import { HttpInterceptorFn } from '@angular/common/http';
import { inject } from '@angular/core';
import { LocationService } from '../services/location.service';
import { LanguageService } from '../services/language.service';
import { environment } from '../../environments/environment';

/**
 * Interceptor that attaches X-Region and X-Language headers
 * to every outgoing request aimed at our API.
 *
 * The backend reads these headers to:
 *  - filter catalog by region
 *  - return translated content in the requested language
 */
export const apiHeadersInterceptor: HttpInterceptorFn = (req, next) => {
  // Only attach headers to our own API requests
  if (!req.url.startsWith(environment.apiUrl)) {
    return next(req);
  }

  const locationService = inject(LocationService);
  const languageService = inject(LanguageService);

  const regionId = locationService.regionId();       // '' when global
  const lang = languageService.currentLanguage();     // 'ru' | 'en' | 'hy'

  let headers = req.headers;

  if (regionId) {
    headers = headers.set('X-Region', regionId);
  }
  if (lang) {
    headers = headers.set('X-Language', lang);
  }

  return next(req.clone({ headers }));
};