import 'dart:convert';

import 'package:http/http.dart' as http;

class FirebaseAuthVerifier {
  FirebaseAuthVerifier(this._webApiKey);

  final String _webApiKey;

  Future<String?> verifyBearerToken(String? authorization) async {
    if (authorization == null || !authorization.startsWith('Bearer ')) {
      return null;
    }
    final String idToken = authorization.substring('Bearer '.length).trim();
    if (idToken.isEmpty) {
      return null;
    }

    final Uri uri = Uri.parse(
      'https://identitytoolkit.googleapis.com/v1/accounts:lookup?key=$_webApiKey',
    );
    final http.Response response = await http.post(
      uri,
      headers: const <String, String>{'Content-Type': 'application/json'},
      body: jsonEncode(<String, dynamic>{'idToken': idToken}),
    );

    if (response.statusCode != 200) {
      return null;
    }

    final Map<String, dynamic> data =
        jsonDecode(response.body) as Map<String, dynamic>;
    final List<dynamic> users = data['users'] as List<dynamic>? ?? <dynamic>[];
    if (users.isEmpty) {
      return null;
    }
    return users.first['localId'] as String?;
  }
}