// Copyright 2019 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'dart:async';
import 'package:shared_preferences/shared_preferences.dart';

// This is just a development prototype for locally storing consumables. Do not
// use this.
class ConsumableStore {
  static const String _kPrefKey = 'consumables';
  static Future<void> _writes = Future.value();

  static Future<void> save(String id) {
    _writes = _writes.then((void _) => _doSave(id));
    return _writes;
  }

  static Future<void> consume(String id) {
    _writes = _writes.then((void _) => _doConsume(id));
    return _writes;
  }

  static Future<List<String>> load() async {
    return (await SharedPreferences.getInstance()).getStringList(_kPrefKey) ??
        [];
  }

  static Future<void> _doSave(String id) async {
    List<String> cached = await load();
    SharedPreferences prefs = await SharedPreferences.getInstance();
    cached.add(id);
    await prefs.setStringList(_kPrefKey, cached);
  }

  static Future<void> _doConsume(String id) async {
    List<String> cached = await load();
    SharedPreferences prefs = await SharedPreferences.getInstance();
    cached.remove(id);
    await prefs.setStringList(_kPrefKey, cached);
  }
}