// Copyright (c) 2012-2023 Wojciech Figat. All rights reserved.

#include "SkinnedModel.h"
#include "Animation.h"
#include "Engine/Core/Log.h"
#include "Engine/Engine/Engine.h"
#include "Engine/Serialization/MemoryReadStream.h"
#include "Engine/Streaming/StreamingGroup.h"
#include "Engine/Threading/ThreadPoolTask.h"
#include "Engine/Threading/Threading.h"
#include "Engine/Graphics/RenderTools.h"
#include "Engine/Graphics/RenderTask.h"
#include "Engine/Graphics/Models/ModelInstanceEntry.h"
#include "Engine/Graphics/Models/Config.h"
#include "Engine/Content/Content.h"
#include "Engine/Content/WeakAssetReference.h"
#include "Engine/Content/Factories/BinaryAssetFactory.h"
#include "Engine/Content/Upgraders/SkinnedModelAssetUpgrader.h"
#include "Engine/Debug/Exceptions/ArgumentOutOfRangeException.h"
#include "Engine/Profiler/ProfilerCPU.h"
#include "Engine/Renderer/DrawCall.h"

#define CHECK_INVALID_BUFFER(model, buffer) \
    if (buffer->IsValidFor(model) == false) \
	{ \
		LOG(Warning, "Invalid Skinned Model Instance Buffer size {0} for Skinned Model {1}. It should be {2}. Manual update to proper size.", buffer->Count(), model->ToString(), model->MaterialSlots.Count()); \
		buffer->Setup(model); \
	}

/// <summary>
/// Skinned model data streaming task
/// </summary>
class StreamSkinnedModelLODTask : public ThreadPoolTask
{
private:
    WeakAssetReference<SkinnedModel> _asset;
    int32 _lodIndex;
    FlaxStorage::LockData _dataLock;

public:
    /// <summary>
    /// Init
    /// </summary>
    /// <param name="model">Parent model</param>
    /// <param name="lodIndex">LOD to stream index</param>
    StreamSkinnedModelLODTask(SkinnedModel* model, int32 lodIndex)
        : _asset(model)
        , _lodIndex(lodIndex)
        , _dataLock(model->Storage->Lock())
    {
    }

public:
    // [ThreadPoolTask]
    bool HasReference(Object* resource) const override
    {
        return _asset == resource;
    }

protected:
    // [ThreadPoolTask]
    bool Run() override
    {
        AssetReference<SkinnedModel> model = _asset.Get();
        if (model == nullptr)
        {
            return true;
        }

        // Get data
        BytesContainer data;
        model->GetLODData(_lodIndex, data);
        if (data.IsInvalid())
        {
            LOG(Warning, "Missing data chunk");
            return true;
        }
        MemoryReadStream stream(data.Get(), data.Length());

        // Note: this is running on thread pool task so we must be sure that updated LOD is not used at all (for rendering)

        // Load model LOD (initialize vertex and index buffers)
        if (model->LODs[_lodIndex].Load(stream))
        {
            LOG(Warning, "Cannot load LOD{1} for model \'{0}\'", model->ToString(), _lodIndex);
            return true;
        }

        // Update residency level
        model->_loadedLODs++;
        model->ResidencyChanged();

        return false;
    }

    void OnEnd() override
    {
        // Unlink
        if (_asset)
        {
            ASSERT(_asset->_streamingTask == this);
            _asset->_streamingTask = nullptr;
            _asset = nullptr;
        }
        _dataLock.Release();

        // Base
        ThreadPoolTask::OnEnd();
    }
};

REGISTER_BINARY_ASSET_WITH_UPGRADER(SkinnedModel, "FlaxEngine.SkinnedModel", SkinnedModelAssetUpgrader, true);

SkinnedModel::SkinnedModel(const SpawnParams& params, const AssetInfo* info)
    : ModelBase(params, info, StreamingGroups::Instance()->SkinnedModels())
{
}

SkinnedModel::~SkinnedModel()
{
    ASSERT(_streamingTask == nullptr);
    ASSERT(_skeletonMappingCache.Count() == 0);
}

bool SkinnedModel::HasAnyLODInitialized() const
{
    return LODs.HasItems() && LODs.Last().HasAnyMeshInitialized();
}

Array<String> SkinnedModel::GetBlendShapes()
{
    Array<String> result;
    if (LODs.HasItems())
    {
        for (auto& mesh : LODs[0].Meshes)
        {
            for (auto& blendShape : mesh.BlendShapes)
            {
                if (!result.Contains(blendShape.Name))
                    result.Add(blendShape.Name);
            }
        }
    }
    return result;
}

ContentLoadTask* SkinnedModel::RequestLODDataAsync(int32 lodIndex)
{
    const int32 chunkIndex = MODEL_LOD_TO_CHUNK_INDEX(lodIndex);
    return RequestChunkDataAsync(chunkIndex);
}

void SkinnedModel::GetLODData(int32 lodIndex, BytesContainer& data) const
{
    const int32 chunkIndex = MODEL_LOD_TO_CHUNK_INDEX(lodIndex);
    GetChunkData(chunkIndex, data);
}

SkinnedModel::SkeletonMapping SkinnedModel::GetSkeletonMapping(Asset* source)
{
    SkeletonMapping mapping;
    mapping.TargetSkeleton = this;
    if (WaitForLoaded() || !source || source->WaitForLoaded())
        return mapping;
    ScopeLock lock(Locker);
    SkeletonMappingData mappingData;
    if (!_skeletonMappingCache.TryGet(source, mappingData))
    {
        PROFILE_CPU();

        // Initialize the mapping
        const int32 nodesCount = Skeleton.Nodes.Count();
        mappingData.NodesMapping = Span<int32>((int32*)Allocator::Allocate(nodesCount * sizeof(int32)), nodesCount);
        for (int32 i = 0; i < nodesCount; i++)
            mappingData.NodesMapping[i] = -1;
        SkeletonRetarget* retarget = nullptr;
        const Guid sourceId = source->GetID();
        for (auto& e : _skeletonRetargets)
        {
            if (e.SourceAsset == sourceId)
            {
                retarget = &e;
                break;
            }
        }
        if (const auto* sourceAnim = Cast<Animation>(source))
        {
            const auto& channels = sourceAnim->Data.Channels;
            if (retarget && retarget->SkeletonAsset)
            {
                // Map retarget skeleton nodes from animation channels
                if (auto* skeleton = Content::Load<SkinnedModel>(retarget->SkeletonAsset))
                {
                    const SkeletonMapping skeletonMapping = GetSkeletonMapping(skeleton);
                    mappingData.SourceSkeleton = skeleton;
                    if (skeletonMapping.NodesMapping.Length() == nodesCount)
                    {
                        const auto& nodes = skeleton->Skeleton.Nodes;
                        for (int32 j = 0; j < nodesCount; j++)
                        {
                            if (skeletonMapping.NodesMapping[j] != -1)
                            {
                                const Char* nodeName = nodes[skeletonMapping.NodesMapping[j]].Name.GetText();
                                for (int32 i = 0; i < channels.Count(); i++)
                                {
                                    if (StringUtils::CompareIgnoreCase(nodeName, channels[i].NodeName.GetText()) == 0)
                                    {
                                        mappingData.NodesMapping[j] = i;
                                        break;
                                    }
                                }
                            }
                        }
                    }
                }
                else
                {
    #if !BUILD_RELEASE
                    LOG(Error, "Missing asset {0} to use for skeleton mapping of {1}", retarget->SkeletonAsset, ToString());
    #endif
                    return mapping;
                }
            }
            else
            {
                // Map animation channels to the skeleton nodes (by name)
                for (int32 i = 0; i < channels.Count(); i++)
                {
                    const NodeAnimationData& nodeAnim = channels[i];
                    for (int32 j = 0; j < nodesCount; j++)
                    {
                        if (StringUtils::CompareIgnoreCase(Skeleton.Nodes[j].Name.GetText(), nodeAnim.NodeName.GetText()) == 0)
                        {
                            mappingData.NodesMapping[j] = i;
                            break;
                        }
                    }
                }
            }
        }
        else if (const auto* sourceModel = Cast<SkinnedModel>(source))
        {
            if (retarget)
            {
                // Use nodes retargeting
                for (const auto& e : retarget->NodesMapping)
                {
                    const int32 dstIndex = Skeleton.FindNode(e.Key);
                    const int32 srcIndex = sourceModel->Skeleton.FindNode(e.Value);
                    if (dstIndex != -1 && srcIndex != -1)
                    {
                        mappingData.NodesMapping[dstIndex] = srcIndex;
                    }
                }
            }
            else
            {
                // Map source skeleton nodes to the target skeleton nodes (by name)
                const auto& nodes = sourceModel->Skeleton.Nodes;
                for (int32 i = 0; i < nodes.Count(); i++)
                {
                    const SkeletonNode& node = nodes[i];
                    for (int32 j = 0; j < nodesCount; j++)
                    {
                        if (StringUtils::CompareIgnoreCase(Skeleton.Nodes[j].Name.GetText(), node.Name.GetText()) == 0)
                        {
                            mappingData.NodesMapping[j] = i;
                            break;
                        }
                    }
                }
            }
        }
        else
        {
#if !BUILD_RELEASE
            LOG(Error, "Invalid asset type {0} to use for skeleton mapping of {1}", source->GetTypeName(), ToString());
#endif
        }

        // Add to cache
        _skeletonMappingCache.Add(source, mappingData);
        source->OnUnloaded.Bind<SkinnedModel, &SkinnedModel::OnSkeletonMappingSourceAssetUnloaded>(this);
#if USE_EDITOR
        source->OnReloading.Bind<SkinnedModel, &SkinnedModel::OnSkeletonMappingSourceAssetUnloaded>(this);
#endif
    }
    mapping.SourceSkeleton = mappingData.SourceSkeleton;
    mapping.NodesMapping = mappingData.NodesMapping;
    return mapping;
}

bool SkinnedModel::Intersects(const Ray& ray, const Matrix& world, Real& distance, Vector3& normal, SkinnedMesh** mesh, int32 lodIndex)
{
    if (LODs.Count() == 0)
        return false;
    return LODs[lodIndex].Intersects(ray, world, distance, normal, mesh);
}

bool SkinnedModel::Intersects(const Ray& ray, const Transform& transform, Real& distance, Vector3& normal, SkinnedMesh** mesh, int32 lodIndex)
{
    if (LODs.Count() == 0)
        return false;
    return LODs[lodIndex].Intersects(ray, transform, distance, normal, mesh);
}

BoundingBox SkinnedModel::GetBox(const Matrix& world, int32 lodIndex) const
{
    if (LODs.Count() == 0)
        return BoundingBox::Zero;
    return LODs[lodIndex].GetBox(world);
}

BoundingBox SkinnedModel::GetBox(int32 lodIndex) const
{
    if (LODs.Count() == 0)
        return BoundingBox::Zero;
    return LODs[lodIndex].GetBox();
}

template<typename ContextType>
FORCE_INLINE void SkinnedModelDraw(SkinnedModel* model, const RenderContext& renderContext, const ContextType& context, const SkinnedMesh::DrawInfo& info)
{
    ASSERT(info.Buffer);
    if (!model->CanBeRendered())
        return;
    const auto frame = Engine::FrameCount;
    const auto modelFrame = info.DrawState->PrevFrame + 1;
    CHECK_INVALID_BUFFER(model, info.Buffer);

    // Select a proper LOD index (model may be culled)
    int32 lodIndex;
    if (info.ForcedLOD != -1)
    {
        lodIndex = info.ForcedLOD;
    }
    else
    {
        lodIndex = RenderTools::ComputeSkinnedModelLOD(model, info.Bounds.Center, (float)info.Bounds.Radius, renderContext);
        if (lodIndex == -1)
        {
            // Handling model fade-out transition
            if (modelFrame == frame && info.DrawState->PrevLOD != -1 && !renderContext.View.IsSingleFrame)
            {
                // Check if start transition
                if (info.DrawState->LODTransition == 255)
                {
                    info.DrawState->LODTransition = 0;
                }

                RenderTools::UpdateModelLODTransition(info.DrawState->LODTransition);

                // Check if end transition
                if (info.DrawState->LODTransition == 255)
                {
                    info.DrawState->PrevLOD = lodIndex;
                }
                else
                {
                    const auto prevLOD = model->ClampLODIndex(info.DrawState->PrevLOD);
                    const float normalizedProgress = static_cast<float>(info.DrawState->LODTransition) * (1.0f / 255.0f);
                    model->LODs.Get()[prevLOD].Draw(renderContext, info, normalizedProgress);
                }
            }

            return;
        }
    }
    lodIndex += info.LODBias + renderContext.View.ModelLODBias;
    lodIndex = model->ClampLODIndex(lodIndex);

    if (renderContext.View.IsSingleFrame)
    {
    }
    // Check if it's the new frame and could update the drawing state (note: model instance could be rendered many times per frame to different viewports)
    else if (modelFrame == frame)
    {
        // Check if start transition
        if (info.DrawState->PrevLOD != lodIndex && info.DrawState->LODTransition == 255)
        {
            info.DrawState->LODTransition = 0;
        }

        RenderTools::UpdateModelLODTransition(info.DrawState->LODTransition);

        // Check if end transition
        if (info.DrawState->LODTransition == 255)
        {
            info.DrawState->PrevLOD = lodIndex;
        }
    }
    // Check if there was a gap between frames in drawing this model instance
    else if (modelFrame < frame || info.DrawState->PrevLOD == -1)
    {
        // Reset state
        info.DrawState->PrevLOD = lodIndex;
        info.DrawState->LODTransition = 255;
    }

    // Draw
    if (info.DrawState->PrevLOD == lodIndex || renderContext.View.IsSingleFrame)
    {
        model->LODs.Get()[lodIndex].Draw(context, info, 0.0f);
    }
    else if (info.DrawState->PrevLOD == -1)
    {
        const float normalizedProgress = static_cast<float>(info.DrawState->LODTransition) * (1.0f / 255.0f);
        model->LODs.Get()[lodIndex].Draw(context, info, 1.0f - normalizedProgress);
    }
    else
    {
        const auto prevLOD = model->ClampLODIndex(info.DrawState->PrevLOD);
        const float normalizedProgress = static_cast<float>(info.DrawState->LODTransition) * (1.0f / 255.0f);
        model->LODs.Get()[prevLOD].Draw(context, info, normalizedProgress);
        model->LODs.Get()[lodIndex].Draw(context, info, normalizedProgress - 1.0f);
    }
}

void SkinnedModel::Draw(const RenderContext& renderContext, const SkinnedMesh::DrawInfo& info)
{
    SkinnedModelDraw(this, renderContext, renderContext, info);
}

void SkinnedModel::Draw(const RenderContextBatch& renderContextBatch, const SkinnedMesh::DrawInfo& info)
{
    SkinnedModelDraw(this, renderContextBatch.GetMainContext(), renderContextBatch, info);
}

bool SkinnedModel::SetupLODs(const Span<int32>& meshesCountPerLod)
{
    ScopeLock lock(Locker);

    // Validate input and state
    if (!IsVirtual())
    {
        LOG(Error, "Only virtual models can be updated at runtime.");
        return true;
    }

    return Init(meshesCountPerLod);;
}

bool SkinnedModel::SetupSkeleton(const Array<SkeletonNode>& nodes)
{
    // Validate input
    if (nodes.Count() <= 0 || nodes.Count() > MAX_uint16)
        return true;
    auto model = this;
    if (!model->IsVirtual())
        return true;

    ScopeLock lock(model->Locker);

    // Setup
    model->Skeleton.Nodes = nodes;
    model->Skeleton.Bones.Resize(nodes.Count());
    for (int32 i = 0; i < nodes.Count(); i++)
    {
        auto& node = model->Skeleton.Nodes[i];
        model->Skeleton.Bones[i].ParentIndex = node.ParentIndex;
        model->Skeleton.Bones[i].LocalTransform = node.LocalTransform;
        model->Skeleton.Bones[i].NodeIndex = i;
    }
    ClearSkeletonMapping();

    // Calculate offset matrix (inverse bind pose transform) for every bone manually
    for (int32 i = 0; i < model->Skeleton.Bones.Count(); i++)
    {
        Matrix t = Matrix::Identity;
        int32 idx = model->Skeleton.Bones[i].NodeIndex;

        do
        {
            t *= model->Skeleton.Nodes[idx].LocalTransform.GetWorld();
            idx = model->Skeleton.Nodes[idx].ParentIndex;
        } while (idx != -1);

        t.Invert();

        model->Skeleton.Bones[i].OffsetMatrix = t;
    }

    return false;
}

bool SkinnedModel::SetupSkeleton(const Array<SkeletonNode>& nodes, const Array<SkeletonBone>& bones, bool autoCalculateOffsetMatrix)
{
    // Validate input
    if (nodes.Count() <= 0 || nodes.Count() > MAX_uint16)
        return true;
    if (bones.Count() <= 0 || bones.Count() > MAX_BONES_PER_MODEL)
        return true;
    auto model = this;
    if (!model->IsVirtual())
        return true;

    ScopeLock lock(model->Locker);

    // Setup
    model->Skeleton.Nodes = nodes;
    model->Skeleton.Bones = bones;
    ClearSkeletonMapping();

    // Calculate offset matrix (inverse bind pose transform) for every bone manually
    if (autoCalculateOffsetMatrix)
    {
        for (int32 i = 0; i < model->Skeleton.Bones.Count(); i++)
        {
            Matrix t = Matrix::Identity;
            int32 idx = model->Skeleton.Bones[i].NodeIndex;

            do
            {
                t *= model->Skeleton.Nodes[idx].LocalTransform.GetWorld();
                idx = model->Skeleton.Nodes[idx].ParentIndex;
            } while (idx != -1);

            t.Invert();

            model->Skeleton.Bones[i].OffsetMatrix = t;
        }
    }

    return false;
}

#if USE_EDITOR

bool SkinnedModel::Save(bool withMeshDataFromGpu, const StringView& path)
{
    // Validate state
    if (WaitForLoaded())
    {
        LOG(Error, "Asset loading failed. Cannot save it.");
        return true;
    }
    if (IsVirtual() && path.IsEmpty())
    {
        LOG(Error, "To save virtual asset asset you need to specify the target asset path location.");
        return true;
    }
    if (withMeshDataFromGpu && IsInMainThread())
    {
        LOG(Error, "To save model with GPU mesh buffers it needs to be called from the other thread (not the main thread).");
        return true;
    }
    if (IsVirtual() && !withMeshDataFromGpu)
    {
        LOG(Error, "To save virtual model asset you need to specify 'withMeshDataFromGpu' (it has no other storage container to get data).");
        return true;
    }

    ScopeLock lock(Locker);

    // Create model data header
    MemoryWriteStream headerStream(1024);
    MemoryWriteStream* stream = &headerStream;
    {
        // Header Version
        stream->WriteByte(1);

        // Min Screen Size
        stream->WriteFloat(MinScreenSize);

        // Amount of material slots
        stream->WriteInt32(MaterialSlots.Count());

        // For each material slot
        for (int32 materialSlotIndex = 0; materialSlotIndex < MaterialSlots.Count(); materialSlotIndex++)
        {
            auto& slot = MaterialSlots[materialSlotIndex];

            const auto id = slot.Material.GetID();
            stream->Write(id);
            stream->WriteByte(static_cast<byte>(slot.ShadowsMode));
            stream->WriteString(slot.Name, 11);
        }

        // Amount of LODs
        const int32 lods = LODs.Count();
        stream->WriteByte(lods);

        // For each LOD
        for (int32 lodIndex = 0; lodIndex < lods; lodIndex++)
        {
            auto& lod = LODs[lodIndex];

            // Screen Size
            stream->WriteFloat(lod.ScreenSize);

            // Amount of meshes
            const int32 meshes = lod.Meshes.Count();
            stream->WriteUint16(meshes);

            // For each mesh
            for (int32 meshIndex = 0; meshIndex < meshes; meshIndex++)
            {
                const auto& mesh = lod.Meshes[meshIndex];

                // Material Slot index
                stream->WriteInt32(mesh.GetMaterialSlotIndex());

                // Box
                const auto box = mesh.GetBox();
                stream->WriteBoundingBox(box);

                // Sphere
                const auto sphere = mesh.GetSphere();
                stream->WriteBoundingSphere(sphere);

                // Blend Shapes
                stream->WriteUint16(mesh.BlendShapes.Count());
                for (int32 blendShapeIndex = 0; blendShapeIndex < mesh.BlendShapes.Count(); blendShapeIndex++)
                {
                    auto& blendShape = mesh.BlendShapes[blendShapeIndex];
                    stream->WriteString(blendShape.Name, 13);
                    stream->WriteFloat(blendShape.Weight);
                }
            }
        }

        // Skeleton
        {
            stream->WriteInt32(Skeleton.Nodes.Count());

            // For each node
            for (int32 nodeIndex = 0; nodeIndex < Skeleton.Nodes.Count(); nodeIndex++)
            {
                auto& node = Skeleton.Nodes[nodeIndex];

                stream->Write(node.ParentIndex);
                stream->WriteTransform(node.LocalTransform);
                stream->WriteString(node.Name, 71);
            }

            stream->WriteInt32(Skeleton.Bones.Count());

            // For each bone
            for (int32 boneIndex = 0; boneIndex < Skeleton.Bones.Count(); boneIndex++)
            {
                auto& bone = Skeleton.Bones[boneIndex];

                stream->Write(bone.ParentIndex);
                stream->Write(bone.NodeIndex);
                stream->WriteTransform(bone.LocalTransform);
                stream->Write(bone.OffsetMatrix);
            }
        }

        // Retargeting
        {
            stream->WriteInt32(_skeletonRetargets.Count());
            for (const auto& retarget : _skeletonRetargets)
            {
                stream->Write(retarget.SourceAsset);
                stream->Write(retarget.SkeletonAsset);
                stream->Write(retarget.NodesMapping);
            }
        }
    }

    // Use a temporary chunks for data storage for virtual assets
    FlaxChunk* tmpChunks[ASSET_FILE_DATA_CHUNKS];
    Platform::MemoryClear(tmpChunks, sizeof(tmpChunks));
    Array<FlaxChunk> chunks;
    if (IsVirtual())
        chunks.Resize(ASSET_FILE_DATA_CHUNKS);
#define GET_CHUNK(index) (IsVirtual() ? tmpChunks[index] = &chunks[index] : GetOrCreateChunk(index))

    // Check if use data from drive or from GPU
    if (withMeshDataFromGpu)
    {
        // Download all meshes buffers
        Array<Task*> tasks;
        for (int32 lodIndex = 0; lodIndex < LODs.Count(); lodIndex++)
        {
            auto& lod = LODs[lodIndex];

            const int32 meshesCount = lod.Meshes.Count();
            struct MeshData
            {
                BytesContainer VB0;
                BytesContainer IB;

                uint32 DataSize() const
                {
                    return VB0.Length() + IB.Length();
                }
            };
            Array<MeshData> meshesData;
            meshesData.Resize(meshesCount);
            tasks.EnsureCapacity(meshesCount * 4);

            for (int32 meshIndex = 0; meshIndex < meshesCount; meshIndex++)
            {
                const auto& mesh = lod.Meshes[meshIndex];
                auto& meshData = meshesData[meshIndex];

                // Vertex Buffer 0 (required)
                auto task = mesh.DownloadDataGPUAsync(MeshBufferType::Vertex0, meshData.VB0);
                if (task == nullptr)
                    return true;
                task->Start();
                tasks.Add(task);

                // Index Buffer (required)
                task = mesh.DownloadDataGPUAsync(MeshBufferType::Index, meshData.IB);
                if (task == nullptr)
                    return true;
                task->Start();
                tasks.Add(task);
            }
            if (Task::WaitAll(tasks))
                return true;
            tasks.Clear();

            // Create meshes data
            {
                int32 dataSize = meshesCount * (2 * sizeof(uint32) + sizeof(bool));
                for (int32 meshIndex = 0; meshIndex < meshesCount; meshIndex++)
                    dataSize += meshesData[meshIndex].DataSize();
                MemoryWriteStream meshesStream(Math::RoundUpToPowerOf2(dataSize));

                meshesStream.WriteByte(1);
                for (int32 meshIndex = 0; meshIndex < meshesCount; meshIndex++)
                {
                    const auto& mesh = lod.Meshes[meshIndex];
                    const auto& meshData = meshesData[meshIndex];

                    const uint32 vertices = mesh.GetVertexCount();
                    const uint32 triangles = mesh.GetTriangleCount();
                    const uint32 vb0Size = vertices * sizeof(VB0SkinnedElementType);
                    const uint32 indicesCount = triangles * 3;
                    const bool shouldUse16BitIndexBuffer = indicesCount <= MAX_uint16;
                    const bool use16BitIndexBuffer = mesh.Use16BitIndexBuffer();
                    const uint32 ibSize = indicesCount * (use16BitIndexBuffer ? sizeof(uint16) : sizeof(uint32));

                    if (vertices == 0 || triangles == 0)
                    {
                        LOG(Warning, "Cannot save model with empty meshes.");
                        return true;
                    }
                    if ((uint32)meshData.VB0.Length() < vb0Size)
                    {
                        LOG(Warning, "Invalid vertex buffer 0 size.");
                        return true;
                    }
                    if ((uint32)meshData.IB.Length() < ibSize)
                    {
                        LOG(Warning, "Invalid index buffer size.");
                        return true;
                    }

                    // #MODEL_DATA_FORMAT_USAGE
                    meshesStream.WriteUint32(vertices);
                    meshesStream.WriteUint32(triangles);
                    meshesStream.WriteUint16(mesh.BlendShapes.Count());
                    for (const auto& blendShape : mesh.BlendShapes)
                    {
                        meshesStream.WriteBool(blendShape.UseNormals);
                        meshesStream.WriteUint32(blendShape.MinVertexIndex);
                        meshesStream.WriteUint32(blendShape.MaxVertexIndex);
                        meshesStream.WriteUint32(blendShape.Vertices.Count());
                        meshesStream.WriteBytes(blendShape.Vertices.Get(), blendShape.Vertices.Count() * sizeof(BlendShapeVertex));
                    }
                    meshesStream.WriteBytes(meshData.VB0.Get(), vb0Size);
                    if (shouldUse16BitIndexBuffer == use16BitIndexBuffer)
                    {
                        meshesStream.WriteBytes(meshData.IB.Get(), ibSize);
                    }
                    else if (shouldUse16BitIndexBuffer)
                    {
                        const auto ib = reinterpret_cast<const int32*>(meshData.IB.Get());
                        for (uint32 i = 0; i < indicesCount; i++)
                        {
                            meshesStream.WriteUint16(ib[i]);
                        }
                    }
                    else
                    {
                        CRASH;
                    }
                }

                // Override meshes data chunk with the fetched GPU meshes memory
                auto lodChunk = GET_CHUNK(MODEL_LOD_TO_CHUNK_INDEX(lodIndex));
                if (lodChunk == nullptr)
                    return true;
                lodChunk->Data.Copy(meshesStream.GetHandle(), meshesStream.GetPosition());
            }
        }
    }
    else
    {
        ASSERT(!IsVirtual());

        // Load all chunks with a mesh data
        for (int32 lodIndex = 0; lodIndex < LODs.Count(); lodIndex++)
        {
            if (LoadChunk(MODEL_LOD_TO_CHUNK_INDEX(lodIndex)))
                return true;
        }
    }

    // Set mesh header data
    auto headerChunk = GET_CHUNK(0);
    ASSERT(headerChunk != nullptr);
    headerChunk->Data.Copy(headerStream.GetHandle(), headerStream.GetPosition());

#undef GET_CHUNK

    // Save
    AssetInitData data;
    data.SerializedVersion = SerializedVersion;
    if (IsVirtual())
        Platform::MemoryCopy(_header.Chunks, tmpChunks, sizeof(_header.Chunks));
    const bool saveResult = path.HasChars() ? SaveAsset(path, data) : SaveAsset(data, true);
    if (IsVirtual())
        Platform::MemoryClear(_header.Chunks, sizeof(_header.Chunks));
    if (saveResult)
    {
        LOG(Error, "Cannot save \'{0}\'", ToString());
        return true;
    }

    return false;
}

#endif

bool SkinnedModel::Init(const Span<int32>& meshesCountPerLod)
{
    if (meshesCountPerLod.IsInvalid() || meshesCountPerLod.Length() > MODEL_MAX_LODS)
    {
        Log::ArgumentOutOfRangeException();
        return true;
    }

    // Dispose previous data and disable streaming (will start data uploading tasks manually)
    StopStreaming();

    // Setup
    MaterialSlots.Resize(1);
    MinScreenSize = 0.0f;
    for (int32 lodIndex = 0; lodIndex < LODs.Count(); lodIndex++)
        LODs[lodIndex].Dispose();
    LODs.Resize(meshesCountPerLod.Length());
    _initialized = true;

    // Setup meshes
    for (int32 lodIndex = 0; lodIndex < meshesCountPerLod.Length(); lodIndex++)
    {
        auto& lod = LODs[lodIndex];
        lod._model = this;
        lod._lodIndex = lodIndex;
        lod.ScreenSize = 1.0f;
        const int32 meshesCount = meshesCountPerLod[lodIndex];
        if (meshesCount <= 0 || meshesCount > MODEL_MAX_MESHES)
            return true;

        lod.Meshes.Resize(meshesCount);
        for (int32 meshIndex = 0; meshIndex < meshesCount; meshIndex++)
        {
            lod.Meshes[meshIndex].Init(this, lodIndex, meshIndex, 0, BoundingBox::Zero, BoundingSphere::Empty);
        }
    }

    // Update resource residency
    _loadedLODs = meshesCountPerLod.Length();
    ResidencyChanged();

    return false;
}

void SkinnedModel::ClearSkeletonMapping()
{
    for (auto& e : _skeletonMappingCache)
    {
        e.Key->OnUnloaded.Unbind<SkinnedModel, &SkinnedModel::OnSkeletonMappingSourceAssetUnloaded>(this);
#if USE_EDITOR
        e.Key->OnReloading.Unbind<SkinnedModel, &SkinnedModel::OnSkeletonMappingSourceAssetUnloaded>(this);
#endif
        Allocator::Free(e.Value.NodesMapping.Get());
    }
    _skeletonMappingCache.Clear();
}

void SkinnedModel::OnSkeletonMappingSourceAssetUnloaded(Asset* obj)
{
    ScopeLock lock(Locker);
    auto i = _skeletonMappingCache.Find(obj);
    ASSERT(i != _skeletonMappingCache.End());

    // Unlink event
    obj->OnUnloaded.Unbind<SkinnedModel, &SkinnedModel::OnSkeletonMappingSourceAssetUnloaded>(this);
#if USE_EDITOR
    obj->OnReloading.Unbind<SkinnedModel, &SkinnedModel::OnSkeletonMappingSourceAssetUnloaded>(this);
#endif

    // Clear cache
    Allocator::Free(i->Value.NodesMapping.Get());
    _skeletonMappingCache.Remove(i);
}

uint64 SkinnedModel::GetMemoryUsage() const
{
    Locker.Lock();
    uint64 result = BinaryAsset::GetMemoryUsage();
    result += sizeof(SkinnedModel) - sizeof(BinaryAsset);
    result += Skeleton.GetMemoryUsage();
    result += _skeletonMappingCache.Capacity() * sizeof(Dictionary<Asset*, Span<int32>>::Bucket);
    for (const auto& e : _skeletonMappingCache)
        result += e.Value.NodesMapping.Length();
    Locker.Unlock();
    return result;
}

void SkinnedModel::SetupMaterialSlots(int32 slotsCount)
{
    ModelBase::SetupMaterialSlots(slotsCount);

    // Adjust meshes indices for slots
    for (int32 lodIndex = 0; lodIndex < LODs.Count(); lodIndex++)
    {
        for (int32 meshIndex = 0; meshIndex < LODs[lodIndex].Meshes.Count(); meshIndex++)
        {
            auto& mesh = LODs[lodIndex].Meshes[meshIndex];
            if (mesh.GetMaterialSlotIndex() >= slotsCount)
                mesh.SetMaterialSlotIndex(slotsCount - 1);
        }
    }
}

int32 SkinnedModel::GetLODsCount() const
{
    return LODs.Count();
}

void SkinnedModel::GetMeshes(Array<MeshBase*>& meshes, int32 lodIndex)
{
    auto& lod = LODs[lodIndex];
    meshes.Resize(lod.Meshes.Count());
    for (int32 meshIndex = 0; meshIndex < lod.Meshes.Count(); meshIndex++)
        meshes[meshIndex] = &lod.Meshes[meshIndex];
}

void SkinnedModel::InitAsVirtual()
{
    // Init with one mesh and single bone
    int32 meshesCount = 1;
    Init(ToSpan(&meshesCount, 1));
    ClearSkeletonMapping();
    Skeleton.Dispose();
    //
    Skeleton.Nodes.Resize(1);
    Skeleton.Nodes[0].Name = TEXT("Root");
    Skeleton.Nodes[0].LocalTransform = Transform::Identity;
    Skeleton.Nodes[0].ParentIndex = -1;
    //
    Skeleton.Bones.Resize(1);
    Skeleton.Bones[0].NodeIndex = 0;
    Skeleton.Bones[0].OffsetMatrix = Matrix::Identity;
    Skeleton.Bones[0].LocalTransform = Transform::Identity;
    Skeleton.Bones[0].ParentIndex = -1;

    // Base
    BinaryAsset::InitAsVirtual();
}

void SkinnedModel::CancelStreaming()
{
    CancelStreamingTasks();
}

#if USE_EDITOR

void SkinnedModel::GetReferences(Array<Guid>& output) const
{
    // Base
    BinaryAsset::GetReferences(output);

    for (int32 i = 0; i < MaterialSlots.Count(); i++)
    {
        output.Add(MaterialSlots[i].Material.GetID());
    }
}

#endif

int32 SkinnedModel::GetMaxResidency() const
{
    return LODs.Count();
}

int32 SkinnedModel::GetCurrentResidency() const
{
    return _loadedLODs;
}

int32 SkinnedModel::GetAllocatedResidency() const
{
    return LODs.Count();
}

bool SkinnedModel::CanBeUpdated() const
{
    // Check if is ready and has no streaming tasks running
    return IsInitialized() && _streamingTask == nullptr;
}

Task* SkinnedModel::UpdateAllocation(int32 residency)
{
    // SkinnedModels are not using dynamic allocation feature
    return nullptr;
}

Task* SkinnedModel::CreateStreamingTask(int32 residency)
{
    ScopeLock lock(Locker);

    ASSERT(IsInitialized() && Math::IsInRange(residency, 0, LODs.Count()) && _streamingTask == nullptr);
    Task* result = nullptr;
    const int32 lodCount = residency - GetCurrentResidency();

    // Switch if go up or down with residency
    if (lodCount > 0)
    {
        // Allow only to change LODs count by 1
        ASSERT(Math::Abs(lodCount) == 1);

        int32 lodIndex = HighestResidentLODIndex() - 1;

        // Request LOD data
        result = (Task*)RequestLODDataAsync(lodIndex);

        // Add upload data task
        _streamingTask = New<StreamSkinnedModelLODTask>(this, lodIndex);
        if (result)
            result->ContinueWith(_streamingTask);
        else
            result = _streamingTask;
    }
    else
    {
        // Do the quick data release
        for (int32 i = HighestResidentLODIndex(); i < LODs.Count() - residency; i++)
            LODs[i].Unload();
        _loadedLODs = residency;
        ResidencyChanged();
    }

    return result;
}

void SkinnedModel::CancelStreamingTasks()
{
    if (_streamingTask)
    {
        _streamingTask->Cancel();
        ASSERT_LOW_LAYER(_streamingTask == nullptr);
    }
}

Asset::LoadResult SkinnedModel::load()
{
    // Get header chunk
    auto chunk0 = GetChunk(0);
    if (chunk0 == nullptr || chunk0->IsMissing())
        return LoadResult::MissingDataChunk;
    MemoryReadStream headerStream(chunk0->Get(), chunk0->Size());
    ReadStream* stream = &headerStream;

    // Header Version
    byte version = stream->ReadByte();

    // Min Screen Size
    stream->ReadFloat(&MinScreenSize);

    // Amount of material slots
    int32 materialSlotsCount;
    stream->ReadInt32(&materialSlotsCount);
    if (materialSlotsCount < 0 || materialSlotsCount > 4096)
        return LoadResult::InvalidData;
    MaterialSlots.Resize(materialSlotsCount, false);

    // For each material slot
    for (int32 materialSlotIndex = 0; materialSlotIndex < materialSlotsCount; materialSlotIndex++)
    {
        auto& slot = MaterialSlots[materialSlotIndex];

        // Material
        Guid materialId;
        stream->Read(materialId);
        slot.Material = materialId;

        // Shadows Mode
        slot.ShadowsMode = static_cast<ShadowsCastingMode>(stream->ReadByte());

        // Name
        stream->ReadString(&slot.Name, 11);
    }

    // Amount of LODs
    byte lods;
    stream->ReadByte(&lods);
    if (lods > MODEL_MAX_LODS)
        return LoadResult::InvalidData;
    LODs.Resize(lods);
    _initialized = true;

    // For each LOD
    for (int32 lodIndex = 0; lodIndex < lods; lodIndex++)
    {
        auto& lod = LODs[lodIndex];
        lod._model = this;
        lod._lodIndex = lodIndex;

        // Screen Size
        stream->ReadFloat(&lod.ScreenSize);

        // Amount of meshes
        uint16 meshesCount;
        stream->ReadUint16(&meshesCount);
        if (meshesCount == 0 || meshesCount > MODEL_MAX_MESHES)
            return LoadResult::InvalidData;
        ASSERT(lodIndex == 0 || LODs[0].Meshes.Count() >= meshesCount);

        // Allocate memory
        lod.Meshes.Resize(meshesCount, false);

        // For each mesh
        for (uint16 meshIndex = 0; meshIndex < meshesCount; meshIndex++)
        {
            auto& mesh = lod.Meshes[meshIndex];

            // Material Slot index
            int32 materialSlotIndex;
            stream->ReadInt32(&materialSlotIndex);
            if (materialSlotIndex < 0 || materialSlotIndex >= materialSlotsCount)
            {
                LOG(Warning, "Invalid material slot index {0} for mesh {1}. Slots count: {2}.", materialSlotIndex, meshIndex, materialSlotsCount);
                return LoadResult::InvalidData;
            }

            // Box
            BoundingBox box;
            stream->ReadBoundingBox(&box);

            // Sphere
            BoundingSphere sphere;
            stream->ReadBoundingSphere(&sphere);

            // Create mesh object
            mesh.Init(this, lodIndex, meshIndex, materialSlotIndex, box, sphere);

            // Blend Shapes
            uint16 blendShapes;
            stream->ReadUint16(&blendShapes);
            mesh.BlendShapes.Resize(blendShapes);
            for (int32 blendShapeIndex = 0; blendShapeIndex < blendShapes; blendShapeIndex++)
            {
                auto& blendShape = mesh.BlendShapes[blendShapeIndex];
                stream->ReadString(&blendShape.Name, 13);
                stream->ReadFloat(&blendShape.Weight);
            }
        }
    }

    // Skeleton
    {
        int32 nodesCount;
        stream->ReadInt32(&nodesCount);
        if (nodesCount <= 0)
            return LoadResult::InvalidData;
        Skeleton.Nodes.Resize(nodesCount, false);
        for (int32 nodeIndex = 0; nodeIndex < nodesCount; nodeIndex++)
        {
            auto& node = Skeleton.Nodes.Get()[nodeIndex];
            stream->Read(node.ParentIndex);
            stream->ReadTransform(&node.LocalTransform);
            stream->ReadString(&node.Name, 71);
        }

        int32 bonesCount;
        stream->ReadInt32(&bonesCount);
        if (bonesCount <= 0)
            return LoadResult::InvalidData;
        Skeleton.Bones.Resize(bonesCount, false);
        for (int32 boneIndex = 0; boneIndex < bonesCount; boneIndex++)
        {
            auto& bone = Skeleton.Bones.Get()[boneIndex];
            stream->Read(bone.ParentIndex);
            stream->Read(bone.NodeIndex);
            stream->ReadTransform(&bone.LocalTransform);
            stream->Read(bone.OffsetMatrix);
        }
    }

    // Retargeting
    {
        int32 entriesCount;
        stream->ReadInt32(&entriesCount);
        _skeletonRetargets.Resize(entriesCount);
        for (int32 entryIndex = 0; entryIndex < entriesCount; entryIndex++)
        {
            auto& retarget = _skeletonRetargets[entryIndex];
            stream->Read(retarget.SourceAsset);
            stream->Read(retarget.SkeletonAsset);
            stream->Read(retarget.NodesMapping);
        }
    }

    // Request resource streaming
    StartStreaming(true);

    return LoadResult::Ok;
}

void SkinnedModel::unload(bool isReloading)
{
    // End streaming (if still active)
    if (_streamingTask != nullptr)
    {
        // Cancel streaming task
        _streamingTask->Cancel();
        _streamingTask = nullptr;
    }

    // Cleanup
    MaterialSlots.Resize(0);
    for (int32 i = 0; i < LODs.Count(); i++)
        LODs[i].Dispose();
    LODs.Clear();
    Skeleton.Dispose();
    _initialized = false;
    _loadedLODs = 0;
    _skeletonRetargets.Clear();
    ClearSkeletonMapping();
}

bool SkinnedModel::init(AssetInitData& initData)
{
    // Validate
    if (initData.SerializedVersion != SerializedVersion)
    {
        LOG(Error, "Invalid serialized model version.");
        return true;
    }

    return false;
}

AssetChunksFlag SkinnedModel::getChunksToPreload() const
{
    // Note: we don't preload any meshes here because it's done by the Streaming Manager
    return GET_CHUNK_FLAG(0);
}