using System;
using System.Collections.Generic;
using AcDream.Core.Meshing;
using Chorizite.OpenGLSDLBackend;
using Chorizite.OpenGLSDLBackend.Lib;
using DatReaderWriter;
using DatReaderWriter.DBObjs;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Logging.Abstractions;
using Silk.NET.OpenGL;
using WorldBuilder.Shared.Models;
using WorldBuilder.Shared.Services;

namespace AcDream.App.Rendering.Wb;

/// <summary>
/// Single seam between acdream and WB's render pipeline. Owns the
/// <c>ObjectMeshManager</c> instance and exposes a stable acdream-shaped API
/// so the rest of the renderer doesn't need to know about WB's types directly.
///
/// <para>
/// The adapter constructs its own <c>DefaultDatReaderWriter</c> internally; it
/// does NOT share file handles with our <c>DatCollection</c>. This duplicates
/// index-cache memory (~50–100 MB) but keeps the two subsystems fully decoupled.
/// Acceptable for Phase N.4 foundation work (plan Adjustment 1).
/// </para>
/// </summary>
public sealed class WbMeshAdapter : IDisposable, IWbMeshAdapter
{
    private readonly OpenGLGraphicsDevice? _graphicsDevice;
    private readonly DefaultDatReaderWriter? _wbDats;
    private readonly ObjectMeshManager? _meshManager;
    private readonly DatCollection? _dats;
    private readonly AcSurfaceMetadataTable _metadataTable = new();
    private readonly HashSet<ulong> _metadataPopulated = new();

    /// <summary>
    /// True when this instance was created via <see cref="CreateUninitialized"/>;
    /// all public methods no-op when uninitialized.
    /// </summary>
    private readonly bool _isUninitialized;

    private bool _disposed;

    /// <summary>
    /// Constructs the full WB pipeline: OpenGLGraphicsDevice → DefaultDatReaderWriter
    /// → ObjectMeshManager.
    /// </summary>
    /// <param name="gl">Active Silk.NET GL context. Must be bound to the current
    /// thread (construction runs GL queries; call from OnLoad).</param>
    /// <param name="datDir">Path to the dat directory (same as the one supplied
    /// to our DatCollection). DefaultDatReaderWriter opens its own file handles.</param>
    /// <param name="dats">acdream's DatCollection, used to populate the surface
    /// metadata side-table via <c>GfxObjMesh.Build</c>. Shares file handles with
    /// the rest of the client; read-only access from the render thread.</param>
    /// <param name="logger">Logger for the adapter; ObjectMeshManager uses
    /// NullLogger internally.</param>
    public WbMeshAdapter(GL gl, string datDir, DatCollection dats, ILogger<WbMeshAdapter> logger)
    {
        ArgumentNullException.ThrowIfNull(gl);
        ArgumentNullException.ThrowIfNull(datDir);
        ArgumentNullException.ThrowIfNull(dats);
        ArgumentNullException.ThrowIfNull(logger);

        _dats = dats;
        _graphicsDevice = new OpenGLGraphicsDevice(gl, logger, new DebugRenderSettings());
        _wbDats = new DefaultDatReaderWriter(datDir);
        _meshManager = new ObjectMeshManager(
            _graphicsDevice,
            _wbDats,
            NullLogger<ObjectMeshManager>.Instance);
    }

    private WbMeshAdapter()
    {
        // Uninitialized constructor — only for tests / flag-off cases where
        // the caller wants a Dispose-safe no-op instance.
        _isUninitialized = true;
    }

    /// <summary>Test/init helper — produces a Dispose-safe instance with no
    /// underlying mesh manager. Public methods are all no-ops.</summary>
    public static WbMeshAdapter CreateUninitialized() => new();

    /// <summary>
    /// The surface metadata side-table populated on each first
    /// <see cref="IncrementRefCount"/>. Queried by the draw dispatcher
    /// to determine translucency, luminosity, and fog behavior per batch.
    /// </summary>
    public AcSurfaceMetadataTable MetadataTable => _metadataTable;

    /// <summary>
    /// Returns the WB render data for <paramref name="id"/>, or null if not
    /// yet uploaded or if this adapter is uninitialized. Increments WB's
    /// internal usage counter — use <see cref="TryGetRenderData"/> for
    /// render-loop lookups that should not affect lifecycle.
    /// </summary>
    public ObjectRenderData? GetRenderData(ulong id)
    {
        if (_isUninitialized || _meshManager is null) return null;
        return _meshManager.GetRenderData(id);
    }

    /// <summary>
    /// Returns the WB render data for <paramref name="id"/> without
    /// modifying reference counts. Returns null if the mesh is not yet
    /// uploaded. Safe for render-loop lookups.
    /// </summary>
    public ObjectRenderData? TryGetRenderData(ulong id)
    {
        if (_isUninitialized || _meshManager is null) return null;
        return _meshManager.TryGetRenderData(id);
    }

    /// <inheritdoc/>
    public void IncrementRefCount(ulong id)
    {
        if (_isUninitialized || _meshManager is null) return;
        _meshManager.IncrementRefCount(id);

        if (_metadataPopulated.Add(id))
        {
            PopulateMetadata(id);

            // WB's IncrementRefCount alone only bumps a usage counter; it does
            // NOT trigger mesh loading. We must explicitly call PrepareMeshDataAsync
            // so the background workers actually decode the GfxObj. The result
            // auto-enqueues into _stagedMeshData (ObjectMeshManager line 510),
            // which Tick() drains onto the GPU. Until that completes,
            // TryGetRenderData(id) returns null and the dispatcher silently
            // skips the entity — standard streaming flicker.
            //
            // isSetup: false — acdream's MeshRefs already carry expanded
            // per-part GfxObj ids (0x01XXXXXX). WB's Setup-expansion path is
            // unused.
            _ = _meshManager.PrepareMeshDataAsync(id, isSetup: false);
        }
    }

    /// <inheritdoc/>
    public void DecrementRefCount(ulong id)
    {
        if (_isUninitialized || _meshManager is null) return;
        _meshManager.DecrementRefCount(id);
    }

    /// <summary>
    /// Per-frame drain of the WB pipeline's main-thread work queues. MUST be
    /// called once per frame from the render thread. Without this, the staged
    /// mesh data queue grows unbounded (memory leak) and queued GL actions
    /// never execute.
    ///
    /// <para>
    /// Order matters: <c>ProcessGLQueue</c> runs first to apply any pending GL
    /// state changes (e.g., texture uploads queued by background workers
    /// during mesh prep). Then we drain staged mesh data, calling
    /// <c>UploadMeshData</c> on each item to materialize the actual GL VAO /
    /// VBO / IBO resources. After Tick, <c>GetRenderData</c> for any id
    /// previously passed to <c>IncrementRefCount</c> may return non-null.
    /// </para>
    ///
    /// <para>
    /// No-op when the adapter is uninitialized (e.g., flag is off and the
    /// adapter was constructed via <c>CreateUninitialized</c>).
    /// </para>
    /// </summary>
    public void Tick()
    {
        if (_isUninitialized) return;
        if (_disposed) return;

        _graphicsDevice!.ProcessGLQueue();
        while (_meshManager!.StagedMeshData.TryDequeue(out var meshData))
        {
            _meshManager.UploadMeshData(meshData);
        }
    }

    private void PopulateMetadata(ulong id)
    {
        if (_dats is null) return;
        if (!_dats.Portal.TryGet<GfxObj>((uint)id, out var gfxObj)) return;

        var subMeshes = GfxObjMesh.Build(gfxObj, _dats);
        for (int i = 0; i < subMeshes.Count; i++)
        {
            var sm = subMeshes[i];
            _metadataTable.Add(id, i, new AcSurfaceMetadata(
                sm.Translucency, sm.Luminosity, sm.Diffuse,
                sm.SurfOpacity, sm.NeedsUvRepeat, sm.DisableFog));
        }
    }

    /// <inheritdoc/>
    public void Dispose()
    {
        if (_disposed) return;
        _disposed = true;
        _meshManager?.Dispose();
        _wbDats?.Dispose();
        _graphicsDevice?.Dispose();
    }
}