Class AssetManager

packages/asset-system/src/core/AssetManager.ts:50–738

 * 资产管理器实现
 */
export class AssetManager implements IAssetManager {
    private readonly _assets = new Map<AssetGUID, AssetEntry>();
    private readonly _handleToGuid = new Map<AssetHandle, AssetGUID>();
    private readonly _pathToGuid = new Map<string, AssetGUID>();
    private readonly _cache: AssetCache;
    private readonly _loadQueue: IAssetLoadQueue;
    private readonly _loaderFactory: IAssetLoaderFactory;
    private readonly _database: AssetDatabase;

    /** Asset reader for file operations. | 用于文件操作的资产读取器。 */
    private _reader: IAssetReader | null = null;

    private _nextHandle: AssetHandle = 1;

    private _statistics = {
        loadedCount: 0,
        failedCount: 0
    };

    private _isDisposed = false;
    private _loadingCount = 0;

    constructor(catalog?: IAssetCatalog) {
        this._cache = new AssetCache();
        this._loadQueue = new AssetLoadQueue();
        this._loaderFactory = new AssetLoaderFactory();
        this._database = new AssetDatabase();

        if (catalog) {
            this.initializeFromCatalog(catalog);
        }
    }

    /**
     * Set asset reader.
     * 设置资产读取器。
     */
    setReader(reader: IAssetReader): void {
        this._reader = reader;
    }

    /**
     * Set project root path for resolving relative paths.
     * 设置项目根路径用于解析相对路径。
     */
    setProjectRoot(path: string): void {
        this._database.setProjectRoot(path);
    }

    /**
     * Get the asset database.
     * 获取资产数据库。
     */
    getDatabase(): AssetDatabase {
        return this._database;
    }

    /**