export class LanguageService {

  private listeners: Array<() => void> = [];
  private document: Document = document;

  constructor (private lsKey: string, private defaultLang = 'pt') {
    this.setupListener();
  }

  setupListener (): void {
    if(this.document !== null) {
      this.document.addEventListener("storage",(event => {
        const e = event as StorageEvent;
        if(e.key === this.lsKey) {
          this.listeners.forEach(l => l());         
        }
      }));
    }
  }

  getLang (): string {
    const lang = localStorage.getItem(this.lsKey);
    if(lang === null || lang === undefined) {
      console.warn("Internal Error: User language information has not been set. Returning default...");
      return this.getDefaultLang();
    }
    return lang;
  }

  getDefaultLang (): string {
    return this.defaultLang;
  }

  registerLanguageChangeListener (listener: () => void) {
    this.listeners.push(listener);
  }
}