using System;
using System.Collections.Generic;

namespace Assets.Common
{
    public static class PointUtils
    {
        public static Point Mean(IEnumerable<Point> points)
        {
            var result = new Point(0, 0);
            var i = 0;

            foreach (var point in points)
            {
                result.x = (result.x * i + point.x) / (i + 1);
                result.y = (result.y * i + point.y) / (i + 1);
                
                i++;
            }

            return result;
        }

        public static double AngleBetween(Point center, Point a, Point b)
        {
            a = a - center;
            b = b - center;

            return Math.Acos((a.x*b.x+a.y*b.y)/(a.Length * b.Length));
        }

        public static bool IsClockwise(Point center, Point a, Point b)
        {
            var xa = a.x - center.x;
            var xb = b.x - center.x;
            var ya = a.y - center.y;
            var yb = b.y - center.y;

            return xa * yb - xb * ya < 0;
        }

        public static bool IsPointInside(Point point, Point[] polygon)
        {
            var j = polygon.Length - 1;
            var inside = false;

            for (int i = 0; i < polygon.Length; j = i++)
            {
                var pi = polygon[i];
                var pj = polygon[j];

                if (((pi.y <= point.y && point.y < pj.y) || (pj.y <= point.y && point.y < pi.y)) &&
                    (point.x < (pj.x - pi.x) * (point.y - pi.y) / (pj.y - pi.y) + pi.x))
                    inside = !inside;
            }

            return inside;
        }
    }
}