import 'dart:convert';

import 'package:filesize/filesize.dart';
import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:hydrated_bloc/hydrated_bloc.dart';

import '../../extensions/date_time.dart';
import '../../routing/app_routes.dart';
import '../../state/app/infrastructure/utility_widgets/loadable_hydrated_bloc/loadable_hydrated_bloc.dart';
import '../../state/app/modules/breaker/bloc/breaker_bloc.dart';
import '../../state/app/modules/capabilities/bloc/capabilities_cubit.dart';
import '../../state/app/modules/chat/bloc/chat_bloc.dart';
import '../../state/app/modules/chat_list/bloc/chat_list_bloc.dart';
import '../../state/app/modules/nextcloud_capabilities/bloc/nextcloud_capabilities_cubit.dart';
import '../../state/app/modules/settings/bloc/settings_cubit.dart';
import '../../state/app/modules/timetable/bloc/timetable_bloc.dart';
import '../../storage/account_storage.dart';
import '../../storage/hydrated_storage_bootstrap.dart';
import '../confirm_dialog.dart';
import '../placeholder_view.dart';
import 'json_viewer.dart';

/// Lists every key persisted by the active account's blocs and the app-wide
/// settings.
class BlocStorageView extends StatefulWidget {
  const BlocStorageView({super.key});

  static List<Storage> get _storages => [
    HydratedBloc.storage,
    AccountStorage.global,
  ];

  /// All persisted keys; `null` when a storage can't be enumerated.
  static List<String>? keys() {
    final keys = <String>{};
    for (final storage in _storages) {
      final own = hydratedStorageKeys(storage);
      if (own == null) return null;
      keys.addAll(own);
    }
    return keys.toList()..sort();
  }

  static Storage _storageOf(String key) => _storages.firstWhere(
    (storage) => hydratedStorageKeys(storage)?.contains(key) ?? false,
    orElse: () => HydratedBloc.storage,
  );

  @override
  State<BlocStorageView> createState() => _BlocStorageViewState();
}

class _Entry {
  final String key;
  final Object? value;
  final int size;
  final DateTime? lastFetch;

  _Entry(this.key, this.value)
    : size = utf8.encode(jsonEncode(JsonViewer.toEncodable(value))).length,
      lastFetch = _lastFetch(value);

  static DateTime? _lastFetch(Object? value) {
    if (value is! Map) return null;
    final meta = value['meta'];
    if (meta is! Map || meta['timestamp'] is! int) return null;
    final ts = meta['timestamp'] as int;
    return ts > 0 ? DateTime.fromMillisecondsSinceEpoch(ts) : null;
  }
}

class _BlocStorageViewState extends State<BlocStorageView> {
  List<_Entry>? _entries;

  @override
  void initState() {
    super.initState();
    _load();
  }

  void _load() {
    final keys = BlocStorageView.keys();
    setState(
      () => _entries = keys
          ?.map((k) => _Entry(k, BlocStorageView._storageOf(k).read(k)))
          .toList(),
    );
  }

  /// Blocs that live for the whole app session would simply re-persist their
  /// in-memory state, so those are reset through the bloc itself.
  Future<void> Function()? _liveReset(String key) {
    Future<void> Function() loadable(
      LoadableHydratedBloc<dynamic, dynamic, dynamic> bloc,
    ) => () async {
      await bloc.reset();
      bloc.retry();
    };
    return switch (key) {
      'TimetableBloc' => loadable(context.read<TimetableBloc>()),
      'ChatListBloc' => loadable(context.read<ChatListBloc>()),
      'ChatBloc' => loadable(context.read<ChatBloc>()),
      'BreakerBloc' => loadable(context.read<BreakerBloc>()),
      'CapabilitiesCubit' => () async {
        final cubit = context.read<CapabilitiesCubit>();
        await cubit.reset();
        await cubit.load();
      },
      'NextcloudCapabilitiesCubit' => () async {
        final cubit = context.read<NextcloudCapabilitiesCubit>();
        await cubit.reset();
        await cubit.load();
      },
      'SettingsCubit' => context.read<SettingsCubit>().reset,
      _ => null,
    };
  }

  Future<void> _delete(String key) async {
    final reset = _liveReset(key);
    if (reset != null) {
      await reset();
    } else {
      await BlocStorageView._storageOf(key).delete(key);
    }
  }

  void _confirmDelete(_Entry entry) {
    final isSettings = entry.key == 'SettingsCubit';
    ConfirmDialog(
      title: isSettings ? 'Einstellungen zurücksetzen' : 'Eintrag löschen',
      content: isSettings
          ? 'Alle Einstellungen werden auf die Standardwerte zurückgesetzt.'
          : '„${entry.key}“ wird gelöscht und bei Bedarf neu geladen.',
      confirmButton: 'Löschen',
      errorBuilder: (e) => '$e',
      onConfirmAsync: () async {
        await _delete(entry.key);
        if (mounted) _load();
      },
    ).asDialog(context);
  }

  void _confirmDeleteAll() {
    ConfirmDialog(
      title: 'BLoC-Speicher leeren',
      content:
          'Alle gespeicherten Modul-Zustände außer den Einstellungen werden '
          'gelöscht und bei Bedarf neu geladen.',
      confirmButton: 'Alles löschen',
      errorBuilder: (e) => '$e',
      onConfirmAsync: () async {
        for (final entry in [...?_entries]) {
          if (entry.key == 'SettingsCubit') continue;
          await _delete(entry.key);
        }
        if (mounted) _load();
      },
    ).asDialog(context);
  }

  @override
  Widget build(BuildContext context) {
    final entries = _entries;
    return Scaffold(
      appBar: AppBar(
        title: const Text('BLoC-Speicher'),
        actions: [
          IconButton(
            tooltip: 'Neu laden',
            icon: const Icon(Icons.refresh),
            onPressed: _load,
          ),
          if (entries != null && entries.isNotEmpty)
            IconButton(
              tooltip: 'Alles löschen',
              icon: const Icon(Icons.delete_sweep_outlined),
              onPressed: _confirmDeleteAll,
            ),
        ],
      ),
      body: entries == null
          ? const PlaceholderView(
              icon: Icons.error_outline,
              text: 'Speicher lässt sich nicht auflisten',
            )
          : entries.isEmpty
          ? const PlaceholderView(
              icon: Icons.hourglass_empty,
              text: 'Keine Daten',
            )
          : ListView.builder(
              itemCount: entries.length,
              itemBuilder: (context, index) {
                final entry = entries[index];
                final live = _liveReset(entry.key) != null;
                return ListTile(
                  leading: Icon(
                    live ? Icons.bolt_outlined : Icons.inventory_2_outlined,
                  ),
                  title: Text(entry.key),
                  subtitle: Text(
                    [
                      filesize(entry.size),
                      if (entry.lastFetch != null)
                        'geladen ${entry.lastFetch!.formatRelative()}',
                    ].join(' · '),
                  ),
                  onTap: () => AppRoutes.openJsonViewer(
                    context,
                    entry.value,
                    title: entry.key,
                  ),
                  trailing: IconButton(
                    tooltip: 'Löschen',
                    icon: const Icon(Icons.delete_outline),
                    onPressed: () => _confirmDelete(entry),
                  ),
                );
              },
            ),
    );
  }
}