// Copyright (c) Six Labors.
// Licensed under the Six Labors Split License.

using System;
using System.Numerics;

namespace SixLabors.ImageSharp.Drawing {
  /// <summary>
  /// A star-shaped polygon defined by alternating inner and outer radii.
  /// </summary>
  public sealed class StarPolygon : Polygon
  {
      /// <summary>
      /// Initializes a new instance of the <see cref="StarPolygon" /> class.
      /// </summary>
      /// <param name="location">The center point of the star.</param>
      /// <param name="prongs">The number of star prongs.</param>
      /// <param name="innerRadii">The inner star radius.</param>
      /// <param name="outerRadii">The outer star radius.</param>
      /// <param name="angle">The angle of rotation in degrees.</param>
      public StarPolygon(PointF location, int prongs, float innerRadii, float outerRadii, float angle)
          : base(CreateSegment(location, innerRadii, outerRadii, prongs, angle))
      {
      }

      /// <summary>
      /// Initializes a new instance of the <see cref="StarPolygon" /> class.
      /// </summary>
      /// <param name="location">The center point of the star.</param>
      /// <param name="prongs">The number of star prongs.</param>
      /// <param name="innerRadii">The inner star radius.</param>
      /// <param name="outerRadii">The outer star radius.</param>
      public StarPolygon(PointF location, int prongs, float innerRadii, float outerRadii)
          : this(location, prongs, innerRadii, outerRadii, 0)
      {
      }

      /// <summary>
      /// Initializes a new instance of the <see cref="StarPolygon" /> class.
      /// </summary>
      /// <param name="x">The x-coordinate of the star center.</param>
      /// <param name="y">The y-coordinate of the star center.</param>
      /// <param name="prongs">The number of star prongs.</param>
      /// <param name="innerRadii">The inner star radius.</param>
      /// <param name="outerRadii">The outer star radius.</param>
      /// <param name="angle">The angle of rotation in degrees.</param>
      public StarPolygon(float x, float y, int prongs, float innerRadii, float outerRadii, float angle)
          : this(new PointF(x, y), prongs, innerRadii, outerRadii, angle)
      {
      }

      /// <summary>
      /// Initializes a new instance of the <see cref="StarPolygon" /> class.
      /// </summary>
      /// <param name="x">The x-coordinate of the star center.</param>
      /// <param name="y">The y-coordinate of the star center.</param>
      /// <param name="prongs">The number of star prongs.</param>
      /// <param name="innerRadii">The inner star radius.</param>
      /// <param name="outerRadii">The outer star radius.</param>
      public StarPolygon(float x, float y, int prongs, float innerRadii, float outerRadii)
          : this(new PointF(x, y), prongs, innerRadii, outerRadii)
      {
      }

      private static LinearLineSegment CreateSegment(Vector2 location, float innerRadii, float outerRadii, int prongs, float angle)
      {
          Guard.MustBeGreaterThan(prongs, 2, nameof(prongs));
          Guard.MustBeGreaterThan(innerRadii, 0, nameof(innerRadii));
          Guard.MustBeGreaterThan(outerRadii, 0, nameof(outerRadii));

          Vector2 distanceVectorInner = new(0, innerRadii);
          Vector2 distanceVectorOuter = new(0, outerRadii);

          int vertices = prongs * 2;
          float anglePerSegments = (float)(2 * Math.PI / vertices);
          float current = GeometryUtilities.DegreeToRadian(angle);
          PointF[] points = new PointF[vertices];
          Vector2 distance = distanceVectorInner;
          for (int i = 0; i < vertices; i++)
          {
              if (distance == distanceVectorInner)
              {
                  distance = distanceVectorOuter;
              }
              else
              {
                  distance = distanceVectorInner;
              }

              Vector2 rotated = PointF.Transform(distance, Matrix4x4.CreateRotationZ(current));

              points[i] = rotated + location;

              current += anglePerSegments;
          }

          return new LinearLineSegment(points);
      }
  }
}