using AcDream.Core.Rendering.Wb;
using Chorizite.Core.Render;
using Chorizite.Core.Render.Enums;
// Use our extracted TextureHelpers (T3), not the WB original — disambiguate explicitly
using TextureHelpers = AcDream.Core.Rendering.Wb.TextureHelpers;
using Microsoft.Extensions.Logging;
using Silk.NET.OpenGL;
using System.Runtime.InteropServices;
using AcDream.App.Rendering;

namespace AcDream.App.Rendering.Wb {
    public class ManagedGLTextureArray : ITextureArray {
        private readonly bool[] _usedLayers;
        private readonly GL GL;
        private readonly OpenGLGraphicsDevice _device;
        private readonly ILogger _logger;
        private static int _nextId = 0;
        private bool _needsMipmapRegeneration = false;
        private readonly bool _isCompressed;
        private int _mipmapDirtyCount = 0;
        private readonly object _mipmapLock = new object();
        private readonly List<TextureLayerUpdate> _pendingUpdates = new();
        private int _disposeQueued;
        private int _disposePublicationQueued;
        private int _disposeRetirementAccepted;
        private RetryableGpuResourceRelease? _disposeRelease;

        private struct TextureLayerUpdate {
            public int Layer;
            public required byte[] Data;
            public PixelFormat? UploadPixelFormat;
            public PixelType? UploadPixelType;
        }

        public int Slot { get; } = _nextId++;
        public int Width { get; private set; }
        public int Height { get; private set; }
        public int Size { get; private set; }
        public TextureFormat Format { get; private set; }
        public nint NativePtr { get; private set; }
        public ulong BindlessWrapHandle { get; private set; }
        public ulong BindlessClampHandle { get; private set; }
        public long TotalSizeInBytes => CalculateTotalSize();

        /// <summary>
        /// #105 diagnostic: staged layer updates (retained decoded payloads) not yet
        /// applied to the GL texture by <see cref="ProcessDirtyUpdates"/>. Layers with
        /// a pending update sample UNDEFINED content (TexStorage3D contents) until the
        /// flush runs — a stuck non-zero count at standstill is the white-walls mechanism.
        /// </summary>
        public int PendingUpdateCount {
            get { lock (_mipmapLock) { return _pendingUpdates.Count; } }
        }

        public ManagedGLTextureArray(OpenGLGraphicsDevice graphicsDevice, TextureFormat format, int width, int height,
            int size, ILogger logger, TextureParameters? texParams = null) {
            var p = texParams ?? TextureParameters.Default;
            if (width <= 0 || height <= 0 || size <= 0) {
                throw new ArgumentException($"Invalid texture array dimensions: {width}x{height}x{size}");
            }

            Format = format;
            Width = width;
            Height = height;
            Size = size;
            _usedLayers = new bool[size];
            _device = graphicsDevice;
            GL = graphicsDevice.GL;
            _logger = logger;
            _isCompressed = IsCompressedFormat(format);
            GLHelpers.CheckErrors(GL);

            uint textureName = 0;
            ulong wrapHandle = 0;
            ulong clampHandle = 0;
            bool textureTracked = false;
            bool textureBytesTracked = false;
            bool wrapResident = false;
            bool clampResident = false;
            long textureBytes = CalculateTotalSize();

            try {
                textureName = GL.GenTexture();
                if (textureName == 0)
                    throw new InvalidOperationException("Failed to generate texture array.");
                GpuMemoryTracker.TrackResourceAllocation(GpuResourceType.Texture);
                textureTracked = true;

                GL.BindTexture(GLEnum.Texture2DArray, textureName);

                int maxDimension = Math.Max(width, height);
                int mipLevels = (int)Math.Floor(Math.Log2(maxDimension)) + 1;

                GL.TexStorage3D(GLEnum.Texture2DArray, (uint)mipLevels, format.ToGL(), (uint)width, (uint)height,
                    (uint)size);
                GL.TexParameter(GLEnum.Texture2DArray, TextureParameterName.TextureMinFilter,
                    (int)p.MinFilter);
                GL.TexParameter(GLEnum.Texture2DArray, TextureParameterName.TextureMaxLevel, mipLevels - 1);
                GL.TexParameter(GLEnum.Texture2DArray, TextureParameterName.TextureMagFilter, (int)p.MagFilter);
                GL.TexParameter(GLEnum.Texture2DArray, TextureParameterName.TextureWrapS, (int)p.WrapS);
                GL.TexParameter(GLEnum.Texture2DArray, TextureParameterName.TextureWrapT, (int)p.WrapT);

                if (p.EnableAnisotropicFiltering
                    && graphicsDevice.RenderSettings.EnableAnisotropicFiltering
                    && graphicsDevice.MaxSupportedAnisotropy > 0) {
                    GL.TexParameter(
                        GLEnum.Texture2DArray,
                        GLEnum.TextureMaxAnisotropy,
                        graphicsDevice.MaxSupportedAnisotropy);
                }

                if (format == TextureFormat.A8) {
                    GL.TexParameter(GLEnum.Texture2DArray, TextureParameterName.TextureSwizzleR, (int)GLEnum.One);
                    GL.TexParameter(GLEnum.Texture2DArray, TextureParameterName.TextureSwizzleG, (int)GLEnum.One);
                    GL.TexParameter(GLEnum.Texture2DArray, TextureParameterName.TextureSwizzleB, (int)GLEnum.One);
                    GL.TexParameter(GLEnum.Texture2DArray, TextureParameterName.TextureSwizzleA, (int)GLEnum.Red);
                }

                GLHelpers.ThrowOnResourceError(
                    GL,
                    $"creating texture array {format} {width}x{height}x{size} ({mipLevels} mip levels)");
                GpuMemoryTracker.TrackAllocation(textureBytes, GpuResourceType.Texture);
                textureBytesTracked = true;

                if (_device.HasBindless && _device.BindlessExtension != null) {
                    wrapHandle = _device.BindlessExtension.GetTextureSamplerHandle(textureName, _device.WrapSampler);
                    clampHandle = _device.BindlessExtension.GetTextureSamplerHandle(textureName, _device.ClampSampler);
                    _device.BindlessExtension.MakeTextureHandleResident(wrapHandle);
                    wrapResident = true;
                    _device.BindlessExtension.MakeTextureHandleResident(clampHandle);
                    clampResident = true;
                    GLHelpers.ThrowOnResourceError(GL, "making texture-array sampler handles resident");
                }

                NativePtr = (nint)textureName;
                BindlessWrapHandle = wrapHandle;
                BindlessClampHandle = clampHandle;
            }
            catch (Exception constructionFailure) {
                // Constructor failure cannot use Dispose: the object was never
                // published and queued teardown would make retries accumulate
                // invalid resident handles. Attempt every independent cleanup.
                List<Exception>? cleanupFailures = null;
                void Attempt(Action cleanup) {
                    try { cleanup(); }
                    catch (Exception ex) { (cleanupFailures ??= []).Add(ex); }
                }
                if (_device.BindlessExtension != null) {
                    if (clampResident)
                        Attempt(() => {
                            _device.BindlessExtension.MakeTextureHandleNonResident(clampHandle);
                            GLHelpers.ThrowOnResourceError(GL, "rolling back clamp texture-array handle");
                            clampResident = false;
                        });
                    if (wrapResident)
                        Attempt(() => {
                            _device.BindlessExtension.MakeTextureHandleNonResident(wrapHandle);
                            GLHelpers.ThrowOnResourceError(GL, "rolling back wrap texture-array handle");
                            wrapResident = false;
                        });
                }
                // Deleting a texture while either bindless sampler handle is
                // still resident is undefined. A pre-commit residency failure
                // therefore retains the texture instead of risking a driver
                // reset during constructor rollback.
                if (textureName != 0 && !clampResident && !wrapResident)
                    Attempt(() => {
                        GL.DeleteTexture(textureName);
                        GLHelpers.ThrowOnResourceError(GL, "rolling back texture array");
                        if (textureBytesTracked)
                            GpuMemoryTracker.TrackDeallocation(textureBytes, GpuResourceType.Texture);
                        if (textureTracked)
                            GpuMemoryTracker.TrackResourceDeallocation(GpuResourceType.Texture);
                    });
                if (cleanupFailures is not null) {
                    cleanupFailures.Insert(0, constructionFailure);
                    throw new AggregateException(
                        "Texture-array construction and rollback both failed.",
                        cleanupFailures);
                }
                throw;
            }
            finally {
                GL.ActiveTexture(TextureUnit.Texture0);
                GL.BindTexture(GLEnum.Texture2DArray, 0);
                RenderStateCache.CurrentAtlas = 0;
            }
        }

        public long CalculateTotalSize() {
            int maxDimension = Math.Max(Width, Height);
            int mipLevels = (int)Math.Floor(Math.Log2(maxDimension)) + 1;
            long layerSize = GetExpectedDataSize();
            long totalSize = 0;

            for (int i = 0; i < mipLevels; i++) {
                int w = Math.Max(1, Width >> i);
                int h = Math.Max(1, Height >> i);
                if (_isCompressed) {
                    totalSize += TextureHelpers.GetCompressedLayerSize(w, h, Format) * Size;
                }
                else {
                    totalSize += (long)w * h * (layerSize / (Width * Height)) * Size;
                }
            }
            return totalSize;
        }

        private static bool IsCompressedFormat(TextureFormat format) {
            return format == TextureFormat.DXT1 ||
                   format == TextureFormat.DXT3 ||
                   format == TextureFormat.DXT5;
        }

        public void Bind(int slot = 0) {
            if (NativePtr == 0) {
                return;
            }

            GL.GetInteger(GLEnum.ActiveTexture, out int oldActiveTexture);
            GLEnum targetTextureUnit = GLEnum.Texture0 + slot;
            bool changedUnit = (GLEnum)oldActiveTexture != targetTextureUnit;

            if (changedUnit) {
                GL.ActiveTexture(targetTextureUnit);
            }

            GL.BindSampler((uint)slot, 0);
            GL.BindTexture(GLEnum.Texture2DArray, (uint)NativePtr);

            if (changedUnit) {
                GL.ActiveTexture((GLEnum)oldActiveTexture);
            }
            GLHelpers.CheckErrors(GL);
        }

        public unsafe int AddLayer(byte[] data) {
            return AddLayer(data, null, null);
        }

        public unsafe int AddLayer(byte[] data, PixelFormat? uploadPixelFormat, PixelType? uploadPixelType) {
            for (int i = 0; i < _usedLayers.Length; i++) {
                if (!_usedLayers[i]) {
                    UpdateLayerInternal(i, data, uploadPixelFormat, uploadPixelType);
                    _usedLayers[i] = true;
                    return i;
                }
            }

            throw new InvalidOperationException(
                $"No free layers available in texture array (Slot={Slot}, Size={Width}x{Height}x{Size}).");
        }

        public unsafe int AddLayer(Span<byte> data) {
            return AddLayer(data.ToArray());
        }

        public void UpdateLayer(int layer, byte[] data) {
            UpdateLayer(layer, data, null, null);
        }

        public void UpdateLayer(int layer, byte[] data, PixelFormat? uploadPixelFormat, PixelType? uploadPixelType) {
            UpdateLayerInternal(layer, data, uploadPixelFormat, uploadPixelType);
            _usedLayers[layer] = true;
        }

        private unsafe void UpdateLayerInternal(int layer, byte[] data, PixelFormat? uploadPixelFormat,
            PixelType? uploadPixelType) {
            if (NativePtr == 0) {
                throw new InvalidOperationException("Texture array not created.");
            }

            if (layer < 0 || layer >= Size) {
                throw new ArgumentOutOfRangeException(nameof(layer),
                    $"Layer index {layer} is out of range [0, {Size - 1}] (Slot={Slot}).");
            }

            ValidateUploadPayload(
                Format,
                Width,
                Height,
                data.Length,
                uploadPixelFormat,
                uploadPixelType);

            lock (_mipmapLock) {
                // Retain the immutable decoded payload until the once-per-frame
                // atlas flush. The former per-atlas PBO permanently reserved
                // several MiB for every array and duplicated each upload
                // through BufferSubData before TexSubImage3D.
                var update = new TextureLayerUpdate {
                    Layer = layer,
                    Data = data,
                    UploadPixelFormat = uploadPixelFormat,
                    UploadPixelType = uploadPixelType
                };
                int existingIndex = _pendingUpdates.FindLastIndex(pending => pending.Layer == layer);
                if (existingIndex >= 0)
                    _pendingUpdates[existingIndex] = update;
                else
                    _pendingUpdates.Add(update);

                _needsMipmapRegeneration = true;
                if (existingIndex < 0)
                    _mipmapDirtyCount++;
            }
        }

        public long ProcessDirtyUpdates() {
            lock (_mipmapLock) {
                return ProcessDirtyUpdatesInternal(generateMipmaps: true);
            }
        }

        private unsafe long ProcessDirtyUpdatesInternal(bool generateMipmaps) {
            if (_pendingUpdates.Count == 0
                && (!generateMipmaps || !_needsMipmapRegeneration)) return 0;

            long generatedBytes = 0;

            GLHelpers.CheckErrors(GL);

            // This runs in WbMeshAdapter.Tick before any draw pass. Establish
            // the upload phase's canonical texture state directly instead of
            // synchronously querying driver state for every dirty array.
            GL.ActiveTexture(TextureUnit.Texture0);
            RenderStateCache.CurrentAtlas = 0;

            bool mipmapWorkCompleted = false;
            try {
                GL.BindTexture(GLEnum.Texture2DArray, (uint)NativePtr);

                if (_pendingUpdates.Count > 0) {
                    // A non-zero pixel-unpack binding changes pointer arguments
                    // into byte offsets. Direct client-memory uploads therefore
                    // establish the canonical zero binding once for the batch.
                    GL.BindBuffer(GLEnum.PixelUnpackBuffer, 0);
                    GL.PixelStore(PixelStoreParameter.UnpackAlignment, 1);
                    GL.PixelStore(PixelStoreParameter.UnpackRowLength, 0);
                    GL.PixelStore(PixelStoreParameter.UnpackSkipRows, 0);
                    GL.PixelStore(PixelStoreParameter.UnpackSkipPixels, 0);

                    foreach (var update in _pendingUpdates) {
                        fixed (byte* data = update.Data) {
                            if (_isCompressed) {
                                var internalFormat = Format.ToCompressedGL();
                                GL.CompressedTexSubImage3D(
                                    GLEnum.Texture2DArray,
                                    0,
                                    0,
                                    0,
                                    update.Layer,
                                    (uint)Width,
                                    (uint)Height,
                                    1,
                                    internalFormat,
                                    (uint)update.Data.Length,
                                    data);
                            }
                            else {
                                var pixelFormat = update.UploadPixelFormat ?? Format.ToPixelFormat();
                                var pixelType = update.UploadPixelType ?? Format.ToPixelType();
                                GL.TexSubImage3D(
                                    GLEnum.Texture2DArray,
                                    0,
                                    0,
                                    0,
                                    update.Layer,
                                    (uint)Width,
                                    (uint)Height,
                                    1,
                                    pixelFormat,
                                    pixelType,
                                    data);
                            }
                        }
                    }
                }

                if (generateMipmaps && _needsMipmapRegeneration && _mipmapDirtyCount > 0) {
                    if (_isCompressed) {
                        _logger.LogDebug("Skipping automatic mipmap generation for compressed texture array (Slot={Slot})", Slot);
                    }
                    else {
                        try {
                            // Width, height and format were validated when the
                            // immutable storage was allocated. Re-reading them
                            // here forced three CPU/GPU synchronization points
                            // for every dirty atlas without adding safety.
                            GL.GenerateMipmap(GLEnum.Texture2DArray);
                            generatedBytes = TotalSizeInBytes;
                        }
                        catch (Exception ex) {
                            _logger.LogWarning(ex, "Failed to generate mipmaps for texture array (Slot={Slot}); retaining upload state for retry.", Slot);
                            throw;
                        }
                    }
                }

                // Release builds must observe transfer/OOM/context errors
                // before the pending offsets and dirty mip state are cleared.
                // One check covers every layer in this array plus its single
                // mip generation, keeping the synchronization cost bounded by
                // dirty arrays rather than uploaded textures.
                GLHelpers.ThrowOnResourceError(
                    GL,
                    $"committing texture-array updates (Slot={Slot}, Layers={_pendingUpdates.Count})");
                mipmapWorkCompleted = generateMipmaps
                    && _needsMipmapRegeneration
                    && _mipmapDirtyCount > 0;
            }
            finally {
                GL.BindBuffer(GLEnum.PixelUnpackBuffer, 0);
                GL.BindTexture(GLEnum.Texture2DArray, 0);
                GL.ActiveTexture(TextureUnit.Texture0);
            }

            // Commit CPU-side completion only after glGetError confirms the
                // uploads/mipmap work succeeded. If the driver rejects an
                // operation, the retained payloads and dirty flags remain intact and the
            // atlas stays in ObjectMeshManager's dirty set for a later retry.
            _pendingUpdates.Clear();
            if (mipmapWorkCompleted) {
                _mipmapDirtyCount = 0;
                _needsMipmapRegeneration = false;
            }
            return generatedBytes;
        }

        private void ClearLayerForMipmap(int layer) {
            // Upload a single black/transparent pixel to make layer defined
            byte[] clearData = new byte[GetExpectedDataSize()];
            Array.Clear(clearData, 0, clearData.Length); // Zero-fill (black/transparent)
            UpdateLayerInternal(layer, clearData, null, null);
        }

        private int GetExpectedDataSize() {
            return CalculateExpectedDataSize(Format, Width, Height);
        }

        internal static int CalculateExpectedDataSize(TextureFormat format, int width, int height) {
            if (IsCompressedFormat(format))
                return TextureHelpers.GetCompressedLayerSize(width, height, format);

            return format switch {
                TextureFormat.RGBA8 => checked(width * height * 4),
                TextureFormat.RGB8 => checked(width * height * 3),
                TextureFormat.A8 => checked(width * height),
                TextureFormat.Rgba32f => checked(width * height * 16),
                _ => throw new NotSupportedException($"Unsupported format {format}")
            };
        }

        internal static void ValidateUploadPayload(
            TextureFormat format,
            int width,
            int height,
            int dataLength,
            PixelFormat? uploadPixelFormat,
            PixelType? uploadPixelType) {
            int expectedBytes = CalculateExpectedDataSize(format, width, height);
            if (dataLength != expectedBytes) {
                throw new ArgumentException(
                    $"Texture-array layer payload has {dataLength} bytes; expected exactly {expectedBytes} "
                    + $"for {format} {width}x{height}.",
                    nameof(dataLength));
            }

            if (IsCompressedFormat(format)) {
                if (uploadPixelFormat.HasValue || uploadPixelType.HasValue)
                    throw new ArgumentException("Compressed texture uploads cannot specify pixel format/type overrides.");
                return;
            }

            PixelFormat expectedFormat = format.ToPixelFormat();
            PixelType expectedType = format.ToPixelType();
            if ((uploadPixelFormat ?? expectedFormat) != expectedFormat
                || (uploadPixelType ?? expectedType) != expectedType) {
                throw new ArgumentException(
                    $"Upload descriptor {uploadPixelFormat}/{uploadPixelType} does not match "
                    + $"the {expectedFormat}/{expectedType} transfer required by {format}.");
            }
        }

        public void RemoveLayer(int layer) {
            if (layer < 0 || layer >= Size) {
                throw new ArgumentOutOfRangeException(nameof(layer),
                    $"Layer index {layer} is out of range [0, {Size - 1}] (Slot={Slot}).");
            }

            if (!_usedLayers[layer]) {
                throw new InvalidOperationException($"Layer {layer} is already free (Slot={Slot}).");
            }

            _usedLayers[layer] = false;

            // An unreferenced layer needs no clear or whole-array mip
            // regeneration before AddTexture overwrites it on reuse.
        }

        public bool IsLayerUsed(int layer) {
            if (layer < 0 || layer >= Size) return false;
            return _usedLayers[layer];
        }

        public int GetUsedLayerCount() {
            return _usedLayers.Count(x => x);
        }

        /// <summary>
        /// True once disposal is durably owned by a queued GL publication,
        /// the frame-retirement queue, or a completed retained release. A
        /// caller may only commit its own logical disposal after this becomes
        /// true; otherwise a synchronous enqueue failure still needs retry.
        /// </summary>
        internal bool HasDurableDisposeOwnership {
            get {
                if (Volatile.Read(ref _disposeQueued) == 0)
                    return false;
                return Volatile.Read(ref _disposePublicationQueued) != 0
                    || Volatile.Read(ref _disposeRetirementAccepted) != 0
                    || Volatile.Read(ref _disposeRelease) is null;
            }
        }

        public void Unbind() {
            GL.BindTexture(GLEnum.Texture2DArray, 0);
            GLHelpers.CheckErrors(GL);
        }

        public void GenerateMipmaps() {
            _needsMipmapRegeneration = true;
            lock (_mipmapLock) {
                _mipmapDirtyCount++;
            }
        }

        public void Dispose() {
            if (Interlocked.CompareExchange(ref _disposeQueued, 1, 0) != 0) {
                ScheduleDisposeRelease();
                return;
            }

            uint textureName = (uint)NativePtr;
            ulong bindlessWrapHandle = BindlessWrapHandle;
            ulong bindlessClampHandle = BindlessClampHandle;
            long textureBytes = CalculateTotalSize();

            NativePtr = 0;
            BindlessWrapHandle = 0;
            BindlessClampHandle = 0;

            _disposeRelease = new RetryableGpuResourceRelease(
                () => {
                    if (_device.BindlessExtension != null && bindlessWrapHandle != 0)
                        GLHelpers.ThrowOnResourceError(GL, "releasing wrap texture-array handle (precondition)");
                },
                () => {
                    if (_device.BindlessExtension != null && bindlessWrapHandle != 0) {
                        _device.BindlessExtension.MakeTextureHandleNonResident(bindlessWrapHandle);
                        GLHelpers.ThrowOnResourceError(GL, "releasing wrap texture-array handle");
                    }
                },
                () => {
                    if (_device.BindlessExtension != null && bindlessClampHandle != 0)
                        GLHelpers.ThrowOnResourceError(GL, "releasing clamp texture-array handle (precondition)");
                },
                () => {
                    if (_device.BindlessExtension != null && bindlessClampHandle != 0) {
                        _device.BindlessExtension.MakeTextureHandleNonResident(bindlessClampHandle);
                        GLHelpers.ThrowOnResourceError(GL, "releasing clamp texture-array handle");
                    }
                },
                () => {
                    if (textureName != 0)
                        GLHelpers.ThrowOnResourceError(GL, $"deleting texture array {textureName} (precondition)");
                },
                () => {
                    if (textureName != 0) {
                        GL.DeleteTexture(textureName);
                        GLHelpers.ThrowOnResourceError(GL, $"deleting texture array {textureName}");
                    }
                },
                () => {
                    if (textureName != 0)
                        GpuMemoryTracker.TrackDeallocation(textureBytes, GpuResourceType.Texture);
                },
                () => {
                    if (textureName != 0)
                        GpuMemoryTracker.TrackResourceDeallocation(GpuResourceType.Texture);
                },
                () => _disposeRelease = null);

            ScheduleDisposeRelease();
        }

        private void ScheduleDisposeRelease(bool forNextPass = false) {
            RetryableGpuResourceRelease? release = _disposeRelease;
            if (release is null || release.IsComplete || Volatile.Read(ref _disposeRetirementAccepted) != 0)
                return;
            if (Interlocked.CompareExchange(ref _disposePublicationQueued, 1, 0) != 0)
                return;

            try {
                Action<GL> publish = GL => {
                    Volatile.Write(ref _disposePublicationQueued, 0);
                    try {
                        _device.RetireGpuResource(release.Run);
                        Volatile.Write(ref _disposeRetirementAccepted, 1);
                    }
                    catch {
                        // Retire may fail before accepting the callback, or an
                        // immediate queue may surface a partial release. The
                        // release cursor makes this next-pass retry exact.
                        ScheduleDisposeRelease(forNextPass: true);
                        throw;
                    }
                };
                if (forNextPass)
                    _device.QueueGLActionForNextPass(publish);
                else
                    _device.QueueGLAction(publish);
            }
            catch {
                Volatile.Write(ref _disposePublicationQueued, 0);
                throw;
            }
        }
    }
}