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

/** Map internal language codes to API header values */
const LANG_HEADER_MAP: Record<string, string> = {
  'ru': 'RU',
  'en': 'EN',
  'hy': 'AM',
};

/** Map region IDs to API header values */
const REGION_HEADER_MAP: Record<string, string> = {
  'moscow': 'Moscow',
  'spb': 'ST. Petersburg',
  'yerevan': 'Yerevan',
};

const SESSION_STORAGE_KEY = 'web_session_id';

/** Generate a 32-char hex string (GUID without dashes) */
function generateSessionId(): string {
  const bytes = new Uint8Array(16);
  crypto.getRandomValues(bytes);
  return Array.from(bytes, b => b.toString(16).padStart(2, '0')).join('');
}

/** Get or create a persistent anonymous session ID */
function getAnonymousSessionId(): string {
  let id = localStorage.getItem(SESSION_STORAGE_KEY);
  if (!id || id.length !== 32) {
    id = generateSessionId();
    localStorage.setItem(SESSION_STORAGE_KEY, id);
  }
  return id;
}

export const apiHeadersInterceptor: HttpInterceptorFn = (req, next) => {
  if (!req.url.startsWith(environment.apiUrl)) {
    return next(req);
  }

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

  const regionId = locationService.regionId();
  const lang = languageService.currentLanguage();
  const currency = languageService.currentCurrency();
  const session = authService.session();

  let headers = req.headers;

  if (regionId) {
    headers = headers.set('X-Region', REGION_HEADER_MAP[regionId] ?? regionId);
  }
  if (lang) {
    headers = headers.set('X-Language', LANG_HEADER_MAP[lang] ?? lang.toUpperCase());
  }
  headers = headers.set('Currency', currency || 'RUB');
  headers = headers.set('WebSessionID', session?.sessionId || getAnonymousSessionId());

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