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

using System;
using System.Collections.Generic;

namespace SixLabors.ImageSharp.Drawing.Processing.Backends {
  /// <summary>
  /// One prepared draw-order command batch consumed by a drawing backend.
  /// </summary>
  public readonly struct DrawingCommandBatch
  {
      /// <summary>
      /// Initializes a new instance of the <see cref="DrawingCommandBatch"/> struct.
      /// </summary>
      /// <param name="commands">The draw-order scene commands.</param>
      /// <param name="hasLayers">Indicates whether the command stream contains layer boundaries.</param>
      public DrawingCommandBatch(
          IReadOnlyList<CompositionSceneCommand> commands,
          bool hasLayers)
      {
          this.Commands = commands;
          this.HasLayers = hasLayers;
      }

      /// <summary>
      /// Initializes a new instance of the <see cref="DrawingCommandBatch"/> struct.
      /// </summary>
      /// <param name="commands">The backing command buffer.</param>
      /// <param name="commandCount">The number of commands in the prepared batch.</param>
      /// <param name="hasLayers">Indicates whether the command stream contains layer boundaries.</param>
      internal DrawingCommandBatch(
          CompositionSceneCommand[] commands,
          int commandCount,
          bool hasLayers)
          : this(new ArraySegment<CompositionSceneCommand>(commands, 0, commandCount), hasLayers)
      {
      }

      /// <summary>
      /// Initializes a new instance of the <see cref="DrawingCommandBatch"/> struct.
      /// </summary>
      /// <param name="commands">The backing command buffer.</param>
      /// <param name="startIndex">The first command index.</param>
      /// <param name="commandCount">The number of commands in the prepared batch.</param>
      /// <param name="hasLayers">Indicates whether the command stream contains layer boundaries.</param>
      internal DrawingCommandBatch(
          CompositionSceneCommand[] commands,
          int startIndex,
          int commandCount,
          bool hasLayers)
          : this(new ArraySegment<CompositionSceneCommand>(commands, startIndex, commandCount), hasLayers)
      {
      }

      /// <summary>
      /// Gets the draw-order scene commands.
      /// </summary>
      public IReadOnlyList<CompositionSceneCommand> Commands { get; }

      /// <summary>
      /// Gets the total number of draw-order commands in the scene.
      /// </summary>
      public int CommandCount => this.Commands.Count;

      /// <summary>
      /// Gets a value indicating whether this scene contains inline layer commands.
      /// </summary>
      public bool HasLayers { get; }
  }
}