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) {


	LineSegment ls = new LineSegment();
	    ls.x1 = 0.0;
	    ls.y1 = 0.0;
	    ls.x2 = 0.0;
	    ls.y2 = 0.0;
	    ls.setClipType("external");

	int     code1, code2, tmpCod;
	boolean done = false;
	double  tmpEnd, m = 0;

	while ( !done ) {
	    /* update both outcodes on each iteration */
	    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 ) { /* trivially accept */
		ls.setClipType("internal");
		done = true;
	    }
	    else if ( (code1 & code2) != 0 ) { /* trivially reject */
		ls.setClipType("external");
		done = true;
	    }
	    else {
		ls.setClipType("clipped");
	        if ( code1 != 0 ) {
		    /* pt1 is outside center; swap pts so pt2 is outside */
		    tmpEnd = x1;  x1 = x2;  x2 = tmpEnd;
		    tmpEnd = y1;  y1 = y2;  y2 = tmpEnd;
		    tmpCod = code1;  code1 = code2;  code2 = tmpCod;
		}
		if ( x2 != x1 )
		    /* don't want to divide by 0 */
		    m = (y2 - y1) / (x2 - x1);
		if ( (code2 & LEFT) != 0 ) {
		    y1 += (vp.left - x1) * m;
		    x1 = vp.left;
		}
		else if ( (code2 & RIGHT) != 0 ) {
		    y1 += (vp.right - x1) * m;
		    x1 = vp.right;
		}
		else if ( (code2 & BOTTOM) != 0 ) {
		    /* only update x1 if line is not vertical */
		    if ( x2 != x1 )
		        x1 += (vp.bottom - y1) / m;
		    y1 = vp.bottom;
		}
		else if ( (code2 & TOP) != 0 ) {
		    if ( x2 != x1 )
		        x1 += (vp.top - y1) / m;
		    y1 = vp.top;
		}
	    }
	}
	//for debugging:
	System.out.println("Entering Cohen-Sutherland");

	ls.setEndPoints( x1, y1, x2, y2 );
	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 += LEFT;
	else if ( x > right )
	    result += RIGHT;

	if ( y < bottom )
	    result += BOTTOM;
	else if ( y > top )
	    result += TOP;

	return result;
    }	
}