import 'dart:async';

import 'package:halkyon_app/l10n/halkyon_app_localizations.dart';
import 'package:halkyon_app/src/app/app_frame.dart';
import 'package:halkyon_app/src/app/app_scope.dart';
import 'package:halkyon_app/src/auth/model/auth_status.dart';
import 'package:material_ui/material_ui.dart';

/// Opens [person]'s dependencies (`AppDependencies.openPerson`), shows
/// [child] with them, and disposes them when it goes away. `SessionGate`
/// gives every person a new `PersonScope`.
class const PersonScope({
  /// Whose dependencies these are.
  required final SignedIn person,

  /// What the person sees.
  required final Widget child,
  super.key,
}) extends StatefulWidget {
  /// The dependencies of the person signed in above [context], as the app's
  /// own type [P] (`PersonScope.of<PersonDependencies>(context)`).
  static P of<P extends Disposable>(BuildContext context) {
    final scope = context
        .getInheritedWidgetOfExactType<_PersonDependenciesScope>();
    assert(scope != null, 'No PersonScope above this widget.');
    return scope!.dependencies as P;
  }

  @override
  State<PersonScope> createState() => _PersonScopeState();
}

class _PersonScopeState() extends State<PersonScope> {
  Future<Disposable>? _opening;

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    _opening ??= AppScope.of(context).openPerson(widget.person);
  }

  @override
  void dispose() {
    unawaited(
      _opening?.then(
        (dependencies) => dependencies.dispose(),
        // Opening failed and said so on screen; there is nothing to close.
        onError: (Object _) {},
      ),
    );
    super.dispose();
  }

  @override
  Widget build(BuildContext context) => FutureBuilder(
    future: _opening,
    builder: (context, snapshot) => switch (snapshot) {
      AsyncSnapshot(:final data?) => _PersonDependenciesScope(
        dependencies: data,
        child: widget.child,
      ),
      AsyncSnapshot(hasError: true) => Scaffold(
        body: Center(
          child: Column(
            mainAxisSize: MainAxisSize.min,
            children: [
              Text(HalkyonAppLocalizations.of(context).personDataFailed),
              const SizedBox(height: 16),
              FilledButton(
                onPressed: () => setState(() {
                  _opening = AppScope.of(context).openPerson(widget.person);
                }),
                child: Text(HalkyonAppLocalizations.of(context).tryAgain),
              ),
            ],
          ),
        ),
      ),
      _ => AppFrameScope.of(context).launchScreen,
    },
  );
}

class const _PersonDependenciesScope({
  required final Disposable dependencies,
  required super.child,
}) extends InheritedWidget {
  @override
  bool updateShouldNotify(_PersonDependenciesScope oldWidget) =>
      dependencies != oldWidget.dependencies;
}