import display.*;

public class CohenSutherland {

    public static final int LEFT = 1;
    public static final int RIGHT = 2;
    public static final int TOP = 4;
    public static final int BOTTOM = 8;
    
    /*
      Inputs: the original line from (x1,y1) to (x2,y2), and a
      viewport The viewport object has four public instance variables,
      which can be accessed by: 
      var1 = viewport.top; 
      var2 = viewport.bottom; 
      var3 = viewport.left; 
      var4 = viewport.right;

      Output: a LineSegment object 
            You can create a LineSegment object by making the call
			      LineSegment ls = new LineSegment()

            Having created it, you must set five values: 
	    x1, y1, x2, y2    the coordinates of each of the
                              endpoints of the clipped line You set
                              these values by including the line
                              ls.setEndPoints(x1, y1, x2, y2); 
			      or alternatively, by setting each of
                              the endpoints individually: 
			      ls.x1 = x1;
                              ls.y1 = y1; 
			      etc.

	    clipType          The clip type can be set to three
	                      values:

			      "internal" if the input line segment
			      falls entirely within the clip region,
			      otherwise:

                              "clipped" if it was determined that
                              some part of the input line segment does
                              fall within the boundaries defined by the
                              clip region, otherwise:

			      "external" if NO part of the input
			      line segment falls within the clip region
			      (i.e. the entire line was clipped.)
                              
			      You can set these values by including
			      the java statements:
                                    ls.setClipType("internal");
			      OR
                                    ls.setClipType("clipped");
                              OR
                                    ls.setClipType("external");
    
	NOTE: If you want to have any auxiliary methods (helpers), you
	must make sure to declare them "static" as well.
    */

    public static LineSegment ClipSegment(double x1, double y1, 
				       double x2, double y2, 
				       Viewport vp) {

        int code1, code2;
	boolean done = false;
	boolean draw = false;
	
	LineSegment ls = new LineSegment();
	ls.x1 = 0.0;
	ls.y1 = 0.0;
	ls.x2 = 0.0;
	ls.y2 = 0.0;
	ls.setClipType("internal");

	double m = 0;

	while (!done) {
	    code1 = outcode(x1, y1, vp.top, vp.bottom, vp.left,
			    vp.right);
	    code2 = outcode(x2, y2, vp.top, vp.bottom, vp.left,
			    vp.right);
	    if ((code1|code2) == 0) {
		done = true;
		draw = true;
	    }
	    else {
		if ((code1&code2) != 0) {
		    done = true;
		    ls.setClipType("external");
		}
		else {
		    ls.setClipType("clipped");
		    if (code1 == 0) {  // p1 is inside window
			double temp = x1;
			x1 = x2;
			x2 = temp;
			temp = y1;
			y1 = y2;
			y2 = temp;
			int temp2 = code1;
			code1 = code2;
			code2 = temp2;
		    }
		    if (x2 != x1) {
			m = (y2 - y1)/(x2-x1);
		    }
		    if ((code1 & LEFT) != 0) {
			y1 += (vp.left - x1) *m;
			x1 = vp.left;
		    }
		    else if ((code1 & RIGHT) != 0) {
			y1 += (vp.right - x1)*m;
			x1 = vp.right;
		    }
		    else if ((code1 & BOTTOM) != 0) {
			if (x2 != x1) 
			    x1 += (vp.bottom - y1)/m;
			y1 = vp.bottom;
		    }
		    else if ((code1 & TOP) != 0) {
			if (x2 != x1) {
			    x1 += (vp.top - y1)/m;
			}
			y1 = vp.top;
		    }
		}
	    }
	}
	
	//for debugging:
	System.out.println("Entering Cohen-Sutherland");

	if (draw) {
	    ls.x1 = (x2);
	    ls.x2 = (x1);
	    ls.y1 = (y2);
	    ls.y2 = (y1);
	}

	return ls;
    }

    /*
      This method, given a point (x,y) and some clip region
      boundaries, should produce the binary clip codes for the
      Cohen-Sutherland algorithm.  
    */
    public static int outcode(double x, double y,
			      double top, double bottom, 
			      double left, double right) {

	int result = 0;
	if (x < left) {
	    result = result | LEFT;
	};
	if (x > right) {
	    result = result | RIGHT;
	};
	if (y > top) {
	    result = result | TOP;
	}
	if (y < bottom) {
	    result = result | BOTTOM;
	}
	return result;
    }	
}