using System.Linq;
using UnityEngine;
using System.Collections;


public static class Matrix4x4Extension {
    public static Vector3 Scale(this Matrix4x4 m) {
        return new Vector3(((Vector3)m.GetColumn(0)).magnitude, ((Vector3)m.GetColumn(1)).magnitude, ((Vector3)m.GetColumn(2)).magnitude);
    }
}


public static class Collider2DExtension {

    public static Vector2 ClosestPointOnBounds(this Collider2D collider, Vector2 point) {
        if (collider is CircleCollider2D) {
            var circle = collider as CircleCollider2D;
            var mat = circle.gameObject.transform.localToWorldMatrix;
            var scale = mat.Scale();
            var radiusScale = Mathf.Max(scale.x, scale.y);
            var radius = circle.radius*radiusScale;

            var circlePos = (Vector2)circle.gameObject.transform.position + circle.offset;

            return (point - circlePos).normalized * radius + (Vector2)collider.transform.position;

        }else if (collider is BoxCollider2D) {
            var box = collider as BoxCollider2D;
            float hw = box.size.x * 0.5f;
            float hh = box.size.y * 0.5f;

            Vector3[] corners = new Vector3[4] {
                new Vector3(-hw, hh, 0), 
                new Vector3(hw, hh, 0),
                new Vector3(hw, -hh, 0),
                new Vector3(-hw, -hh, 0)
            };

            Color[] c = new Color[4]{Color.red, Color.green, Color.blue, Color.white};

            for (int i = 0; i < 4; ++i) {
                corners[i] = collider.transform.TransformPoint(corners[i]) + new Vector3(box.offset.x, box.offset.y, 0);
                corners[i].z = 0;
            }

            Vector2[] points = new Vector2[4];

            for (int i = 0; i < 4; ++i) {
                var p0 = corners[i];
                var p1 = corners[(i + 1) % 4];
                var pt = AdvancedMath.SegmentNearestPoint(p0, p1, (Vector3)point);
                points[i] = pt;
            }

            return points.OrderBy(v => (point - v).magnitude).First();
        }
        return Vector3.zero;
    }
}