package lab03;

import java.util.Arrays;
import java.util.HashSet;

import javafx.geometry.Point2D;

public class ConvexHull {

    public static HashSet<Point2D> bruteForceConvexHull( Point2D[] listPoints ) {

        HashSet<Point2D> vertices = new HashSet<>();

        boolean foundProblem = false;
        Point2D firstPoint;
        Point2D secondPoint;
        Point2D thirdPoint;
        for (int i = 0 ; i< listPoints.length-2; ++i) {

            for (int j = i+1 ; j< listPoints.length-1; ++j ) {

                double initialSign = 0.0;

                firstPoint= listPoints[i];
                secondPoint = listPoints[j];

                double a = secondPoint.getY() - firstPoint.getY();
                double b = firstPoint.getX() - secondPoint.getX();
                double c = firstPoint.getX()*secondPoint.getY() - firstPoint.getY() * secondPoint.getX();

                foundProblem = false;

                for (int k= 0; k< listPoints.length && (!listPoints[k].equals(firstPoint) || !listPoints[k].equals(secondPoint)); ++k) {

                    thirdPoint = listPoints[k];

                    double check = a*thirdPoint.getX() + b*thirdPoint.getY() - c;


                    if( initialSign != 0.0  ) {
                        if( ( check>0 && initialSign < 0 )  || (check <0 && initialSign >0)) {
                            foundProblem = true;
                            break;
                        }
                    }else {
                        initialSign = (check > 0) ? 1:-1;
                    }
                }

                if (!foundProblem) {
                    vertices.add(firstPoint);
                    vertices.add(secondPoint);
                }


            }

        }


        return vertices;

    }

    public static void main(String[] args) {

        System.out.println("Hi");
        Point2D[] pointsTest = new Point2D[] {
                new Point2D(1.0, 1.0),
                new Point2D(1.0, 0.5),
                new Point2D(2.0, 1.0),
                new Point2D(5.0, 2.0),
                new Point2D(4.0, 2.0)
        };

        System.out.println(Arrays.toString(pointsTest));

        HashSet<Point2D> vertices = bruteForceConvexHull(pointsTest);
        for (Point2D point: vertices) {
            System.out.println(point.toString());
        }

    }

}