Quick and dirty translation service in Angular

langservice.service.ts

import { Injectable } from '@angular/core';
import { STRING_MESSAGES } from '../components/comet-chat-components/utils/messageConstants';
import { DA_MESSAGES } from '../i18n/da';
import { DE_MESSAGES } from '../i18n/de';
import { EN_MESSAGES } from '../i18n/en';
import { ES_MESSAGES } from '../i18n/es';
import { FR_MESSAGES } from '../i18n/fr';
import { HU_MESSAGES } from '../i18n/hu';
import { IT_MESSAGES } from '../i18n/it';
import { NL_MESSAGES } from '../i18n/nl';
import { NO_MESSAGES } from '../i18n/no';
import { PT_MESSAGES } from '../i18n/pt';
import { SL_MESSAGES } from '../i18n/sl';
import { SV_MESSAGES } from '../i18n/sv';

interface HashTable<T> {
  [key: string]: T;
}

@Injectable({
  providedIn: 'root',
})
export class LangService {
  private _defaultLang: string = 'en';
  private _currentLang: string = 'en';
  private translations: { [key: string]: HashTable<string> };
  private fallback: HashTable<string> = STRING_MESSAGES;

  get defaultLang(): string {
    return this._defaultLang;
  }

  get currentLang(): string {
    return this._currentLang;
  }

  get languages(): string[] {
    return Object.keys(this.translations);
  }

  constructor() {
    this.translations = {
      da: DA_MESSAGES,
      de: DE_MESSAGES,
      en: EN_MESSAGES,
      es: ES_MESSAGES,
      fr: FR_MESSAGES,
      hu: HU_MESSAGES,
      it: IT_MESSAGES,
      nl: NL_MESSAGES,
      no: NO_MESSAGES,
      pt: PT_MESSAGES,
      sl: SL_MESSAGES,
      sv: SV_MESSAGES,
    };
  }

  setDefaultLang(lang: string) {
    this._defaultLang = lang.toLowerCase();
  }

  use(lang: string) {
    if (this.languages.includes(lang.toLowerCase())) this._currentLang = lang;
  }

  trans(key, fallbackValue: string = undefined) {
    let source = this.translations[this.currentLang];
    if (source.hasOwnProperty(key)) return source[key];
    source = this.translations[this.defaultLang];
    if (source.hasOwnProperty(key)) return source[key];
    source = this.fallback;
    if (source.hasOwnProperty(key)) return source[key];
    return fallbackValue || key;
  }

  resolveLocale(url: string, segmentIndex: number, defaultLanguage = 'en') {
    // look for either ISO 3166-1 alpha-2 or combined with ISO 3166-2
    const pattern = /\b\w{2}(-\w{2})?\b/gim;
    const segments = url.split('/');
    return segmentIndex < segments.length && pattern.test(segments[segmentIndex]) ? segments[segmentIndex] : defaultLanguage;
  }
}