import { ApplicationConfig, provideBrowserGlobalErrorListeners, importProvidersFrom, APP_INITIALIZER } from '@angular/core';
import { provideRouter } from '@angular/router';
import { provideHttpClient, withInterceptors } from '@angular/common/http';
import { TranslateModule, TranslateLoader, TranslateService } from '@ngx-translate/core';
import { TranslateHttpLoader, TRANSLATE_HTTP_LOADER_CONFIG } from '@ngx-translate/http-loader';
import { routes } from './app.routes';
import { authInterceptor } from './interceptors/auth.interceptor';

const SUPPORTED_LANGS = ['de', 'fr', 'it', 'en'];

function preloadTranslations(translate: TranslateService): () => Promise<any> {
  return () => {
    const stored = localStorage.getItem('app_language');
    const browser = navigator.language?.split('-')[0].toLowerCase();
    const lang = SUPPORTED_LANGS.includes(stored ?? '') ? stored!
      : SUPPORTED_LANGS.includes(browser) ? browser
      : 'de';
    translate.setDefaultLang('de');
    return translate.use(lang).toPromise();
  };
}

export const appConfig: ApplicationConfig = {
  providers: [
    provideBrowserGlobalErrorListeners(),
    provideRouter(routes),
    provideHttpClient(withInterceptors([authInterceptor])),
    importProvidersFrom(
      TranslateModule.forRoot({
        loader: {
          provide: TranslateLoader,
          useClass: TranslateHttpLoader,
        },
      })
    ),
    { provide: TRANSLATE_HTTP_LOADER_CONFIG, useValue: { prefix: '/assets/i18n/', suffix: '.json' } },
    {
      provide: APP_INITIALIZER,
      useFactory: preloadTranslations,
      deps: [TranslateService],
      multi: true,
    },
  ]
};