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

using System;
using System.Collections.Generic;

namespace SixLabors.ImageSharp.Drawing.Processing.Backends {
  /// <summary>
  /// Base type for retained drawing backend scenes.
  /// </summary>
  public abstract class DrawingBackendScene : IDisposable
  {
      private readonly IReadOnlyList<IDisposable>? ownedResources;
      private bool isDisposed;

      /// <summary>
      /// Initializes a new instance of the <see cref="DrawingBackendScene"/> class.
      /// </summary>
      /// <param name="bounds">The target bounds used to create the scene.</param>
      /// <param name="ownedResources">Resources that must stay alive for the retained scene.</param>
      protected DrawingBackendScene(
          Rectangle bounds,
          IReadOnlyList<IDisposable>? ownedResources)
      {
          this.Bounds = bounds;
          this.ownedResources = ownedResources;
      }

      /// <summary>
      /// Gets the target bounds used to create the scene.
      /// </summary>
      public Rectangle Bounds { get; }

      /// <inheritdoc />
      public void Dispose()
      {
          if (this.isDisposed)
          {
              return;
          }

          this.DisposeCore();
          this.DisposeOwnedResources();
          this.isDisposed = true;
          GC.SuppressFinalize(this);
      }

      /// <summary>
      /// Disposes backend-specific resources retained by this scene.
      /// </summary>
      protected virtual void DisposeCore()
      {
      }

      /// <summary>
      /// Disposes resources retained for image-brush commands in this scene.
      /// </summary>
      private void DisposeOwnedResources()
      {
          if (this.ownedResources is null)
          {
              return;
          }

          for (int i = 0; i < this.ownedResources.Count; i++)
          {
              this.ownedResources[i].Dispose();
          }
      }
  }
}