import 'dart:async';

import 'package:flutter/material.dart';
import 'package:geolocator/geolocator.dart';

enum SpeedUnit { milesPerHour, kilometersPerHour }

extension on SpeedUnit {
  double fromMetersPerSecond(double metersPerSecond) => switch (this) {
    SpeedUnit.kilometersPerHour => metersPerSecond * 3.6,
    SpeedUnit.milesPerHour => metersPerSecond * 2.236936,
  };

  get acronym => switch (this) {
    SpeedUnit.kilometersPerHour => 'kmph',
    SpeedUnit.milesPerHour => 'mph',
  };
}

void main() {
  runApp(const MyApp());
}

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

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Speedometer',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.red),
      ),
      darkTheme: ThemeData(
        colorScheme: ColorScheme.fromSeed(
          seedColor: Colors.red,
          brightness: Brightness.dark,
        ),
      ),
      home: const MyHomePage(title: 'Speedometer'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  StreamSubscription<Position>? _positionStream;
  double _speed = 0.0;
  double _speedAccuracy = 0.0;
  SpeedUnit _speedUnit = SpeedUnit.milesPerHour;
  LocationSettings _locationSettings = LocationSettings();

  @override
  void initState() {
    super.initState();
    _positionStream =
        Geolocator.getPositionStream(
          locationSettings: _locationSettings,
        ).listen((Position? position) {
          if (position != null) {
            _speed = position.speed;
            _speedAccuracy = position.speedAccuracy;
          }
        });
  }

  @override
  void dispose() {
    super.dispose();
    _positionStream?.cancel();
  }

  @override
  Widget build(BuildContext context) {
    // This method is rerun every time setState is called, for instance as done
    // by the _incrementCounter method above.
    //
    // The Flutter framework has been optimized to make rerunning build methods
    // fast, so that you can just rebuild anything that needs updating rather
    // than having to individually change instances of widgets.
    return Scaffold(
      appBar: AppBar(
        // TRY THIS: Try changing the color here to a specific color (to
        // Colors.amber, perhaps?) and trigger a hot reload to see the AppBar
        // change color while the other colors stay the same.
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
        // Here we take the value from the MyHomePage object that was created by
        // the App.build method, and use it to set our appbar title.
        title: Text(widget.title),
      ),
      body: Center(
        // Center is a layout widget. It takes a single child and positions it
        // in the middle of the parent.
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          crossAxisAlignment: CrossAxisAlignment.center,
          children: [
            Flex(direction: Axis.horizontal),
            Text(
              '${_speedUnit.fromMetersPerSecond(_speed)} ${_speedUnit.acronym}',
              style: Theme.of(context).textTheme.displayLarge,
            ),
            Text(
              '± ${_speedUnit.fromMetersPerSecond(_speedAccuracy)} ${_speedUnit.acronym}',
              style: Theme.of(context).textTheme.displaySmall,
            ),
          ],
        ),
      ),
    );
  }
}