import display.*;

//The class that the students will fill up with the correct algorithm.

public class Bresenham {

    /*
      Inputs: x1, y1, x2 and y2 -- the endpoints of the line. The line
				   stretches from (x1, y1) to (x2, y2)
              Grid view         -- an object representing the display

      Outputs: none, just draw the line

      Something useful: in order to draw the line, you must set a
	 	 	series of individual pixels. You can do this
	 	 	by making a call to the setPixel method of the
	 	 	Grid object. In other words, the command
	 	 	         view.setPixel(3,4); 
			would turn the pixel at position (3, 4) black.


      NOTE: If you want to have any auxiliary methods (helpers), you
	    must make sure to declare them "static" as well.

     */
    public static void BresenhamAlgorithm(int x1, int y1, 
					  int x2, int y2, Grid view) {

        int x = x1, y = y1,

	    dx = ( x2 - x1 ),
	    dy = ( y2 - y1 ),

	    e = (2 * dy) - dx,

	    twoDy   = 2 * dy,
	    twoDyDx = 2 * (dy - dx);

	while ( x <= x2 ) {
	    view.setPixel( x, y );  x++;
	    if ( e > 0 ) {
		e += twoDyDx;  y++; /* step x and y */
	    }
	    else
		e += twoDy; /* step only y */
	}
	//For debugging:
	System.out.println("Entering BresenhamAlgorithm");
    }
}