bw-expo-app/components/CategoryTabs.tsx

import React, { useMemo } from 'react';
import {
  View,
  Text,
  ScrollView,
  StyleSheet,
  StyleProp,
  ViewStyle,
  TouchableOpacity,
  useWindowDimensions,
} from 'react-native';
import Animated, {
  useAnimatedStyle,
  withTiming,
  useDerivedValue,
} from 'react-native-reanimated';
import { Colors, Spacing, FontSize, Animation } from '@/constants/theme';

interface Category {
  id: string;
  name: string;
}

interface CategoryTabsProps {
  categories?: Category[];
  activeId?: string;
  onChange?: (category: Category) => void;
  style?: StyleProp<ViewStyle>;
}

const DEFAULT_CATEGORIES: Category[] = [
  { id: 'all', name: '全部' },
  { id: 'finance', name: '财经' },
  { id: 'entertainment', name: '娱乐' },
  { id: 'education', name: '教育' },
  { id: 'technology', name: '科技' },
  { id: 'sports', name: '体育' },
  { id: 'lifestyle', name: '生活' },
  { id: 'travel', name: '旅行' },
];

const CategoryTabs: React.FC<CategoryTabsProps> = ({
  categories = DEFAULT_CATEGORIES,
  activeId = 'all',
  onChange,
  style,
}) => {
  const { width: screenWidth } = useWindowDimensions();

  const activeIndex = useMemo(() => {
    return categories.findIndex(cat => cat.id === activeId);
  }, [categories, activeId]);

  const indicatorPosition = useDerivedValue(() => {
    if (categories.length === 0) return 0;

    const activeIndexSafe = activeIndex >= 0 ? activeIndex : 0;
    const padding = 16;
    const gap = 8;
    let offset = padding;

    for (let i = 0; i < activeIndexSafe; i++) {
      const item = categories[i];
      const itemWidth = Math.min(
        Math.max(44, item.name.length * 16 + 32),
        screenWidth / 3
      );
      offset += itemWidth + gap;
    }

    return offset;
  }, [activeIndex, categories, screenWidth]);

  const activeCategory = categories[activeIndex] || categories[0];

  const indicatorStyle = useAnimatedStyle(() => {
    if (!activeCategory) {
      return { width: 0, left: 0 };
    }

    const width = Math.min(
      Math.max(44, activeCategory.name.length * 16 + 32),
      screenWidth / 3
    );

    return {
      width: withTiming(width, { duration: Animation.duration.normal }),
      left: withTiming(indicatorPosition.value, { duration: Animation.duration.normal }),
    };
  });

  const renderCategory = (category: Category, index: number) => {
    const isActive = category.id === activeId;

    return (
      <TouchableOpacity
        key={category.id}
        style={styles.tabItem}
        onPress={() => onChange?.(category)}
        activeOpacity={0.7}
      >
        <Text style={[styles.tabText, isActive && styles.activeTabText]}>
          {category.name}
        </Text>
      </TouchableOpacity>
    );
  };

  return (
    <View style={[styles.container, style]}>
      <ScrollView
        horizontal
        showsHorizontalScrollIndicator={false}
        contentContainerStyle={styles.scrollContent}
        decelerationRate="fast"
        snapToInterval={1}
      >
        {categories.map(renderCategory)}
      </ScrollView>

      <Animated.View style={[styles.indicator, indicatorStyle]} />
    </View>
  );
};

const styles = StyleSheet.create({
  container: {
    backgroundColor: Colors.background.secondary,
    width: '100%',
  },
  scrollContent: {
    paddingHorizontal: Spacing.md,
    paddingVertical: Spacing.sm,
    gap: Spacing.sm,
  },
  tabItem: {
    minWidth: 44,
    paddingHorizontal: Spacing.md,
    paddingVertical: Spacing.sm,
    height: 40,
    justifyContent: 'center',
    alignItems: 'center',
  },
  tabText: {
    fontSize: FontSize.sm,
    color: Colors.text.secondary,
    fontWeight: '500',
  },
  activeTabText: {
    color: Colors.brand.primary,
    fontWeight: '600',
  },
  indicator: {
    position: 'absolute',
    bottom: 0,
    height: 2,
    backgroundColor: Colors.brand.primary,
    borderRadius: 1,
  },
});

export default React.memo(CategoryTabs);