import 'dart:async';
import 'dart:convert';

import 'package:flutter/foundation.dart' show ValueNotifier, debugPrint, kIsWeb;
import 'package:shared_preferences/shared_preferences.dart';
import 'package:supabase_flutter/supabase_flutter.dart';

import '../models/announcement.model.dart';
import '../models/announcement_comment.model.dart';
import '../models/attendance_log.model.dart';
import '../models/duty_schedule.model.dart';
import '../models/it_service_request.model.dart';
import '../models/leave_of_absence.model.dart';
import '../models/notification_item.model.dart';
import '../models/office.model.dart';
import '../models/pass_slip.model.dart';
import '../models/profile.model.dart';
import '../models/service.model.dart';
import '../models/swap_request.model.dart';
import '../models/task.model.dart';
import '../models/team.model.dart';
import '../models/ticket.model.dart';
import 'repository.dart';

/// Proactively seeds the local Brick SQLite cache with the data the app needs
/// to render correctly when launched offline.
///
/// Triggered:
/// - After successful login.
/// - After the connectivity monitor flips offline → online.
/// - On a 1-hour timer in the foreground (defensive refresh).
///
/// Never throws — a single table failure must not abort the rest. Each table
/// is wrapped in try/catch and only logs the error.
///
/// Web is a no-op because Brick's SQLite is unavailable on web.
class CacheWarmer {
  CacheWarmer._();

  /// Window of mutable data to keep locally. 30 days is enough for the
  /// "month of tasks/tickets" the user requested without bloating SQLite.
  static const Duration window = Duration(days: 30);

  /// SharedPreferences keys for association tables (no PK → not Brick models).
  static const _kTeamMembersKey = 'cache_team_members_json';
  static const _kUserOfficesKey = 'cache_user_offices_json';

  /// Prefix for per-table row-count stamps written after each successful warm.
  static const _kCountPrefix = 'cache_count_';

  /// Foreground timer handle so [start]/[stop] is idempotent.
  static Timer? _refreshTimer;

  /// True when at least one warm has completed since app start.
  static bool _hasWarmedOnce = false;
  static bool get hasWarmedOnce => _hasWarmedOnce;

  /// Fires true when a warm starts, false when it completes.
  static final ValueNotifier<bool> warmingNotifier = ValueNotifier<bool>(false);

  /// Single-flight guard to prevent overlapping warms.
  static Future<void>? _inflight;

  /// Warm every cacheable table. Safe to call repeatedly.
  static Future<void> warmAll(SupabaseClient client) {
    if (kIsWeb) return Future.value();
    if (!AppRepository.isConfigured) return Future.value();
    final existing = _inflight;
    if (existing != null) return existing;

    warmingNotifier.value = true;
    final future = _runWarmAll(client);
    _inflight = future;
    // Guarantee the warming flag is cleared within 90 s even if an HTTP request
    // hangs (no per-request timeout on the Supabase client by default).
    return future
        .timeout(
          const Duration(seconds: 90),
          onTimeout: () =>
              debugPrint('[CacheWarmer] warmAll timeout — clearing warming flag'),
        )
        .whenComplete(() {
          _inflight = null;
          warmingNotifier.value = false;
        });
  }

  static Future<void> _runWarmAll(SupabaseClient client) async {
    final stopwatch = Stopwatch()..start();
    final since = DateTime.now().toUtc().subtract(window);
    final sinceIso = since.toIso8601String();

    debugPrint('[CacheWarmer] starting (since=$sinceIso)');

    // Run reference + per-module warms in parallel — a single failure in one
    // table must not block the others.
    await Future.wait<void>([
      _safe('reference', () => _warmReference(client)),
      _safe('tasks', () => _warmTasks(client, sinceIso)),
      _safe('tickets', () => _warmTickets(client, sinceIso)),
      _safe('itsr', () => _warmItServiceRequests(client, sinceIso)),
      _safe('announcements', () => _warmAnnouncements(client, sinceIso)),
      _safe('attendance', () => _warmAttendance(client, sinceIso)),
      _safe('pass_slips', () => _warmPassSlips(client, sinceIso)),
      _safe('leaves', () => _warmLeaves(client, sinceIso)),
      _safe('duty_schedules', () => _warmDutySchedules(client, sinceIso)),
      _safe('swap_requests', () => _warmSwapRequests(client, sinceIso)),
      _safe('notifications', () => _warmNotifications(client, sinceIso)),
    ]);

    _hasWarmedOnce = true;
    stopwatch.stop();
    debugPrint('[CacheWarmer] done in ${stopwatch.elapsedMilliseconds}ms');
  }

  /// Schedule a periodic re-warm. Idempotent.
  static void startPeriodicRefresh(SupabaseClient client) {
    if (kIsWeb) return;
    _refreshTimer?.cancel();
    _refreshTimer = Timer.periodic(const Duration(hours: 1), (_) {
      warmAll(client);
    });
  }

  /// Cancel periodic re-warm (e.g. on sign-out).
  static void stopPeriodicRefresh() {
    _refreshTimer?.cancel();
    _refreshTimer = null;
  }

  // ------------------------------------------------------------------
  // Reference data — small, rarely-mutating. Pulled in full.
  // ------------------------------------------------------------------

  static Future<void> _warmReference(SupabaseClient client) async {
    await Future.wait<void>([
      _safe('offices', () async {
        final rows = await client.from('offices').select();
        for (final row in rows) {
          await _localUpsert<Office>(Office.fromMap(row));
        }
        await _writeCount('offices', rows.length);
      }),
      _safe('services', () async {
        final rows = await client.from('services').select();
        for (final row in rows) {
          await _localUpsert<Service>(Service.fromMap(row));
        }
        await _writeCount('services', rows.length);
      }),
      _safe('profiles', () async {
        final rows = await client.from('profiles').select();
        for (final row in rows) {
          await _localUpsert<Profile>(Profile.fromMap(row));
        }
        await _writeCount('profiles', rows.length);
      }),
      _safe('teams', () async {
        final rows = await client.from('teams').select();
        for (final row in rows) {
          await _localUpsert<Team>(Team.fromMap(row));
        }
        await _writeCount('teams', rows.length);
      }),
      // Association tables have composite PKs, so we cache them as JSON in
      // SharedPreferences instead of Brick. The list is small and read-only.
      _safe('team_members', () async {
        final rows = await client.from('team_members').select();
        final prefs = await SharedPreferences.getInstance();
        await prefs.setString(_kTeamMembersKey, jsonEncode(rows));
        await _writeCount('team_members', rows.length);
      }),
      _safe('user_offices', () async {
        final rows = await client.from('user_offices').select();
        final prefs = await SharedPreferences.getInstance();
        await prefs.setString(_kUserOfficesKey, jsonEncode(rows));
      }),
    ]);
  }

  /// Read cached team_members rows from SharedPreferences.
  /// Returns the same shape as the Supabase select (`[{team_id, user_id}, ...]`).
  static Future<List<Map<String, dynamic>>> readCachedTeamMembers() async {
    final prefs = await SharedPreferences.getInstance();
    final raw = prefs.getString(_kTeamMembersKey);
    if (raw == null) return const [];
    try {
      final list = jsonDecode(raw);
      if (list is! List) return const [];
      return list.cast<Map<String, dynamic>>();
    } catch (_) {
      return const [];
    }
  }

  /// Read cached user_offices rows from SharedPreferences.
  static Future<List<Map<String, dynamic>>> readCachedUserOffices() async {
    final prefs = await SharedPreferences.getInstance();
    final raw = prefs.getString(_kUserOfficesKey);
    if (raw == null) return const [];
    try {
      final list = jsonDecode(raw);
      if (list is! List) return const [];
      return list.cast<Map<String, dynamic>>();
    } catch (_) {
      return const [];
    }
  }

  // ------------------------------------------------------------------
  // Per-module warms — windowed by created_at >= since
  // ------------------------------------------------------------------

  static Future<void> _warmTasks(SupabaseClient client, String sinceIso) async {
    final rows = await client.from('tasks').select().gte('created_at', sinceIso);
    for (final row in rows) { await _localUpsert<Task>(Task.fromMap(row)); }
    await _writeCount('tasks', rows.length);
  }

  static Future<void> _warmTickets(SupabaseClient client, String sinceIso) async {
    final rows = await client.from('tickets').select().gte('created_at', sinceIso);
    for (final row in rows) { await _localUpsert<Ticket>(Ticket.fromMap(row)); }
    await _writeCount('tickets', rows.length);
  }

  static Future<void> _warmItServiceRequests(SupabaseClient client, String sinceIso) async {
    final rows = await client.from('it_service_requests').select().gte('created_at', sinceIso);
    for (final row in rows) { await _localUpsert<ItServiceRequest>(ItServiceRequest.fromMap(row)); }
    await _writeCount('it_service_requests', rows.length);
  }

  static Future<void> _warmAnnouncements(SupabaseClient client, String sinceIso) async {
    final rows = await client.from('announcements').select().gte('created_at', sinceIso);
    for (final row in rows) { await _localUpsert<Announcement>(Announcement.fromMap(row)); }
    await _writeCount('announcements', rows.length);
    // Also pull comments so detail screens have them offline.
    try {
      final commentRows = await client
          .from('announcement_comments')
          .select()
          .gte('created_at', sinceIso);
      for (final row in commentRows) {
        await _localUpsert<AnnouncementComment>(AnnouncementComment.fromMap(row));
      }
    } catch (e) {
      debugPrint('[CacheWarmer] announcement_comments failed: $e');
    }
  }

  static Future<void> _warmAttendance(SupabaseClient client, String sinceIso) async {
    final rows = await client.from('attendance_logs').select().gte('check_in_at', sinceIso);
    for (final row in rows) { await _localUpsert<AttendanceLog>(AttendanceLog.fromMap(row)); }
    await _writeCount('attendance_logs', rows.length);
  }

  static Future<void> _warmPassSlips(SupabaseClient client, String sinceIso) async {
    final rows = await client.from('pass_slips').select().gte('created_at', sinceIso);
    for (final row in rows) { await _localUpsert<PassSlip>(PassSlip.fromMap(row)); }
    await _writeCount('pass_slips', rows.length);
  }

  static Future<void> _warmLeaves(SupabaseClient client, String sinceIso) async {
    final rows = await client.from('leave_of_absence').select().gte('created_at', sinceIso);
    for (final row in rows) { await _localUpsert<LeaveOfAbsence>(LeaveOfAbsence.fromMap(row)); }
    await _writeCount('leave_of_absence', rows.length);
  }

  static Future<void> _warmDutySchedules(SupabaseClient client, String sinceIso) async {
    // Duty schedules are upcoming-focused; pull a wider window so the user
    // can see today + the next several weeks while offline.
    final rows = await client.from('duty_schedules').select().gte('start_time', sinceIso);
    for (final row in rows) { await _localUpsert<DutySchedule>(DutySchedule.fromMap(row)); }
    await _writeCount('duty_schedules', rows.length);
  }

  static Future<void> _warmSwapRequests(SupabaseClient client, String sinceIso) async {
    final rows = await client.from('swap_requests').select().gte('created_at', sinceIso);
    for (final row in rows) { await _localUpsert<SwapRequest>(SwapRequest.fromMap(row)); }
    await _writeCount('swap_requests', rows.length);
  }

  static Future<void> _warmNotifications(SupabaseClient client, String sinceIso) async {
    final rows = await client.from('notifications').select().gte('created_at', sinceIso);
    for (final row in rows) { await _localUpsert<NotificationItem>(NotificationItem.fromMap(row)); }
    await _writeCount('notifications', rows.length);
  }

  // ------------------------------------------------------------------
  // Helpers
  // ------------------------------------------------------------------

  /// Writes [model] to local SQLite only, bypassing Brick's bidirectional
  /// sync. AppRepository.upsert would re-POST rows to Supabase, causing RLS
  /// violations for other users' records and deadlocks from concurrent writes.
  static Future<void> _localUpsert<T extends OfflineFirstWithSupabaseModel>(
    T model,
  ) async {
    await AppRepository.instance.sqliteProvider
        .upsert<T>(model, repository: AppRepository.instance);
  }

  static Future<void> _safe(String label, Future<void> Function() task) async {
    try {
      await task();
    } catch (e, st) {
      debugPrint('[CacheWarmer] $label failed: $e');
      assert(() {
        debugPrint('$st');
        return true;
      }());
    }
  }

  /// Persist the number of rows cached for [table] to SharedPreferences.
  /// Called at the end of each per-table warm so the Offline Readiness screen
  /// can display cache coverage without issuing SQLite count queries.
  static Future<void> _writeCount(String table, int count) async {
    try {
      final prefs = await SharedPreferences.getInstance();
      await prefs.setInt('$_kCountPrefix$table', count);
    } catch (_) {}
  }

  /// Returns cached row counts written by the last successful warm, keyed by
  /// table name. A value of -1 means the table has never been warmed.
  static Future<Map<String, int>> readCacheCounts() async {
    final prefs = await SharedPreferences.getInstance();
    const tables = [
      'tasks', 'tickets', 'announcements', 'attendance_logs',
      'duty_schedules', 'pass_slips', 'leave_of_absence', 'profiles',
      'teams', 'team_members', 'it_service_requests', 'notifications',
      'swap_requests', 'offices', 'services',
    ];
    return {
      for (final t in tables) t: prefs.getInt('$_kCountPrefix$t') ?? -1,
    };
  }
}