/*
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 */

/** \file
 * \ingroup bke
 */

#pragma once

#ifndef __cplusplus
#  error This is a C++-only header file.
#endif

#include "BKE_asset_library.hh"

#include "BLI_map.hh"

#include <memory>

namespace blender::bke {

/**
 * Global singleton-ish that provides access to individual #AssetLibrary instances.
 *
 * Whenever a blend file is loaded, the existing instance of AssetLibraryService is destructed, and
 * a new one is created -- hence the "singleton-ish". This ensures only information about relevant
 * asset libraries is loaded.
 *
 * \note How Asset libraries are identified may change in the future.
 *  For now they are assumed to be:
 * - on disk (identified by the absolute directory), or
 * - the "current file" library (which is in memory but could have catalogs
 *   loaded from a file on disk).
 */
class AssetLibraryService {
 public:
  using AssetLibraryPtr = std::unique_ptr<AssetLibrary>;

  AssetLibraryService() = default;
  ~AssetLibraryService() = default;

  /** Return the AssetLibraryService singleton, allocating it if necessary. */
  static AssetLibraryService *get();

  /** Destroy the AssetLibraryService singleton. It will be reallocated by #get() if necessary. */
  static void destroy();

  /**
   * Get the given asset library. Opens it (i.e. creates a new AssetLibrary instance) if necessary.
   */
  AssetLibrary *get_asset_library_on_disk(StringRefNull top_level_directory);

  /** Get the "Current File" asset library. */
  AssetLibrary *get_asset_library_current_file();

  /** Returns whether there are any known asset libraries with unsaved catalog edits. */
  bool has_any_unsaved_catalogs() const;

 protected:
  static std::unique_ptr<AssetLibraryService> instance_;

  /* Mapping absolute path of the library's top-level directory to the AssetLibrary instance. */
  Map<std::string, AssetLibraryPtr> on_disk_libraries_;
  AssetLibraryPtr current_file_library_;

  /* Handlers for managing the life cycle of the AssetLibraryService instance. */
  bCallbackFuncStore on_load_callback_store_;
  static bool atexit_handler_registered_;

  /** Allocate a new instance of the service and assign it to `instance_`. */
  static void allocate_service_instance();

  /**
   * Ensure the AssetLibraryService instance is destroyed before a new blend file is loaded.
   * This makes memory management simple, and ensures a fresh start for every blend file. */
  void app_handler_register();
  void app_handler_unregister();
};

}  // namespace blender::bke