//  SPDX-License-Identifier: MIT
//
//  ES-DE
//  TextureDataManager.h
//
//  Loading and unloading of texture data.
//

#ifndef ES_CORE_RESOURCES_TEXTURE_DATA_MANAGER_H
#define ES_CORE_RESOURCES_TEXTURE_DATA_MANAGER_H

#include <atomic>
#include <condition_variable>
#include <list>
#include <map>
#include <memory>
#include <mutex>
#include <thread>

class TextureData;
class TextureResource;

class TextureLoader
{
public:
    TextureLoader();
    ~TextureLoader();

    void load(std::shared_ptr<TextureData> textureData);
    void remove(std::shared_ptr<TextureData> textureData);

    void setExit() { mExit = true; }
    size_t getQueueSize();

private:
    void processQueue();
    void threadProc();

    std::list<std::shared_ptr<TextureData>> mTextureDataQ;
    std::map<TextureData*, std::list<std::shared_ptr<TextureData>>::const_iterator>
        mTextureDataLookup;

    std::unique_ptr<std::thread> mThread;
    std::mutex mMutex;
    std::condition_variable mEvent;
    std::atomic<bool> mExit;
};

//
// This class manages the loading and unloading of textures.
//
// When textures are added, the texture data is just stored as-is. The texture
// data should only have been constructed and not loaded for this to work correctly.
// When the get() function is called it indicates that a texture wants to be used so
// at this point the texture data is loaded (via a call to load()).
//
// Once the load is complete (which may not be on the first call to get() if the
// data is loaded in a background thread) then the get() function call uploadAndBind()
// to upload to VRAM if necessary and bind the texture. This is followed by a call
// to releaseRAM() which frees the memory buffer if the texture can be reloaded from
// disk if needed again.
//
class TextureDataManager
{
public:
    TextureDataManager();

    std::shared_ptr<TextureData> add(const TextureResource* key, bool tiled);

    // The texturedata being removed may be loading in a different thread. However it will
    // be referenced by a smart pointer so we only need to remove it from our array and it
    // will be deleted when the other thread has finished with it.
    void remove(const TextureResource* key);

    std::shared_ptr<TextureData> get(const TextureResource* key);
    bool bind(const TextureResource* key, const unsigned int texUnit);

    // Get the total size of all textures managed by this object, loaded and unloaded in bytes.
    size_t getTotalSize();
    // Get the total size of all committed textures (in VRAM) in bytes.
    size_t getCommittedSize();
    // Get the total size of all load-pending textures in the queue - these will
    // be committed to VRAM as the queue is processed.
    size_t getQueueSize();
    // Load a texture, freeing resources as necessary to make space.
    void load(std::shared_ptr<TextureData> tex, bool block = false);
    // Make sure that threadProc() does not continue to run during application shutdown.
    void setExit()
    {
        if (mLoader)
            mLoader->setExit();
    }

private:
    std::list<std::shared_ptr<TextureData>> mTextures;
    std::map<const TextureResource*, std::list<std::shared_ptr<TextureData>>::const_iterator>
        mTextureLookup;
    std::shared_ptr<TextureData> mBlank;
    std::unique_ptr<TextureLoader> mLoader;
};

#endif // ES_CORE_RESOURCES_TEXTURE_DATA_MANAGER_H