package org.opentrafficsim.road.gtu.lane.tactical.following;
   
   import java.io.Serializable;
   
   import org.djunits.unit.AccelerationUnit;
   import org.djunits.unit.DurationUnit;
   import org.djunits.unit.LengthUnit;
   import org.djunits.unit.SpeedUnit;
   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.opentrafficsim.base.parameters.ParameterException;
  import org.opentrafficsim.base.parameters.Parameters;
  import org.opentrafficsim.road.gtu.lane.perception.PerceptionIterable;
  import org.opentrafficsim.road.gtu.lane.perception.headway.Headway;
  import org.opentrafficsim.road.network.speed.SpeedLimitInfo;
  import org.opentrafficsim.road.network.speed.SpeedLimitTypes;
  
  /**
   * IDMPlus implements the <i>Integrated Lane Change Model with Relaxation and Synchronization</i> as published by Wouter J.
   * Schakel, Bart van Arem, Member, IEEE, and Bart D. Netten. 2012. <br>
   * There are two nasty type setting errors in equation 7 in this published version of the paper. Both times an equals sign
   * (<cite>=</cite>) after <cite>a<sub>gain</sub></cite> should <b>not</b> be there.
   * <p>
   * Copyright (c) 2013-2018 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>
   * @version $Revision: 1408 $, $LastChangedDate: 2015-09-24 15:17:25 +0200 (Thu, 24 Sep 2015) $, by $Author: pknoppers $,
   *          initial version Jul 4, 2014 <br>
   * @author <a href="http://www.tudelft.nl/pknoppers">Peter Knoppers</a>
   */
  public class IDMPlusOld extends AbstractGTUFollowingModelMobil implements Serializable
  {
      /** */
      private static final long serialVersionUID = 20140704L;
  
      /** Preferred net longitudinal distance when stopped [m]. */
      private final Length s0;
  
      /** Longitudinal acceleration [m/s^2]. */
      private Acceleration a;
  
      /** Longitudinal deceleration [m/s^2]. (Should be a positive value even though it is a <b>de</b>celeration.) */
      private final Acceleration b;
  
      /** Safe time headway. */
      private Duration tSafe;
  
      /**
       * Mean speed limit adherence (1.0: mean free speed equals the speed limit; 1.1: mean free speed equals 110% of the speed
       * limit, etc.).
       */
      private double delta;
  
      /**
       * Default step size used by IDMPlus (not defined in the paper, but 0.5s is a reasonable trade-off between computational
       * speed and accuracy).
       */
      private static final Duration DEFAULT_STEP_SIZE = new Duration(0.5, DurationUnit.SECOND);
  
      /**
       * Construct a new IDM+ car following model with reasonable values (reasonable for passenger cars). <br>
       * These values are from <b>Integrated Lane Change Model with Relaxation and Synchronization</b> by Wouter J. Schakel,
       * Victor L. Knoop, and Bart van Arem, published in Transportation Research Record: Journal of the Transportation Research
       * Board, No. 2316, Transportation Research Board of the National Academies, Washington, D.C., 2012, pp. 47–57.
       */
      public IDMPlusOld()
      {
          this.a = new Acceleration(1.56, AccelerationUnit.METER_PER_SECOND_2);
          this.b = new Acceleration(2.09, AccelerationUnit.METER_PER_SECOND_2);
          this.s0 = new Length(3, LengthUnit.METER);
          this.tSafe = new Duration(1.2, DurationUnit.SECOND);
          this.delta = 1d;
      }
  
      /**
       * Construct a new IDMPlus car following model.
       * @param a Acceleration; the maximum acceleration of a stationary vehicle (normal value is 1 m/s/s)
       * @param b Acceleration; the maximum deemed-safe deceleration (this is a positive value)
       * @param s0 Length; the minimum stationary headway
       * @param tSafe Duration; the minimum time-headway
       * @param delta double; the speed limit adherence (1.0; mean free speed equals the speed limit; 1.1: mean free speed equals
       *            110% of the speed limit; etc.)
       */
      public IDMPlusOld(final Acceleration a, final Acceleration b, final Length s0, final Duration tSafe, final double delta)
      {
          this.a = a;
          this.b = b;
          this.s0 = s0;
          this.tSafe = tSafe;
          this.delta = delta;
      }
  
      /**
       * Desired speed (taking into account the urge to drive a little faster or slower than the posted speed limit).
       * @param speedLimit DoubleScalarAbs&lt;SpeedUnit&gt;; the speed limit
       * @param followerMaximumSpeed Speed; the maximum speed that the follower can drive
       * @return DoubleScalarRel&lt;SpeedUnit&gt;; the desired speed
      */
     private Speed vDes(final Speed speedLimit, final Speed followerMaximumSpeed)
     {
         return new Speed(Math.min(this.delta * speedLimit.getSI(), followerMaximumSpeed.getSI()), SpeedUnit.SI);
     }
 
     /** {@inheritDoc} */
     @Override
     public final Acceleration computeAcceleration(final Speed followerSpeed, final Speed followerMaximumSpeed,
             final Speed leaderSpeed, final Length headway, final Speed speedLimit)
     {
         return computeAcceleration(followerSpeed, followerMaximumSpeed, leaderSpeed, headway, speedLimit, DEFAULT_STEP_SIZE);
     }
 
     /** {@inheritDoc} */
     @Override
     public final Acceleration computeAcceleration(final Speed followerSpeed, final Speed followerMaximumSpeed,
             final Speed leaderSpeed, final Length headway, final Speed speedLimit, final Duration stepSize)
     {
         // TODO maxDistance
         double leftComponent = 1 - Math.pow(followerSpeed.getSI() / vDes(speedLimit, followerMaximumSpeed).getSI(), 4);
         if (Double.isNaN(leftComponent))
         {
             leftComponent = 0;
         }
         // limit deceleration for free term (= leftComponent)
         if (leftComponent * this.a.si < -0.5)
         {
             leftComponent = -0.5 / this.a.si;
         }
         Acceleration logWeightedAccelerationTimes2 =
                 new Acceleration(Math.sqrt(this.a.getSI() * this.b.getSI()), AccelerationUnit.SI).multiplyBy(2);
         // don't forget the times 2
 
         Speed dV = followerSpeed.minus(leaderSpeed);
         Length sStar = this.s0.plus(followerSpeed.multiplyBy(this.tSafe))
                 .plus(dV.multiplyBy(followerSpeed.divideBy(logWeightedAccelerationTimes2)));
 
         /*-
         this.s0.plus(Calc.speedTimesTime(followerSpeed, this.tSafe)).plus(
         Calc.speedTimesTime(dV, Calc.speedDividedByAcceleration(followerSpeed, logWeightedAccelerationTimes2)));
          */
         if (sStar.getSI() < 0)
         {
             // Negative value should be treated as 0? This is NOT in the LMRS paper
             // Without this "fix" a higher speed of the leader may cause a lower acceleration (which is crazy)
             sStar = new Length(0, LengthUnit.SI);
         }
 
         double rightComponent = 1 - Math.pow(sStar.getSI() / headway.getSI(), 2);
         Acceleration newAcceleration = new Acceleration(this.a).multiplyBy(Math.min(leftComponent, rightComponent));
         if (newAcceleration.getSI() * stepSize.getSI() + followerSpeed.getSI() < 0)
         {
             newAcceleration = new Acceleration(-followerSpeed.getSI() / stepSize.getSI(), AccelerationUnit.SI);
         }
         return newAcceleration;
     }
 
     /** {@inheritDoc} */
     @Override
     public final Duration getStepSize()
     {
         return DEFAULT_STEP_SIZE;
     }
 
     /** {@inheritDoc} */
     @Override
     public final Acceleration getMaximumSafeDeceleration()
     {
         return this.b;
     }
 
     /** {@inheritDoc} */
     @Override
     public final String getName()
     {
         return "IDM+";
     }
 
     /** {@inheritDoc} */
     @Override
     public final String getLongName()
     {
         return String.format("%s (a=%.1fm/s\u00b2, b=%.1fm/s\u00b2, s0=%.1fm, tSafe=%.1fs, delta=%.2f)", getName(),
                 this.a.getSI(), this.b.getSI(), this.s0.getSI(), this.tSafe.getSI(), this.delta);
     }
 
     /** {@inheritDoc} */
     @Override
     public final void setA(final Acceleration a)
     {
         this.a = a;
     }
 
     /** {@inheritDoc} */
     @Override
     public final void setT(final Duration t)
     {
         this.tSafe = t;
     }
 
     /** {@inheritDoc} */
     @Override
     public final void setFspeed(final double fSpeed)
     {
         this.delta = fSpeed;
     }
 
     // The following is inherited from CarFollowingModel
 
     /** {@inheritDoc} */
     @Override
     public final Speed desiredSpeed(final Parameters parameters, final SpeedLimitInfo speedInfo) throws ParameterException
     {
         throw new UnsupportedOperationException("Old car-following model does not support desired speed.");
     }
 
     /** {@inheritDoc} */
     @Override
     public final Length desiredHeadway(final Parameters parameters, final Speed speed) throws ParameterException
     {
         throw new UnsupportedOperationException("Old car-following model does not support desired headway.");
     }
 
     /** {@inheritDoc} */
     @Override
     public final Acceleration followingAcceleration(final Parameters parameters, final Speed speed,
             final SpeedLimitInfo speedInfo, final PerceptionIterable<? extends Headway> leaders) throws ParameterException
     {
         Length headway;
         Speed leaderSpeed;
         if (leaders.isEmpty())
         {
             headway = new Length(Double.MAX_VALUE, LengthUnit.SI);
             leaderSpeed = speed;
         }
         else
         {
             Headway leader = leaders.first();
             headway = leader.getDistance();
             leaderSpeed = leader.getSpeed();
         }
         return this.computeAcceleration(speed, speedInfo.getSpeedInfo(SpeedLimitTypes.MAX_VEHICLE_SPEED), leaderSpeed, headway,
                 speedInfo.getSpeedInfo(SpeedLimitTypes.FIXED_SIGN));
     }
 
     /** {@inheritDoc} */
     @Override
     public final String toString()
     {
         return "IDMPlusOld [s0=" + this.s0 + ", a=" + this.a + ", b=" + this.b + ", tSafe=" + this.tSafe + ", delta="
                 + this.delta + ", stepSize=" + DEFAULT_STEP_SIZE + "]";
     }
 
 }