, crossing at end
             distance = distance.plus(conflict.getLength());
         }
         // based on acceleration, limited by free acceleration
         AnticipationInfo ttcOa = AnticipationInfo.anticipateMovementFreeAcceleration(distance, speed, parameters,
                 carFollowingModel, speedLimitInfo, TIME_STEP);
         // time till downstream vehicle will make the conflict passible, under constant speed or safe deceleration
         AnticipationInfo ttpDz = null;
         AnticipationInfo ttpDs = null;
         if (conflict.isCrossing())
         {
             if (!leaders.isEmpty())
             {
                 distance = conflict.getDistance().minus(leaders.first().getDistance()).plus(conflict.getLength())
                         .plus(passableDistance(vehicleLength, parameters));
                 ttpDz = AnticipationInfo.anticipateMovement(distance, leaders.first().getSpeed(), Acceleration.ZERO);
                 ttpDs = AnticipationInfo.anticipateMovement(distance, leaders.first().getSpeed(), b);
             }
             else
             {
                 // no leader so conflict is passible within a duration of 0
                 ttpDz = new AnticipationInfo(Duration.ZERO, Speed.ZERO);
                 ttpDs = new AnticipationInfo(Duration.ZERO, Speed.ZERO);
             }
         }
 
         PerceptionCollectable<HeadwayGTU, LaneBasedGTU> conflictingVehiclesCollectable = conflict.getUpstreamConflictingGTUs();
         Iterable<HeadwayGTU> conflictingVehicles;
         if (conflictingVehiclesCollectable.isEmpty())
         {
             if (conflict.getConflictingTrafficLightDistance() == null)
             {
                 // none within visibility, assume a conflicting vehicle just outside of visibility driving at speed limit
                 try
                 {
                     HeadwayGTUSimple conflictGtu = new HeadwayGTUSimple("virtual " + UUID.randomUUID().toString(), GTUType.CAR,
                             conflict.getConflictingVisibility(), new Length(4.0, LengthUnit.SI), new Length(2.0, LengthUnit.SI),
                             conflict.getConflictingSpeedLimit(), Acceleration.ZERO, Speed.ZERO);
                     List<HeadwayGTU> conflictingVehiclesList = new ArrayList<>();
                     conflictingVehiclesList.add(conflictGtu);
                     conflictingVehicles = conflictingVehiclesList;
                 }
                 catch (GTUException exception)
                 {
                     throw new RuntimeException("Could not create a virtual conflicting vehicle at visibility range.",
                             exception);
                 }
             }
             else
             {
                 // no conflicting vehicles
                 return false;
             }
         }
         else
         {
             conflictingVehicles = conflictingVehiclesCollectable;
         }
 
         // Loop over conflicting vehicles
         boolean first = true;
         for (HeadwayGTU conflictingVehicle : conflictingVehicles)
         {
 
             // do not stop if conflicting vehicle is standing still
             if (first && conflictingVehicle.getSpeed().eq0() && conflictingVehicle.isAhead())
             {
                 return false;
             }
             first = false;
 
             // skip if not on route
             if (!isOnRoute(conflict.getConflictingLink(), conflictingVehicle))
             {
                 continue;
             }
 
             // time till conflict vehicle will enter, under free acceleration and safe deceleration
             AnticipationInfo tteCa;
             if (conflictingVehicle instanceof HeadwayGTUSimple)
             {
                 tteCa = AnticipationInfo.anticipateMovement(conflictingVehicle.getDistance(), conflictingVehicle.getSpeed(),
                         conflictingVehicle.getAcceleration());
             }
             else
             {
                 Parameters params = conflictingVehicle.getParameters();
                 SpeedLimitInfo sli = conflictingVehicle.getSpeedLimitInfo();
                 CarFollowingModel cfm = conflictingVehicle.getCarFollowingModel();
                 // Constant acceleration creates inf at stand still, triggering passing trough a congested stream
                 tteCa = AnticipationInfo.anticipateMovementFreeAcceleration(conflictingVehicle.getDistance(),
                         conflictingVehicle.getSpeed(), params, cfm, sli, TIME_STEP);
             }
             AnticipationInfo tteCs =
                     AnticipationInfo.anticipateMovement(conflictingVehicle.getDistance(), conflictingVehicle.getSpeed(), b);
 
             // check gap
             if (conflict.isMerge())
             {
 
                 // Merge, will be each others followers, add time to overcome speed difference
                 double vSelf = ttcOa.getEndSpeed().si;
                 double speedDiff = conflictingVehicle.getSpeed().si - vSelf;
                 speedDiff = speedDiff > 0 ? speedDiff : 0;
                 Duration additionalTime = new Duration(speedDiff / -b.si, DurationUnit.SI);
                 // check if conflict vehicle will be upstream after that time, position beyond conflict after additional time
                 double followerFront = conflictingVehicle.getSpeed().si * ttcOa.getDuration().si
                         - conflictingVehicle.getDistance().si + (conflictingVehicle.getSpeed().si * additionalTime.si
                                 + 0.5 * b.si * additionalTime.si * additionalTime.si);
                 double ownRear = vSelf * additionalTime.si; // constant speed after clearing
                 Duration tMax = parameters.getParameter(ParameterTypes.TMAX);
                 Length s0 = parameters.getParameter(S0);
                 // 1) will clear the conflict after the conflict vehicle enters
                 // 2) not sufficient time to overcome speed difference
                 // 3) conflict vehicle will be too near after adjusting speed
                 if (ttcOa.getDuration().multiplyBy(f).plus(gap).gt(tteCa.getDuration())
                         || ttcOa.getDuration().plus(additionalTime).multiplyBy(f).plus(gap).gt(tteCs.getDuration())
                         || ownRear < (followerFront + (tMax.si + gap.si) * vSelf + s0.si) * f)
                 {
                     return true;
                 }
 
             }
             else if (conflict.isCrossing())
             {
 
                 // Crossing, stop if order of events is not ok
                 // Should go before the conflict vehicle
                 // 1) downstream vehicle must supply sufficient space before conflict vehicle will enter
                 // 2) must clear the conflict before the conflict vehicle will enter
                 // 3) if leader decelerates with b, conflict vehicle should be able to safely delay entering conflict
                 if (ttpDz.getDuration().multiplyBy(f).plus(gap).gt(tteCa.getDuration())
                         || ttcOa.getDuration().multiplyBy(f).plus(gap).gt(tteCa.getDuration())
                         || ttpDs.getDuration().multiplyBy(f).plus(gap).gt(tteCs.getDuration()))
                 {
                     return true;
                 }
 
             }
             else
             {
                 throw new RuntimeException(
                         "Conflict is of unknown type " + conflict.getConflictType() + ", which is not merge nor a crossing.");
             }
         }
 
         // No conflict vehicle triggered stopping
         return false;
 
     }
 
     /**
      * Approach a stop conflict. Currently this is equal to approaching a give-way conflict.
      * @param conflict HeadwayConflict; conflict
      * @param leaders PerceptionCollectable&lt;HeadwayGTU,LaneBasedGTU&gt;; leaders
      * @param speed Speed; current speed
      * @param acceleration Acceleration; current acceleration
      * @param vehicleLength Length; vehicle length
      * @param parameters Parameters; parameters
      * @param speedLimitInfo SpeedLimitInfo; speed limit info
      * @param carFollowingModel CarFollowingModel; car-following model
      * @param bType ParameterTypeAcceleration; parameter type for considered deceleration
      * @return whether to stop for this conflict
      * @throws ParameterException if a parameter is not defined
      */
     @SuppressWarnings("checkstyle:parameternumber")
     public static boolean stopForStopConflict(final HeadwayConflict conflict,
             final PerceptionCollectable<HeadwayGTU, LaneBasedGTU> leaders, final Speed speed, final Acceleration acceleration,
             final Length vehicleLength, final Parameters parameters, final SpeedLimitInfo speedLimitInfo,
             final CarFollowingModel carFollowingModel, final ParameterTypeAcceleration bType) throws ParameterException
     {
         // TODO stopping
         return stopForGiveWayConflict(conflict, leaders, speed, acceleration, vehicleLength, parameters, speedLimitInfo,
                 carFollowingModel, bType);
     }
 
     /**
      * Approach an all-stop conflict.
      * @param conflict HeadwayConflict; conflict to approach
      * @param conflictPlans ConflictPlans; set of plans for conflict
      * @return whether to stop for this conflict
      */
     public static boolean stopForAllStopConflict(final HeadwayConflict conflict, final ConflictPlans conflictPlans)
     {
         // TODO all-stop behavior
 
         if (conflictPlans.isStopPhaseRun(conflict.getStopLine()))
         {
             return false;
         }
 
         return false;
     }
 
     /**
      * Returns whether the conflicting link is on the route of the given gtu.
      * @param conflictingLink CrossSectionLink; conflicting link
      * @param gtu HeadwayGTU; gtu
      * @return whether the conflict is on the route of the given gtu
      */
     private static boolean isOnRoute(final CrossSectionLink conflictingLink, final HeadwayGTU gtu)
     {
         try
         {
             Route route = gtu.getRoute();
             if (route == null)
             {
                 // conservative assumption: it's on the route (gtu should be upstream of the conflict)
                 return true;
             }
             Node startNode = conflictingLink.getStartNode();
             Node endNode = conflictingLink.getEndNode();
             return route.contains(startNode) && route.contains(endNode)
                     && Math.abs(route.indexOf(endNode) - route.indexOf(startNode)) == 1;
         }
         catch (UnsupportedOperationException uoe)
         {
             // conservative assumption: it's on the route (gtu should be upstream of the conflict)
             return true;
         }
     }
 
     /**
      * Returns a speed dependent distance needed behind the leader to completely pass the conflict.
      * @param vehicleLength Length; vehicle length
      * @param parameters Parameters; parameters
      * @return speed dependent distance needed behind the leader to completely pass the conflict
      * @throws ParameterException if parameter is not available
      */
     private static Length passableDistance(final Length vehicleLength, final Parameters parameters) throws ParameterException
     {
         return parameters.getParameter(S0).plus(vehicleLength);
     }
 
     /**
      * Holds the tactical plans of a driver considering conflicts. These are remembered for consistency. For instance, if the
      * decision is made to yield as current deceleration suggests it's safe to do so, but the trajectory for stopping in front
      * of the conflict results in deceleration slightly above what is considered safe deceleration, the plan should not be
      * abandoned. Decelerations above what is considered safe deceleration may result due to numerical overshoot or other factor
      * coming into play in car-following models. Many other examples exist where a driver sticks to a certain plan.
      * <p>
      * Copyright (c) 2013-2019 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/current/license.html">OpenTrafficSim License</a>.
      * <p>
      * @version $Revision$, $LastChangedDate$, by $Author$, initial version Jun 7, 2016 <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 static final class ConflictPlans implements Blockable, Serializable
     {
 
         /** */
         private static final long serialVersionUID = 20160811L;
 
         /** Phases of navigating an all-stop intersection per intersection. */
         private final HashMap<String, StopPhase> stopPhases = new HashMap<>();
 
         /** Estimated arrival times of vehicles at all-stop intersection. */
         private final HashMap<String, Time> arrivalTimes = new HashMap<>();
 
         /** Indicator intent. */
         private TurnIndicatorIntent indicatorIntent = TurnIndicatorIntent.NONE;
 
         /** Distance to object causing turn indicator intent. */
         private Length indicatorObjectDistance = null;
 
         /** Whether the GTU is blocking conflicts. */
         private boolean blocking;
 
         /**
          * Clean any yield plan that was no longer kept active in the last evaluation of conflicts.
          */
         void cleanPlans()
         {
             this.indicatorIntent = TurnIndicatorIntent.NONE;
             this.indicatorObjectDistance = null;
         }
 
         /**
          * Sets the estimated arrival time of a GTU.
          * @param gtu AbstractHeadwayGTU; GTU
          * @param time Time; estimated arrival time
          */
         void setArrivalTime(final AbstractHeadwayGTU gtu, final Time time)
         {
             this.arrivalTimes.put(gtu.getId(), time);
         }
 
         /**
          * Returns the estimated arrival time of given GTU.
          * @param gtu AbstractHeadwayGTU; GTU
          * @return estimated arrival time of given GTU
          */
         Time getArrivalTime(final AbstractHeadwayGTU gtu)
         {
             return this.arrivalTimes.get(gtu.getId());
         }
 
         /**
          * Sets the current phase to 'approach' for the given stop line.
          * @param stopLine HeadwayStopLine; stop line
          */
         void setStopPhaseApproach(final HeadwayStopLine stopLine)
         {
             this.stopPhases.put(stopLine.getId(), StopPhase.APPROACH);
         }
 
         /**
          * Sets the current phase to 'yield' for the given stop line.
          * @param stopLine HeadwayStopLine; stop line
          * @throws RuntimeException if the phase was not set to approach before
          */
         void setStopPhaseYield(final HeadwayStopLine stopLine)
         {
             Throw.when(
                     !this.stopPhases.containsKey(stopLine.getId())
                             || !this.stopPhases.get(stopLine.getId()).equals(StopPhase.APPROACH),
                     RuntimeException.class, "Yield stop phase is set for stop line that was not approached.");
             this.stopPhases.put(stopLine.getId(), StopPhase.YIELD);
         }
 
         /**
          * Sets the current phase to 'run' for the given stop line.
          * @param stopLine HeadwayStopLine; stop line
          * @throws RuntimeException if the phase was not set to approach before
          */
         void setStopPhaseRun(final HeadwayStopLine stopLine)
         {
             Throw.when(!this.stopPhases.containsKey(stopLine.getId()), RuntimeException.class,
                     "Run stop phase is set for stop line that was not approached.");
             this.stopPhases.put(stopLine.getId(), StopPhase.YIELD);
         }
 
         /**
          * @param stopLine HeadwayStopLine; stop line
          * @return whether the current phase is 'approach' for the given stop line
          */
         boolean isStopPhaseApproach(final HeadwayStopLine stopLine)
         {
             return this.stopPhases.containsKey(stopLine.getId())
                     && this.stopPhases.get(stopLine.getId()).equals(StopPhase.APPROACH);
         }
 
         /**
          * @param stopLine HeadwayStopLine; stop line
          * @return whether the current phase is 'yield' for the given stop line
          */
         boolean isStopPhaseYield(final HeadwayStopLine stopLine)
         {
             return this.stopPhases.containsKey(stopLine.getId())
                     && this.stopPhases.get(stopLine.getId()).equals(StopPhase.YIELD);
         }
 
         /**
          * @param stopLine HeadwayStopLine; stop line
          * @return whether the current phase is 'run' for the given stop line
          */
         boolean isStopPhaseRun(final HeadwayStopLine stopLine)
         {
             return this.stopPhases.containsKey(stopLine.getId()) && this.stopPhases.get(stopLine.getId()).equals(StopPhase.RUN);
         }
 
         /** {@inheritDoc} */
         @Override
         public String toString()
         {
             return "ConflictPlans";
         }
 
         /**
          * @return indicatorIntent.
          */
         public TurnIndicatorIntent getIndicatorIntent()
         {
             return this.indicatorIntent;
         }
 
         /**
          * @return indicatorObjectDistance.
          */
         public Length getIndicatorObjectDistance()
         {
             return this.indicatorObjectDistance;
         }
 
         /**
          * @param intent TurnIndicatorIntent; indicator intent
          * @param distance Length; distance to object pertaining to the turn indicator intent
          */
         public void setIndicatorIntent(final TurnIndicatorIntent intent, final Length distance)
         {
             if (this.indicatorObjectDistance == null || this.indicatorObjectDistance.gt(distance))
             {
                 this.indicatorIntent = intent;
                 this.indicatorObjectDistance = distance;
             }
         }
 
         /** {@inheritDoc} */
         @Override
         public boolean isBlocking()
         {
             return this.blocking;
         }
 
         /**
          * Sets the GTU as blocking conflicts or not.
          * @param blocking boolean; whether the GTU is blocking conflicts
          */
         public void setBlocking(final boolean blocking)
         {
             this.blocking = blocking;
         }
 
     }
 
     /**
      * Phases of navigating an all-stop intersection.
      * <p>
      * Copyright (c) 2013-2019 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/current/license.html">OpenTrafficSim License</a>.
      * <p>
      * @version $Revision$, $LastChangedDate$, by $Author$, initial version Jun 30, 2016 <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>
      */
     private enum StopPhase
     {
         /** Approaching stop intersection. */
         APPROACH,
 
         /** Yielding for stop intersection. */
         YIELD,
 
         /** Running over stop intersection. */
         RUN;
     }
 
 }