rojects/source/locales/LocaleManager.ts

export class LocaleManager
{
  static _instance:LocaleManager;

  static get $()
  {
    if ( ! this._instance )
    {
      this._instance = new LocaleManager();
    }

    return this._instance;
  }

  _currentLocale = 'en';
  _cache = new Map<string, string>();

  get currentLocale(): string 
  {
    return this._currentLocale;
  }

  setLocale( locale: string ):void 
  {
    this._currentLocale = locale;
  }

  async get( localePath:string ):Promise<string>
  {
    return this._loadLocale( localePath );
  }

  async _loadLocale( relativePath: string ): Promise<string>
  {
    const key = `${this._currentLocale}/${relativePath}`;

    if ( this._cache.has( key ) ) 
    {
      return this._cache.get( key );
    }

    const res = await fetch(`/api/locales/${this._currentLocale}/${relativePath}`);
    
    if ( ! res.ok ) 
    {
      return relativePath;
    }

    const ext = relativePath.split('.').pop() ?? '';
    let value: string;

    if ( ext === 'json' ) 
    {
      const data = await res.json() as { value: string };
      value = data.value;
    } 
    else 
    {
      value = await res.text();
    }

    this._cache.set( key, value );
    return value;
  }

  invalidateCache(): void 
  {
    this._cache.clear();
  }

}