package org.opentrafficsim.road.gtu.lane.perception;
   
   import java.io.Serializable;
   
   import org.djutils.exceptions.Throw;
   import org.opentrafficsim.core.network.LateralDirectionality;
   
   /**
    * Defines a lane relative to the current lane.
   * <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 May 2, 2016 <br>
   * @author <a href="http://www.transport.citg.tudelft.nl">Wouter Schakel</a>
   */
  public class RelativeLane implements Comparable<RelativeLane>, Serializable
  {
  
      /** */
      private static final long serialVersionUID = 20160502L;
  
      /** Second left lane. */
      public static final RelativeLane SECOND_LEFT = new RelativeLane(LateralDirectionality.LEFT, 2);
  
      /** Left lane. */
      public static final RelativeLane LEFT = new RelativeLane(LateralDirectionality.LEFT, 1);
  
      /** Current lane. */
      public static final RelativeLane CURRENT = new RelativeLane(LateralDirectionality.NONE, 0);
  
      /** right lane. */
      public static final RelativeLane RIGHT = new RelativeLane(LateralDirectionality.RIGHT, 1);
  
      /** Second right lane. */
      public static final RelativeLane SECOND_RIGHT = new RelativeLane(LateralDirectionality.RIGHT, 2);
  
      /** Lateral direction. */
      private final LateralDirectionality lat;
  
      /** Number of lanes to lateral direction. */
      private final int numLanes;
  
      /** Rank, for sorting. Is equal to number of lanes, but negative for left lanes. */
      private final int rank;
  
      /**
       * Constructor.
       * @param lat LateralDirectionality; lateral direction (use {@code null} for the current lane)
       * @param numLanes int; number of lanes in the lateral direction (not important for the current lane)
       * @throws IllegalArgumentException if numLanes is not at least 1, except if {@code lat == null} (current lane)
       * @throws IllegalArgumentException if numLanes is not 0 if {@code lat == null} (current lane)
       */
      public RelativeLane(final LateralDirectionality lat, final int numLanes)
      {
          Throw.whenNull(lat, "Lateral directionality may not be null.");
          Throw.when(lat.isNone() && numLanes != 0, IllegalArgumentException.class,
                  "Number of lanes must be zero if the lateral directionality is NONE.");
          Throw.when(numLanes < 0, IllegalArgumentException.class,
                  "Relative lane with %d lanes in %s direction is not allowed, use values > 0.", numLanes, lat);
          this.lat = lat;
          this.numLanes = numLanes;
          this.rank = lat.isLeft() ? -numLanes : numLanes;
      }
  
      /**
       * Returns the lateral direction.
       * @return lat lateral direction
       */
      public final LateralDirectionality getLateralDirectionality()
      {
          return this.lat;
      }
  
      /**
       * Returns the number of lanes in the lateral direction.
       * @return number of lanes in the lateral direction
       */
      public final int getNumLanes()
      {
          return this.numLanes;
      }
  
      /**
       * Returns whether the second left lane is referred to.
       * @return whether the second left lane is referred to
       */
      public final boolean isSecondLeft()
      {
          return this.equals(SECOND_LEFT);
      }
  
      /**
       * Returns whether the left lane is referred to.
       * @return whether the left lane is referred to
       */
      public final boolean isLeft()
      {
          return this.equals(LEFT);
     }
 
     /**
      * Returns whether the current lane is referred to.
      * @return whether the current lane is referred to
      */
     public final boolean isCurrent()
     {
         return this.equals(CURRENT);
     }
 
     /**
      * Returns whether the right lane is referred to.
      * @return whether the right lane is referred to
      */
     public final boolean isRight()
     {
         return this.equals(RIGHT);
     }
 
     /**
      * Returns whether the second right lane is referred to.
      * @return whether the second right lane is referred to
      */
     public final boolean isSecondRight()
     {
         return this.equals(SECOND_RIGHT);
     }
 
     /**
      * Returns the left hand relative lane of this relative lane.
      * @return left hand relative lane of this relative lane.
      */
     public final RelativeLane getLeft()
     {
         return this.add(LEFT);
     }
 
     /**
      * Returns the right hand relative lane of this relative lane.
      * @return right hand relative lane of this relative lane.
      */
     public final RelativeLane getRight()
     {
         return this.add(RIGHT);
     }
 
     /**
      * Returns the relative lane relative to this lane, for example "the left lane" of "the 3rd right lane" is "the 2nd right
      * lane".
      * @param relativeLane RelativeLane; relative lane to get of this lane
      * @return relative lane relative to this lane
      */
     public final RelativeLane add(final RelativeLane relativeLane)
     {
         int rankSum = this.rank + relativeLane.rank;
         if (rankSum < 0)
         {
             return new RelativeLane(LateralDirectionality.LEFT, -rankSum);
         }
         if (rankSum > 0)
         {
             return new RelativeLane(LateralDirectionality.RIGHT, rankSum);
         }
         return CURRENT;
     }
 
     /** {@inheritDoc} */
     @Override
     public int hashCode()
     {
         final int prime = 31;
         int result = 1;
         result = prime * result + this.rank;
         return result;
     }
 
     /** {@inheritDoc} */
     @Override
     public boolean equals(final Object obj)
     {
         if (this == obj)
         {
             return true;
         }
         if (obj == null)
         {
             return false;
         }
         if (getClass() != obj.getClass())
         {
             return false;
         }
         RelativeLane other = (RelativeLane) obj;
         if (this.rank != other.rank) // relative lane us uniquely defined by the rank
         {
             return false;
         }
         return true;
     }
 
     /** {@inheritDoc} */
     @Override
     public final String toString()
     {
         if (this.equals(CURRENT))
         {
             return "RelativeLane [CURRENT]";
         }
         return new StringBuilder("RelativeLane [").append(this.lat).append(", ").append(this.numLanes).append("]").toString();
     }
 
     /** {@inheritDoc} */
     @Override
     public final int compareTo(final RelativeLane rel)
     {
         return this.rank - rel.rank;
     }
 
 }