/// Bottom navigation: products, lists, add, and shop log.
library;

import 'package:flutter/material.dart';

import 'products_screen.dart';
import 'scan_screen.dart';
import 'services/app_settings.dart';
import 'services/product_repository.dart';
import 'shop_log_screen.dart';
import 'shopping_lists_screen.dart';

class HomeShell extends StatefulWidget {
  const HomeShell({super.key, required this.repository});

  final ProductRepository repository;

  @override
  State<HomeShell> createState() => _HomeShellState();
}

class _HomeShellState extends State<HomeShell> {
  static const _addIndex = 2;
  static const _shopLogIndex = 3;
  static const _fabGap = 56.0;

  int _index = _addIndex;
  int _revision = 0;
  AppSettings? _settings;
  int _seenGeneration = 0;

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    final settings = SettingsScope.maybeOf(context);
    if (settings != _settings) {
      _settings?.removeListener(_onSettings);
      _settings = settings;
      _seenGeneration = settings?.catalogGeneration ?? 0;
      _settings?.addListener(_onSettings);
    }
  }

  @override
  void dispose() {
    _settings?.removeListener(_onSettings);
    super.dispose();
  }

  void _onSettings() {
    final generation = _settings?.catalogGeneration ?? 0;
    if (generation == _seenGeneration) return;
    _seenGeneration = generation;
    if (mounted) setState(() => _revision++);
  }

  void _onTripSaved() {
    setState(() {
      _index = _shopLogIndex;
      _revision++;
    });
    WidgetsBinding.instance.addPostFrameCallback((_) {
      if (!mounted) return;
      ScaffoldMessenger.of(context)
          .showSnackBar(const SnackBar(content: Text('Shopping trip saved.')));
    });
  }

  void _select(int index) {
    if (index == _index) return;
    setState(() => _index = index);
  }

  @override
  Widget build(BuildContext context) {
    final scheme = Theme.of(context).colorScheme;

    return Scaffold(
      body: switch (_index) {
        0 => ProductsScreen(
          key: ValueKey('products-$_revision'),
          repository: widget.repository,
        ),
        1 => ShoppingListsScreen(
          key: ValueKey('lists-$_revision'),
          repository: widget.repository,
        ),
        2 => ScanScreen(
          repository: widget.repository,
          onTripSaved: _onTripSaved,
        ),
        _ => ShopLogScreen(
          key: ValueKey('shops-$_revision'),
          repository: widget.repository,
        ),
      },
      floatingActionButtonLocation: FloatingActionButtonLocation.centerDocked,
      floatingActionButton: FloatingActionButton.small(
        onPressed: () => _select(_addIndex),
        tooltip: 'Add',
        elevation: _index == _addIndex ? 4 : 1,
        shape: const CircleBorder(),
        backgroundColor: scheme.primary,
        foregroundColor: scheme.onPrimary,
        child: const Icon(Icons.add, size: 24),
      ),
      bottomNavigationBar: BottomAppBar(
        shape: const CircularNotchedRectangle(),
        notchMargin: 6,
        elevation: 2,
        height: 52,
        padding: EdgeInsets.zero,
        color: scheme.surfaceContainer,
        child: Row(
          children: [
            Expanded(
              child: Row(
                children: [
                  Expanded(
                    child: _NavButton(
                      icon: Icons.inventory_2_outlined,
                      selectedIcon: Icons.inventory_2,
                      label: 'Products',
                      selected: _index == 0,
                      onTap: () => _select(0),
                    ),
                  ),
                  Expanded(
                    child: _NavButton(
                      icon: Icons.checklist_outlined,
                      selectedIcon: Icons.checklist,
                      label: 'Lists',
                      selected: _index == 1,
                      onTap: () => _select(1),
                    ),
                  ),
                ],
              ),
            ),
            const SizedBox(width: _fabGap),
            Expanded(
              child: _NavButton(
                icon: Icons.receipt_long_outlined,
                selectedIcon: Icons.receipt_long,
                label: 'Shop log',
                selected: _index == _shopLogIndex,
                onTap: () => _select(_shopLogIndex),
              ),
            ),
          ],
        ),
      ),
    );
  }
}

class _NavButton extends StatelessWidget {
  const _NavButton({
    required this.icon,
    required this.selectedIcon,
    required this.label,
    required this.selected,
    required this.onTap,
  });

  final IconData icon;
  final IconData selectedIcon;
  final String label;
  final bool selected;
  final VoidCallback onTap;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final scheme = theme.colorScheme;
    final color = selected ? scheme.primary : scheme.onSurfaceVariant;

    return InkWell(
      onTap: onTap,
      borderRadius: BorderRadius.circular(12),
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        mainAxisSize: MainAxisSize.min,
        children: [
          Icon(selected ? selectedIcon : icon, color: color, size: 20),
          Text(
            label,
            maxLines: 1,
            overflow: TextOverflow.ellipsis,
            style: theme.textTheme.labelSmall?.copyWith(
              color: color,
              height: 1.1,
              fontSize: 10,
              fontWeight: selected ? FontWeight.w600 : FontWeight.w500,
            ),
          ),
        ],
      ),
    );
  }
}