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

import '../brick/cache_helpers.dart';
import '../models/leave_of_absence.dart';
import '../utils/app_time.dart';
import '../utils/snackbar.dart' show isOfflineSaveError;
import 'connectivity_provider.dart';
import 'profile_provider.dart';
import 'supabase_provider.dart';
import 'stream_recovery.dart';
import 'realtime_controller.dart';

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

/// Leaves filed offline that haven't been confirmed by Supabase yet. Merged
/// into [leavesProvider] so the UI shows them immediately. Cleared as the
/// realtime stream confirms each id.
final offlinePendingLeavesProvider =
    StateProvider<List<LeaveOfAbsence>>((ref) => const []);

/// Status changes (approve/reject/cancel) made offline, keyed by leave id.
/// On reconnect the listener PATCHes each entry and clears the map.
final offlinePendingLeaveUpdatesProvider =
    StateProvider<Map<String, Map<String, dynamic>>>((ref) => const {});

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

/// All visible leaves (own for standard, all for admin/dispatcher/it_staff).
///
/// Consumers should **not** treat every record as an active absence; the UI
/// layers (dashboard, logbook) explicitly filter to `status == 'approved'` and
/// verify the leave overlaps the current time.
final leavesProvider = StreamProvider<List<LeaveOfAbsence>>((ref) {
  final client = ref.watch(supabaseClientProvider);
  final profileAsync = ref.watch(currentProfileProvider);
  final profile = profileAsync.valueOrNull;
  if (profile == null) return Stream.value(const <LeaveOfAbsence>[]);

  final hasFullAccess =
      profile.role == 'admin' ||
      profile.role == 'programmer' ||
      profile.role == 'dispatcher' ||
      profile.role == 'it_staff';

  // Watch pending state — provider rebuilds when offline writes arrive so the
  // closed-over `pending*` values feed into `onOfflineData` synchronously.
  final pendingNew = ref.watch(offlinePendingLeavesProvider);
  final pendingUpdates = ref.watch(offlinePendingLeaveUpdatesProvider);

  List<LeaveOfAbsence> applyPending(List<LeaveOfAbsence> rows) {
    final byId = {for (final r in rows) r.id: r};
    // Merge offline status updates onto existing leaves
    pendingUpdates.forEach((id, fields) {
      final existing = byId[id];
      if (existing == null) return;
      byId[id] = LeaveOfAbsence(
        id: existing.id,
        userId: existing.userId,
        leaveType: existing.leaveType,
        justification: existing.justification,
        startTime: existing.startTime,
        endTime: existing.endTime,
        status: (fields['status'] as String?) ?? existing.status,
        filedBy: existing.filedBy,
        createdAt: existing.createdAt,
      );
    });
    // Append offline-created leaves not yet on the server
    for (final p in pendingNew) {
      if (hasFullAccess || p.userId == profile.id) {
        byId.putIfAbsent(p.id, () => p);
      }
    }
    final merged = byId.values.toList()
      ..sort((a, b) => b.startTime.compareTo(a.startTime));
    return merged;
  }

  final wrapper = StreamRecoveryWrapper<LeaveOfAbsence>(
    stream: hasFullAccess
        ? client
              .from('leave_of_absence')
              .stream(primaryKey: ['id'])
              .order('start_time', ascending: false)
        : client
              .from('leave_of_absence')
              .stream(primaryKey: ['id'])
              .eq('user_id', profile.id)
              .order('start_time', ascending: false),
    onPollData: () async {
      final query = client.from('leave_of_absence').select();
      final data = hasFullAccess
          ? await query.order('start_time', ascending: false)
          : await query
                .eq('user_id', profile.id)
                .order('start_time', ascending: false);
      return data.map(LeaveOfAbsence.fromMap).toList();
    },
    fromMap: LeaveOfAbsence.fromMap,
    channelName: 'leave_of_absence',
    onStatusChanged: ref.read(realtimeControllerProvider).handleChannelStatus,
    onOfflineData: () async {
      final all = await cachedListFromBrick<LeaveOfAbsence>();
      final filtered = hasFullAccess
          ? all
          : all.where((l) => l.userId == profile.id).toList();
      return applyPending(filtered);
    },
    onCacheMirror: (rows) =>
        mirrorBatchToBrick<LeaveOfAbsence>(rows, tag: 'leave_of_absence'),
  );

  ref.onDispose(wrapper.dispose);

  // Reconnect-replay: directly POST queued items, bypassing Brick's queue
  // which can block on stale entries (504, deadlock, etc.).
  ref.listen<bool>(isOnlineProvider, (wasOnline, isNowOnline) async {
    if (wasOnline == true || !isNowOnline) return;

    // 1. Replay offline-created leaves
    final pending = List<LeaveOfAbsence>.from(ref.read(offlinePendingLeavesProvider));
    if (pending.isNotEmpty) {
      debugPrint('[leavesProvider] reconnected — syncing ${pending.length} leave(s)');
      final synced = <String>[];
      for (final leave in pending) {
        try {
          await client.from('leave_of_absence').insert({
            'id': leave.id,
            'user_id': leave.userId,
            'leave_type': leave.leaveType,
            'justification': leave.justification,
            'start_time': leave.startTime.toIso8601String(),
            'end_time': leave.endTime.toIso8601String(),
            'status': leave.status,
            'filed_by': leave.filedBy,
          });
          synced.add(leave.id);
        } catch (e) {
          final msg = e.toString();
          if (msg.contains('23505') || msg.contains('duplicate key')) {
            synced.add(leave.id); // already in DB — drop pending entry
          } else {
            debugPrint('[leavesProvider] failed to sync leave id=${leave.id}: $e');
          }
        }
      }
      if (synced.isNotEmpty) {
        final remaining = ref.read(offlinePendingLeavesProvider)
            .where((l) => !synced.contains(l.id))
            .toList();
        ref.read(offlinePendingLeavesProvider.notifier).state =
            List.unmodifiable(remaining);
      }
    }

    // 2. Replay offline status updates
    final pendingMap = Map<String, Map<String, dynamic>>.from(
      ref.read(offlinePendingLeaveUpdatesProvider),
    );
    if (pendingMap.isNotEmpty) {
      debugPrint(
        '[leavesProvider] reconnected — syncing ${pendingMap.length} status edit(s)',
      );
      final syncedIds = <String>[];
      for (final entry in pendingMap.entries) {
        try {
          await client
              .from('leave_of_absence')
              .update(entry.value)
              .eq('id', entry.key);
          syncedIds.add(entry.key);
        } catch (e) {
          debugPrint('[leavesProvider] failed to sync edit id=${entry.key}: $e');
        }
      }
      if (syncedIds.isNotEmpty) {
        final remaining = Map<String, Map<String, dynamic>>.from(
          ref.read(offlinePendingLeaveUpdatesProvider),
        );
        for (final id in syncedIds) {
          remaining.remove(id);
        }
        ref.read(offlinePendingLeaveUpdatesProvider.notifier).state = remaining;
      }
    }
  });

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

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

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

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

  final SupabaseClient _client;
  final Ref? _ref;

  /// File a leave of absence for the current user.
  /// Caller controls auto-approval based on role policy.
  /// Offline: queues a local row + raw payload, returns silently.
  Future<void> fileLeave({
    required String leaveType,
    required String justification,
    required DateTime startTime,
    required DateTime endTime,
    required bool autoApprove,
  }) async {
    final uid = _client.auth.currentUser!.id;
    final id = const Uuid().v4();
    final status = autoApprove ? 'approved' : 'pending';
    final payload = {
      'id': id,
      'user_id': uid,
      'leave_type': leaveType,
      'justification': justification,
      'start_time': startTime.toIso8601String(),
      'end_time': endTime.toIso8601String(),
      'status': status,
      'filed_by': uid,
    };

    Map<String, dynamic>? inserted;
    try {
      final insertedRaw = await _client
          .from('leave_of_absence')
          .insert(payload)
          .select()
          .maybeSingle();
      inserted = insertedRaw is Map<String, dynamic> ? insertedRaw : null;
    } catch (e) {
      if (!isOfflineSaveError(e)) rethrow;
      _queuePendingLeave(
        LeaveOfAbsence(
          id: id,
          userId: uid,
          leaveType: leaveType,
          justification: justification,
          startTime: startTime,
          endTime: endTime,
          status: status,
          filedBy: uid,
          createdAt: AppTime.now(),
        ),
      );
      return; // Don't try to notify admins — we're offline.
    }

    // If this was filed as pending, notify admins for approval
    if (status != 'pending') return;
    await _notifyAdminsOfFiling(inserted: inserted, leaveId: id, actorId: uid);
  }

  void _queuePendingLeave(LeaveOfAbsence leave) {
    final ref = _ref;
    if (ref == null) return;
    final current = List<LeaveOfAbsence>.from(
      ref.read(offlinePendingLeavesProvider),
    );
    current.add(leave);
    ref.read(offlinePendingLeavesProvider.notifier).state =
        List.unmodifiable(current);
    mirrorBatchToBrick<LeaveOfAbsence>([leave], tag: 'offline_leave');
  }

  void _queueLeaveStatusUpdate(String leaveId, Map<String, dynamic> fields) {
    final ref = _ref;
    if (ref == null) return;
    final current = Map<String, Map<String, dynamic>>.from(
      ref.read(offlinePendingLeaveUpdatesProvider),
    );
    current[leaveId] = {...?current[leaveId], ...fields};
    ref.read(offlinePendingLeaveUpdatesProvider.notifier).state = current;
  }

  Future<void> _notifyAdminsOfFiling({
    required Map<String, dynamic>? inserted,
    required String leaveId,
    required String actorId,
  }) async {
    try {
      final adminIds = await _fetchRoleUserIds(
        roles: const ['admin'],
        excludeUserId: actorId,
      );
      if (adminIds.isEmpty) return;

      String actorName = 'Someone';
      try {
        final p = await _client
            .from('profiles')
            .select('full_name,display_name,name')
            .eq('id', actorId)
            .maybeSingle();
        if (p != null) {
          if (p['full_name'] != null) {
            actorName = p['full_name'].toString();
          } else if (p['display_name'] != null) {
            actorName = p['display_name'].toString();
          } else if (p['name'] != null) {
            actorName = p['name'].toString();
          }
        }
      } catch (_) {}

      final title = 'Leave Filed for Approval';
      final body = '$actorName filed a leave request that requires approval.';
      final notificationId = (inserted ?? <String, dynamic>{})['id']?.toString();

      final dataPayload = <String, dynamic>{
        'type': 'leave_filed',
        'leave_id': leaveId,
        ...?(notificationId != null ? {'notification_id': notificationId} : null),
      };

      await _client.from('notifications').insert(
            adminIds
                .map((userId) => {
                      'user_id': userId,
                      'actor_id': actorId,
                      'type': 'leave_filed',
                      'leave_id': leaveId,
                    })
                .toList(),
          );

      final res = await _client.functions.invoke(
        'send_fcm',
        body: {
          'user_ids': adminIds,
          'title': title,
          'body': body,
          'data': dataPayload,
        },
      );
      debugPrint('leave filing send_fcm result: $res');
    } catch (e) {
      debugPrint('leave filing send_fcm error: $e');
      // Non-fatal: keep leave filing working even if send_fcm fails
    }
  }

  /// Approve a leave request.
  Future<void> approveLeave(String leaveId) async {
    final userId = _client.auth.currentUser?.id;
    if (userId == null) throw Exception('Not authenticated');

    try {
      await _client
          .from('leave_of_absence')
          .update({'status': 'approved'})
          .eq('id', leaveId);
    } catch (e) {
      if (!isOfflineSaveError(e)) rethrow;
      _queueLeaveStatusUpdate(leaveId, {'status': 'approved'});
      return;
    }

    // Notify requestor (best-effort)
    try {
      await _notifyRequester(leaveId: leaveId, actorId: userId, approved: true);
    } catch (_) {}
  }

  /// Reject a leave request.
  Future<void> rejectLeave(String leaveId) async {
    final userId = _client.auth.currentUser?.id;
    if (userId == null) throw Exception('Not authenticated');

    try {
      await _client
          .from('leave_of_absence')
          .update({'status': 'rejected'})
          .eq('id', leaveId);
    } catch (e) {
      if (!isOfflineSaveError(e)) rethrow;
      _queueLeaveStatusUpdate(leaveId, {'status': 'rejected'});
      return;
    }

    try {
      await _notifyRequester(leaveId: leaveId, actorId: userId, approved: false);
    } catch (_) {}
  }

  Future<void> _notifyRequester({
    required String leaveId,
    required String actorId,
    required bool approved,
  }) async {
    try {
      final row = await _client
          .from('leave_of_absence')
          .select('user_id')
          .eq('id', leaveId)
          .maybeSingle();
      // ignore: unnecessary_cast
      final rowMap = row as Map<String, dynamic>?;
      final userId = rowMap?['user_id']?.toString();
      if (userId == null || userId.isEmpty) return;

      String actorName = 'Someone';
      try {
        final p = await _client
            .from('profiles')
            .select('full_name,display_name,name')
            .eq('id', actorId)
            .maybeSingle();
        if (p != null) {
          if (p['full_name'] != null) {
            actorName = p['full_name'].toString();
          } else if (p['display_name'] != null) {
            actorName = p['display_name'].toString();
          } else if (p['name'] != null) {
            actorName = p['name'].toString();
          }
        }
      } catch (_) {}

      final title = approved ? 'Leave Approved' : 'Leave Rejected';
      final body = approved
          ? '$actorName approved your leave request.'
          : '$actorName rejected your leave request.';

      final dataPayload = <String, dynamic>{
        'type': approved ? 'leave_approved' : 'leave_rejected',
        'leave_id': leaveId,
      };

      await _client.from('notifications').insert({
        'user_id': userId,
        'actor_id': actorId,
        'type': approved ? 'leave_approved' : 'leave_rejected',
        'leave_id': leaveId,
      });

      await _client.functions.invoke(
        'send_fcm',
        body: {
          'user_ids': [userId],
          'title': title,
          'body': body,
          'data': dataPayload,
        },
      );
    } catch (_) {
      // non-fatal
    }
  }

  /// Cancel an approved leave.
  Future<void> cancelLeave(String leaveId) async {
    try {
      await _client
          .from('leave_of_absence')
          .update({'status': 'cancelled'})
          .eq('id', leaveId);
    } catch (e) {
      if (!isOfflineSaveError(e)) rethrow;
      _queueLeaveStatusUpdate(leaveId, {'status': 'cancelled'});
    }
  }

  Future<List<String>> _fetchRoleUserIds({
    required List<String> roles,
    required String? excludeUserId,
  }) async {
    try {
      final data = await _client
          .from('profiles')
          .select('id, role')
          .inFilter('role', roles);
      final rows = data as List<dynamic>;
      final ids = rows
          .map((row) => row['id'] as String?)
          .whereType<String>()
          .where((id) => id.isNotEmpty && id != excludeUserId)
          .toList();
      return ids;
    } catch (_) {
      return [];
    }
  }
}