using System;
using System.IO;
using System.Runtime.CompilerServices;
using Dashboard.Pal;

namespace Dashboard.Drawing
{
    public class Image(ImageData data) : IDisposable
    {
        protected readonly ConditionalWeakTable<DeviceContext, ITexture> Textures =
            new ConditionalWeakTable<DeviceContext, ITexture>();

        public virtual TextureType Type => data.Type;
        public PixelFormat Format { get; } = data.Format;
        public int Width { get; } = data.Width;
        public int Height { get; } = data.Height;
        public int Depth { get; } = data.Depth;
        public int Levels { get; } = data.Levels;
        public bool Premultiplied { get; } = data.Premultiplied;

        public bool IsDisposed { get; private set; } = false;

        ~Image()
        {
            InvokeDispose(false);
        }

        public virtual ITexture InternTexture(DeviceContext dc)
        {
            if (Textures.TryGetValue(dc, out ITexture? texture))
                return texture;

            ITextureExtension ext = dc.ExtensionRequire<ITextureExtension>();
            texture = ext.CreateTexture(Type);
            texture.SetStorage(Format, Width, Height, Depth, Levels);
            for (int i = 0; i < Levels; i++)
            {
                texture.Write<byte>(Format, data.Bitmap.AsSpan()[(int)data.GetLevelOffset(i)..], level: i, align: data.Alignment);
            }
            texture.Premultiplied = Premultiplied;
            texture.GenerateMipmaps();
            Textures.Add(dc, texture);

            return texture;
        }

        private void InvokeDispose(bool disposing)
        {
            if (IsDisposed)
                return;
            IsDisposed = true;

            Dispose(disposing);
        }

        protected virtual void Dispose(bool disposing)
        {
            foreach ((DeviceContext dc, ITexture texture) in Textures)
            {
                texture.Dispose();
            }
        }

        public void Dispose() => InvokeDispose(true);

        public static Image Load(Stream stream)
        {
            IImageLoader imageLoader = Application.Current.ExtensionRequire<IImageLoader>();
            return new Image(imageLoader.LoadImageData(stream));
        }
    }
}