package org.opentrafficsim.road.gtu.lane.tactical.following;
   
   import static org.opentrafficsim.base.parameters.constraint.NumericConstraint.POSITIVE;
   
   import org.djunits.unit.AccelerationUnit;
   import org.djunits.value.vdouble.scalar.Acceleration;
   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.ParameterTypeInteger;
  import org.opentrafficsim.base.parameters.Parameters;
  import org.opentrafficsim.road.gtu.lane.perception.PerceptionIterable;
  import org.opentrafficsim.road.gtu.lane.perception.headway.Headway;
  
  /**
   * <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 Apr 22, 2016 <br>
   * @author <a href="http://www.transport.citg.tudelft.nl">Wouter Schakel</a>
   */
  
  public class IDMPlusMulti extends AbstractIDM
  {
  
      /** Number of leaders considered parameter. */
      public static final ParameterTypeInteger NLEADERS =
              new ParameterTypeInteger("nLeaders", "Number of leaders in car-following model.", 2, POSITIVE);
  
      /**
       * Default constructor using default models for desired headway and desired speed.
       */
      public IDMPlusMulti()
      {
          super(HEADWAY, DESIRED_SPEED);
      }
  
      /**
       * Constructor with modular models for desired headway and desired speed.
       * @param desiredHeadwayModel DesiredHeadwayModel; desired headway model
       * @param desiredSpeedModel DesiredSpeedModel; desired speed model
       */
      public IDMPlusMulti(final DesiredHeadwayModel desiredHeadwayModel, final DesiredSpeedModel desiredSpeedModel)
      {
          super(desiredHeadwayModel, desiredSpeedModel);
      }
  
      /** {@inheritDoc} */
      @Override
      public final String getName()
      {
          return "IDM+multi";
      }
  
      /** {@inheritDoc} */
      @Override
      public final String getLongName()
      {
          return "Intelligent Driver Model+ with multi-leader anticipation.";
      }
  
      /** {@inheritDoc} */
      @Override
      protected final Acceleration combineInteractionTerm(final Acceleration aFree, final Parameters parameters,
              final Speed speed, final Speed desiredSpeed, final Length desiredHeadway,
              final PerceptionIterable<? extends Headway> leaders) throws ParameterException
      {
          Acceleration a = parameters.getParameter(A);
          double aIntMulti = Double.POSITIVE_INFINITY;
          int i = 1;
          double cumulVehicleLengths = 0;
          int n = parameters.getParameter(NLEADERS);
          for (Headway leader : leaders)
          {
              // desired headway is scaled to the i'th leader
              // current headway is the sum of net headways (i.e. vehicle lengths of vehicles in between are subtracted)
              double sRatio = dynamicDesiredHeadway(parameters, speed, desiredHeadway.multiplyBy(i), leader.getSpeed()).si
                      / (leader.getDistance().si - cumulVehicleLengths);
              double aIntSingle = a.si * (1 - sRatio * sRatio);
              aIntMulti = aIntMulti < aIntSingle ? aIntMulti : aIntSingle;
              i++;
              if (i > n)
              {
                  break;
              }
              cumulVehicleLengths += leader.getLength().si;
          }
          return new Acceleration(aIntMulti < aFree.si ? aIntMulti : aFree.si, AccelerationUnit.SI);
      }
  
  }