using System;
using System.Collections.Generic;

using Microsoft.Xna.Framework;

namespace Syntriax.Engine.Physics2D.Primitives;

public record Shape(IList<Vector2> Vertices)
{
    public Triangle SuperTriangle
    {
        get
        {
            float minX = float.MaxValue, minY = float.MaxValue;
            float maxX = float.MinValue, maxY = float.MinValue;

            foreach (Vector2 point in Vertices)
            {
                minX = Math.Min(minX, point.X);
                minY = Math.Min(minY, point.Y);
                maxX = Math.Max(maxX, point.X);
                maxY = Math.Max(maxY, point.Y);
            }

            float dx = maxX - minX;
            float dy = maxY - minY;
            float deltaMax = Math.Max(dx, dy);
            float midX = (minX + maxX) / 2;
            float midY = (minY + maxY) / 2;

            Vector2 p1 = new Vector2((float)midX - 20f * (float)deltaMax, (float)midY - (float)deltaMax);
            Vector2 p2 = new Vector2((float)midX, (float)midY + 20 * (float)deltaMax);
            Vector2 p3 = new Vector2((float)midX + 20 * (float)deltaMax, (float)midY - (float)deltaMax);

            return new Triangle(p1, p2, p3);
        }
    }

    public List<Line> Lines
    {
        get
        {
            List<Line> lines = new List<Line>(Vertices.Count - 1);
            GetLinesNonAlloc(lines);
            return lines;
        }
    }

    public void GetLinesNonAlloc(IList<Line> lines)
    {
        lines.Clear();
        for (int i = 0; i < Vertices.Count - 1; i++)
            lines.Add(new(Vertices[i], Vertices[i + 1]));
        lines.Add(new(Vertices[^1], Vertices[0]));
    }

    public bool ApproximatelyEquals(Shape other)
    {
        if (Vertices.Count != other.Vertices.Count)
            return false;

        for (int i = 0; i < Vertices.Count; i++)
            if (!Vertices[i].ApproximatelyEquals(other.Vertices[i]))
                return false;

        return true;
    }
}