package model;

public class CollisionDetector {
		
	public static boolean figuresCollide(MovingFigure f1, MovingFigure f2) {
		if(f1 instanceof MovingCircle && f2 instanceof MovingCircle) return circlesCollide( (MovingCircle) f1, (MovingCircle) f2);
		if(f1 instanceof MovingSquare && f2 instanceof MovingSquare) return squaresCollide( (MovingSquare) f1, (MovingSquare) f2);
		if(f1 instanceof MovingCircle && f2 instanceof MovingSquare) return circleAndSquareCollide((MovingCircle) f1, (MovingSquare) f2);
		if(f1 instanceof MovingSquare && f2 instanceof MovingCircle) return circleAndSquareCollide((MovingCircle) f2, (MovingSquare) f1);
		else throw new IllegalArgumentException("Unsupported classes"); 
	}
	
	private static boolean circlesCollide(MovingCircle c1, MovingCircle c2){
		float centerDistance = distanceBetweenPoints(c1.getPosX(), c1.getPosY(), c2.getPosX(), c2.getPosY());						
		float radiusDistance = c1.getRadius() + c2.getRadius(); 
		return centerDistance <= radiusDistance;
	}
	
	private static boolean squaresCollide(MovingSquare s1, MovingSquare s2) {
		if( s1.getPosY2() < s2.getPosY()  ) return false;
		if( s1.getPosX2() < s2.getPosX()  ) return false;
		if( s1.getPosY()  > s2.getPosY2() ) return false;
		if( s1.getPosX()  > s2.getPosX2() ) return false;
		return true;
	}
	
	private static boolean circleAndSquareCollide(MovingCircle c, MovingSquare s) {
		int x1 = s.getPosX();
		int y1 = s.getPosY();
		int x2 = s.getPosX2();
		int y2 = s.getPosY2();
		if( c.getPosX() > x1 && c.getPosX() < x2 && c.getPosY() > y1 && c.getPosY() < y2) return true;
		if( lineIntersectsWithCircle(x1, y1, x2, y1, c)) return true;
		if( lineIntersectsWithCircle(x2, y1, x2, y2, c)) return true;
		if( lineIntersectsWithCircle(x1, y2, x2, y2, c)) return true;
		if( lineIntersectsWithCircle(x1, y1, x1, y2, c)) return true;
		return false;
	}
	
	private static float distanceBetweenPoints(int posX1, int posY1, int posX2, int posY2) {
		int dx = posX2 - posX1;
		int dy = posY2 - posY1;
		int d2 = dx*dx + dy*dy;
		return (float) Math.sqrt((int) d2);
	}
	
	private static boolean lineIntersectsWithCircle(int x1, int y1, int x2, int y2, MovingCircle c) {
		int dx = x2 - x1;
		int dy = y2 - y1;
		dx -= c.getPosX(); //offset
		dy -= c.getPosY(); //offset
		double dr = Math.sqrt(dx*dx + dy*dy);
		double D = x1*y2 - x2*y1;
		double incidence = Math.pow(c.getRadius(), 2) * Math.pow(dr, 2) - Math.pow(D, 2); // r²dr² - D²
		return incidence >= 0;
	}
	
	private static int sgn(int x) { 
		if ( x < 0 ) return -1;
		return 1;
	}
}