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

void main() {
  runApp(const PickerFilesProvider(child: MaterialApp(home: MyHomePage())));
}

Future<Iterable<XFile>> pickFiles() async {
  try {
    final maybeFiles = await ImagePicker().pickMultiImage();
    return [if (maybeFiles != null) ...maybeFiles];
  } on Exception catch (e, s) {
    debugPrint('$e, $s');
    return [];
  } on Error catch (e) {
    debugPrint('$e, ${e.stackTrace}');
    return [];
  }
}

extension XfilesNamesX on Iterable<XFile> {
  Iterable<String> get names sync* {
    for (final file in this) {
      yield file.name;
    }
  }
}

class PickerFilesProvider extends StatefulWidget {
  final Widget child;
  const PickerFilesProvider({
    required this.child,
  }) : super(key: const ValueKey('PickerFilesProvider'));

  @override
  State<PickerFilesProvider> createState() => _PickerFilesProviderState();
}

class _PickerFilesProviderState extends State<PickerFilesProvider> {
  late final ValueNotifier<Iterable<String>> _notifier;

  @override
  void initState() {
    super.initState();
    _notifier = ValueNotifier(<String>[]);
  }

  @override
  void dispose() {
    _notifier.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return _PickedFiles(
      child: widget.child,
      notifier: _notifier,
    );
  }
}

class _PickedFiles extends InheritedWidget {
  final ValueNotifier<Iterable<String>> notifier;
  const _PickedFiles({
    required this.notifier,
    required Widget child,
  }) : super(key: const ValueKey('PickedFiles'), child: child);

  static _PickedFiles of(BuildContext context) {
    final _PickedFiles? result =
        context.dependOnInheritedWidgetOfExactType<_PickedFiles>();
    assert(result != null, 'No PickedFiles found in context');
    return result!;
  }

  @override
  // ignore: avoid_renaming_method_parameters
  bool updateShouldNotify(_) => false;
}

extension PickedFilesX on BuildContext {
  ValueNotifier<Iterable<String>> get pickerfiles =>
      _PickedFiles.of(this).notifier;
}

class PickerButton extends StatefulWidget {
  const PickerButton({
    final key = const ValueKey('PickerButton'),
  }) : super(key: key);

  @override
  State<PickerButton> createState() => _PickerWidgetState();
}

class _PickerWidgetState extends State<PickerButton> {
  late final ValueNotifier<bool> _busy;

  @override
  void initState() {
    super.initState();
    _busy = ValueNotifier(false);
  }

  @override
  void dispose() {
    _busy.dispose();
    super.dispose();
  }

  void _pickFiles() async {
    _busy.value = true;
    context.pickerfiles.value = (await pickFiles()).names;
    _busy.value = false;
  }

  @override
  Widget build(BuildContext context) {
    return FloatingActionButton(
      child: ValueListenableBuilder<bool>(
          valueListenable: _busy,
          builder: (context, busy, _) => busy
              ? const CircularProgressIndicator(color: Colors.black)
              : const Icon(Icons.upload)),
      onPressed: _pickFiles,
    );
  }
}

class MyHomePage extends StatelessWidget {
  const MyHomePage({
    final key = const ValueKey('MyHomePage'),
  }) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return const Scaffold(
      body: PickedFilesListView(),
      floatingActionButton: PickerButton(),
    );
  }
}

class PickedFilesListView extends StatelessWidget {
  const PickedFilesListView({
    final key = const ValueKey('PickedFilesListView'),
  }) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return ValueListenableBuilder<Iterable<String>>(
      valueListenable: context.pickerfiles,
      builder: (context, names, _) => ListView(children: [
        for (final name in names) Center(child: Text(name)),
      ]),
    );
  }
}