import 'package:flutter_riverpod/flutter_riverpod.dart';

import '../../../app/providers.dart';
import '../../../core/constants/app_constants.dart';
import '../../../data/remote/mqtt_order_transport.dart';
import '../../../data/sync/presence_reporter.dart';
import '../../../domain/entities/shift_report.dart';
import '../../../domain/entities/sync_event.dart';
import '../../../domain/repositories/sync_repository.dart';
import '../../auth/providers/auth_controller.dart';
import '../../pos/providers/catalog_providers.dart';

/// Bumped after every import so catalogue-backed providers refetch.
final catalogueVersionProvider = StateProvider<int>((ref) => 0);

/// Bumped after every sale or sync so order-backed providers refetch.
final orderVersionProvider = StateProvider<int>((ref) => 0);

/// Whether products exist on this terminal. Billing is gated on it.
final catalogueReadyProvider = Provider<bool>((ref) {
  ref.watch(catalogueVersionProvider);
  return ref.watch(syncRepositoryProvider).hasCatalogue;
});

final lastImportAtProvider = Provider<DateTime?>((ref) {
  ref.watch(catalogueVersionProvider);
  return ref.watch(syncRepositoryProvider).lastImportAt;
});

// ------------------------------------------------------- Morning: import
sealed class ImportState {
  const ImportState();
}

class ImportIdle extends ImportState {
  const ImportIdle();
}

class ImportRunning extends ImportState {
  const ImportRunning(this.progress, this.stage);

  final double progress;
  final String stage;
}

class ImportDone extends ImportState {
  const ImportDone(this.event);

  final SyncEvent event;
}

class ImportFailed extends ImportState {
  const ImportFailed(this.message);

  final String message;
}

class CatalogueImportController extends StateNotifier<ImportState> {
  CatalogueImportController(this._ref) : super(const ImportIdle());

  final Ref _ref;

  Future<bool> run() async {
    if (state is ImportRunning) return false;
    state = const ImportRunning(0, 'Starting…');

    final event = await _ref.read(syncRepositoryProvider).importCatalogue(
          onProgress: (progress, stage) {
            if (mounted) state = ImportRunning(progress, stage);
          },
        );

    if (event.status == SyncStatus.synced) {
      _ref.read(catalogueVersionProvider.notifier).state++;
      _ref.invalidate(allProductsProvider);
      _ref.invalidate(visibleProductsProvider);
      _ref.invalidate(categoryCountsProvider);
      _ref.invalidate(lowStockProductsProvider);
      state = ImportDone(event);
      return true;
    }

    state = ImportFailed(event.error ?? 'Import failed.');
    return false;
  }

  /// Drops a stale success or failure banner.
  void reset() => state = const ImportIdle();
}

final catalogueImportProvider =
    StateNotifierProvider<CatalogueImportController, ImportState>(
  (ref) => CatalogueImportController(ref),
);

// ---------------------------------------------------- Business hours: read
/// Bills still held on this terminal at sync_status = 0.
final unsyncedCountProvider = FutureProvider<int>((ref) {
  ref.watch(orderVersionProvider);
  return ref.watch(syncRepositoryProvider).unsyncedCount();
});

/// Everything this terminal traded today, across every operator.
final todayReportProvider = FutureProvider<ShiftReport>((ref) {
  ref.watch(orderVersionProvider);
  final session = ref.watch(cashierSessionProvider);
  final user = ref.watch(currentUserProvider);

  return ref.watch(syncRepositoryProvider).todayReport(
        terminalId: session.terminalId,
        cashierName: user?.name ?? session.name,
      );
});

/// Only the bills the signed-in operator rang.
///
/// This is the figure a cashier counts their drawer against at the end of a
/// shift, so it must not include anyone else's sales.
final myShiftReportProvider = FutureProvider<ShiftReport>((ref) {
  ref.watch(orderVersionProvider);
  final session = ref.watch(cashierSessionProvider);
  final user = ref.watch(currentUserProvider);

  return ref.watch(syncRepositoryProvider).todayReport(
        terminalId: session.terminalId,
        cashierName: user?.name ?? session.name,
        scopeToCashier: true,
      );
});

/// Per-order sync state for the events log.
final orderSyncRowsProvider = FutureProvider<List<OrderSyncRow>>((ref) {
  ref.watch(orderVersionProvider);
  return ref.watch(syncRepositoryProvider).orderSyncRows();
});

final syncEventsProvider = Provider<List<SyncEvent>>((ref) {
  ref.watch(orderVersionProvider);
  ref.watch(catalogueVersionProvider);
  return ref.watch(syncRepositoryProvider).events;
});

// ------------------------------------------------------ End of day: upload
sealed class OrderSyncState {
  const OrderSyncState();
}

class SyncIdle extends OrderSyncState {
  const SyncIdle();
}

class SyncRunning extends OrderSyncState {
  const SyncRunning(this.progress, this.stage);

  final double progress;
  final String stage;
}

class SyncFinished extends OrderSyncState {
  const SyncFinished(this.outcome);

  final SyncOutcome outcome;
}

class OrderSyncController extends StateNotifier<OrderSyncState> {
  OrderSyncController(this._ref) : super(const SyncIdle());

  final Ref _ref;

  bool get isRunning => state is SyncRunning;

  /// Uploads every bill at sync_status = 0 and flips the accepted ones to 1.
  ///
  /// Goes through the engine rather than straight to the repository, so a
  /// cashier pressing sync while a background drain is already mid-flight
  /// joins it instead of starting a second pass over the same rows. It also
  /// clears a halt: pressing the button is how you retry after the back office
  /// has been fixed.
  Future<SyncOutcome> run() async {
    if (isRunning) {
      return const SyncOutcome(attempted: 0, uploaded: 0);
    }

    state = const SyncRunning(0, 'Starting…');

    final outcome = await _ref.read(syncEngineProvider).syncNow(
          onProgress: (progress, stage) {
            if (mounted) state = SyncRunning(progress, stage);
          },
        );

    _ref.read(orderVersionProvider.notifier).state++;
    if (mounted) state = SyncFinished(outcome);
    return outcome;
  }

  void reset() => state = const SyncIdle();
}

final orderSyncProvider =
    StateNotifierProvider<OrderSyncController, OrderSyncState>(
  (ref) => OrderSyncController(ref),
);

// ------------------------------------------------------- Background drain
/// Brings the queue-and-drain machinery up, once, when the shell mounts.
///
/// Deliberately not gated on sign-in: a terminal that boots holding yesterday's
/// bills should be emptying its queue before anyone reaches the till.
///
/// Overridden to a no-op in widget tests, which have no network stack and
/// cannot drive real disk I/O on a fake clock.
final syncBootstrapProvider = FutureProvider<void>((ref) async {
  // Restore the route this terminal was pointed at. Without this the settings
  // are written on Save and then silently ignored on the next launch, which
  // reads exactly like they never saved.
  final store = ref.read(localStoreProvider);
  if (store.isReady) {
    ref.read(syncConfigProvider.notifier).state =
        await store.syncConfig.load(ref.read(syncConfigProvider));
  }

  await ref.read(connectivityServiceProvider).start();

  final engine = ref.read(syncEngineProvider);

  // A background drain moves bills out of the pending set, so the tallies and
  // shift totals on screen are stale the moment one finishes.
  var wasSyncing = false;
  final subscription = engine.states.listen((state) {
    if (wasSyncing && !state.isSyncing) {
      ref.read(orderVersionProvider.notifier).state++;
    }
    wasSyncing = state.isSyncing;
  });
  ref.onDispose(subscription.cancel);

  await engine.start();

  // Fleet presence only exists on a transport that can carry it.
  final transport = ref.read(orderTransportProvider);
  if (transport is MqttOrderTransport) {
    final reporter = PresenceReporter(
      transport: transport,
      terminal: ref.read(terminalIdentityProvider),
      config: ref.read(syncConfigProvider),
      engine: engine,
      appVersion: AppConstants.appVersion,
      catalogueRevision: () async =>
          ref.read(syncRepositoryProvider).catalogueRevision,
    );
    ref.onDispose(reporter.dispose);
    await reporter.start();
  }
});