using Chorizite.Core.Lib;
using Chorizite.Core.Render;
using Chorizite.Core.Render.Enums;
using DatReaderWriter.DBObjs;
using DatReaderWriter.Enums;
using CullMode = DatReaderWriter.Enums.CullMode;
using DatReaderWriter.Types;
using Microsoft.Extensions.Logging;
using Silk.NET.OpenGL;
using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Linq;
using System.Numerics;
using System.Runtime.InteropServices;
using System.Threading;
using System.Threading.Tasks;
using AcDream.Content;
using AcDream.Core.Rendering.Wb;
using PixelFormat = Silk.NET.OpenGL.PixelFormat;
using BoundingBox = Chorizite.Core.Lib.BoundingBox;

namespace AcDream.App.Rendering.Wb {
    /// <summary>
    /// GPU-side render data created on the main thread.
    /// </summary>
    public class ObjectRenderData {
        public uint VAO { get; set; }
        public uint VBO { get; set; }
        public int VertexCount { get; set; }
        public List<ObjectRenderBatch> Batches { get; set; } = new();
        public bool IsSetup { get; set; }
        public List<(ulong GfxObjId, Matrix4x4 Transform)> SetupParts { get; set; } = new();

        /// <summary>Particle emitters from physics scripts.</summary>
        public List<StagedEmitter> ParticleEmitters { get; set; } = new();

        /// <summary>CPU-side vertex positions for raycasting.</summary>
        public Vector3[] CPUPositions { get; set; } = Array.Empty<Vector3>();

        /// <summary>CPU-side indices for raycasting.</summary>
        public ushort[] CPUIndices { get; set; } = Array.Empty<ushort>();

        /// <summary>CPU-side edge line vertices for Environment wireframe rendering.</summary>
        public Vector3[] CPUEdgeLines { get; set; } = Array.Empty<Vector3>();

        /// <summary>Local bounding box.</summary>
        public BoundingBox BoundingBox { get; set; }

        /// <summary>Approximate center point used for depth sorting / transparency ordering.</summary>
        public Vector3 SortCenter { get; set; }

        /// <summary>DataID of a simpler GfxObj to use at long distance / low quality, or GfxObjDegradeInfo.</summary>
        public uint DIDDegrade { get; set; }

        /// <summary>Sphere used for mouse selection.</summary>
        public Sphere? SelectionSphere { get; set; }

        /// <summary>Estimated GPU memory usage in bytes.</summary>
        public long MemorySize { get; set; }
    }

    /// <summary>
    /// A single GPU draw batch: IBO + texture array layer.
    /// </summary>
    public class ObjectRenderBatch {
        public uint IBO { get; set; }
        public int IndexCount { get; set; }
        public TextureAtlasManager Atlas { get; set; } = null!;
        public int TextureIndex { get; set; }
        public (int Width, int Height) TextureSize { get; set; }
        public TextureFormat TextureFormat { get; set; }
        public uint SurfaceId { get; set; }
        public TextureKey Key { get; set; }
        public DatReaderWriter.Enums.CullMode CullMode { get; set; }
        public bool IsTransparent { get; set; }
        public bool IsAdditive { get; set; }
        public bool HasWrappingUVs { get; set; }

        // Modern rendering path fields
        public uint FirstIndex { get; set; }
        public uint BaseVertex { get; set; }
        public ulong BindlessTextureHandle { get; set; }
    }

    /// <summary>
    /// Manages scenery mesh loading, GPU resource creation, and reference counting.
    /// Key design: mesh data is prepared on background threads via PrepareMeshData(),
    /// then GPU resources are created on the main thread via UploadMeshData().
    /// </summary>
    public class ObjectMeshManager : IDisposable {
        private readonly OpenGLGraphicsDevice _graphicsDevice;
        private readonly IDatReaderWriter _dats;
        private readonly ILogger _logger;

        /// <summary>
        /// MP1a (2026-07-05): the GL-free CPU extraction half, verbatim-moved to
        /// AcDream.Content so the MP1b bake tool can run it without a GL context.
        /// Owns the dat read → mesh build → inline texture decode pipeline; this
        /// class keeps the queue/worker lifecycle and all GL upload.
        /// </summary>
        private readonly MeshExtractor _extractor;

        internal IDatReaderWriter Dats => _dats;

        public bool IsDisposed { get; private set; }
        private readonly ConcurrentDictionary<ulong, ObjectRenderData> _renderData = new();
        private readonly ConcurrentDictionary<ulong, int> _usageCount = new();
        private readonly ConcurrentDictionary<ulong, (Vector3 Min, Vector3 Max)?> _boundsCache = new();
        private readonly ConcurrentDictionary<ulong, Task<ObjectMeshData?>> _preparationTasks = new();

        // LRU Cache for Unused objects
        private readonly LinkedList<ulong> _lruList = new();
        private readonly long _maxGpuMemory = 1024 * 1024 * 1024; // 1GB
        private readonly int _maxCachedObjects = 50; // Max number of cached objects (count-based limit)
        private long _currentGpuMemory = 0;

        // Shared atlases grouped by (Width, Height, Format)
        private readonly Dictionary<(int Width, int Height, TextureFormat Format), List<TextureAtlasManager>> _globalAtlases = new();

        // CPU-side cache for prepared mesh data (to avoid re-reading/decoding from DAT)
        private readonly Dictionary<ulong, ObjectMeshData> _cpuMeshCache = new();
        private readonly LinkedList<ulong> _cpuLruList = new();
        private readonly int _maxCpuCacheSize = 100;

        private readonly ConcurrentQueue<ObjectMeshData> _stagedMeshData = new();
        public ConcurrentQueue<ObjectMeshData> StagedMeshData => _stagedMeshData;

        /// <summary>#125: how many times a failed GL upload is re-staged before
        /// giving up loudly. Small — a transient GL error clears on the next
        /// frame; anything that fails this many times is a genuine defect to
        /// surface, not retry forever. See <see cref="ObjectMeshData.UploadAttempts"/>.</summary>
        public const int MaxUploadRetries = 3;

        /// <summary>
        /// #125: drain one staged upload, returning whether it should be
        /// re-staged for a later frame. The caller (the per-frame Tick drain)
        /// collects the re-stages and re-enqueues them AFTER the drain loop —
        /// never inside it — so a deterministic failure can't spin the queue in
        /// a single frame. Increments the mesh-data's own attempt counter (resets
        /// on re-prepare) and gives up loudly past <see cref="MaxUploadRetries"/>.
        /// </summary>
        public bool UploadOrRequeue(ObjectMeshData meshData) {
            if (UploadMeshData(meshData) is not null)
                return false;                       // success (incl. legitimate 0-vertex → empty render data)
            if (HasRenderData(meshData.ObjectId))
                return false;                       // raced to present by another path
            meshData.UploadAttempts++;
            if (meshData.UploadAttempts < MaxUploadRetries)
                return true;                        // re-stage for next frame
            Console.WriteLine($"[up-retry] 0x{meshData.ObjectId:X10} upload failed {meshData.UploadAttempts}x — giving up (was the #125 silent sticky drop; a GL error is being surfaced, not hidden)");
            return false;
        }

        public GlobalMeshBuffer? GlobalBuffer { get; }
        private readonly bool _useModernRendering;

        private readonly List<(ulong Id, bool IsSetup, TaskCompletionSource<ObjectMeshData?> Tcs, CancellationToken Ct)> _pendingRequests = new();
        private int _activeWorkers = 0;
        private const int MaxParallelLoads = 4;
        public ObjectMeshManager(OpenGLGraphicsDevice graphicsDevice, IDatReaderWriter dats, ILogger<ObjectMeshManager> logger) {
            _graphicsDevice = graphicsDevice;
            _dats = dats;
            _logger = logger;
            // Side-stage sink: particle-preload meshes staged mid-extraction go
            // straight onto the staged-upload queue, exactly as the pre-MP1a code
            // did — immediate enqueue, surviving a later throw in the same
            // Prepare* call. ConcurrentQueue.Enqueue is thread-safe for the
            // extractor's up-to-4 concurrent decode workers.
            _extractor = new MeshExtractor(_dats, _logger, data => _stagedMeshData.Enqueue(data));
            _useModernRendering = _graphicsDevice.HasOpenGL43 && _graphicsDevice.HasBindless;
            if (_useModernRendering) {
                GlobalBuffer = new GlobalMeshBuffer(_graphicsDevice.GL);
            }
        }

        /// <summary>
        /// Get existing GPU render data for an object, or null if not yet uploaded.
        /// Increments reference count.
        /// </summary>
        public ObjectRenderData? GetRenderData(ulong id) {
            if (_renderData.TryGetValue(id, out var data)) {
                _usageCount.AddOrUpdate(id, 1, (_, count) => count + 1);

                if (data.IsSetup) {
                    foreach (var (partId, _) in data.SetupParts) {
                        IncrementRefCount(partId);
                    }
                }
                else {
                    // Increment ref counts for all textures in this GfxObj
                    foreach (var batch in data.Batches) {
                        if (batch.Atlas != null) {
                            batch.Atlas.AddTexture(batch.Key, Array.Empty<byte>());
                        }
                    }
                }

                // If it was in LRU, remove it as it's now in use
                lock (_lruList) {
                    _lruList.Remove(id);
                }

                return data;
            }
            return null;
        }

        /// <summary>
        /// Check if GPU render data exists for an object.
        /// </summary>
        public bool HasRenderData(ulong id) => _renderData.ContainsKey(id);

        /// <summary>
        /// Get existing GPU render data without modifying reference count.
        /// Use this for render-loop lookups where you don't want to affect lifecycle.
        /// </summary>
        public ObjectRenderData? TryGetRenderData(ulong id) {
            return _renderData.TryGetValue(id, out var data) ? data : null;
        }

        /// <summary>
        /// Increment reference count for an object (e.g. when a landblock starts using it).
        /// </summary>
        public void IncrementRefCount(ulong id) {
            _usageCount.AddOrUpdate(id, 1, (_, count) => count + 1);
            lock (_lruList) {
                _lruList.Remove(id);
            }
        }

        public void GenerateMipmaps() {
            foreach (var atlasList in _globalAtlases.Values) {
                foreach (var atlas in atlasList) {
                    atlas.TextureArray.ProcessDirtyUpdates();
                }
            }
        }

        /// <summary>
        /// #105 diagnostic: counts staged-but-unflushed texture layer updates across all
        /// shared atlases (see <see cref="ManagedGLTextureArray.PendingUpdateCount"/>).
        /// Render thread only — <c>_globalAtlases</c> is render-thread-owned.
        /// </summary>
        public (int PendingUpdates, int ArraysWithPending, int TotalArrays) GetPendingTextureUpdateStats() {
            int pending = 0, arraysWith = 0, total = 0;
            foreach (var atlasList in _globalAtlases.Values) {
                foreach (var atlas in atlasList) {
                    total++;
                    int p = atlas.TextureArray.PendingUpdateCount;
                    if (p > 0) { arraysWith++; pending += p; }
                }
            }
            return (pending, arraysWith, total);
        }

        /// <summary>
        /// Decrement reference count and unload GPU resources if no longer needed.
        /// </summary>
        public void DecrementRefCount(ulong id) {
            var newCount = _usageCount.AddOrUpdate(id, 0, (_, c) => c - 1);
            if (newCount <= 0) {
                // Instead of unloading, move to LRU
                lock (_lruList) {
                    _lruList.Remove(id);
                    _lruList.AddLast(id);
                }
            }
        }

        /// <summary>
        /// Decrement reference count and unload if no longer needed.
        /// </summary>
        public void ReleaseRenderData(ulong id) {
            if (_usageCount.TryGetValue(id, out var count) && count > 0) {
                var newCount = _usageCount.AddOrUpdate(id, 0, (_, c) => c - 1);
                if (newCount <= 0) {
                    // Instead of unloading, move to LRU
                    lock (_lruList) {
                        _lruList.Remove(id);
                        _lruList.AddLast(id);
                    }
                }
            }
        }

        private void EvictOldResources(long neededBytes = 0) {
            lock (_lruList) {
                // Evict based on memory OR count limit
                while ((_currentGpuMemory + neededBytes) > _maxGpuMemory || _lruList.Count > _maxCachedObjects) {
                    var idToEvict = _lruList.First!.Value;
                    _lruList.RemoveFirst();

                    if (_usageCount.TryGetValue(idToEvict, out var count) && count <= 0) {
                        UnloadObject(idToEvict);
                        _usageCount.TryRemove(idToEvict, out _);
                    }
                }
            }
        }

        /// <summary>
        /// Force evict all unused objects from the cache.
        /// Use this when navigating away from a view or changing filters to free memory.
        /// </summary>
        public void EvictAllUnused() {
            lock (_lruList) {
                while (_lruList.Count > 0) {
                    var idToEvict = _lruList.First!.Value;
                    _lruList.RemoveFirst();

                    if (_usageCount.TryGetValue(idToEvict, out var count) && count <= 0) {
                        UnloadObject(idToEvict);
                        _usageCount.TryRemove(idToEvict, out _);
                    }
                }
            }

            // Also clear CPU mesh cache
            lock (_cpuMeshCache) {
                _cpuMeshCache.Clear();
                _cpuLruList.Clear();
            }
        }

        public struct EnvCellGeomRequest {
            public uint EnvironmentId;
            public ushort CellStructure;
            public List<ushort> Surfaces;
        }

        private readonly ConcurrentDictionary<ulong, EnvCellGeomRequest> _pendingEnvCellRequests = new();

        /// <summary>
        /// Phase 1 (Background Thread): Prepare CPU-side mesh data for deduplicated EnvCell geometry.
        /// </summary>
        public Task<ObjectMeshData?> PrepareEnvCellGeomMeshDataAsync(ulong geomId, uint environmentId, ushort cellStructure, List<ushort> surfaces, CancellationToken ct = default) {
            if (IsDisposed || HasRenderData(geomId)) return Task.FromResult<ObjectMeshData?>(null);

            // Check CPU cache first
            lock (_cpuMeshCache) {
                if (_cpuMeshCache.TryGetValue(geomId, out var cachedData)) {
                    _cpuLruList.Remove(geomId);
                    _cpuLruList.AddLast(geomId);
                    return Task.FromResult<ObjectMeshData?>(cachedData);
                }
            }

            // Return existing task if already running or queued
            if (_preparationTasks.TryGetValue(geomId, out var existing)) {
                return existing;
            }

            var tcs = new TaskCompletionSource<ObjectMeshData?>();
            var task = tcs.Task;
            _preparationTasks[geomId] = task;

            lock (_pendingRequests) {
                if (IsDisposed) {
                    tcs.TrySetCanceled();
                    _preparationTasks.TryRemove(geomId, out _);
                    return task;
                }
                // Special handling for EnvCell geometry - we need to store the cell data for the worker
                _pendingEnvCellRequests[geomId] = new EnvCellGeomRequest {
                    EnvironmentId = environmentId,
                    CellStructure = cellStructure,
                    Surfaces = surfaces
                };
                _pendingRequests.Add((geomId, false, tcs, ct));
                if (_activeWorkers < MaxParallelLoads) {
                    _activeWorkers++;
                    Task.Run(ProcessQueueAsync);
                }
            }

            return task;
        }

        public Task<ObjectMeshData?> PrepareMeshDataAsync(ulong id, bool isSetup, CancellationToken ct = default) {
            if (IsDisposed || HasRenderData(id)) return Task.FromResult<ObjectMeshData?>(null);

            // Check CPU cache first
            lock (_cpuMeshCache) {
                if (_cpuMeshCache.TryGetValue(id, out var cachedData)) {
                    _cpuLruList.Remove(id);
                    _cpuLruList.AddLast(id);
                    return Task.FromResult<ObjectMeshData?>(cachedData);
                }
            }

            // Return existing task if already running or queued
            if (_preparationTasks.TryGetValue(id, out var existing)) {
                if (!existing.IsFaulted && !existing.IsCanceled) {
                    lock (_pendingRequests) {
                        int idx = _pendingRequests.FindIndex(r => r.Id == id);
                        if (idx >= 0) {
                            var req = _pendingRequests[idx];
                            _pendingRequests.RemoveAt(idx);
                            _pendingRequests.Add(req);
                        }
                    }
                    return existing;
                }
                _preparationTasks.TryRemove(id, out _);
            }

            var tcs = new TaskCompletionSource<ObjectMeshData?>();
            var task = tcs.Task;
            _preparationTasks[id] = task;

            lock (_pendingRequests) {
                if (IsDisposed) {
                    tcs.TrySetCanceled();
                    _preparationTasks.TryRemove(id, out _);
                    return task;
                }
                _pendingRequests.Add((id, isSetup, tcs, ct));
                if (_activeWorkers < MaxParallelLoads) {
                    _activeWorkers++;
                    Task.Run(ProcessQueueAsync);
                }
            }

            return task;
        }

        private async Task ProcessQueueAsync() {
            try {
                while (true) {
                    ulong id;
                    bool isSetup;
                    TaskCompletionSource<ObjectMeshData?> tcs;
                    CancellationToken ct;

                    lock (_pendingRequests) {
                        // IsDisposed re-check: lets Dispose() drain the queue and
                        // observe _activeWorkers reach 0 before the dats unmap.
                        if (IsDisposed || _pendingRequests.Count == 0) {
                            return;
                        }

                        // LIFO: Pick the most recent request
                        var index = _pendingRequests.Count - 1;
                        (id, isSetup, tcs, ct) = _pendingRequests[index];
                        _pendingRequests.RemoveAt(index);
                    }

                    try {
                        ObjectMeshData? data = null;
                        if (_pendingEnvCellRequests.TryRemove(id, out var req)) {
                            uint envId = 0x0D000000u | req.EnvironmentId;
                            if (_dats.Portal.TryGet<DatReaderWriter.DBObjs.Environment>(envId, out var environment)) {
                                if (environment.Cells.TryGetValue(req.CellStructure, out var cellStruct)) {
                                    data = _extractor.PrepareCellStructMeshData(id, cellStruct, req.Surfaces, Matrix4x4.Identity, CancellationToken.None);
                                    // TEMP diagnostic #105 (strip with fix): a null prep here means
                                    // this deduplicated cell geometry will NEVER render anywhere.
                                    if (data == null)
                                        Console.WriteLine($"[geom-null] prepare-null geom=0x{id:X10} env=0x{envId:X8} cs=0x{req.CellStructure:X4}");
                                }
                                else {
                                    Console.WriteLine($"[geom-null] cellstruct-missing geom=0x{id:X10} env=0x{envId:X8} cs=0x{req.CellStructure:X4}");
                                }
                            }
                            else {
                                Console.WriteLine($"[geom-null] env-read-failed geom=0x{id:X10} env=0x{envId:X8}");
                            }
                        }
                        else {
                            // TEMP diagnostic #105 (strip with fix): an EnvCell geom id (bit 33)
                            // whose pending request vanished gets misrouted to the generic path,
                            // where its hash-derived low bits resolve to nothing -> silent null.
                            if ((id & 0x2_0000_0000UL) != 0)
                                Console.WriteLine($"[geom-misroute] envcell geom 0x{id:X10} had no pending request — generic path will null it");
                            // If it's a direct setup or gfxobj, make sure background loads don't abort half-way
                            data = _extractor.PrepareMeshData(id, isSetup, CancellationToken.None);
                        }
                        if (data != null) {
                            lock (_cpuMeshCache) {
                                if (_cpuMeshCache.Count >= _maxCpuCacheSize) {
                                    var oldest = _cpuLruList.First!.Value;
                                    _cpuLruList.RemoveFirst();
                                    _cpuMeshCache.Remove(oldest);
                                }
                                _cpuMeshCache[id] = data;
                                _cpuLruList.AddLast(id);
                            }
                            _stagedMeshData.Enqueue(data);
                        }
                        tcs.TrySetResult(data);
                    }
                    catch (OperationCanceledException) {
                        tcs.TrySetCanceled(ct);
                    }
                    catch (Exception ex) {
                        _logger.LogError(ex, "Error preparing mesh data for 0x{Id:X8}", id);
                        tcs.TrySetException(ex);
                    }
                    finally {
                        _preparationTasks.TryRemove(id, out _);
                    }
                }
            }
            finally {
                lock (_pendingRequests) {
                    _activeWorkers--;
                }
            }
        }

        /// <summary>
        /// Phase 1 (Background Thread): Prepare CPU-side mesh data from DAT.
        /// This loads vertices, indices, and texture data but creates NO GPU resources.
        /// Thread-safe: only reads from DAT files.
        ///
        /// MP1a (2026-07-05): delegates to <see cref="MeshExtractor.PrepareMeshData"/>,
        /// the verbatim-moved GL-free extraction dispatcher. See <see cref="_extractor"/>.
        /// </summary>
        public ObjectMeshData? PrepareMeshData(ulong id, bool isSetup, CancellationToken ct = default) {
            return _extractor.PrepareMeshData(id, isSetup, ct);
        }

        /// <summary>
        /// Cancel preparation tasks for IDs that are no longer needed.
        /// </summary>
        public void CancelStagedUploads(IEnumerable<ulong> ids) {
            foreach (var id in ids) {
                _preparationTasks.TryRemove(id, out _);
            }
        }

        /// <summary>
        /// Phase 2 (Main Thread): Upload prepared mesh data to GPU.
        /// Creates VAO, VBO, IBOs, and texture arrays.
        /// Must be called from the GL thread.
        /// </summary>
        public ObjectRenderData? UploadMeshData(ObjectMeshData meshData) {
            try {
                if (_renderData.TryGetValue(meshData.ObjectId, out var existing)) {
                    _preparationTasks.TryRemove(meshData.ObjectId, out _);
                    if (existing.IsSetup) {
                        foreach (var (partId, _) in existing.SetupParts) {
                            IncrementRefCount(partId);
                            lock (_lruList) {
                                _lruList.Remove(partId);
                            }
                        }
                    }
                    else {
                        // Increment ref counts for all textures in this GfxObj
                        foreach (var batch in existing.Batches) {
                            if (batch.Atlas != null) {
                                batch.Atlas.AddTexture(batch.Key, Array.Empty<byte>()); 
                            }
                        }
                    }
                    IncrementRefCount(meshData.ObjectId);
                    lock (_lruList) {
                        _lruList.Remove(meshData.ObjectId);
                    }
                    return existing;
                }

                // Estimated size - evict before allocation
                long estimatedSize = meshData.IsSetup ? 1024 : 
                    (meshData.Vertices.Length * VertexPositionNormalTexture.Size) +
                    meshData.TextureBatches.Values.SelectMany(l => l).Sum(b => (long)b.Indices.Count * sizeof(ushort));
                
                EvictOldResources(estimatedSize);

                _preparationTasks.TryRemove(meshData.ObjectId, out _);
                if (meshData.IsSetup) {
                    // Upload EnvCell geometry if present to ensure it's in _renderData
                    if (meshData.EnvCellGeometry != null) {
                        UploadMeshData(meshData.EnvCellGeometry);
                    }

                    // Setup objects are multi-part - each part needs its own render data
                    var data = new ObjectRenderData {
                        IsSetup = true,
                        SetupParts = meshData.SetupParts,
                        ParticleEmitters = meshData.ParticleEmitters,
                        Batches = new List<ObjectRenderBatch>(),
                        BoundingBox = meshData.BoundingBox,
                        SortCenter = meshData.SortCenter,
                        DIDDegrade = meshData.DIDDegrade,
                        SelectionSphere = meshData.SelectionSphere,
                        MemorySize = 1024 // Small overhead for the setup itself
                    };
                    _renderData.TryAdd(meshData.ObjectId, data);
                    IncrementRefCount(meshData.ObjectId);
                    _currentGpuMemory += data.MemorySize;

                    // Increment ref counts for all parts
                    foreach (var (partId, _) in meshData.SetupParts) {
                        IncrementRefCount(partId);
                    }

                    return data;
                }

                var renderData = UploadGfxObjMeshData(meshData);
                if (renderData == null) {
                    // 0-vertex mesh: every polygon was gated out at extraction. #119
                    // (2026-06-11) dat-verified this is LEGITIMATE for all-no-draw
                    // models (all polys NoPos + Base1Solid surfaces — retail's
                    // skipNoTexture never draws them either; 0x010002B4/0x010008A8
                    // are this class, Issue119UpNullGfxObjDumpTests). The empty
                    // cache is the correct terminal state for those. The line stays
                    // as a tripwire for the OTHER way to get here (extraction
                    // dropped textured polys — a real defect; dat-verify with the
                    // dump test before treating as one).
                    Console.WriteLine($"[up-null] 0x{meshData.ObjectId:X10} produced a 0-vertex mesh — caching empty render data (legitimate for all-no-draw models; dat-verify via Issue119UpNullGfxObjDumpTests)");
                    renderData = new ObjectRenderData();
                }

                renderData.BoundingBox = meshData.BoundingBox;
                renderData.SortCenter = meshData.SortCenter;
                renderData.DIDDegrade = meshData.DIDDegrade;
                renderData.SelectionSphere = meshData.SelectionSphere;
                _renderData.TryAdd(meshData.ObjectId, renderData);
                IncrementRefCount(meshData.ObjectId);
                _currentGpuMemory += renderData.MemorySize;

                // Clear texture data after upload to save RAM
                foreach (var batchList in meshData.TextureBatches.Values) {
                    foreach (var batch in batchList) {
                        batch.TextureData = Array.Empty<byte>();
                    }
                }
                return renderData;
            }
            catch (Exception ex) {
                _logger.LogError(ex, "Error uploading mesh data for 0x{Id:X8}", meshData.ObjectId);
                return null;
            }
        }

        /// <summary>
        /// Gets bounding box for an object (for frustum culling).
        /// </summary>
        public (Vector3 Min, Vector3 Max)? GetBounds(ulong id, bool isSetup) {
            if (_boundsCache.TryGetValue(id, out var cachedBounds)) {
                return cachedBounds;
            }

            try {
                (Vector3 Min, Vector3 Max)? result = null;
                uint datId = (uint)(id & 0xFFFFFFFFu);
                var resolutions = _dats.ResolveId(datId).ToList();
                var selectedResolution = resolutions.OrderByDescending(r => r.Database == _dats.Portal).FirstOrDefault();
                if (selectedResolution == null) return null;

                var type = selectedResolution.Type;
                var db = selectedResolution.Database;

                if (type == DBObjType.Setup) {
                    var min = new Vector3(float.MaxValue);
                    var max = new Vector3(float.MinValue);
                    bool hasBounds = false;
                    var parts = new List<(ulong GfxObjId, Matrix4x4 Transform)>();

                    _extractor.CollectParts(datId, Matrix4x4.Identity, parts, ref min, ref max, ref hasBounds, CancellationToken.None);
                    result = hasBounds ? (min, max) : null;
                }
                else if (type == DBObjType.EnvCell) {
                    if (!db.TryGet<EnvCell>(datId, out var envCell)) return null;

                    // If bit 32 is set, this is a request for the cell's synthetic geometry only
                    if ((id & 0x1_0000_0000UL) != 0) {
                        uint envId = 0x0D000000u | envCell.EnvironmentId;
                        if (_dats.Portal.TryGet<DatReaderWriter.DBObjs.Environment>(envId, out var environment)) {
                            if (environment.Cells.TryGetValue(envCell.CellStructure, out var cellStruct)) {
                                var min = new Vector3(float.MaxValue);
                                var max = new Vector3(float.MinValue);
                                foreach (var vert in cellStruct.VertexArray.Vertices.Values) {
                                    min = Vector3.Min(min, vert.Origin);
                                    max = Vector3.Max(max, vert.Origin);
                                }
                                result = (min, max);
                            }
                        }
                    }
                    else {
                        var min = new Vector3(float.MaxValue);
                        var max = new Vector3(float.MinValue);
                        bool hasBounds = false;
                        var parts = new List<(ulong GfxObjId, Matrix4x4 Transform)>();

                        _extractor.CollectParts(datId, Matrix4x4.Identity, parts, ref min, ref max, ref hasBounds, CancellationToken.None);
                        result = hasBounds ? (min, max) : null;
                    }
                }
                else {
                    if (!db.TryGet<GfxObj>(datId, out var gfxObj)) return null;
                    result = _extractor.ComputeBounds(gfxObj, Vector3.One);
                }
                _boundsCache[id] = result;
                return result;
            }
            catch (Exception ex) {
                _logger.LogError(ex, "Error computing bounds for 0x{Id:X8}", id);
                return null;
            }
        }

        #region Private: Background Preparation

        /// <summary>
        /// #113: the set of polygon ids referenced by the GfxObj's drawing BSP —
        /// the polys retail actually renders (D3DPolyRender traverses the BSP;
        /// dictionary-orphaned polys are physics/no-draw geometry). Returns null
        /// when the model has no drawing BSP (caller draws everything).
        /// </summary>
        internal static HashSet<ushort>? CollectDrawingBspPolygonIds(GfxObj gfxObj) {
            if (gfxObj.DrawingBSP?.Root is null) return null;
            var ids = new HashSet<ushort>();
            CollectDrawingBspPolygonIds(gfxObj.DrawingBSP.Root, ids);
            return ids;
        }

        private static void CollectDrawingBspPolygonIds(DatReaderWriter.Types.DrawingBSPNode node, HashSet<ushort> ids) {
            if (node.Polygons is not null)
                foreach (var pid in node.Polygons)
                    ids.Add((ushort)pid);
            if (node.PosNode is not null) CollectDrawingBspPolygonIds(node.PosNode, ids);
            if (node.NegNode is not null) CollectDrawingBspPolygonIds(node.NegNode, ids);
        }

        #endregion

        #region Private: GPU Upload

        private unsafe ObjectRenderData? UploadGfxObjMeshData(ObjectMeshData meshData) {
            if (meshData.Vertices.Length == 0) return null;

            var gl = _graphicsDevice.GL;
            uint vao = 0, vbo = 0;

            if (_useModernRendering) {
                // Everything goes into the global VBO/IBO
                vao = GlobalBuffer!.VAO;
                vbo = GlobalBuffer!.VBO;
            }
            else {
                gl.GenVertexArrays(1, out vao);
                gl.BindVertexArray(vao);

                gl.GenBuffers(1, out vbo);
                gl.BindBuffer(GLEnum.ArrayBuffer, vbo);
                fixed (VertexPositionNormalTexture* ptr = meshData.Vertices) {
                    gl.BufferData(GLEnum.ArrayBuffer, (nuint)(meshData.Vertices.Length * VertexPositionNormalTexture.Size), ptr, GLEnum.StaticDraw);
                }
                GpuMemoryTracker.TrackAllocation(meshData.Vertices.Length * VertexPositionNormalTexture.Size, GpuResourceType.Buffer);

                int stride = VertexPositionNormalTexture.Size;
                // Position (location 0)
                gl.EnableVertexAttribArray(0);
                gl.VertexAttribPointer(0, 3, GLEnum.Float, false, (uint)stride, (void*)0);
                // Normal (location 1)
                gl.EnableVertexAttribArray(1);
                gl.VertexAttribPointer(1, 3, GLEnum.Float, false, (uint)stride, (void*)(3 * sizeof(float)));
                // TexCoord (location 2)
                gl.EnableVertexAttribArray(2);
                gl.VertexAttribPointer(2, 2, GLEnum.Float, false, (uint)stride, (void*)(6 * sizeof(float)));

                // Instance data (shared VBO)
                gl.BindBuffer(GLEnum.ArrayBuffer, _graphicsDevice.InstanceVBO);
                for (uint i = 0; i < 4; i++) {
                    var loc = 3 + i;
                    gl.EnableVertexAttribArray(loc);
                    gl.VertexAttribPointer(loc, 4, GLEnum.Float, false, (uint)sizeof(InstanceData), (void*)(i * 16));
                    gl.VertexAttribDivisor(loc, 1);
                }
                gl.EnableVertexAttribArray(8);
                gl.VertexAttribIPointer(8, 1, GLEnum.UnsignedInt, (uint)sizeof(InstanceData), (void*)64);
                gl.VertexAttribDivisor(8, 1);
            }

            var renderBatches = new List<ObjectRenderBatch>();

            foreach (var (format, batches) in meshData.TextureBatches) {
                foreach (var batch in batches) {
                    if (batch.Indices.Count == 0) continue;

                    uint ibo = 0;
                    TextureAtlasManager? atlasManager = null;
                    int textureIndex = 0;
                    uint firstIndex = 0;
                    int batchBaseVertex = 0;

                    // Find or create a shared atlas with free space
                    if (!_globalAtlases.TryGetValue(format, out var atlasList)) {
                        atlasList = new List<TextureAtlasManager>();
                        _globalAtlases[format] = atlasList;
                    }

                    atlasManager = atlasList.FirstOrDefault(a => a.FreeSlots > 0 || a.HasTexture(batch.Key));
                    if (atlasManager == null) {
                        atlasManager = new TextureAtlasManager(_graphicsDevice, format.Width, format.Height, format.Format);
                        atlasList.Add(atlasManager);
                    }

                    // MP1a: AcDream.Content is Silk.NET-free — the extraction records
                    // carry Content-owned UploadPixelFormat/UploadPixelType enums whose
                    // underlying values are the GL ABI constants (numerically identical
                    // to Silk.NET.OpenGL.PixelFormat/PixelType), so this lifted nullable
                    // cast is value- and null-preserving.
                    textureIndex = atlasManager.AddTexture(batch.Key, batch.TextureData,
                        (PixelFormat?)batch.UploadPixelFormat, (PixelType?)batch.UploadPixelType);

                    if (_useModernRendering) {
                        ibo = GlobalBuffer!.IBO;
                        var appended = GlobalBuffer.Append(meshData.Vertices, batch.Indices.ToArray());
                        batchBaseVertex = appended.baseVertex;
                        firstIndex = (uint)appended.firstIndex;
                    }
                    else {
                        gl.GenBuffers(1, out ibo);
                        gl.BindBuffer(GLEnum.ElementArrayBuffer, ibo);
                        var indexArray = batch.Indices.ToArray();
                        fixed (ushort* iptr = indexArray) {
                            gl.BufferData(GLEnum.ElementArrayBuffer, (nuint)(indexArray.Length * sizeof(ushort)), iptr, GLEnum.StaticDraw);
                        }
                        GpuMemoryTracker.TrackAllocation(indexArray.Length * sizeof(ushort), GpuResourceType.Buffer);
                    }

                    ulong bindlessHandle = batch.HasWrappingUVs 
                        ? atlasManager.TextureArray.BindlessWrapHandle 
                        : atlasManager.TextureArray.BindlessClampHandle;

                    renderBatches.Add(new ObjectRenderBatch {
                        IBO = ibo,
                        IndexCount = batch.Indices.Count,
                        Atlas = atlasManager!,
                        TextureIndex = textureIndex,
                        TextureSize = (format.Width, format.Height),
                        TextureFormat = format.Format,
                        IsTransparent = batch.IsTransparent,
                        IsAdditive = batch.IsAdditive,
                        HasWrappingUVs = batch.HasWrappingUVs,
                        Key = batch.Key,
                        CullMode = batch.CullMode,
                        FirstIndex = firstIndex,
                        BaseVertex = (uint)batchBaseVertex,
                        BindlessTextureHandle = bindlessHandle,
                    });
                }
            }

            var renderData = new ObjectRenderData {
                VAO = vao,
                VBO = vbo,
                VertexCount = meshData.Vertices.Length,
                Batches = renderBatches,
                ParticleEmitters = meshData.ParticleEmitters,
                DIDDegrade = meshData.DIDDegrade,
                CPUPositions = meshData.Vertices.Select(v => v.Position).ToArray(),
                CPUIndices = meshData.TextureBatches.Values.SelectMany(l => l).SelectMany(b => b.Indices).ToArray(),
                CPUEdgeLines = meshData.EdgeLines,
                MemorySize = (meshData.Vertices.Length * VertexPositionNormalTexture.Size) +
                             renderBatches.Sum(b => (long)b.IndexCount * sizeof(ushort))
            };

            if (!_useModernRendering) {
                gl.BindVertexArray(0);
            }
            return renderData;
        }

        #endregion

        #region Private: Utilities

        #region Raycasting

        public bool IntersectMesh(ObjectRenderData renderData, Matrix4x4 transform, Vector3 rayOrigin, Vector3 rayDirection, out float distance, out Vector3 normal) {
            return IntersectMeshInternal(renderData, transform, rayOrigin, rayDirection, 0, out distance, out normal);
        }

        private bool IntersectMeshInternal(ObjectRenderData renderData, Matrix4x4 transform, Vector3 rayOrigin, Vector3 rayDirection, int depth, out float distance, out Vector3 normal) {
            distance = float.MaxValue;
            normal = Vector3.UnitZ;
            bool hit = false;

            if (depth > 32) return false; // Prevent stack overflow from circular setups

            if (renderData.IsSetup) {
                foreach (var part in renderData.SetupParts) {
                    var partData = TryGetRenderData(part.GfxObjId);
                    if (partData != null) {
                        if (IntersectMeshInternal(partData, part.Transform * transform, rayOrigin, rayDirection, depth + 1, out float d, out Vector3 n)) {
                            if (d < distance) {
                                distance = d;
                                normal = n;
                                hit = true;
                            }
                        }
                    }
                }
                return hit;
            }

            if (renderData.CPUPositions.Length == 0 || renderData.CPUIndices.Length == 0) {
                // Fallback to sphere if no CPU mesh data
                if (renderData.SelectionSphere != null && renderData.SelectionSphere.Radius > 0.001f) {
                    var worldOrigin = Vector3.Transform(renderData.SelectionSphere.Origin, transform);
                    float radius = renderData.SelectionSphere.Radius * transform.Translation.Length(); // Rough scale
                    if (GeometryUtils.RayIntersectsSphere(rayOrigin, rayDirection, worldOrigin, radius, out distance)) {
                        normal = Vector3.Normalize(rayOrigin + rayDirection * distance - worldOrigin);
                        return true;
                    }
                }
                return false;
            }

            // Transform ray to local space
            if (!Matrix4x4.Invert(transform, out var invTransform)) return false;
            Vector3 localOrigin = Vector3.Transform(rayOrigin, invTransform);
            Vector3 localDirection = Vector3.Normalize(Vector3.TransformNormal(rayDirection, invTransform));

            // Iterate through triangles
            for (int i = 0; i < renderData.CPUIndices.Length; i += 3) {
                Vector3 v0 = renderData.CPUPositions[renderData.CPUIndices[i]];
                Vector3 v1 = renderData.CPUPositions[renderData.CPUIndices[i + 1]];
                Vector3 v2 = renderData.CPUPositions[renderData.CPUIndices[i + 2]];

                if (GeometryUtils.RayIntersectsTriangle(localOrigin, localDirection, v0, v1, v2, out float t)) {
                    // Convert t back to world space distance
                    Vector3 hitPointLocal = localOrigin + localDirection * t;
                    Vector3 hitPointWorld = Vector3.Transform(hitPointLocal, transform);
                    float worldDist = Vector3.Distance(rayOrigin, hitPointWorld);

                    if (worldDist < distance) {
                        distance = worldDist;

                        // Calculate normal in local space and transform to world space
                        Vector3 localNormal = Vector3.Normalize(Vector3.Cross(v1 - v0, v2 - v0));
                        normal = Vector3.Normalize(Vector3.TransformNormal(localNormal, transform));

                        // Ensure normal faces the ray
                        if (Vector3.Dot(normal, rayDirection) > 0) {
                            normal = -normal;
                        }

                        hit = true;
                    }
                }
            }

            return hit;
        }

        #endregion

        private void UnloadObject(ulong key) {
            if (!_renderData.TryGetValue(key, out var data)) return;

            var gl = _graphicsDevice.GL;
            if (!_useModernRendering) {
                if (data.VAO != 0) gl.DeleteVertexArray(data.VAO);
                if (data.VBO != 0) {
                    gl.DeleteBuffer(data.VBO);
                    GpuMemoryTracker.TrackDeallocation(data.VertexCount * VertexPositionNormalTexture.Size, GpuResourceType.Buffer);
                }

                foreach (var batch in data.Batches) {
                    if (batch.IBO != 0) {
                        gl.DeleteBuffer(batch.IBO);
                        GpuMemoryTracker.TrackDeallocation(batch.IndexCount * sizeof(ushort), GpuResourceType.Buffer);
                    }
                    if (batch.Atlas != null) {
                        batch.Atlas.ReleaseTexture(batch.Key);
                        if (batch.Atlas.UsedSlots == 0) {
                            batch.Atlas.Dispose();
                            var keyTuple = (batch.TextureSize.Width, batch.TextureSize.Height, batch.TextureFormat);
                            if (_globalAtlases.TryGetValue(keyTuple, out var list)) {
                                list.Remove(batch.Atlas);
                            }
                        }
                    }
                }
            }
            else {
                foreach (var batch in data.Batches) {
                    if (batch.Atlas != null) {
                        batch.Atlas.ReleaseTexture(batch.Key);
                        if (batch.Atlas.UsedSlots == 0) {
                            batch.Atlas.Dispose();
                            var keyTuple = (batch.TextureSize.Width, batch.TextureSize.Height, batch.TextureFormat);
                            if (_globalAtlases.TryGetValue(keyTuple, out var list)) {
                                list.Remove(batch.Atlas);
                            }
                        }
                    }
                }
            }

            if (data.IsSetup) {
                foreach (var (partId, _) in data.SetupParts) {
                    DecrementRefCount(partId);
                }
            }

            _currentGpuMemory -= data.MemorySize;
            _renderData.TryRemove(key, out _);
            lock (_lruList) {
                _lruList.Remove(key);
            }
        }

        #endregion

        public void Dispose() {
            if (IsDisposed) return;

            // Quiesce the background decode workers BEFORE returning: the owner
            // disposes the DatCollection right after this adapter chain, which
            // unmaps the dats' memory-mapped views. A worker still inside
            // MemoryMappedBlockAllocator.ReadBlock at that point dereferences the
            // dead view pointer — an uncatchable, process-fatal AccessViolation
            // (dat-race investigation 2026-06-09). Setting IsDisposed under the
            // queue lock publishes it to workers, which re-check it before every
            // dequeue; draining the queue means each worker exits after at most
            // its current (millisecond-scale) item.
            lock (_pendingRequests) {
                IsDisposed = true;
                foreach (var (id, _, tcs, _) in _pendingRequests) {
                    tcs.TrySetCanceled();
                    _preparationTasks.TryRemove(id, out _);
                }
                _pendingRequests.Clear();
                _pendingEnvCellRequests.Clear();
            }
            var deadline = System.Environment.TickCount64 + 10_000;
            while (System.Environment.TickCount64 < deadline) {
                lock (_pendingRequests) {
                    if (_activeWorkers == 0) break;
                }
                Thread.Sleep(5);
            }
            lock (_pendingRequests) {
                if (_activeWorkers > 0)
                    _logger.LogError(
                        "Dispose: {Count} mesh-decode workers still active after 10s — dat teardown may race in-flight reads",
                        _activeWorkers);
            }

            _graphicsDevice.QueueGLAction(gl => {
                foreach (var data in _renderData.Values) {
                    if (!_useModernRendering) {
                        if (data.VAO != 0) gl.DeleteVertexArray(data.VAO);
                        if (data.VBO != 0) {
                            gl.DeleteBuffer(data.VBO);
                            GpuMemoryTracker.TrackDeallocation(data.VertexCount * VertexPositionNormalTexture.Size, GpuResourceType.Buffer);
                        }
                        foreach (var batch in data.Batches) {
                            if (batch.IBO != 0) {
                                gl.DeleteBuffer(batch.IBO);
                                GpuMemoryTracker.TrackDeallocation(batch.IndexCount * sizeof(ushort), GpuResourceType.Buffer);
                            }
                        }
                    }
                }
                _renderData.Clear();

                foreach (var atlasList in _globalAtlases.Values) {
                    foreach (var atlas in atlasList) {
                        atlas.Dispose();
                    }
                }
                _globalAtlases.Clear();

                if (_useModernRendering) {
                    GlobalBuffer?.Dispose();
                }
            });
        }
    }
}