JuLearn/lib/main.dart

import 'dart:convert';
import 'dart:io';

import 'package:file_picker/file_picker.dart';
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:ju_learn/learn.dart';
import 'package:shared_preferences/shared_preferences.dart';

void main() => runApp(const LearnApp());

class LearnApp extends StatelessWidget {
  const LearnApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Learn App',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MainPage(),
    );
  }
}

class MainPage extends StatefulWidget {
  const MainPage({super.key});

  @override
  _MainPageState createState() => _MainPageState();
}

class _MainPageState extends State<MainPage> {
  List<Vault> _vaults = [];
  _MainPageState() {
    loadList();
  }
  loadList() async {
    final prefs = await SharedPreferences.getInstance();
    List<String>? json = prefs.getStringList("vaults");
    if (json == null) return;
    setState(() {
      _vaults = json.map((e) => Vault.fromJson(jsonDecode(e))).toList();
    });
  }

  saveList() async {
    final prefs = await SharedPreferences.getInstance();
    prefs.setStringList(
        "vaults", _vaults.map((e) => jsonEncode(e.toJson())).toList());
  }

  askToDeleteVault(Vault v) async {
    showDialog(
      context: context,
      builder: (BuildContext context) {
        return AlertDialog(
          title: const Text('Delete Vault'),
          content: Text('Do you want to delete „${v.name}“ Vault?'),
          actions: [
            TextButton(
              child: const Text('Delete'),
              onPressed: () {
                setState(() {
                  _vaults.remove(v);
                });
                saveList();
                Navigator.of(context).pop();
              },
            ),
            TextButton(
                onPressed: () {
                  Navigator.of(context).pop();
                },
                child: const Text('Cancle'))
          ],
        );
      },
    );
  }

  _pickFile() async {
    FilePickerResult? result = await FilePicker.platform.pickFiles(
        type: FileType.custom,
        allowedExtensions: ['json'],
        allowMultiple: false);
    if (result != null && result.files.single.path != null) {
      File file = File(result.files.single.path ?? "");
      String data = file.readAsStringSync();
      try {
        Vault v = Vault.fromJson(jsonDecode(data));
        setState(() {
          _vaults.add(v);
        });
        saveList();
      } catch (e) {
        if (kDebugMode) {
          print(e);
        }
        AlertDialog(
            title: const Text('Error'),
            content: const Text('An error has occurred.'),
            actions: [
              TextButton(
                child: const Text('OK'),
                onPressed: () {
                  Navigator.of(context).pop();
                },
              ),
            ]);
        return;
      }
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Learn App'),
      ),
      body: Padding(
        padding: const EdgeInsets.all(16.0),
        child:
            Column(crossAxisAlignment: CrossAxisAlignment.stretch, children: [
          ..._vaults.map((e) => Container(
              margin: const EdgeInsets.symmetric(vertical: 8.0),
              child: ElevatedButton(
                onPressed: () {
                  Navigator.push(
                    context,
                    MaterialPageRoute(builder: (context) => QuizPage(e)),
                  );
                },
                onLongPress: () {
                  askToDeleteVault(e);
                },
                child: Text(e.name),
              )))
        ]),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _pickFile,
        backgroundColor: Colors.blue,
        child: const Icon(Icons.add),
      ),
    );
  }
}

class Question {
  String quest;
  List<String> answers;
  int correct;
  String explanation;

  Question(this.quest, this.answers, this.correct, this.explanation);

  Map<String, dynamic> toJson() {
    return {
      "quest": quest,
      "answers": answers,
      "correct": correct,
      "explanation": explanation,
    };
  }

  factory Question.fromJson(Map<String, dynamic> json) {
    if (json["quest"] is! String) {
      throw ErrorDescription("fromJSON Error: quest");
    }
    if (json["answers"] is! List<dynamic>) {
      throw ErrorDescription("fromJSON Error: awnsers");
    }
    if (json["correct"] is! int ||
        json["correct"] < 0 ||
        json["correct"] >= json["answers"].length) {
      throw ErrorDescription("fromJSON Error: correct");
    }
    if (json["explanation"] is! String) {
      throw ErrorDescription("fromJSON Error: explanation");
    }
    return Question(
      json["quest"],
      (json["answers"] as List<dynamic>).map((d) => d.toString()).toList(),
      json["correct"],
      json["explanation"],
    );
  }
}

class Vault {
  String name;
  List<Question> questions;
  Vault(this.name, this.questions);

  Map<String, dynamic> toJson() {
    return {"name": name, "questions": questions.map((e) => e.toJson()).toList()};
  }

  factory Vault.fromJson(Map<String, dynamic> json) {
    if (json["name"] is! String) {
      throw ErrorDescription("fromJSON Error: name");
    }
    if (json["questions"] is! List<dynamic>) {
      throw ErrorDescription("fromJSON Error: questions");
    }
    return Vault(
      json["name"],
      (json["questions"] as List<dynamic>)
          .map((d) => Question.fromJson(d))
          .toList(),
    );
  }
}