frontend/app/(app)/(tabs)/_layout.tsx

import { useMemo, useCallback } from 'react';
import { Platform, Pressable, useWindowDimensions } from 'react-native';
import { Tabs, usePathname, useRouter } from 'expo-router';
import { MaterialCommunityIcons } from '@expo/vector-icons';
import { useSafeAreaInsets } from 'react-native-safe-area-context';
import type { PressableProps } from 'react-native';

import { useAppColors, shadows } from '../../../src/theme';
import { BREAKPOINTS } from '../../../src/hooks';
import { useHomeTabBarVisibilityStore, useTotalUnreadCount, useHomeTabPressStore } from '../../../src/stores';
import { hrefHome } from '../../../src/navigation/hrefs';

const TAB_BAR_HEIGHT = 56;
const TAB_BAR_FLOATING_MARGIN = 12;
const TAB_BAR_MARGIN = 20;

const TabBarButton = ({ children, style, ...rest }: PressableProps) => (
  <Pressable
    {...rest}
    style={style}
    android_ripple={null}
  >
    {children}
  </Pressable>
);

export default function TabsLayout() {
  const colors = useAppColors();
  const { width } = useWindowDimensions();
  const insets = useSafeAreaInsets();
  const pathname = usePathname();
  const router = useRouter();
  const unreadCount = useTotalUnreadCount();
  const scrollHideTabBar = useHomeTabBarVisibilityStore((s) => s.bottomTabBarHiddenByScroll);
  const triggerHomeTabPress = useHomeTabPressStore((s) => s.triggerPress);
  const hideTabBar = Platform.OS === 'web' && width >= BREAKPOINTS.desktop;

  const isHomeStackRoute = pathname === '/home' || pathname.startsWith('/home/');

  const handleHomeTabPress = useCallback(
    (e: { preventDefault: () => void }) => {
      if (!isHomeStackRoute) return;
      e.preventDefault();
      if (pathname === '/home') {
        triggerHomeTabPress();
      } else {
        router.navigate(hrefHome());
      }
    },
    [isHomeStackRoute, pathname, triggerHomeTabPress, router]
  );

  const tabBarStyle = useMemo(() => {
    if (hideTabBar) {
      return { display: 'none' as const, height: 0, overflow: 'hidden' as const };
    }
    const visibleStyle = {
      position: 'absolute' as const,
      left: 0,
      right: 0,
      marginHorizontal: TAB_BAR_MARGIN,
      bottom: TAB_BAR_FLOATING_MARGIN + insets.bottom,
      height: TAB_BAR_HEIGHT,
      borderRadius: 22,
      backgroundColor: colors.background.paper,
      ...shadows.lg,
      borderTopWidth: 0,
      elevation: 100,
      zIndex: 100,
    };
    if (isHomeStackRoute && scrollHideTabBar) {
      return {
        ...visibleStyle,
        display: 'none' as const,
        height: 0,
        opacity: 0,
        overflow: 'hidden' as const,
      };
    }
    return visibleStyle;
  }, [hideTabBar, insets.bottom, isHomeStackRoute, scrollHideTabBar, colors]);

  return (
    <Tabs
      screenOptions={{
        headerShown: false,
        tabBarActiveTintColor: colors.primary.main,
        tabBarInactiveTintColor: colors.text.secondary,
        tabBarStyle,
        tabBarItemStyle: {
          borderRadius: 16,
          marginHorizontal: 2,
          paddingVertical: 1,
        },
        tabBarButton: (props) => <TabBarButton {...props} />,
        tabBarShowLabel: true,
        tabBarLabelStyle: { fontSize: 11, fontWeight: '600', marginTop: -1 },
      }}
    >
      <Tabs.Screen
        name="home"
        options={{
          title: '首页',
          tabBarIcon: ({ color, focused }) => (
            <MaterialCommunityIcons
              name={focused ? 'home' : 'home-outline'}
              size={focused ? 24 : 22}
              color={color}
            />
          ),
        }}
        listeners={{
          tabPress: handleHomeTabPress,
        }}
      />
      <Tabs.Screen
        name="apps"
        options={{
          title: '应用',
          tabBarIcon: ({ color, focused }) => (
            <MaterialCommunityIcons
              name={focused ? 'view-grid' : 'view-grid-outline'}
              size={focused ? 24 : 22}
              color={color}
            />
          ),
        }}
      />
      <Tabs.Screen
        name="messages"
        options={{
          title: '消息',
          tabBarBadge: unreadCount > 0 ? (unreadCount > 99 ? 99 : unreadCount) : undefined,
          tabBarIcon: ({ color, focused }) => (
            <MaterialCommunityIcons
              name={focused ? 'message-text' : 'message-text-outline'}
              size={focused ? 24 : 22}
              color={color}
            />
          ),
        }}
      />
      <Tabs.Screen
        name="profile"
        options={{
          title: '我的',
          tabBarIcon: ({ color, focused }) => (
            <MaterialCommunityIcons
              name={focused ? 'account' : 'account-outline'}
              size={focused ? 24 : 22}
              color={color}
            />
          ),
        }}
      />
    </Tabs>
  );
}