// src/AcDream.App/Rendering/TextureCache.cs
using AcDream.Core.Textures;
using DatReaderWriter;
using DatReaderWriter.DBObjs;
using Silk.NET.OpenGL;

namespace AcDream.App.Rendering;

public sealed unsafe class TextureCache : IDisposable
{
    private readonly GL _gl;
    private readonly DatCollection _dats;
    private readonly Dictionary<uint, uint> _handlesBySurfaceId = new();
    private uint _magentaHandle;

    public TextureCache(GL gl, DatCollection dats)
    {
        _gl = gl;
        _dats = dats;
    }

    /// <summary>
    /// Get or upload the GL texture handle for a Surface id. Returns a
    /// 1x1 magenta fallback if the Surface or its RenderSurface chain is
    /// missing or uses an unsupported format.
    /// </summary>
    public uint GetOrUpload(uint surfaceId)
    {
        if (_handlesBySurfaceId.TryGetValue(surfaceId, out var h))
            return h;

        var decoded = DecodeFromDats(surfaceId);
        h = UploadRgba8(decoded);
        _handlesBySurfaceId[surfaceId] = h;
        return h;
    }

    private DecodedTexture DecodeFromDats(uint surfaceId)
    {
        var surface = _dats.Get<Surface>(surfaceId);
        if (surface is null)
            return DecodedTexture.Magenta;

        var surfaceTexture = _dats.Get<SurfaceTexture>((uint)surface.OrigTextureId);
        if (surfaceTexture is null || surfaceTexture.Textures.Count == 0)
            return DecodedTexture.Magenta;

        var rs = _dats.Get<RenderSurface>((uint)surfaceTexture.Textures[0]);
        if (rs is null)
            return DecodedTexture.Magenta;

        return SurfaceDecoder.DecodeRenderSurface(rs);
    }

    private uint UploadRgba8(DecodedTexture decoded)
    {
        uint tex = _gl.GenTexture();
        _gl.BindTexture(TextureTarget.Texture2D, tex);

        fixed (byte* p = decoded.Rgba8)
            _gl.TexImage2D(
                TextureTarget.Texture2D,
                0,
                InternalFormat.Rgba8,
                (uint)decoded.Width,
                (uint)decoded.Height,
                0,
                PixelFormat.Rgba,
                PixelType.UnsignedByte,
                p);

        _gl.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMinFilter, (int)TextureMinFilter.Linear);
        _gl.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMagFilter, (int)TextureMagFilter.Linear);
        _gl.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureWrapS, (int)TextureWrapMode.Repeat);
        _gl.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureWrapT, (int)TextureWrapMode.Repeat);

        _gl.BindTexture(TextureTarget.Texture2D, 0);
        return tex;
    }

    public void Dispose()
    {
        foreach (var h in _handlesBySurfaceId.Values)
            _gl.DeleteTexture(h);
        _handlesBySurfaceId.Clear();
        if (_magentaHandle != 0)
        {
            _gl.DeleteTexture(_magentaHandle);
            _magentaHandle = 0;
        }
    }
}