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

using System.Numerics;
using SixLabors.Fonts.Rendering;
using SixLabors.ImageSharp.PixelFormats;

namespace SixLabors.ImageSharp.Drawing.Text {
  /// <summary>
  /// Describes a single painted layer as a span within the glyph's path list.
  /// </summary>
  public readonly struct GlyphLayerInfo
  {
      /// <summary>
      /// Initializes a new instance of the <see cref="GlyphLayerInfo"/> struct.
      /// </summary>
      /// <param name="startIndex">Start index (inclusive) of the layer's paths within the glyph's path list.</param>
      /// <param name="count">Number of paths in this layer.</param>
      /// <param name="paint">The layer paint (null means use renderer default).</param>
      /// <param name="fillRule">The fill rule to use for this layer.</param>
      /// <param name="bounds">Axis-aligned bounds of the layer geometry.</param>
      /// <param name="kind">An optional semantic hint for the layer type.</param>
      internal GlyphLayerInfo(
          int startIndex,
          int count,
          Paint? paint,
          FillRule fillRule,
          RectangleF bounds,
          GlyphLayerKind kind)
      {
          this.StartIndex = startIndex;
          this.Count = count;
          this.Paint = paint;
          this.IntersectionRule = TextUtilities.MapFillRule(fillRule);

          CompositeMode compositeMode = paint?.CompositeMode ?? CompositeMode.SrcOver;
          this.PixelAlphaCompositionMode = TextUtilities.MapCompositionMode(compositeMode);
          this.PixelColorBlendingMode = TextUtilities.MapBlendingMode(compositeMode);
          this.Bounds = bounds;
          this.Kind = kind;
      }

      private GlyphLayerInfo(
          int startIndex,
          int count,
          Paint? paint,
          IntersectionRule intersectionRule,
          PixelAlphaCompositionMode compositionMode,
          PixelColorBlendingMode colorBlendingMode,
          RectangleF bounds,
          GlyphLayerKind kind)
      {
          this.StartIndex = startIndex;
          this.Count = count;
          this.Paint = paint;
          this.IntersectionRule = intersectionRule;
          this.PixelAlphaCompositionMode = compositionMode;
          this.PixelColorBlendingMode = colorBlendingMode;
          this.Bounds = bounds;
          this.Kind = kind;
      }

      /// <summary>
      /// Gets the start index (inclusive) of the layer span within the glyph's path list.
      /// </summary>
      public int StartIndex { get; }

      /// <summary>
      /// Gets the number of paths in this layer.
      /// </summary>
      public int Count { get; }

      /// <summary>
      /// Gets the paint definition to use for this layer; may be <see langword="null"/>.
      /// </summary>
      public Paint? Paint { get; }

      /// <summary>
      /// Gets the fill rule for rasterization of this layer.
      /// </summary>
      public IntersectionRule IntersectionRule { get; }

      /// <summary>
      /// Gets the pixel alpha composition mode to use for this layer.
      /// </summary>
      public PixelAlphaCompositionMode PixelAlphaCompositionMode { get; }

      /// <summary>
      /// Gets the pixel color blending mode to use for this layer.
      /// </summary>
      public PixelColorBlendingMode PixelColorBlendingMode { get; }

      /// <summary>
      /// Gets the bounds of the layer geometry (device space).
      /// </summary>
      public RectangleF Bounds { get; }

      /// <summary>
      /// Gets the semantic kind of the layer (for policy decisions).
      /// </summary>
      public GlyphLayerKind Kind { get; }

      internal static GlyphLayerInfo Transform(in GlyphLayerInfo info, Matrix4x4 matrix)
          => new(
              info.StartIndex,
              info.Count,
              info.Paint,
              info.IntersectionRule,
              info.PixelAlphaCompositionMode,
              info.PixelColorBlendingMode,
              RectangleF.Transform(info.Bounds, matrix),
              info.Kind);
  }
}