package nl.tudelft.simulation.language.d2;
   
   import java.awt.geom.Line2D;
   import java.awt.geom.Point2D;
   
   /**
    * A directional line with normal vector. Based on the BSPLine-example from the book Developing games in Java from David
    * Brackeen. 
    * <p>
   * Copyright (c) 2003-2024 Delft University of Technology, Jaffalaan 5, 2628 BX Delft, the Netherlands. All rights reserved. See
   * for project information <a href="https://simulation.tudelft.nl/" target="_blank"> https://simulation.tudelft.nl</a>. The DSOL
   * project is distributed under a three-clause BSD-style license, which can be found at
   * <a href="https://https://simulation.tudelft.nl/dsol/docs/latest/license.html" target="_blank">
   * https://https://simulation.tudelft.nl/dsol/docs/latest/license.html</a>.
   * </p>
   * @author <a href="mailto:royc@tbm.tudelft.nl">Roy Chin </a>
   */
  public class DirectionalLine extends Line2D.Double
  {
      /** the default serialVersionUId. */
      private static final long serialVersionUID = 1L;
  
      /** different values for the side a point can be at w.r.t. the line. */
      public enum Side
      {
          /** point at the back of the line. */
          BACKSIDE(-1),
  
          /** point collinear with the line. */
          COLLINEAR(0),
  
          /** point in front of the line. */
          FRONTSIDE(1),
  
          /** other line is spanning this line. */
          SPANNING(2);
      
          /** the value from DSOL-1 before enum was introduced. */
          private final int value;
          
          /**
           * Create a side; store the value from DSOL-1 as well.
           * @param value int; the value from DSOL-1 before enum was introduced
           */
          Side(final int value)
          {
              this.value = value;
          }
  
          /**
           * Returns the value from DSOL-1 before enum was introduced.
           * @return int; the value from DSOL-1 before enum was introduced
           */
          public int getValue()
          {
              return this.value;
          }
      }
  
      /** the thickness of the line. */
      private double lineThickness = 1;
  
      /** x coordinate of the line normal. */
      private double normalX;
  
      /** y coordinate of the line normal. */
      private double normalY;
  
      /**
       * Creates a new DirectionalLine based on the specified coordinates.
       * @param x1 double; Coordinate x1
       * @param y1 double; Coordinate y1
       * @param x2 double; Coordinate x2
       * @param y2 double; Coordinate y2
       */
      public DirectionalLine(final double x1, final double y1, final double x2, final double y2)
      {
          this.setLine(x1, y1, x2, y2);
      }
  
      /**
       * Creates a new DirectionalLine based on the specified (float) coordinates.
       * @param x1 float; Coordinate x1
       * @param y1 float; Coordinate y1
       * @param x2 float; Coordinate x2
       * @param y2 float; Coordinate y2
       */
      public DirectionalLine(final float x1, final float y1, final float x2, final float y2)
      {
          this.setLine(x1, y1, x2, y2);
      }
  
      /**
       * Calculates the normal to this line. The normal of (a, b) is (-b, a).
       */
      public void calcNormal()
      {
          this.normalX = this.y1 - this.y2;
          this.normalY = this.x2 - this.x1;
     }
 
     /**
      * Normalizes the normal of this line (make the normal's length 1).
      */
     public void normalize()
     {
         double length = Math.sqrt(this.normalX * this.normalX + this.normalY * this.normalY);
         this.normalX /= length;
         this.normalY /= length;
     }
 
     /**
      * Set the line using floats.
      * @param x1 float; x1 coordinate
      * @param y1 float; y1 coordinate
      * @param x2 float; x2 coordinate
      * @param y2 float; y2 coordinate
      */
     public void setLine(final float x1, final float y1, final float x2, final float y2)
     {
         super.setLine(x1, y1, x2, y2);
         this.calcNormal();
     }
 
     /** {@inheritDoc} */
     @Override
     public void setLine(final double x1, final double y1, final double x2, final double y2)
     {
         super.setLine(x1, y1, x2, y2);
         this.calcNormal();
     }
 
     /**
      * Flips this line so that the end points are reversed (in other words, (x1,y1) becomes (x2,y2) and vice versa) and the
      * normal is changed to point the opposite direction.
      */
     public void flip()
     {
         double tx = this.x1;
         double ty = this.y1;
         this.x1 = this.x2;
         this.y1 = this.y2;
         this.x2 = tx;
         this.y2 = ty;
         this.normalX = -this.normalX;
         this.normalY = -this.normalY;
     }
 
     /**
      * Returns true if the endpoints of this line match the endpoints of the specified line. Ignores normal and height values.
      * @param line DirectionalLine; another line
      * @return true if this line's coordinates are equal to the other line's coordinates
      */
     public boolean equalsCoordinates(final DirectionalLine line)
     {
         return (this.x1 == line.x1 && this.x2 == line.x2 && this.y1 == line.y1 && this.y2 == line.y2);
     }
 
     /**
      * Returns true if the endpoints of this line match the endpoints of the specified line, ignoring endpoint order (if the
      * first point of this line is equal to the second point of the specified line, and vice versa, returns true). Ignores
      * normal and height values.
      * @param line DirectionalLine; another line
      * @return true if coordinates match independent of the order
      */
     public boolean equalsCoordinatesIgnoreOrder(final DirectionalLine line)
     {
         return equalsCoordinates(line)
                 || ((this.x1 == line.x2 && this.x2 == line.x1 && this.y1 == line.y2 && this.y2 == line.y1));
     }
 
     /** {@inheritDoc} */
     @Override
     public String toString()
     {
         return "(" + this.x1 + "," + this.y1 + ")->(" + this.x2 + "," + this.y2 + ")";
     }
 
     /**
      * Gets the side of this line the specified point is on. This method treats the line as 1-unit thick, so points within this
      * 1-unit border are considered collinear. For this to work correctly, the normal of this line must be normalized, either by
      * setting this line to a polygon or by calling normalize(). Returns either FRONTSIDE, BACKSIDE, or COLLINEAR.
      * @param x double; coordinate x
      * @param y double; coordinate y
      * @return the side
      */
     public Side getSideThick(final double x, final double y)
     {
         double normalX2 = this.normalX * this.lineThickness;
         double normalY2 = this.normalY * this.lineThickness;
 
         Side frontSide = getSideThin(x - normalX2 / 2, y - normalY2 / 2);
         if (frontSide.equals(Side.FRONTSIDE))
         {
             return Side.FRONTSIDE;
         }
         else if (frontSide.equals(Side.BACKSIDE))
         {
             Side backSide = getSideThin(x + normalX2 / 2, y + normalY2 / 2);
             if (backSide.equals(Side.BACKSIDE))
             {
                 return Side.BACKSIDE;
             }
         }
         return Side.COLLINEAR;
     }
 
     /**
      * Gets the side of this line the specified point is on. Because of doubling point inaccuracy, a collinear line will be
      * rare. For this to work correctly, the normal of this line must be normalized, either by setting this line to a polygon or
      * by calling normalize(). Returns either FRONTSIDE, BACKSIDE, or COLLINEAR.
      * @param x double; coordinate x
      * @param y double; coordinate y
      * @return the side
      */
     public Side getSideThin(final double x, final double y)
     {
         // dot product between vector to the point and the normal
         double side = (x - this.x1) * this.normalX + (y - this.y1) * this.normalY;
         if (side < 0)
         {
             return Side.BACKSIDE;
         }
         else if (side > 0)
         {
             return Side.FRONTSIDE;
         }
         else
         {
             return Side.COLLINEAR;
         }
     }
 
     /**
      * Gets the side of this line that the specified line segment is on. Returns either FRONT, BACK, COLINEAR, or SPANNING.
      * @param line Line2D.Double; line segment
      * @return the side
      */
     public Side getSide(final Line2D.Double line)
     {
         if (this.x1 == line.x1 && this.x2 == line.x2 && this.y1 == line.y1 && this.y2 == line.y2)
         {
             return Side.COLLINEAR;
         }
         Side p1Side = getSideThick(line.x1, line.y1);
         Side p2Side = getSideThick(line.x2, line.y2);
         if (p1Side == p2Side)
         {
             return p1Side;
         }
         else if (p1Side == Side.COLLINEAR)
         {
             return p2Side;
         }
         else if (p2Side == Side.COLLINEAR)
         {
             return p1Side;
         }
         else
         {
             return Side.SPANNING;
         }
     }
 
     /**
      * Returns the fraction of intersection along this line. Returns a value from 0 to 1 if the segments intersect. For example,
      * a return value of 0 means the intersection occurs at point (x1, y1), 1 means the intersection occurs at point (x2, y2),
      * and .5 mean the intersection occurs halfway between the two endpoints of this line. Returns -1 if the lines are parallel.
      * @param line Line2D.Double; a line
      * @return the intersection
      */
     public double getIntersection(final Line2D.Double line)
     {
         // The intersection point I, of two vectors, A1->A2 and
         // B1->B2, is:
         // I = A1 + Ua * (A2 - A1)
         // I = B1 + Ub * (B2 - B1)
         //
         // Solving for Ua gives us the following formula.
         // Ua is returned.
         double denominator = (line.y2 - line.y1) * (this.x2 - this.x1) - (line.x2 - line.x1) * (this.y2 - this.y1);
 
         // check if the two lines are parallel
         if (denominator == 0)
         {
             return -1;
         }
 
         double numerator = (line.x2 - line.x1) * (this.y1 - line.y1) - (line.y2 - line.y1) * (this.x1 - line.x1);
 
         return numerator / denominator;
     }
 
     /**
      * Returns the intersection point of this line with the specified line.
      * @param line Line2D.Double; a line
      * @return intersection point
      */
     public Point2D.Double getIntersectionPoint(final Line2D.Double line)
     {
         double fraction = getIntersection(line);
         Point2D.Double intersection = new Point2D.Double();
         intersection.setLocation(this.x1 + fraction * (this.x2 - this.x1), this.y1 + fraction * (this.y2 - this.y1));
         return intersection;
     }
 
     /**
      * Gets the thickness of the line.
      * @return returns the lineThickness
      */
     public double getLineThickness()
     {
         return this.lineThickness;
     }
 
     /**
      * Sets the thickness of the line.
      * @param lineThickness double; the lineThickness to set
      */
     public void setLineThickness(final double lineThickness)
     {
         this.lineThickness = lineThickness;
     }
 
     /**
      * @return returns the normalX
      */
     public double getNormalx()
     {
         return this.normalX;
     }
 
     /**
      * @return returns the normalY
      */
     public double getNormaly()
     {
         return this.normalY;
     }
 }