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

import '../../auth/providers/auth_controller.dart';

/// The modules a cashier needs. Deliberately excludes analytics — this
/// terminal is for billing, not back-office reporting.
enum PosModule {
  pos('Point of Sale', 'POS', Icons.point_of_sale_rounded, NavSection.billing),
  customers('Customers', 'Customers', Icons.people_alt_rounded,
      NavSection.billing,),

  productImport('Product Import', 'Product Import',
      Icons.cloud_download_rounded, NavSection.catalogue,),
  promos('Promotions', 'Promo', Icons.sell_rounded, NavSection.catalogue),

  events('Events', 'Events', Icons.sync_rounded, NavSection.session),
  settings('Settings', 'Settings', Icons.settings_rounded, NavSection.session);

  const PosModule(this.title, this.label, this.icon, this.section);

  /// Long form, shown in the page header.
  final String title;

  /// Short form, shown in the sidebar.
  final String label;

  final IconData icon;
  final NavSection section;
}

/// Groups the navigation into labelled blocks.
enum NavSection {
  billing('Billing'),
  catalogue('Catalogue'),
  session('Session');

  const NavSection(this.label);

  final String label;

  List<PosModule> get modules =>
      PosModule.values.where((m) => m.section == this).toList();
}

/// What a cashier session may open.
///
/// Billing, and nothing else — not the catalogue, the promos, the sync log or
/// the terminal's configuration. The sidebar is hidden in cashier mode anyway,
/// so this is the belt to that braces: a module reached some other way (a scan
/// handler, a deep link, a stale value left in [activeModuleProvider] from the
/// admin's session) still cannot render.
const cashierModules = <PosModule>[PosModule.pos];

final activeModuleProvider = StateProvider<PosModule>((ref) => PosModule.pos);

/// The modules the current session is allowed to reach.
final visibleModulesProvider = Provider<List<PosModule>>((ref) {
  return ref.watch(isCashierModeProvider) ? cashierModules : PosModule.values;
});

/// [activeModuleProvider], clamped to what this session may open.
///
/// Read this rather than the raw value anywhere a module decides what gets
/// built. An admin who leaves the shell on Settings and hands the till to a
/// cashier would otherwise reopen it on Settings.
final resolvedModuleProvider = Provider<PosModule>((ref) {
  final active = ref.watch(activeModuleProvider);
  final visible = ref.watch(visibleModulesProvider);
  return visible.contains(active) ? active : PosModule.pos;
});

/// Sections that still have at least one module this session may open.
final visibleSectionsProvider = Provider<List<NavSection>>((ref) {
  final visible = ref.watch(visibleModulesProvider);
  return NavSection.values
      .where((s) => s.modules.any(visible.contains))
      .toList();
});