model_cache.hpp

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// This file is part of the Rendering Engine project.
// Author: Alexander Obzherin <alexanderobzherin@gmail.com>
// Copyright (c) 2025 Alexander Obzherin
// Distributed under the terms of the zlib License. See LICENSE.md for details.
 
#pragma once
 
#include "i_renderer_observer.hpp"
#include <string>
#include <unordered_map>
#include <memory>
#include <vector>
 
namespace rendering_engine
{
class IRenderer;
class IMeshRenderResources;
class MeshDataGpu;
 
/**
 * @brief Manages loading, caching, and GPU residency of all model/mesh resources.
 *
 * Responsible for importing model files into RAM, uploading mesh data to GPU memory,
 * and managing the lifetime and statistics of all managed models in the rendering engine.
 * Also observes renderer resource lifecycle events (release/rebuild).
 */
class ModelCache : public IRendererObserver
{
public:
    /**
     * @brief Construct a ModelCache and register it with the given renderer.
     * @param renderer Pointer to the owning IRenderer implementation.
     */
    ModelCache(IRenderer* renderer);
 
    /**
     * @brief Destructor. Releases all resources and unregisters observer.
     */
    ~ModelCache();
 
    /**
     * @brief Load all models found in the specified folder into RAM.
     * @param pathToFolder Path to the directory containing model files.
     */
    void LoadModelsFromFolder(std::string pathToFolder);
 
    /**
     * @brief Load all models from the packed asset container.
     *
     * This function behaves similarly to LoadModelsFromFolder(), but instead
     * retrieves model files from the packed asset system created by the
     * Packaging Tool. Each packed file is read into memory and processed via
     * UploadModelToRAM(std::string, const std::vector<uint8_t>&).
     *
     * Only file entries located under the virtual folder:
     *     "Models/"
     * are considered.
     *
     * The resulting MeshDataGpu objects remain cached and ready for GPU upload.
     */
    void LoadModelsFromPackage();
 
    /**
     * @brief Creates a built-in 2D quad mesh.
     *
     * This helper is used by 2D systems (e.g., UI, sprites) to create a reusable
     * quad mesh without external model files.
     */
    void CreateQuad2D();
 
    /**
     * @brief Load a single model from file into RAM.
     * @param path Path to the model file.
     * @return The filename used as a cache key, or empty string on failure.
     */
    std::string UploadModelToRAM(std::string path);
 
    /**
     * @brief Load a single model into RAM from a raw file buffer.
     *
     * This overload is used when the model originates from a packed asset
     * archive or any virtual filesystem source rather than the OS filesystem.
     *
     * @param fileName Cache key (typically relative virtual path, e.g. "Models/cube.fbx").
     * @param fileBytes Raw contents of the model file.
     * @return The cache key on success, or an empty string on failure.
     */
    std::string UploadModelToRAM(std::string fileName, std::vector<uint8_t> const& fileBytes);
 
    /**
     * @brief Upload a cached model's mesh data to the GPU.
     * @param filename The model's cache key (filename without extension).
     */
    void UploadModelToGPU(std::string filename);
 
    /**
     * @brief Release a model's mesh data from GPU memory.
     * @param filename The model's cache key (filename without extension).
     */
    void ReleaseModelFromGPU(std::string filename);
 
    /**
     * @brief Release all model mesh data from GPU memory.
     */
    void ReleaseAllFromGPU();
 
    /**
     * @brief Remove all models from both GPU and RAM, clearing the cache.
     */
    void ReleaseAll();
 
    /**
     * @brief Get a shared pointer to the MeshDataGpu for a model.
     * @param filename The model's cache key (filename without extension).
     * @return Shared pointer to MeshDataGpu, or nullptr if not found.
     */
    std::shared_ptr<MeshDataGpu> GetMeshResources(std::string filename);
 
    /**
     * @brief Get the IMeshRenderResources interface for a model's GPU resources.
     * @param filename The model's cache key (filename without extension).
     * @return Pointer to IMeshRenderResources, or nullptr if not found or not on GPU.
     */
    IMeshRenderResources* GetMeshRenderResources(std::string filename);
 
    /**
     * @brief Get the total size (in bytes) of all models loaded in RAM.
     * @return Total RAM usage in bytes.
     */
    inline size_t GetSizeInRAM() const;
 
    /**
     * @brief Get the total size (in bytes) of all models currently resident on GPU.
     * @return Total GPU usage in bytes.
     */
    inline size_t GetSizeInGPU() const;
 
protected:
    /**
     * @copydoc IRendererObserver::OnRenderResourcesRelease
     */
    void OnRenderResourcesRelease() override;
    /**
     * @copydoc IRendererObserver::OnRenderResourcesRebuild
     */
    void OnRenderResourcesRebuild() override;
 
protected:
    IRenderer* mRenderer;
    std::unordered_map<std::string, std::shared_ptr<MeshDataGpu>> mModels;
 
    size_t mTotalSizeRAM;
    size_t mTotalSizeGPU;
};
 
 
 
} // namespace rendering_engine