//  SPDX-License-Identifier: MIT
//
//  EmulationStation Desktop Edition
//  TextureDataManager.cpp
//
//  Loading and unloading of texture data.
//

#include "resources/TextureDataManager.h"

#include "Log.h"
#include "Settings.h"
#include "resources/TextureData.h"
#include "resources/TextureResource.h"

TextureDataManager::TextureDataManager()
{
    // This blank texture will be used temporarily when there is not yet any data loaded for
    // the requested texture (i.e. it can't be uploaded to the GPU VRAM yet).
    const std::vector<unsigned char> blank(5 * 5 * 4, 0);
    mBlank = std::make_shared<TextureData>(false);
    mBlank->initFromRGBA(&blank[0], 5, 5);

    mLoader = std::make_unique<TextureLoader>();
}

std::shared_ptr<TextureData> TextureDataManager::add(const TextureResource* key, bool tiled)
{
    remove(key);
    std::shared_ptr<TextureData> data {std::make_shared<TextureData>(tiled)};
    mTextures.push_front(data);
    mTextureLookup[key] = mTextures.cbegin();
    return data;
}

void TextureDataManager::remove(const TextureResource* key)
{
    // Find the entry in the list.
    auto it = mTextureLookup.find(key);
    if (it != mTextureLookup.cend()) {
        // Remove the list entry.
        mTextures.erase((*it).second);
        // And the lookup.
        mTextureLookup.erase(it);
    }
}

std::shared_ptr<TextureData> TextureDataManager::get(const TextureResource* key)
{
    // If it's in the cache then we want to remove it from it's current location and
    // move it to the top.
    std::shared_ptr<TextureData> tex;
    auto it = mTextureLookup.find(key);
    if (it != mTextureLookup.cend()) {
        tex = *(*it).second;
        // Remove the list entry.
        mTextures.erase((*it).second);
        // Put it at the top.
        mTextures.push_front(tex);
        // Store it back in the lookup.
        mTextureLookup[key] = mTextures.cbegin();

        // Make sure it's loaded or queued for loading.
        load(tex);
    }
    return tex;
}

bool TextureDataManager::bind(const TextureResource* key, const unsigned int texUnit)
{
    std::shared_ptr<TextureData> tex {get(key)};
    bool bound {false};
    if (tex != nullptr)
        bound = tex->uploadAndBind(texUnit);
    if (!bound)
        mBlank->uploadAndBind(texUnit);
    return bound;
}

size_t TextureDataManager::getTotalSize()
{
    size_t total {0};
    for (auto tex : mTextures)
        total += tex->width() * tex->height() * 4;
    return total;
}

size_t TextureDataManager::getCommittedSize()
{
    size_t total {0};
    for (auto tex : mTextures)
        total += tex->getVRAMUsage();
    return total;
}

size_t TextureDataManager::getQueueSize()
{
    // Return queue size.
    return mLoader->getQueueSize();
}

void TextureDataManager::load(std::shared_ptr<TextureData> tex, bool block)
{
    // See if it's already loaded.
    if (tex->isLoaded())
        return;
    // Not loaded. Make sure there is room.
    size_t size {TextureResource::getTotalMemUsage()};
    size_t settingVRAM {static_cast<size_t>(Settings::getInstance()->getInt("MaxVRAM"))};

    if (settingVRAM < 128) {
        LOG(LogWarning) << "MaxVRAM is too low at " << settingVRAM
                        << " MiB, setting it to the minimum allowed value of 128 MiB";
        Settings::getInstance()->setInt("MaxVRAM", 128);
        settingVRAM = 128;
    }
    else if (settingVRAM > 2048) {
        LOG(LogWarning) << "MaxVRAM is too high at " << settingVRAM
                        << " MiB, setting it to the maximum allowed value of 2048 MiB";
        Settings::getInstance()->setInt("MaxVRAM", 2048);
        settingVRAM = 1024;
    }

    size_t max_texture {settingVRAM * 1024 * 1024};

    for (auto it = mTextures.crbegin(); it != mTextures.crend(); ++it) {
        if (size < max_texture)
            break;
        (*it)->releaseVRAM();
        (*it)->releaseRAM();
        // It may be already in the loader queue. In this case it wouldn't have been using
        // any VRAM yet but it will be. Remove it from the loader queue.
        mLoader->remove(*it);
        size = TextureResource::getTotalMemUsage();
    }

    if (!block)
        mLoader->load(tex);
    else
        tex->load();
}

TextureLoader::TextureLoader()
    : mExit(false)
{
    mThread = std::make_unique<std::thread>(&TextureLoader::threadProc, this);
}

TextureLoader::~TextureLoader()
{
    // Just abort any waiting texture.
    std::unique_lock<std::mutex> lock(mMutex);
    mTextureDataQ.clear();
    mTextureDataLookup.clear();
    lock.unlock();

    // Exit the thread.
    mExit = true;

    mEvent.notify_one();
    mThread->join();
    mThread.reset();
}

void TextureLoader::threadProc()
{
    while (!mExit) {
        std::shared_ptr<TextureData> textureData;
        {
            // Wait for an event to say there is something in the queue.
            std::unique_lock<std::mutex> lock {mMutex};
            mEvent.wait(lock);
            if (!mTextureDataQ.empty()) {
                textureData = mTextureDataQ.front();
                mTextureDataQ.pop_front();
                mTextureDataLookup.erase(mTextureDataLookup.find(textureData.get()));
            }
        }
        // Queue has been released here but we might have a texture to process.
        while (!mExit && textureData) {
            textureData->load();

            // See if there is another item in the queue.
            textureData = nullptr;
            std::unique_lock<std::mutex> lock {mMutex};
            if (!mTextureDataQ.empty()) {
                textureData = mTextureDataQ.front();
                mTextureDataQ.pop_front();
                mTextureDataLookup.erase(mTextureDataLookup.find(textureData.get()));
            }
        }
    }
}

void TextureLoader::load(std::shared_ptr<TextureData> textureData)
{
    // Make sure it's not already loaded.
    if (!textureData->isLoaded()) {
        std::unique_lock<std::mutex> lock {mMutex};
        // Remove it from the queue if it is already there.
        auto td = mTextureDataLookup.find(textureData.get());
        if (td != mTextureDataLookup.cend()) {
            mTextureDataQ.erase((*td).second);
            mTextureDataLookup.erase(td);
        }

        // Put it on the start of the queue as we want the newly requested textures to load first.
        mTextureDataQ.push_front(textureData);
        mTextureDataLookup[textureData.get()] = mTextureDataQ.cbegin();
        mEvent.notify_one();
    }
}

void TextureLoader::remove(std::shared_ptr<TextureData> textureData)
{
    // Just remove it from the queue so we don't attempt to load it.
    std::unique_lock<std::mutex> lock {mMutex};
    auto td = mTextureDataLookup.find(textureData.get());
    if (td != mTextureDataLookup.cend()) {
        mTextureDataQ.erase((*td).second);
        mTextureDataLookup.erase(td);
    }
}

size_t TextureLoader::getQueueSize()
{
    // Get the amount of video memory that will be used once all textures in
    // the queue are loaded.
    size_t mem {0};
    std::unique_lock<std::mutex> lock {mMutex};
    for (auto tex : mTextureDataQ)
        mem += tex->width() * tex->height() * 4;

    return mem;
}
