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

using System;
using System.Numerics;

namespace SixLabors.ImageSharp.Drawing {
  /// <summary>
  /// A shape made up of a single path made up of one of more <see cref="ILineSegment"/>s
  /// </summary>
  public class RegularPolygon : Polygon
  {
      /// <summary>
      /// Initializes a new instance of the <see cref="RegularPolygon" /> class.
      /// </summary>
      /// <param name="location">The location the center of the polygon will be placed.</param>
      /// <param name="vertices">The number of vertices the <see cref="RegularPolygon"/> should have.</param>
      /// <param name="radius">The radius of the circle that would touch all vertices.</param>
      /// <param name="angle">The angle of rotation in degrees.</param>
      public RegularPolygon(PointF location, int vertices, float radius, float angle)
          : base(CreateSegment(location, radius, vertices, angle))
      {
      }

      /// <summary>
      /// Initializes a new instance of the <see cref="RegularPolygon" /> class.
      /// </summary>
      /// <param name="location">The location the center of the polygon will be placed.</param>
      /// <param name="vertices">The number of vertices the <see cref="RegularPolygon"/> should have.</param>
      /// <param name="radius">The radius of the circle that would touch all vertices.</param>
      public RegularPolygon(PointF location, int vertices, float radius)
          : this(location, vertices, radius, 0)
      {
      }

      /// <summary>
      /// Initializes a new instance of the <see cref="RegularPolygon" /> class.
      /// </summary>
      /// <param name="x">The x-coordinate of the center of the polygon.</param>
      /// <param name="y">The y-coordinate of the center of the polygon.</param>
      /// <param name="vertices">The number of vertices the <see cref="RegularPolygon" /> should have.</param>
      /// <param name="radius">The radius of the circle that would touch all vertices.</param>
      /// <param name="angle">The angle of rotation in degrees.</param>
      public RegularPolygon(float x, float y, int vertices, float radius, float angle)
          : this(new PointF(x, y), vertices, radius, angle)
      {
      }

      /// <summary>
      /// Initializes a new instance of the <see cref="RegularPolygon" /> class.
      /// </summary>
      /// <param name="x">The x-coordinate of the center of the polygon.</param>
      /// <param name="y">The y-coordinate of the center of the polygon.</param>
      /// <param name="vertices">The number of vertices the <see cref="RegularPolygon"/> should have.</param>
      /// <param name="radius">The radius of the circle that would touch all vertices.</param>
      public RegularPolygon(float x, float y, int vertices, float radius)
          : this(new PointF(x, y), vertices, radius)
      {
      }

      private static LinearLineSegment CreateSegment(PointF location, float radius, int vertices, float angle)
      {
          Guard.MustBeGreaterThan(vertices, 2, nameof(vertices));
          Guard.MustBeGreaterThan(radius, 0, nameof(radius));

          PointF distanceVector = new(0, radius);

          float anglePerSegments = (float)(2 * Math.PI / vertices);
          float current = GeometryUtilities.DegreeToRadian(angle);
          PointF[] points = new PointF[vertices];
          for (int i = 0; i < vertices; i++)
          {
              PointF rotated = PointF.Transform(distanceVector, Matrix4x4.CreateRotationZ(current));

              points[i] = rotated + location;

              current += anglePerSegments;
          }

          return new LinearLineSegment(points);
      }
  }
}