import java.awt.Graphics;

public class HalfSpace
{
	public double a;
	public double b;
	public double c;
	public Segment s;
	
	public HalfSpace(Segment s) {
		// here i compute the coefficients of line a*x + b*y + c = 0
		// the line contains segment <s>
		this.s = s;
		this.a = s.q.y - s.p.y;
		this.b = s.p.x - s.q.x;
		// average c so there is no bias towards any of the vertices
		this.c = -0.5*(a*(s.p.x + s.q.x) + b*(s.p.y + s.q.y));
	}
	
	public void draw(Graphics g) {
		g.drawLine((int)s.p.x, (int)s.p.y, (int)s.q.x, (int)s.q.y);
	}
	
	public int eval(Vertex v) {
		// classify the vertex <v> wrt <this> taking in account EPSILON
		double d = a*v.x + b*v.y + c;
		if (d > Parameters.EPSILON)
			return Parameters.IN_FRONT;
		else if (d < -Parameters.EPSILON)
			return Parameters.IN_BACK;
		else
			return Parameters.COINCIDENT;
	}
	
	public int eval(Segment s) {
		// this is a hack that does the classification of <s>
		// by combining the classifications of <s>'s endpoints
		int e1 = eval(s.p);
		int e2 = eval(s.q);
		return (e1 == e2) ? e1 : e1 + e2;
	}
}