import 'dart:async';

import 'package:flutter_riverpod/flutter_riverpod.dart';

import 'current_mission_provider.dart';
import 'database_provider.dart';

/// Metadaten der aktuell in Bearbeitung befindlichen Mission - ergaenzt
/// currentMissionProvider (das nur die Wegpunkte haelt) um Name/Ort und die
/// Datenbank-id, sobald die Mission mindestens einmal gespeichert wurde.
class MissionMeta {
  const MissionMeta({this.id, this.name = 'New mission', this.placeName});

  /// Null, solange die Mission noch nie (auto-)gespeichert wurde.
  final int? id;
  final String name;
  final String? placeName;

  MissionMeta copyWith({int? id, String? name, String? placeName}) {
    return MissionMeta(
      id: id ?? this.id,
      name: name ?? this.name,
      placeName: placeName ?? this.placeName,
    );
  }
}

/// Haelt Name/id der aktuellen Mission und autosaved sie ueber
/// MissionRepository (Doku 7.5), sobald sich die Wegpunktliste aendert -
/// analog scheduleAutosave()/flushPendingAutosave() im HTML-Demonstrator
/// (dort 800ms debounce, hier identisch uebernommen).
class CurrentMissionMetaNotifier extends Notifier<MissionMeta> {
  Timer? _autosaveTimer;
  bool _suppressAutosave = false;

  @override
  MissionMeta build() {
    ref.listen(currentMissionProvider, (previous, next) {
      if (!_suppressAutosave) _scheduleAutosave();
    });
    ref.onDispose(() => _autosaveTimer?.cancel());
    return const MissionMeta();
  }

  /// Laedt die zuletzt bearbeitete Mission (falls vorhanden) beim App-Start
  /// wieder, damit ein Autosave-Draft einen Neustart ueberlebt (Doku 7.5).
  Future<void> restoreLastSession() async {
    final settings = await ref.read(appSettingsRepositoryProvider).load();
    final missionId = settings.currentMissionId;
    if (missionId == null) return;
    final loaded = await ref.read(missionRepositoryProvider).load(missionId);
    if (loaded == null) return;

    _suppressAutosave = true;
    ref.read(currentMissionProvider.notifier).replaceAll(loaded.waypoints);
    _suppressAutosave = false;
    state = MissionMeta(id: missionId, name: loaded.name, placeName: loaded.placeName);
  }

  /// Analog startNewMission() im HTML-Demonstrator: sichert zuerst noch
  /// ausstehende Aenderungen der bisherigen Mission, dann leerer Neustart.
  Future<void> startNew() async {
    await _flushNow();
    _suppressAutosave = true;
    ref.read(currentMissionProvider.notifier).replaceAll(const []);
    _suppressAutosave = false;
    state = const MissionMeta();
    await ref.read(appSettingsRepositoryProvider).setCurrentMissionId(null);
  }

  Future<void> loadMission(int id) async {
    await _flushNow();
    final loaded = await ref.read(missionRepositoryProvider).load(id);
    if (loaded == null) return;

    _suppressAutosave = true;
    ref.read(currentMissionProvider.notifier).replaceAll(loaded.waypoints);
    _suppressAutosave = false;
    state = MissionMeta(id: id, name: loaded.name, placeName: loaded.placeName);
    await ref.read(appSettingsRepositoryProvider).setCurrentMissionId(id);
  }

  /// Benennt eine gespeicherte Mission um (Doku 3.6: nur ueber die
  /// Missionsliste moeglich, dort hat jede Zeile immer bereits eine id).
  /// Aktualisiert zusaetzlich den eigenen Zustand, falls [id] die gerade
  /// aktive Mission ist.
  Future<void> renameMission(int id, String name) async {
    await ref.read(missionRepositoryProvider).rename(id, name);
    if (state.id == id) {
      state = state.copyWith(name: name);
    }
  }

  void _scheduleAutosave() {
    if (ref.read(currentMissionProvider).isEmpty) return;
    _autosaveTimer?.cancel();
    _autosaveTimer = Timer(const Duration(milliseconds: 800), () {
      unawaited(_flushNow());
    });
  }

  Future<void> _flushNow() async {
    _autosaveTimer?.cancel();
    _autosaveTimer = null;
    final waypoints = ref.read(currentMissionProvider);
    if (waypoints.isEmpty) return;
    final id = await ref.read(missionRepositoryProvider).upsert(
          id: state.id,
          name: state.name,
          placeName: state.placeName,
          waypoints: waypoints,
        );
    if (state.id == null) {
      state = state.copyWith(id: id);
    }
    await ref.read(appSettingsRepositoryProvider).setCurrentMissionId(id);
  }
}

final currentMissionMetaProvider =
    NotifierProvider<CurrentMissionMetaNotifier, MissionMeta>(
        CurrentMissionMetaNotifier.new);