import 'dart:convert';

import 'package:shared_preferences/shared_preferences.dart';

import '../task.dart';
import 'interfaces/task_repository.dart';

class LocalRepository implements TaskRepository {
  static const String _tasksKey = 'tasks';
  static const String _taskOrderKey = 'taskOrder';
  SharedPreferencesWithCache? _prefs;

  Future<void> initialize() async {
    if (_prefs == null) {
      await SharedPreferencesWithCache.create(
        cacheOptions: const SharedPreferencesWithCacheOptions(
          allowList: <String>{_tasksKey, _taskOrderKey},
        ),
      ).then((value) => _prefs = value);
    }
  }

  // Create

  @override
  Future<void> saveTask(Task task) async {
    final tasks = await loadTasks();
    if (tasks.contains(task)) {
      tasks.remove(task);
    } else {
      final taskOrder = (await loadTaskOrder()).toList();
      taskOrder.add(task.id);
      await saveTaskOrder(taskOrder);
    }
    tasks.add(task);
    return saveTasks(tasks);
  }

  @override
  Future<void> saveTasks(List<Task> tasks) async {
    final jsonList = tasks.map<String>((e) => jsonEncode(e.toJson())).toList();
    return _prefs!.setStringList(_tasksKey, jsonList);
  }

  @override
  Future<void> saveTaskOrder(Iterable<String> taskOrder) {
    final jsonList = taskOrder.map<String>((e) => jsonEncode(e)).toList();
    return _prefs!.setStringList(_taskOrderKey, jsonList);
  }

  // Read

  @override
  Future<Iterable<String>> loadTaskOrder() async {
    final Iterable<String> jsonList =
        _prefs!.getStringList(_taskOrderKey) ?? [];
    return jsonList.map<String>((e) => jsonDecode(e));
  }

  @override
  Future<List<Task>> loadTasks() async {
    final Iterable<String> jsonList = _prefs!.getStringList(_tasksKey) ?? [];
    return jsonList.map<Task>((e) => Task.fromJson(jsonDecode(e))).toList();
  }

  // Delete

  @override
  Future<void> deleteTask(Task task) async {
    final tasks = await loadTasks();
    tasks.remove(task);
    saveTasks(tasks);
  }
}