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

using SixLabors.ImageSharp.PixelFormats;
using System;

namespace SixLabors.ImageSharp.Drawing.Processing {
  /// <summary>
  /// Renders a <see cref="Brush"/> against individual coverage scanlines.
  /// </summary>
  /// <typeparam name="TPixel">The pixel format.</typeparam>
  public abstract class BrushRenderer<TPixel>
      where TPixel : unmanaged, IPixel<TPixel>
  {
      /// <summary>
      /// Initializes a new instance of the <see cref="BrushRenderer{TPixel}"/> class.
      /// </summary>
      /// <param name="configuration">The configuration instance to use when performing operations.</param>
      /// <param name="options">The graphics options.</param>
      /// <param name="canvasWidth">The canvas width for the current render pass.</param>
      protected BrushRenderer(
          Configuration configuration,
          GraphicsOptions options,
          int canvasWidth)
      {
          this.Configuration = configuration;
          this.Options = options;
          this.CanvasWidth = canvasWidth;
          this.Blender = PixelOperations<TPixel>.Instance.GetPixelBlender(options);
      }

      /// <summary>
      /// Gets the configuration instance to use when performing operations.
      /// </summary>
      protected Configuration Configuration { get; }

      /// <summary>
      /// Gets the pixel blender.
      /// </summary>
      internal PixelBlender<TPixel> Blender { get; }

      /// <summary>
      /// Gets the graphics options.
      /// </summary>
      protected GraphicsOptions Options { get; }

      /// <summary>
      /// Gets the canvas width for the current render pass.
      /// </summary>
      protected int CanvasWidth { get; }

      /// <summary>
      /// Applies the opacity weighting for each pixel in a scanline to the target based on the
      /// pattern contained in the brush.
      /// </summary>
      /// <param name="destinationRow">The destination row slice to shade.</param>
      /// <param name="scanline">The coverage values for the current destination scanline.</param>
      /// <param name="x">The x-position in the target pixel space that the start of the scanline data corresponds to.</param>
      /// <param name="y">The y-position in the target pixel space that the scanline corresponds to.</param>
      /// <param name="workspace">The worker-local scratch workspace for temporary blending buffers.</param>
      public abstract void Apply(
          Span<TPixel> destinationRow,
          ReadOnlySpan<float> scanline,
          int x,
          int y,
          BrushWorkspace<TPixel> workspace);
  }
}