import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:syncfusion_flutter_calendar/calendar.dart';

import '../../../extensions/date_time.dart';
import '../../../routing/app_routes.dart';
import '../../../state/app/infrastructure/loadable_state/view/loadable_state_consumer.dart';
import '../../../state/app/modules/settings/bloc/settings_cubit.dart';
import '../../../state/app/modules/timetable/bloc/timetable_bloc.dart';
import '../../../state/app/modules/timetable/bloc/timetable_state.dart';
import '../../../storage/timetable_settings.dart';
import 'custom_events/custom_event_edit_dialog.dart';
import 'data/arbitrary_appointment.dart';
import 'data/lesson_period_schedule.dart';
import 'data/timetable_appointment_factory.dart';
import 'details/appointment_details_dispatcher.dart';
import 'widgets/custom_workweek_calendar.dart';
import 'widgets/special_regions_builder.dart';

enum _CalendarAction { addEvent, viewEvents }

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

  @override
  State<Timetable> createState() => _TimetableState();
}

class _TimetableState extends State<Timetable> {
  final GlobalKey<CustomWorkWeekCalendarState> _calendarKey =
      GlobalKey<CustomWorkWeekCalendarState>();

  List<Appointment>? _cachedAppointments;
  int? _lastDataVersion;
  TimetableSettings? _lastTimetableSettings;

  DateTime _initialDisplayDate() => DateTime.now().add(const Duration(days: 2));

  void _jumpToToday() {
    _calendarKey.currentState?.jumpToDate(_initialDisplayDate());
  }

  void _onAction(_CalendarAction action) {
    switch (action) {
      case _CalendarAction.addEvent:
        showDialog(
          context: context,
          builder: (_) => const CustomEventEditDialog(),
          barrierDismissible: false,
        );
      case _CalendarAction.viewEvents:
        AppRoutes.openCustomEvents(context);
    }
  }

  List<Appointment> _appointments(TimetableState state) {
    final timetableSettings = context
        .watch<SettingsCubit>()
        .val()
        .timetableSettings;
    if (_cachedAppointments != null &&
        _lastDataVersion == state.dataVersion &&
        identical(_lastTimetableSettings, timetableSettings)) {
      return _cachedAppointments!;
    }
    _lastDataVersion = state.dataVersion;
    _lastTimetableSettings = timetableSettings;

    return _cachedAppointments = TimetableAppointmentFactory(
      lessons: state.getAllKnownLessons().toList(),
      customEvents: state.customEvents?.events ?? const [],
      rooms: state.rooms!,
      subjects: state.subjects!,
      settings: timetableSettings,
      now: DateTime.now(),
    ).build();
  }

  bool _isCrossedOut(Appointment appointment) {
    final id = appointment.id;
    if (id is WebuntisAppointment) return id.lesson.code == 'cancelled';
    return false;
  }

  bool _isOnInitialWeek(TimetableState state) {
    final target = _initialDisplayDate();
    final targetMonday = target.subtract(Duration(days: target.weekday - 1));
    final mondayOnly = DateTime(
      targetMonday.year,
      targetMonday.month,
      targetMonday.day,
    );
    return state.startDate == mondayOnly;
  }

  @override
  Widget build(BuildContext context) {
    final bloc = context.read<TimetableBloc>();
    final loadableState = context.watch<TimetableBloc>().state;
    final innerState = loadableState.data;
    final atToday = innerState != null && _isOnInitialWeek(innerState);
    return Scaffold(
      appBar: AppBar(
        title: const Text('Stunden & Vertretungsplan'),
        actions: [
          IconButton(
            icon: const Icon(Icons.home_outlined),
            onPressed: atToday ? null : _jumpToToday,
          ),
          PopupMenuButton<_CalendarAction>(
            icon: const Icon(Icons.edit_calendar_outlined),
            onSelected: _onAction,
            itemBuilder: (_) => const [
              PopupMenuItem(
                value: _CalendarAction.addEvent,
                child: ListTile(
                  title: Text('Kalendereintrag hinzufügen'),
                  leading: Icon(Icons.add),
                ),
              ),
              PopupMenuItem(
                value: _CalendarAction.viewEvents,
                child: ListTile(
                  title: Text('Kalendereinträge anzeigen'),
                  leading: Icon(Icons.perm_contact_calendar_outlined),
                ),
              ),
            ],
          ),
        ],
      ),
      body: LoadableStateConsumer<TimetableBloc, TimetableState>(
        child: (state, _) => _calendar(state, bloc),
      ),
    );
  }

  Widget _calendar(TimetableState state, TimetableBloc bloc) {
    if (!state.hasReferenceData) return const SizedBox.shrink();

    final schedule = LessonPeriodSchedule.fromState(state);
    final appointments = _appointments(state);
    final regions = SpecialRegionsBuilder(
      holidays: state.schoolHolidays!,
      schedule: schedule,
      colorScheme: Theme.of(context).colorScheme,
      disabledColor: Theme.of(context).disabledColor,
    ).build();

    return CustomWorkWeekCalendar(
      key: _calendarKey,
      schedule: schedule,
      appointments: appointments,
      timeRegions: regions,
      initialDate: _initialDisplayDate(),
      minDate: DateTime.now()
          .subtract(const Duration(days: 14))
          .nextWeekday(DateTime.sunday),
      maxDate: DateTime.now()
          .add(const Duration(days: 7))
          .nextWeekday(DateTime.saturday),
      onAppointmentTap: (apt) =>
          AppointmentDetailsDispatcher.show(context, bloc, apt),
      onWeekChanged: (start, end) => bloc.changeWeek(start, end),
      isCrossedOut: _isCrossedOut,
      onCreateEvent: _onCreateEventAt,
    );
  }

  void _onCreateEventAt(DateTime start, DateTime end) {
    showDialog(
      context: context,
      builder: (_) =>
          CustomEventEditDialog(initialStart: start, initialEnd: end),
      barrierDismissible: false,
    );
  }
}