import '../../core/exceptions.dart';
import '../api/events_api.dart';
import '../local/database.dart';
import '../models/calendar_event.dart';

/// Calendar events repository with read-through caching (Phase 1+2) and
/// offline-write queueing (Phase 3). Range-scoped reads: `getEvents(from, to)`
/// mirrors that window into the cache (events outside the window are left
/// alone) so successive disjoint range fetches don't clobber each other.
///
/// CalendarEvent has no `updatedAt` field, so write replay uses last-
/// writer-wins on update/delete (no server-side baseline check).
class EventsRepository {
  final EventsApi _api;
  final FabledDatabase _db;

  const EventsRepository(this._api, this._db);

  Future<List<CalendarEvent>> getEvents(DateTime from, DateTime to) async {
    try {
      final events = await _api.getEvents(from, to);
      await _db.replaceEventsInRange(from, to, events);
      return events;
    } on NetworkException {
      final cached = await _db.getEventsInRange(from, to);
      if (cached.isEmpty) rethrow;
      return cached;
    }
  }

  Future<CalendarEvent> createEvent(Map<String, dynamic> payload) async {
    try {
      final event = await _api.createEvent(payload);
      await _db.upsertEvent(event);
      return event;
    } on NetworkException {
      final tempId = await _db.nextTempId();
      final optimistic = _eventFromPayload(tempId, payload);
      await _db.upsertEvent(optimistic);
      await _db.enqueuePending(
        domain: kSyncDomainEvents,
        verb: kWriteVerbCreate,
        tempId: tempId,
        payload: payload,
      );
      return optimistic;
    }
  }

  Future<CalendarEvent> updateEvent(
      int id, Map<String, dynamic> fields) async {
    try {
      final updated = await _api.updateEvent(id, fields);
      await _db.upsertEvent(updated);
      return updated;
    } on NetworkException {
      final cached = (await _db.getEventsInRange(
        DateTime.fromMicrosecondsSinceEpoch(0),
        DateTime.now().add(const Duration(days: 365 * 100)),
      ))
          .where((e) => e.id == id)
          .firstOrNull;
      if (cached == null) rethrow;
      final optimistic = _applyEventFields(cached, fields);
      await _db.upsertEvent(optimistic);
      if (id < 0) {
        final queued = await _db.findQueuedCreate(kSyncDomainEvents, id);
        if (queued != null) {
          await _db.updatePendingPayload(queued.id, fields);
          return optimistic;
        }
      }
      await _db.enqueuePending(
        domain: kSyncDomainEvents,
        verb: kWriteVerbUpdate,
        targetId: id,
        payload: fields,
      );
      return optimistic;
    }
  }

  Future<void> deleteEvent(int id) async {
    try {
      await _api.deleteEvent(id);
      await _db.deleteEvent(id);
    } on NetworkException {
      if (id < 0) {
        final queued = await _db.findQueuedCreate(kSyncDomainEvents, id);
        if (queued != null) await _db.deletePending(queued.id);
        await _db.deleteEvent(id);
        return;
      }
      await _db.deleteEvent(id);
      await _db.enqueuePending(
        domain: kSyncDomainEvents,
        verb: kWriteVerbDelete,
        targetId: id,
      );
    }
  }
}

CalendarEvent _eventFromPayload(int id, Map<String, dynamic> p) {
  return CalendarEvent(
    id: id,
    title: p['title'] as String? ?? '',
    startDt: _parseIso(p['start_dt'])!,
    endDt: _parseIso(p['end_dt']),
    allDay: p['all_day'] as bool? ?? false,
    description: p['description'] as String? ?? '',
    location: p['location'] as String? ?? '',
    color: p['color'] as String? ?? '',
    recurrence: p['recurrence'] as String?,
    projectId: p['project_id'] as int?,
    reminderMinutes: p['reminder_minutes'] as int?,
  );
}

CalendarEvent _applyEventFields(CalendarEvent e, Map<String, dynamic> f) {
  return CalendarEvent(
    id: e.id,
    title: f['title'] as String? ?? e.title,
    startDt: _parseIso(f['start_dt']) ?? e.startDt,
    endDt: f.containsKey('end_dt') ? _parseIso(f['end_dt']) : e.endDt,
    allDay: f['all_day'] as bool? ?? e.allDay,
    description: f['description'] as String? ?? e.description,
    location: f['location'] as String? ?? e.location,
    color: f['color'] as String? ?? e.color,
    recurrence:
        f.containsKey('recurrence') ? f['recurrence'] as String? : e.recurrence,
    projectId: f.containsKey('project_id')
        ? f['project_id'] as int?
        : e.projectId,
    reminderMinutes: f.containsKey('reminder_minutes')
        ? f['reminder_minutes'] as int?
        : e.reminderMinutes,
  );
}

DateTime? _parseIso(dynamic raw) {
  if (raw is String && raw.isNotEmpty) return DateTime.tryParse(raw)?.toLocal();
  return null;
}