using System.Collections.Generic;
//using System.Numerics;
using UnityEngine;

/// <summary>
///     ClockwiseComparer provides functionality for sorting a collection of Vector2s such
///     that they are ordered clockwise about a given origin.
/// </summary>
public class ClockwiseComparer : IComparer<Vector2>
{
    private Vector2 m_Origin;
 
    /// <summary>
    ///     Gets or sets the origin.
    /// </summary>
    /// <value>The origin.</value>
    public Vector2 origin { get { return m_Origin; } set { m_Origin = value; } }
 
    /// <summary>
    ///     Initializes a new instance of the ClockwiseComparer class.
    /// </summary>
    /// <param name="origin">Origin.</param>
    public ClockwiseComparer(Vector2 origin)
    {
        m_Origin = origin;
    }
 
    /// <summary>
    ///     Compares two objects and returns a value indicating whether one is less than, equal to, or greater than the other.
    /// </summary>
    /// <param name="first">First.</param>
    /// <param name="second">Second.</param>
    public int Compare(Vector2 first, Vector2 second)
    {
        return IsClockwise(first, second, m_Origin);
    }
 
    /// <summary>
    ///     Returns 1 if first comes before second in clockwise order.
    ///     Returns -1 if second comes before first.
    ///     Returns 0 if the points are identical.
    /// </summary>
    /// <param name="first">First.</param>
    /// <param name="second">Second.</param>
    /// <param name="origin">Origin.</param>
    public static int IsClockwise(Vector2 first, Vector2 second, Vector2 origin)
    {
        if (first == second)
            return 0;
 
        Vector2 firstOffset = first - origin;
        Vector2 secondOffset = second - origin;
 
        float angle1 = Mathf.Atan2(firstOffset.x, firstOffset.y);
        float angle2 = Mathf.Atan2(secondOffset.x, secondOffset.y);
 
        if (angle1 < angle2)
            return -1;
 
        if (angle1 > angle2)
            return 1;
 
        // Check to see which point is closest
        return (firstOffset.sqrMagnitude < secondOffset.sqrMagnitude) ? -1 : 1;
    }
}