Client/lib/model/accountData.dart

import 'dart:async';

import 'package:flutter/cupertino.dart';
import 'package:provider/provider.dart';
import 'package:shared_preferences/shared_preferences.dart';

import 'accountModel.dart';

class AccountData {
  static const _usernameField = "username";
  static const _passwordField = "password";
  
  static final AccountData _instance = AccountData._construct();
  final Future<SharedPreferences> _storage = SharedPreferences.getInstance();
  Completer<void> _populated = Completer();

  factory AccountData() {
    return _instance;
  }

  AccountData._construct() {
    _updateFromStorage();
  }

  String? _username;
  String? _password;

  String getUsername() {
    if(_username == null) throw Exception("Username not initialized");
    return _username!;
  }

  String getPassword() {
    if(_password == null) throw Exception("Password not initialized");
    return _password!;
  }

  Future<void> setData(BuildContext context, String username, String password) async {
    SharedPreferences storage = await _storage;

    storage.setString(_usernameField, username);
    storage.setString(_passwordField, password);
    await _updateFromStorage();
  }

  Future<void> removeData(BuildContext context) async {
    _populated = Completer();
    Provider.of<AccountModel>(context, listen: false).setState(AccountModelState.loggedOut);

    SharedPreferences storage = await _storage;
    await storage.remove(_usernameField);
    await storage.remove(_passwordField);
  }

  Future<void> _updateFromStorage() async {
    SharedPreferences storage = await _storage;
    await storage.reload();
    if(storage.containsKey(_usernameField) && storage.containsKey(_passwordField)) {
      _username = storage.getString(_usernameField);
      _password = storage.getString(_passwordField);
    }
    _populated.complete();
  }

  Future<bool> waitForPopulation() async {
    await _populated.future;
    return isPopulated();
  }

  bool isPopulated() {
    return _username != null && _password != null;
  }

  String buildHttpAuthString() {
    if(!isPopulated()) throw Exception("AccountData (e.g. username or password) is not initialized!");
    return "$_username:$_password";
  }
}