#include "BuiltInIcons.h"

#include "ImGuiBackendBridge.h"
#include "Platform/Win32Utf8.h"
#include "StyleTokens.h"

#include <algorithm>
#include <condition_variable>
#include <cstdint>
#include <cwctype>
#include <deque>
#include <cstring>
#include <filesystem>
#include <fstream>
#include <memory>
#include <string>
#include <thread>
#include <unordered_map>
#include <vector>
#include <wrl/client.h>

#include <stb_image.h>

namespace XCEngine {
namespace Editor {
namespace UI {

namespace {

using Microsoft::WRL::ComPtr;

struct BuiltInTexture {
    ImTextureID textureId = {};
    D3D12_CPU_DESCRIPTOR_HANDLE cpuHandle = {};
    D3D12_GPU_DESCRIPTOR_HANDLE gpuHandle = {};
    ComPtr<ID3D12Resource> texture;
    int width = 0;
    int height = 0;

    bool IsValid() const {
        return textureId != ImTextureID{} && texture != nullptr && width > 0 && height > 0;
    }
};

struct LoadedTexturePixels {
    std::vector<stbi_uc> rgbaPixels;
    int width = 0;
    int height = 0;
};

struct PreviewGpuUpload {
    ComPtr<ID3D12Resource> uploadResource;
    ComPtr<ID3D12CommandAllocator> commandAllocator;
    ComPtr<ID3D12GraphicsCommandList> commandList;
    UINT64 fenceValue = 0;
};

struct PreviewDecodeJob {
    std::string key;
    std::filesystem::path filePath;
};

struct PreviewDecodeResult {
    std::string key;
    LoadedTexturePixels pixels;
    bool success = false;
};

struct BuiltInIconState {
    ImGuiBackendBridge* backend = nullptr;
    ID3D12Device* device = nullptr;
    ID3D12CommandQueue* commandQueue = nullptr;
    BuiltInTexture folder;
    BuiltInTexture gameObject;
    BuiltInTexture scene;
    struct CachedAssetPreview {
        BuiltInTexture texture;
        std::unique_ptr<LoadedTexturePixels> decodedPixels;
        std::unique_ptr<PreviewGpuUpload> pendingUpload;
        bool decodeQueued = false;
        bool loadFailed = false;
        int lastUsedFrame = -1;
    };
    std::unordered_map<std::string, CachedAssetPreview> assetPreviews;
    std::vector<std::unique_ptr<PreviewGpuUpload>> pendingIconUploads;
    std::vector<std::thread> previewWorkers;
    std::deque<PreviewDecodeJob> previewDecodeQueue;
    std::deque<PreviewDecodeResult> previewDecodeResults;
    std::mutex previewQueueMutex;
    std::condition_variable previewQueueEvent;
    bool previewWorkersRunning = false;
    size_t pendingPreviewDecodeJobs = 0;
    ComPtr<ID3D12Fence> uploadFence;
    UINT64 nextUploadFenceValue = 1;
    int lastPreviewBudgetFrame = -1;
    int previewLoadsThisFrame = 0;
    int lastMaintenanceFrame = -1;
};

BuiltInIconState g_icons;

constexpr size_t kMaxCachedAssetPreviews = 40;
constexpr int kMaxPreviewLoadsPerFrame = 64;
constexpr size_t kMaxQueuedPreviewDecodeJobs = 64;
constexpr int kMaxPreviewThumbnailExtent = 192;
constexpr size_t kPreviewWorkerCount = 2;

std::filesystem::path ResolveFolderIconPath() {
    const std::filesystem::path exeDir(Platform::GetExecutableDirectoryUtf8());
    return (exeDir / ".." / ".." / "resources" / "Icons" / "folder_icon.png").lexically_normal();
}

std::filesystem::path ResolveGameObjectIconPath() {
    const std::filesystem::path exeDir(Platform::GetExecutableDirectoryUtf8());
    return (exeDir / ".." / ".." / "resources" / "Icons" / "gameobject_icon.png").lexically_normal();
}

std::filesystem::path ResolveSceneIconPath() {
    const std::filesystem::path exeDir(Platform::GetExecutableDirectoryUtf8());
    return (exeDir / ".." / ".." / "resources" / "Icons" / "scene_icon.png").lexically_normal();
}

std::string MakeAssetPreviewKey(const std::string& filePath) {
    std::wstring key = std::filesystem::path(Platform::Utf8ToWide(filePath)).lexically_normal().generic_wstring();
    std::transform(key.begin(), key.end(), key.begin(), ::towlower);
    return Platform::WideToUtf8(key);
}

bool ReadFileBytes(const std::filesystem::path& filePath, std::vector<stbi_uc>& bytes) {
    std::ifstream stream(filePath, std::ios::binary | std::ios::ate);
    if (!stream.is_open()) {
        return false;
    }

    const std::streamsize size = stream.tellg();
    if (size <= 0) {
        return false;
    }

    bytes.resize(static_cast<size_t>(size));
    stream.seekg(0, std::ios::beg);
    return stream.read(reinterpret_cast<char*>(bytes.data()), size).good();
}

void ResizeRgbaImageBilinear(
    const stbi_uc* srcPixels,
    int srcWidth,
    int srcHeight,
    int dstWidth,
    int dstHeight,
    std::vector<stbi_uc>& dstPixels) {
    dstPixels.resize(static_cast<size_t>(dstWidth) * static_cast<size_t>(dstHeight) * 4u);
    if (!srcPixels || srcWidth <= 0 || srcHeight <= 0 || dstWidth <= 0 || dstHeight <= 0) {
        return;
    }

    for (int dstY = 0; dstY < dstHeight; ++dstY) {
        const float srcY = dstHeight > 1
            ? static_cast<float>(dstY) * static_cast<float>(srcHeight - 1) / static_cast<float>(dstHeight - 1)
            : 0.0f;
        const int y0 = static_cast<int>(srcY);
        const int y1 = (std::min)(y0 + 1, srcHeight - 1);
        const float ty = srcY - static_cast<float>(y0);

        for (int dstX = 0; dstX < dstWidth; ++dstX) {
            const float srcX = dstWidth > 1
                ? static_cast<float>(dstX) * static_cast<float>(srcWidth - 1) / static_cast<float>(dstWidth - 1)
                : 0.0f;
            const int x0 = static_cast<int>(srcX);
            const int x1 = (std::min)(x0 + 1, srcWidth - 1);
            const float tx = srcX - static_cast<float>(x0);

            const size_t dstOffset =
                (static_cast<size_t>(dstY) * static_cast<size_t>(dstWidth) + static_cast<size_t>(dstX)) * 4u;
            const size_t srcOffset00 =
                (static_cast<size_t>(y0) * static_cast<size_t>(srcWidth) + static_cast<size_t>(x0)) * 4u;
            const size_t srcOffset10 =
                (static_cast<size_t>(y0) * static_cast<size_t>(srcWidth) + static_cast<size_t>(x1)) * 4u;
            const size_t srcOffset01 =
                (static_cast<size_t>(y1) * static_cast<size_t>(srcWidth) + static_cast<size_t>(x0)) * 4u;
            const size_t srcOffset11 =
                (static_cast<size_t>(y1) * static_cast<size_t>(srcWidth) + static_cast<size_t>(x1)) * 4u;

            for (size_t channel = 0; channel < 4u; ++channel) {
                const float top =
                    static_cast<float>(srcPixels[srcOffset00 + channel]) * (1.0f - tx) +
                    static_cast<float>(srcPixels[srcOffset10 + channel]) * tx;
                const float bottom =
                    static_cast<float>(srcPixels[srcOffset01 + channel]) * (1.0f - tx) +
                    static_cast<float>(srcPixels[srcOffset11 + channel]) * tx;
                dstPixels[dstOffset + channel] = static_cast<stbi_uc>(top * (1.0f - ty) + bottom * ty + 0.5f);
            }
        }
    }
}

bool DownscalePreviewTextureIfNeeded(LoadedTexturePixels& texturePixels) {
    if (texturePixels.width <= 0 || texturePixels.height <= 0 || texturePixels.rgbaPixels.empty()) {
        return false;
    }

    const int maxExtent = (std::max)(texturePixels.width, texturePixels.height);
    if (maxExtent <= kMaxPreviewThumbnailExtent) {
        return true;
    }

    const float scale = static_cast<float>(kMaxPreviewThumbnailExtent) / static_cast<float>(maxExtent);
    const int dstWidth = (std::max)(1, static_cast<int>(static_cast<float>(texturePixels.width) * scale + 0.5f));
    const int dstHeight = (std::max)(1, static_cast<int>(static_cast<float>(texturePixels.height) * scale + 0.5f));

    std::vector<stbi_uc> resizedPixels;
    ResizeRgbaImageBilinear(
        texturePixels.rgbaPixels.data(),
        texturePixels.width,
        texturePixels.height,
        dstWidth,
        dstHeight,
        resizedPixels);
    if (resizedPixels.empty()) {
        return false;
    }

    texturePixels.rgbaPixels = std::move(resizedPixels);
    texturePixels.width = dstWidth;
    texturePixels.height = dstHeight;
    return true;
}

void ResetTexture(BuiltInTexture& texture) {
    if (g_icons.backend && texture.cpuHandle.ptr != 0) {
        g_icons.backend->FreeTextureDescriptor(texture.cpuHandle, texture.gpuHandle);
    }

    texture.texture.Reset();
    texture.textureId = {};
    texture.cpuHandle = {};
    texture.gpuHandle = {};
    texture.width = 0;
    texture.height = 0;
}

void ResetAssetPreviewCache() {
    for (auto& entry : g_icons.assetPreviews) {
        ResetTexture(entry.second.texture);
    }
    g_icons.assetPreviews.clear();
}

bool EnsureUploadFence(ID3D12Device* device) {
    if (g_icons.uploadFence) {
        return true;
    }

    return SUCCEEDED(device->CreateFence(0, D3D12_FENCE_FLAG_NONE, IID_PPV_ARGS(&g_icons.uploadFence)));
}

bool WaitForQueueIdle(ID3D12Device* device, ID3D12CommandQueue* commandQueue) {
    if (!device || !commandQueue) {
        return false;
    }

    ComPtr<ID3D12Fence> fence;
    if (FAILED(device->CreateFence(0, D3D12_FENCE_FLAG_NONE, IID_PPV_ARGS(&fence)))) {
        return false;
    }

    HANDLE eventHandle = CreateEventW(nullptr, FALSE, FALSE, nullptr);
    if (!eventHandle) {
        return false;
    }

    constexpr UINT64 kFenceValue = 1;
    const HRESULT signalHr = commandQueue->Signal(fence.Get(), kFenceValue);
    if (FAILED(signalHr)) {
        CloseHandle(eventHandle);
        return false;
    }

    if (fence->GetCompletedValue() < kFenceValue) {
        if (FAILED(fence->SetEventOnCompletion(kFenceValue, eventHandle))) {
            CloseHandle(eventHandle);
            return false;
        }
        WaitForSingleObject(eventHandle, INFINITE);
    }

    CloseHandle(eventHandle);
    return true;
}

bool DecodeTextureFromFile(
    const std::filesystem::path& filePath,
    LoadedTexturePixels& outTexturePixels) {
    if (!std::filesystem::exists(filePath)) {
        return false;
    }

    std::vector<stbi_uc> fileData;
    if (!ReadFileBytes(filePath, fileData)) {
        return false;
    }

    int width = 0;
    int height = 0;
    int channels = 0;
    stbi_uc* pixels = stbi_load_from_memory(
        fileData.data(),
        static_cast<int>(fileData.size()),
        &width,
        &height,
        &channels,
        STBI_rgb_alpha);
    if (!pixels || width <= 0 || height <= 0) {
        if (pixels) {
            stbi_image_free(pixels);
        }
        return false;
    }

    outTexturePixels.width = width;
    outTexturePixels.height = height;
    outTexturePixels.rgbaPixels.assign(
        pixels,
        pixels + static_cast<size_t>(width) * static_cast<size_t>(height) * 4u);
    stbi_image_free(pixels);

    return DownscalePreviewTextureIfNeeded(outTexturePixels);
}

bool UploadTexturePixels(
    ImGuiBackendBridge& backend,
    ID3D12Device* device,
    ID3D12CommandQueue* commandQueue,
    const LoadedTexturePixels& texturePixels,
    BuiltInTexture& outTexture,
    std::unique_ptr<PreviewGpuUpload>& outPendingUpload) {
    if (!device || !commandQueue || texturePixels.width <= 0 || texturePixels.height <= 0 || texturePixels.rgbaPixels.empty()) {
        return false;
    }

    const UINT srcRowPitch = static_cast<UINT>(texturePixels.width * 4);

    D3D12_RESOURCE_DESC textureDesc = {};
    textureDesc.Dimension = D3D12_RESOURCE_DIMENSION_TEXTURE2D;
    textureDesc.Alignment = 0;
    textureDesc.Width = static_cast<UINT64>(texturePixels.width);
    textureDesc.Height = static_cast<UINT>(texturePixels.height);
    textureDesc.DepthOrArraySize = 1;
    textureDesc.MipLevels = 1;
    textureDesc.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
    textureDesc.SampleDesc.Count = 1;
    textureDesc.Layout = D3D12_TEXTURE_LAYOUT_UNKNOWN;

    D3D12_HEAP_PROPERTIES defaultHeap = {};
    defaultHeap.Type = D3D12_HEAP_TYPE_DEFAULT;

    ComPtr<ID3D12Resource> textureResource;
    if (FAILED(device->CreateCommittedResource(
            &defaultHeap,
            D3D12_HEAP_FLAG_NONE,
            &textureDesc,
            D3D12_RESOURCE_STATE_COPY_DEST,
            nullptr,
            IID_PPV_ARGS(&textureResource)))) {
        return false;
    }

    D3D12_PLACED_SUBRESOURCE_FOOTPRINT footprint = {};
    UINT numRows = 0;
    UINT64 rowSizeInBytes = 0;
    UINT64 uploadBufferSize = 0;
    device->GetCopyableFootprints(&textureDesc, 0, 1, 0, &footprint, &numRows, &rowSizeInBytes, &uploadBufferSize);

    D3D12_RESOURCE_DESC uploadDesc = {};
    uploadDesc.Dimension = D3D12_RESOURCE_DIMENSION_BUFFER;
    uploadDesc.Width = uploadBufferSize;
    uploadDesc.Height = 1;
    uploadDesc.DepthOrArraySize = 1;
    uploadDesc.MipLevels = 1;
    uploadDesc.SampleDesc.Count = 1;
    uploadDesc.Layout = D3D12_TEXTURE_LAYOUT_ROW_MAJOR;

    D3D12_HEAP_PROPERTIES uploadHeap = {};
    uploadHeap.Type = D3D12_HEAP_TYPE_UPLOAD;

    ComPtr<ID3D12Resource> uploadResource;
    if (FAILED(device->CreateCommittedResource(
            &uploadHeap,
            D3D12_HEAP_FLAG_NONE,
            &uploadDesc,
            D3D12_RESOURCE_STATE_GENERIC_READ,
            nullptr,
            IID_PPV_ARGS(&uploadResource)))) {
        return false;
    }

    std::uint8_t* mappedData = nullptr;
    if (FAILED(uploadResource->Map(0, nullptr, reinterpret_cast<void**>(&mappedData)))) {
        return false;
    }

    for (UINT row = 0; row < numRows; ++row) {
        std::memcpy(
            mappedData + footprint.Offset + static_cast<SIZE_T>(row) * footprint.Footprint.RowPitch,
            texturePixels.rgbaPixels.data() + static_cast<size_t>(row) * srcRowPitch,
            srcRowPitch);
    }
    uploadResource->Unmap(0, nullptr);

    ComPtr<ID3D12CommandAllocator> commandAllocator;
    ComPtr<ID3D12GraphicsCommandList> commandList;
    if (FAILED(device->CreateCommandAllocator(D3D12_COMMAND_LIST_TYPE_DIRECT, IID_PPV_ARGS(&commandAllocator)))) {
        return false;
    }
    if (FAILED(device->CreateCommandList(
            0,
            D3D12_COMMAND_LIST_TYPE_DIRECT,
            commandAllocator.Get(),
            nullptr,
            IID_PPV_ARGS(&commandList)))) {
        return false;
    }

    D3D12_TEXTURE_COPY_LOCATION dst = {};
    dst.pResource = textureResource.Get();
    dst.Type = D3D12_TEXTURE_COPY_TYPE_SUBRESOURCE_INDEX;
    dst.SubresourceIndex = 0;

    D3D12_TEXTURE_COPY_LOCATION src = {};
    src.pResource = uploadResource.Get();
    src.Type = D3D12_TEXTURE_COPY_TYPE_PLACED_FOOTPRINT;
    src.PlacedFootprint = footprint;

    commandList->CopyTextureRegion(&dst, 0, 0, 0, &src, nullptr);

    D3D12_RESOURCE_BARRIER barrier = {};
    barrier.Type = D3D12_RESOURCE_BARRIER_TYPE_TRANSITION;
    barrier.Transition.pResource = textureResource.Get();
    barrier.Transition.StateBefore = D3D12_RESOURCE_STATE_COPY_DEST;
    barrier.Transition.StateAfter = D3D12_RESOURCE_STATE_PIXEL_SHADER_RESOURCE;
    barrier.Transition.Subresource = D3D12_RESOURCE_BARRIER_ALL_SUBRESOURCES;
    commandList->ResourceBarrier(1, &barrier);

    if (FAILED(commandList->Close())) {
        return false;
    }

    if (!EnsureUploadFence(device)) {
        return false;
    }

    ResetTexture(outTexture);
    backend.AllocateTextureDescriptor(&outTexture.cpuHandle, &outTexture.gpuHandle);
    if (outTexture.cpuHandle.ptr == 0 || outTexture.gpuHandle.ptr == 0) {
        ResetTexture(outTexture);
        return false;
    }

    D3D12_SHADER_RESOURCE_VIEW_DESC srvDesc = {};
    srvDesc.Shader4ComponentMapping = D3D12_DEFAULT_SHADER_4_COMPONENT_MAPPING;
    srvDesc.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
    srvDesc.ViewDimension = D3D12_SRV_DIMENSION_TEXTURE2D;
    srvDesc.Texture2D.MipLevels = 1;
    device->CreateShaderResourceView(textureResource.Get(), &srvDesc, outTexture.cpuHandle);

    outTexture.texture = textureResource;
    outTexture.textureId = (ImTextureID)(static_cast<intptr_t>(outTexture.gpuHandle.ptr));
    outTexture.width = texturePixels.width;
    outTexture.height = texturePixels.height;

    ID3D12CommandList* commandLists[] = { commandList.Get() };
    commandQueue->ExecuteCommandLists(1, commandLists);
    const UINT64 fenceValue = g_icons.nextUploadFenceValue++;
    if (FAILED(commandQueue->Signal(g_icons.uploadFence.Get(), fenceValue))) {
        ResetTexture(outTexture);
        return false;
    }

    outPendingUpload = std::make_unique<PreviewGpuUpload>();
    outPendingUpload->uploadResource = std::move(uploadResource);
    outPendingUpload->commandAllocator = std::move(commandAllocator);
    outPendingUpload->commandList = std::move(commandList);
    outPendingUpload->fenceValue = fenceValue;
    return true;
}

bool LoadTextureFromFile(
    ImGuiBackendBridge& backend,
    ID3D12Device* device,
    ID3D12CommandQueue* commandQueue,
    const std::filesystem::path& filePath,
    BuiltInTexture& outTexture,
    std::unique_ptr<PreviewGpuUpload>& outPendingUpload) {
    LoadedTexturePixels texturePixels;
    if (!DecodeTextureFromFile(filePath, texturePixels)) {
        return false;
    }

    return UploadTexturePixels(
        backend,
        device,
        commandQueue,
        texturePixels,
        outTexture,
        outPendingUpload);
}

void PreviewWorkerMain() {
    while (true) {
        PreviewDecodeJob job;
        {
            std::unique_lock<std::mutex> lock(g_icons.previewQueueMutex);
            g_icons.previewQueueEvent.wait(lock, [] {
                return !g_icons.previewWorkersRunning || !g_icons.previewDecodeQueue.empty();
            });

            if (!g_icons.previewWorkersRunning && g_icons.previewDecodeQueue.empty()) {
                return;
            }

            job = std::move(g_icons.previewDecodeQueue.front());
            g_icons.previewDecodeQueue.pop_front();
        }

        PreviewDecodeResult result;
        result.key = std::move(job.key);
        result.success = DecodeTextureFromFile(job.filePath, result.pixels);

        {
            std::lock_guard<std::mutex> lock(g_icons.previewQueueMutex);
            g_icons.previewDecodeResults.push_back(std::move(result));
        }
    }
}

void StartPreviewWorkers() {
    if (g_icons.previewWorkersRunning) {
        return;
    }

    g_icons.previewWorkersRunning = true;
    g_icons.previewWorkers.reserve(kPreviewWorkerCount);
    for (size_t workerIndex = 0; workerIndex < kPreviewWorkerCount; ++workerIndex) {
        g_icons.previewWorkers.emplace_back(PreviewWorkerMain);
    }
}

void StopPreviewWorkers() {
    {
        std::lock_guard<std::mutex> lock(g_icons.previewQueueMutex);
        g_icons.previewWorkersRunning = false;
        g_icons.previewDecodeQueue.clear();
        g_icons.previewDecodeResults.clear();
        g_icons.pendingPreviewDecodeJobs = 0;
    }
    g_icons.previewQueueEvent.notify_all();

    for (std::thread& worker : g_icons.previewWorkers) {
        if (worker.joinable()) {
            worker.join();
        }
    }
    g_icons.previewWorkers.clear();
}

bool QueuePreviewDecode(const std::string& key, const std::filesystem::path& filePath) {
    std::lock_guard<std::mutex> lock(g_icons.previewQueueMutex);
    if (!g_icons.previewWorkersRunning || g_icons.pendingPreviewDecodeJobs >= kMaxQueuedPreviewDecodeJobs) {
        return false;
    }

    g_icons.previewDecodeQueue.push_back(PreviewDecodeJob{ key, filePath });
    ++g_icons.pendingPreviewDecodeJobs;
    g_icons.previewQueueEvent.notify_one();
    return true;
}

void DrainPreviewDecodeResults() {
    std::deque<PreviewDecodeResult> completedResults;
    {
        std::lock_guard<std::mutex> lock(g_icons.previewQueueMutex);
        completedResults.swap(g_icons.previewDecodeResults);
    }

    for (PreviewDecodeResult& result : completedResults) {
        if (g_icons.pendingPreviewDecodeJobs > 0) {
            --g_icons.pendingPreviewDecodeJobs;
        }

        auto it = g_icons.assetPreviews.find(result.key);
        if (it == g_icons.assetPreviews.end()) {
            continue;
        }

        BuiltInIconState::CachedAssetPreview& preview = it->second;
        preview.decodeQueued = false;
        if (!result.success) {
            preview.loadFailed = true;
            preview.decodedPixels.reset();
            continue;
        }

        preview.loadFailed = false;
        preview.decodedPixels = std::make_unique<LoadedTexturePixels>(std::move(result.pixels));
    }
}

void PollCompletedUploads() {
    if (!g_icons.uploadFence) {
        return;
    }

    const UINT64 completedFenceValue = g_icons.uploadFence->GetCompletedValue();

    for (auto& entry : g_icons.assetPreviews) {
        auto& preview = entry.second;
        if (preview.pendingUpload && completedFenceValue >= preview.pendingUpload->fenceValue) {
            preview.pendingUpload.reset();
        }
    }

    auto eraseIt = std::remove_if(
        g_icons.pendingIconUploads.begin(),
        g_icons.pendingIconUploads.end(),
        [completedFenceValue](const std::unique_ptr<PreviewGpuUpload>& upload) {
            return upload && completedFenceValue >= upload->fenceValue;
        });
    g_icons.pendingIconUploads.erase(eraseIt, g_icons.pendingIconUploads.end());
}

void MaintainIconRuntimeState() {
    const int frame = ImGui::GetFrameCount();
    if (g_icons.lastMaintenanceFrame == frame) {
        return;
    }

    g_icons.lastMaintenanceFrame = frame;
    DrainPreviewDecodeResults();
    PollCompletedUploads();
}

ImVec2 ComputeFittedIconSize(const BuiltInTexture& texture, const ImVec2& min, const ImVec2& max) {
    const float availableWidth = max.x - min.x;
    const float availableHeight = max.y - min.y;
    if (availableWidth <= 0.0f || availableHeight <= 0.0f || texture.width <= 0 || texture.height <= 0) {
        return ImVec2(0.0f, 0.0f);
    }

    const float scale = (std::min)(
        availableWidth / static_cast<float>(texture.width),
        availableHeight / static_cast<float>(texture.height));
    return ImVec2(
        static_cast<float>(texture.width) * scale,
        static_cast<float>(texture.height) * scale);
}

void DrawTextureIcon(ImDrawList* drawList, const BuiltInTexture& texture, const ImVec2& min, const ImVec2& max) {
    if (!drawList || !texture.IsValid()) {
        return;
    }

    const ImVec2 size = ComputeFittedIconSize(texture, min, max);
    const float x = min.x + ((max.x - min.x) - size.x) * 0.5f;
    const float y = min.y + ((max.y - min.y) - size.y) * 0.5f;
    drawList->AddImage(texture.textureId, ImVec2(x, y), ImVec2(x + size.x, y + size.y));
}

void DrawBuiltInFolderFallback(ImDrawList* drawList, const ImVec2& min, const ImVec2& max) {
    if (!drawList) {
        return;
    }

    const float width = max.x - min.x;
    const float height = max.y - min.y;
    if (width <= 0.0f || height <= 0.0f) {
        return;
    }

    const float rounding = (std::max)(1.0f, (std::min)(width, height) * 0.18f);
    const ImU32 tabColor = ImGui::GetColorU32(BuiltInFolderIconTabColor());
    const ImU32 topColor = ImGui::GetColorU32(BuiltInFolderIconTopColor());
    const ImU32 bodyColor = ImGui::GetColorU32(BuiltInFolderIconBodyColor());

    const ImVec2 tabMin(min.x + width * 0.08f, min.y + height * 0.14f);
    const ImVec2 tabMax(min.x + width * 0.48f, min.y + height * 0.38f);
    const ImVec2 topMin(min.x + width * 0.24f, min.y + height * 0.22f);
    const ImVec2 topMax(min.x + width * 0.90f, min.y + height * 0.42f);
    const ImVec2 bodyMin(min.x + width * 0.06f, min.y + height * 0.32f);
    const ImVec2 bodyMax(min.x + width * 0.94f, min.y + height * 0.88f);

    drawList->AddRectFilled(tabMin, tabMax, tabColor, rounding);
    drawList->AddRectFilled(
        topMin,
        topMax,
        topColor,
        rounding,
        ImDrawFlags_RoundCornersTopLeft | ImDrawFlags_RoundCornersTopRight);
    drawList->AddRectFilled(bodyMin, bodyMax, bodyColor, rounding);
}

void DrawBuiltInFileIcon(ImDrawList* drawList, const ImVec2& min, const ImVec2& max) {
    if (!drawList) {
        return;
    }

    const ImU32 fillColor = ImGui::GetColorU32(AssetFileIconFillColor());
    const ImU32 lineColor = ImGui::GetColorU32(AssetFileIconLineColor());
    const ImVec2 foldA(max.x - 8.0f, min.y);
    const ImVec2 foldB(max.x, min.y + 8.0f);
    drawList->AddRectFilled(min, max, fillColor, 2.0f);
    drawList->AddRect(min, max, lineColor, 2.0f);
    drawList->AddTriangleFilled(foldA, ImVec2(max.x, min.y), foldB, ImGui::GetColorU32(AssetFileFoldColor()));
    drawList->AddLine(foldA, foldB, lineColor);
}

BuiltInIconState::CachedAssetPreview* GetOrCreateAssetPreview(const std::string& filePath) {
    if (!g_icons.backend || !g_icons.device || !g_icons.commandQueue || filePath.empty()) {
        return nullptr;
    }

    MaintainIconRuntimeState();

    const std::string key = MakeAssetPreviewKey(filePath);
    auto [it, inserted] = g_icons.assetPreviews.try_emplace(key);
    BuiltInIconState::CachedAssetPreview& preview = it->second;
    preview.lastUsedFrame = ImGui::GetFrameCount();

    if (!inserted && !std::filesystem::exists(std::filesystem::path(Platform::Utf8ToWide(filePath)))) {
        if (!preview.pendingUpload) {
            ResetTexture(preview.texture);
            preview.decodedPixels.reset();
        }
        preview.loadFailed = true;
        preview.decodeQueued = false;
        return &preview;
    }

    if (preview.texture.IsValid()) {
        if (preview.pendingUpload && preview.pendingUpload->fenceValue <= g_icons.uploadFence->GetCompletedValue()) {
            preview.pendingUpload.reset();
        }
        return &preview;
    }

    if (preview.decodedPixels) {
        std::unique_ptr<PreviewGpuUpload> pendingUpload;
        if (!UploadTexturePixels(
                *g_icons.backend,
                g_icons.device,
                g_icons.commandQueue,
                *preview.decodedPixels,
                preview.texture,
                pendingUpload)) {
            preview.decodedPixels.reset();
            preview.loadFailed = true;
            return &preview;
        }

        preview.decodedPixels.reset();
        preview.loadFailed = false;
        preview.pendingUpload = std::move(pendingUpload);
        return &preview;
    }

    if (preview.decodeQueued || preview.loadFailed) {
        return &preview;
    }

    const int frame = ImGui::GetFrameCount();
    if (g_icons.lastPreviewBudgetFrame != frame) {
        g_icons.lastPreviewBudgetFrame = frame;
        g_icons.previewLoadsThisFrame = 0;
    }
    if (g_icons.previewLoadsThisFrame >= kMaxPreviewLoadsPerFrame) {
        return &preview;
    }

    if (QueuePreviewDecode(key, std::filesystem::path(Platform::Utf8ToWide(filePath)))) {
        preview.decodeQueued = true;
        ++g_icons.previewLoadsThisFrame;
    }
    return &preview;
}

void PruneAssetPreviewCache() {
    if (g_icons.assetPreviews.size() <= kMaxCachedAssetPreviews) {
        return;
    }

    std::vector<std::pair<std::string, int>> candidates;
    candidates.reserve(g_icons.assetPreviews.size());
    for (const auto& entry : g_icons.assetPreviews) {
        if (entry.second.pendingUpload || entry.second.decodeQueued) {
            continue;
        }
        candidates.emplace_back(entry.first, entry.second.lastUsedFrame);
    }

    std::sort(
        candidates.begin(),
        candidates.end(),
        [](const auto& lhs, const auto& rhs) {
            return lhs.second < rhs.second;
        });

    size_t removeCount = g_icons.assetPreviews.size() - kMaxCachedAssetPreviews;
    for (size_t i = 0; i < removeCount && i < candidates.size(); ++i) {
        auto it = g_icons.assetPreviews.find(candidates[i].first);
        if (it == g_icons.assetPreviews.end()) {
            continue;
        }

        ResetTexture(it->second.texture);
        g_icons.assetPreviews.erase(it);
    }
}

} // namespace

void InitializeBuiltInIcons(
    ImGuiBackendBridge& backend,
    ID3D12Device* device,
    ID3D12CommandQueue* commandQueue) {
    ShutdownBuiltInIcons();
    g_icons.backend = &backend;
    g_icons.device = device;
    g_icons.commandQueue = commandQueue;
    StartPreviewWorkers();

    std::unique_ptr<PreviewGpuUpload> pendingUpload;
    if (LoadTextureFromFile(backend, device, commandQueue, ResolveFolderIconPath(), g_icons.folder, pendingUpload)) {
        g_icons.pendingIconUploads.push_back(std::move(pendingUpload));
    }

    pendingUpload.reset();
    if (LoadTextureFromFile(backend, device, commandQueue, ResolveGameObjectIconPath(), g_icons.gameObject, pendingUpload)) {
        g_icons.pendingIconUploads.push_back(std::move(pendingUpload));
    }

    pendingUpload.reset();
    if (LoadTextureFromFile(backend, device, commandQueue, ResolveSceneIconPath(), g_icons.scene, pendingUpload)) {
        g_icons.pendingIconUploads.push_back(std::move(pendingUpload));
    }
}

void ShutdownBuiltInIcons() {
    if (g_icons.device && g_icons.commandQueue) {
        WaitForQueueIdle(g_icons.device, g_icons.commandQueue);
    }
    StopPreviewWorkers();
    ResetAssetPreviewCache();
    g_icons.pendingIconUploads.clear();
    ResetTexture(g_icons.folder);
    ResetTexture(g_icons.gameObject);
    ResetTexture(g_icons.scene);
    g_icons.backend = nullptr;
    g_icons.device = nullptr;
    g_icons.commandQueue = nullptr;
    g_icons.uploadFence.Reset();
    g_icons.nextUploadFenceValue = 1;
    g_icons.lastMaintenanceFrame = -1;
    g_icons.lastPreviewBudgetFrame = -1;
    g_icons.previewLoadsThisFrame = 0;
}

void DrawAssetIcon(ImDrawList* drawList, const ImVec2& min, const ImVec2& max, AssetIconKind kind) {
    MaintainIconRuntimeState();

    if (kind == AssetIconKind::Folder) {
        if (g_icons.folder.IsValid()) {
            DrawTextureIcon(drawList, g_icons.folder, min, max);
            return;
        }

        DrawBuiltInFolderFallback(drawList, min, max);
        return;
    }

    if (kind == AssetIconKind::GameObject) {
        if (g_icons.gameObject.IsValid()) {
            DrawTextureIcon(drawList, g_icons.gameObject, min, max);
            return;
        }

        DrawBuiltInFileIcon(drawList, min, max);
        return;
    }

    if (kind == AssetIconKind::Scene) {
        if (g_icons.scene.IsValid()) {
            DrawTextureIcon(drawList, g_icons.scene, min, max);
            return;
        }

        DrawBuiltInFileIcon(drawList, min, max);
        return;
    }

    DrawBuiltInFileIcon(drawList, min, max);
}

bool DrawTextureAssetPreview(
    ImDrawList* drawList,
    const ImVec2& min,
    const ImVec2& max,
    const std::string& filePath) {
    BuiltInIconState::CachedAssetPreview* preview = GetOrCreateAssetPreview(filePath);
    if (!preview || !preview->texture.IsValid()) {
        return false;
    }

    DrawTextureIcon(drawList, preview->texture, min, max);
    PruneAssetPreviewCache();
    return true;
}

} // namespace UI
} // namespace Editor
} // namespace XCEngine