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

import '../../core/theme/app_colors.dart';
import '../history/history_screen.dart';
import '../home/home_screen.dart';
import '../profile/profile_screen.dart';

/// 底栏：极淡背景渐变 + 图标/标签 [Shadow]，兼顾层次与可读性。
const List<Shadow> _bottomNavItemShadows = [
  Shadow(offset: Offset(0, 1), blurRadius: 3, color: Color(0x72000000)),
  Shadow(offset: Offset(0, 0), blurRadius: 8, color: Color(0x40000000)),
];

/// Root shell: bottom tabs **Home**, **History**, **Profile** (English labels).
class MainScreen extends StatefulWidget {
  const MainScreen({super.key});

  @override
  State<MainScreen> createState() => _MainScreenState();
}

class _MainScreenState extends State<MainScreen> {
  int _index = 0;

  @override
  Widget build(BuildContext context) {
    final parentNav = NavigationBarTheme.of(context);
    return Scaffold(
      // All tabs: body extends under the bottom bar (faint gradient + [NavigationBar]).
      extendBody: true,
      body: IndexedStack(
        index: _index,
        children: [
          const HomeScreen(),
          HistoryScreen(isRootTab: true, isTabSelected: _index == 1),
          const ProfileScreen(isRootTab: true),
        ],
      ),
      bottomNavigationBar: Stack(
        alignment: Alignment.bottomCenter,
        children: [
          Positioned.fill(
            child: DecoratedBox(
              decoration: BoxDecoration(
                gradient: LinearGradient(
                  begin: Alignment.bottomCenter,
                  end: Alignment.topCenter,
                  colors: [
                    AppColors.surface.withValues(alpha: 0.40),
                    AppColors.surface.withValues(alpha: 0.15),
                    AppColors.surface.withValues(alpha: 0),
                  ],
                  stops: const [0.0, 0.48, 1.0],
                ),
              ),
            ),
          ),
          NavigationBarTheme(
            data: parentNav.copyWith(
              labelTextStyle: WidgetStateProperty.resolveWith((states) {
                final selected = states.contains(WidgetState.selected);
                return GoogleFonts.inter(
                  fontSize: 12,
                  fontWeight: selected ? FontWeight.w600 : FontWeight.w500,
                  color: selected ? AppColors.primary : AppColors.onSurface,
                  shadows: _bottomNavItemShadows,
                );
              }),
              iconTheme: WidgetStateProperty.resolveWith((states) {
                final selected = states.contains(WidgetState.selected);
                return IconThemeData(
                  color: selected ? AppColors.primary : AppColors.onSurface,
                  shadows: _bottomNavItemShadows,
                );
              }),
            ),
            child: NavigationBar(
              backgroundColor: Colors.transparent,
              elevation: 0,
              surfaceTintColor: Colors.transparent,
              shadowColor: Colors.transparent,
              selectedIndex: _index,
              onDestinationSelected: (i) => setState(() => _index = i),
              destinations: const [
                NavigationDestination(
                  icon: Icon(Icons.home_outlined),
                  selectedIcon: Icon(Icons.home_rounded),
                  label: 'Home',
                ),
                NavigationDestination(
                  icon: Icon(Icons.history_outlined),
                  selectedIcon: Icon(Icons.history_rounded),
                  label: 'History',
                ),
                NavigationDestination(
                  icon: Icon(Icons.person_outline_rounded),
                  selectedIcon: Icon(Icons.person_rounded),
                  label: 'Profile',
                ),
              ],
            ),
          ),
        ],
      ),
    );
  }
}