import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';

import '../../../core/services/barcode_service.dart';
import '../../../core/theme/app_colors.dart';
import '../../../core/theme/app_dimens.dart';
import '../../../core/theme/app_layout.dart';
import '../../modules/screens/customers_view.dart';
import '../../modules/screens/events_view.dart';
import '../../modules/screens/product_import_view.dart';
import '../../modules/screens/promos_view.dart';
import '../../modules/screens/settings_view.dart';
import '../../sync/providers/sync_controller.dart';
import '../providers/cart_controller.dart';
import '../providers/navigation_provider.dart';
import '../widgets/app_sidebar.dart';
import '../widgets/billing_panel.dart';
import '../widgets/cart_fab.dart';
import '../widgets/page_header.dart';
import 'pos_view.dart';

/// Application shell.
///
/// Owns the sidebar, page header and the body for whichever module is active.
/// Keeping one shell means navigation never rebuilds the chrome, and the
/// scanner stays live across modules.
///
/// Layout collapses in a fixed order as width shrinks:
///
/// * `>= 1300`   sidebar with labels, docked bill
/// * `1120–1300` sidebar as an icon rail, docked bill
/// * `920–1120`  icon rail, bill becomes a bottom sheet
/// * `< 920`     sidebar goes off-canvas behind a menu button
class PosDashboardScreen extends ConsumerStatefulWidget {
  const PosDashboardScreen({super.key});

  @override
  ConsumerState<PosDashboardScreen> createState() => _PosDashboardScreenState();
}

class _PosDashboardScreenState extends ConsumerState<PosDashboardScreen> {
  final GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey<ScaffoldState>();
  final FocusNode _searchFocus = FocusNode();
  late final BarcodeService _barcode;

  @override
  void initState() {
    super.initState();

    // The scanner behaves like a keyboard, so listen globally rather than
    // depending on any one field holding focus. A scan from another module
    // jumps back to billing, which is what a cashier expects.
    _barcode = BarcodeService(
      onScan: (code) {
        // Without an imported catalogue there is nothing to resolve against.
        if (!ref.read(catalogueReadyProvider)) return;
        ref.read(activeModuleProvider.notifier).state = PosModule.pos;
        ref.read(cartControllerProvider.notifier).scanBarcode(code);
      },
    )..attach();
  }

  @override
  void dispose() {
    _barcode.dispose();
    _searchFocus.dispose();
    super.dispose();
  }

  void _openBillingSheet() {
    showModalBottomSheet<void>(
      context: context,
      isScrollControlled: true,
      backgroundColor: Colors.transparent,
      builder: (_) => FractionallySizedBox(
        heightFactor: 0.92,
        child: ClipRRect(
          borderRadius: const BorderRadius.vertical(
            top: Radius.circular(AppRadius.xxl),
          ),
          child: const BillingPanel(inSheet: true),
        ),
      ),
    );
  }

  Widget _body(PosModule module, PosLayout layout) => switch (module) {
        PosModule.pos => PosView(layout: layout, searchFocus: _searchFocus),
        PosModule.customers => const CustomersView(),
        PosModule.productImport => const ProductImportView(),
        PosModule.promos => const PromosView(),
        PosModule.events => const EventsView(),
        PosModule.settings => const SettingsView(),
      };

  @override
  Widget build(BuildContext context) {
    final layout = PosLayout.of(context);
    final module = ref.watch(activeModuleProvider);
    final ready = ref.watch(catalogueReadyProvider);
    final isPos = module == PosModule.pos && ready;

    // Only the terminal itself needs the bill docked beside it.
    final showDockedBill = isPos && !layout.billingIsSheet;
    final showCartFab = isPos && layout.billingIsSheet;

    return Scaffold(
      key: _scaffoldKey,
      backgroundColor: AppColors.background,
      drawer: layout.sidebarIsDrawer
          ? Drawer(
              width: PosLayout.expandedWidth,
              backgroundColor: AppColors.surface,
              child: AppSidebar(
                mode: SidebarMode.expanded,
                onDestinationTap: () => Navigator.of(context).maybePop(),
              ),
            )
          : null,
      floatingActionButton:
          showCartFab ? CartFab(onTap: _openBillingSheet) : null,
      floatingActionButtonLocation: FloatingActionButtonLocation.centerFloat,
      body: CallbackShortcuts(
        bindings: {
          const SingleActivator(LogicalKeyboardKey.f2):
              _searchFocus.requestFocus,
          const SingleActivator(LogicalKeyboardKey.f8): () =>
              ref.read(cartControllerProvider.notifier).undo(),
          const SingleActivator(LogicalKeyboardKey.escape):
              _searchFocus.unfocus,
        },
        child: Focus(
          autofocus: true,
          child: Row(
            crossAxisAlignment: CrossAxisAlignment.stretch,
            children: [
              if (!layout.sidebarIsDrawer) AppSidebar(mode: layout.sidebar),
              Expanded(
                child: Column(
                  children: [
                    PageHeader(
                      layout: layout,
                      onMenuTap: () => _scaffoldKey.currentState?.openDrawer(),
                    ),
                    Expanded(
                      child: AnimatedSwitcher(
                        duration: AppMotion.fast,
                        child: KeyedSubtree(
                          key: ValueKey(module),
                          child: _body(module, layout),
                        ),
                      ),
                    ),
                  ],
                ),
              ),
              if (showDockedBill) ...[
                const VerticalDivider(width: 1),
                SizedBox(
                  width: layout.billingWidth,
                  child: const BillingPanel(),
                ),
              ],
            ],
          ),
        ),
      ),
    );
  }
}