mian.dart

//flutter expose to use
import 'package:flutter/material.dart';
import './result.dart';
import './quiz.dart';

//entry for the application
void main() => runApp(MyApp());

//When external input data change, StatefulWidget should be rebuilt basically
//Why does it have two classes(MyApp, MyAppState)
class MyApp extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return _MyAppState();
  }
}

//State is a generic class, it's attach to MyApp widget
//Implementation: When questionIndex changes, StatefulWidget 'MyApp' also recreates
//MyAppState is a persistant
//underscore turns a public class into private
class _MyAppState extends State<MyApp> {

  final _questions = const [
    {
      'questionText': 'What\'s your favorite color?',
      'answers': [
        {'text': 'Black', 'score': 10},
        {'text': 'Red', 'score': 5},
        {'text': 'Green', 'score': 3},
        {'text': 'White', 'score': 1},
      ],
    },
    {
      'questionText': 'What\'s your favorite animal?',
      'answers': [
        {'text': 'Rabbit', 'score': 3},
        {'text': 'Cat', 'score': 11},
        {'text': 'Elephant', 'score': 5},
        {'text': 'Lion', 'score': 9},
      ],
    },
    {
      'questionText': 'Who\'s your favorite instructor?',
      'answers': [
        {'text': 'Peter', 'score': 1},
        {'text': 'Max', 'score': 1},
        {'text': 'Mohsen', 'score': 1},
        {'text': 'Robin', 'score': 1},
      ],
    },
  ];
  var _questionIndex = 0;
  var _totalScore = 0;

  //restart the quiz
  void _resetQuiz() {
    setState(() {
      _questionIndex = 0;
      _totalScore = 0;
    });
  }

  void _answerQuestion(int score) {
    // var aBool = true;
    // aBool = false;

    _totalScore += score;

    setState(() {
      _questionIndex = _questionIndex + 1;
    });
    print(_questionIndex);
    if (_questionIndex < _questions.length) {
      print('We have more questions!');
    } else {
      print('No more questions!');
    }
  }

  @override
  Widget build(BuildContext context) {

    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('My First App'),
        ),
        body: _questionIndex < _questions.length
            ? Quiz(
                answerQuestion: _answerQuestion,
                questionIndex: _questionIndex,
                questions: _questions,
              )
            : Result(_totalScore, _resetQuiz),
      ),
    );
  }
}