import 'package:flutter/foundation.dart' show debugPrint;
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:supabase_flutter/supabase_flutter.dart';

import '../brick/cache_warmer.dart';
import '../models/user_office.dart';
import '../utils/snackbar.dart' show isOfflineSaveError;
import 'connectivity_provider.dart';
import 'supabase_provider.dart';
import 'stream_recovery.dart';
import 'realtime_controller.dart';

// ---------------------------------------------------------------------------
// Offline-pending state
// ---------------------------------------------------------------------------

/// Queued assign/remove operations made offline.
/// Each entry: {'op': 'assign'|'remove', 'user_id': ..., 'office_id': ...}
final offlinePendingUserOfficeOpsProvider =
    StateProvider<List<Map<String, dynamic>>>((ref) => const []);

// ---------------------------------------------------------------------------
// Read provider
// ---------------------------------------------------------------------------

final userOfficesProvider = StreamProvider<List<UserOffice>>((ref) {
  final client = ref.watch(supabaseClientProvider);

  final pendingOps = ref.watch(offlinePendingUserOfficeOpsProvider);

  List<UserOffice> applyPending(List<UserOffice> rows) {
    if (pendingOps.isEmpty) return rows;
    var result = List<UserOffice>.from(rows);
    for (final op in pendingOps) {
      final userId = op['user_id'] as String;
      final officeId = op['office_id'] as String;
      if (op['op'] == 'assign') {
        final exists = result.any(
          (r) => r.userId == userId && r.officeId == officeId,
        );
        if (!exists) result.add(UserOffice(userId: userId, officeId: officeId));
      } else if (op['op'] == 'remove') {
        result.removeWhere(
          (r) => r.userId == userId && r.officeId == officeId,
        );
      }
    }
    return result;
  }

  final wrapper = StreamRecoveryWrapper<UserOffice>(
    stream: client
        .from('user_offices')
        .stream(primaryKey: ['user_id', 'office_id'])
        .order('created_at'),
    onPollData: () async {
      final data = await client.from('user_offices').select().order('created_at');
      return data.map(UserOffice.fromMap).toList();
    },
    fromMap: UserOffice.fromMap,
    channelName: 'user_offices',
    onStatusChanged: ref.read(realtimeControllerProvider).handleChannelStatus,
    onOfflineData: () async {
      final rows = await CacheWarmer.readCachedUserOffices();
      return applyPending(rows.map(UserOffice.fromMap).toList());
    },
  );

  ref.onDispose(wrapper.dispose);

  // Reconnect-replay
  ref.listen<bool>(isOnlineProvider, (wasOnline, isNowOnline) async {
    if (wasOnline == true || !isNowOnline) return;
    final pending = List<Map<String, dynamic>>.from(
      ref.read(offlinePendingUserOfficeOpsProvider),
    );
    if (pending.isEmpty) return;
    debugPrint(
      '[userOfficesProvider] reconnected — syncing ${pending.length} office op(s)',
    );
    final synced = <int>[];
    for (var i = 0; i < pending.length; i++) {
      final op = pending[i];
      final userId = op['user_id'] as String;
      final officeId = op['office_id'] as String;
      try {
        if (op['op'] == 'assign') {
          await client.from('user_offices').insert({
            'user_id': userId,
            'office_id': officeId,
          });
        } else {
          await client
              .from('user_offices')
              .delete()
              .eq('user_id', userId)
              .eq('office_id', officeId);
        }
        synced.add(i);
      } catch (e) {
        final msg = e.toString();
        if (msg.contains('23505') || msg.contains('duplicate key')) {
          synced.add(i);
        } else {
          debugPrint(
            '[userOfficesProvider] failed to sync op $i: $e',
          );
        }
      }
    }
    if (synced.isNotEmpty) {
      final remaining = <Map<String, dynamic>>[];
      for (var i = 0; i < pending.length; i++) {
        if (!synced.contains(i)) remaining.add(pending[i]);
      }
      ref.read(offlinePendingUserOfficeOpsProvider.notifier).state =
          List.unmodifiable(remaining);
    }
  });

  return wrapper.stream.map((result) => applyPending(result.data));
});

// ---------------------------------------------------------------------------
// Controller
// ---------------------------------------------------------------------------

final userOfficesControllerProvider = Provider<UserOfficesController>((ref) {
  final client = ref.watch(supabaseClientProvider);
  return UserOfficesController(client, ref);
});

class UserOfficesController {
  UserOfficesController(this._client, [this._ref]);

  final SupabaseClient _client;
  final Ref? _ref;

  /// Assign a user to an office. Offline: queues the operation.
  Future<void> assignUserOffice({
    required String userId,
    required String officeId,
  }) async {
    try {
      await _client.from('user_offices').insert({
        'user_id': userId,
        'office_id': officeId,
      });
    } catch (e) {
      if (!isOfflineSaveError(e)) rethrow;
      _queueOp('assign', userId, officeId);
    }
  }

  /// Remove a user from an office. Offline: queues the operation.
  Future<void> removeUserOffice({
    required String userId,
    required String officeId,
  }) async {
    try {
      await _client
          .from('user_offices')
          .delete()
          .eq('user_id', userId)
          .eq('office_id', officeId);
    } catch (e) {
      if (!isOfflineSaveError(e)) rethrow;
      _queueOp('remove', userId, officeId);
    }
  }

  void _queueOp(String op, String userId, String officeId) {
    final ref = _ref;
    if (ref == null) return;
    final current = List<Map<String, dynamic>>.from(
      ref.read(offlinePendingUserOfficeOpsProvider),
    );
    // Dedupe: collapse redundant assign/remove pairs for the same user+office
    current.removeWhere(
      (e) => e['user_id'] == userId && e['office_id'] == officeId,
    );
    current.add({'op': op, 'user_id': userId, 'office_id': officeId});
    ref.read(offlinePendingUserOfficeOpsProvider.notifier).state =
        List.unmodifiable(current);
  }
}