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/* Segment.java -- Abstract segment used for BasicStroke

   Copyright (C) 2006 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify

it under the terms of the GNU General Public License as published by

the Free Software Foundation; either version 2, or (at your option)

any later version.

GNU Classpath is distributed in the hope that it will be useful, but

WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

General Public License for more details.

You should have received a copy of the GNU General Public License

along with GNU Classpath; see the file COPYING.  If not, write to the

Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

02110-1301 USA.

Linking this library statically or dynamically with other modules is

making a combined work based on this library.  Thus, the terms and

conditions of the GNU General Public License cover the whole

combination.

As a special exception, the copyright holders of this library give you

permission to link this library with independent modules to produce an

executable, regardless of the license terms of these independent

modules, and to copy and distribute the resulting executable under

terms of your choice, provided that you also meet, for each linked

independent module, the terms and conditions of the license of that

module.  An independent module is a module which is not derived from

or based on this library.  If you modify this library, you may extend

this exception to your version of the library, but you are not

obligated to do so.  If you do not wish to do so, delete this

exception statement from your version. */

package gnu.java.awt.java2d;

import java.awt.geom.Point2D;

public abstract class Segment implements Cloneable

{

  // Start and end points of THIS segment

  public Point2D P1;

  public Point2D P2;

  // Segments can be linked together internally as a linked list

  public Segment first;

  public Segment next;

  public Segment last;

  // Half the stroke width

  protected double radius;

  /**

   * Create a new, empty segment

   */

  public Segment()

  {

    P1 = P2 = null;

    first = this;

    next = null;

    last = this;

  }

  /**

   * Add a segment to the polygon

   * @param newsegment segment to add

   */

  public void add(Segment newsegment)

  {

    newsegment.first = first;

    last.next = newsegment;

    last = last.next.last;

  }

  /**

   * Reverses the orientation of the whole polygon

   */

  public void reverseAll()

  {

    reverse();

    first = last;

    Segment v = next;

    Segment former = this;

    next = null;

    while (v != null)

      {

        v.reverse();

        v.last = this;

        Segment oldnext = v.next;

        v.next = former;

        former = v;

        v = oldnext; // move to the next in list

      }

  }

  public String toString()

  {

    return "Segment:"+P1+", "+P2;

  }

  /**

   * Get the normal vector to the slope of the line.

   * @return vector of length radius, normal to the (x0,y0)-(x1,y1) vector)

   */

  protected double[] normal(double x0, double y0, double x1, double y1)

  {

    double dx = (x1 - x0);

    double dy = (y1 - y0);

    if( dy == 0 )

      {

        dy = radius * ((dx > 0)?1:-1);

        dx = 0;

      }

    else if( dx == 0 )

      {

        dx = radius * ((dy > 0)?-1:1);

        dy = 0;

      }

    else

      {

        double N = Math.sqrt(dx * dx + dy * dy);

        double odx = dx;

        dx = -radius * dy / N;

        dy = radius * odx / N;

      }

    return new double[]{ dx, dy };

  }

  /**

   * Reverse the current segment

   */

  public abstract void reverse();

  /**

   * Get the "top" and "bottom" segments of a segment.

   * First array element is p0 + normal, second is p0 - normal.

   */

  public abstract Segment[] getDisplacedSegments(double radius);

  /**

   * Returns the coordinates of the first control point, or the start point

   * for a line segment.

   */

  public abstract double[] cp1();

  /**

   * Returns the coordinates of the second control point, or the end point

   * for a line segment.

   */

  public abstract double[] cp2();

}