import { useEffect, useLayoutEffect, useMemo, useState, useCallback, useRef } from 'react';
import { StyleSheet, View, Dimensions, Text, Pressable, PanResponder, Animated as RNAnimated, ImageBackground } from 'react-native';
import { useTranslation } from 'react-i18next';
import { useNavigation, useFocusEffect } from 'expo-router';
import Animated, {
  Easing,
  runOnJS,
  useAnimatedStyle,
  useSharedValue,
  withSequence,
  withTiming,
} from 'react-native-reanimated';

import { MOCK_CONTENT } from '@/src/constants/mockContent';
import {
  addFavorite,
  getThemeMode,
  getUserProfile,
  setReaction,
  setThemeMode,
  getRecoFeedCache,
  setRecoFeedCache,
  getUserProfileScoring,
  getRecoFeedHistory,
  recordRecoFeedServed,
  type ThemeMode,
} from '@/src/storage/appStorage';

import { fetchRecoFeed } from '@/src/services/recoApi';

import ProfileModal from '@/components/home/ProfileModal';
import ThemeModal from '@/components/home/ThemeModal';

import ThemeIcon from '@/assets/images/home/theme.svg';
import MyIcon from '@/assets/images/home/my.svg';
import LikeFilledIcon from '@/assets/images/home/like_filled.svg';
import LikeIcon from '@/assets/images/icon/like_icon.svg';

const { height: SCREEN_HEIGHT } = Dimensions.get('window');

// 预定义风景图列表
const NATURE_IMAGES = [
  require('@/assets/theme/nature/1.png'),
  require('@/assets/theme/nature/2.png'),
  require('@/assets/theme/nature/3.png'),
  require('@/assets/theme/nature/4.png'),
  require('@/assets/theme/nature/5.png'),
  require('@/assets/theme/nature/6.png'),
  require('@/assets/theme/nature/7.png'),
  require('@/assets/theme/nature/8.png'),
  require('@/assets/theme/nature/9.png'),
  require('@/assets/theme/nature/10.png'),
  require('@/assets/theme/nature/11.png'),
  require('@/assets/theme/nature/12.png'),
  require('@/assets/theme/nature/13.png'),
  require('@/assets/theme/nature/14.png'),
  require('@/assets/theme/nature/15.png'),
  require('@/assets/theme/nature/17.png'),
  require('@/assets/theme/nature/18.png'),
  require('@/assets/theme/nature/19.png'),
  require('@/assets/theme/nature/20.png'),
  require('@/assets/theme/nature/22.png'),
];

// 预定义颜色列表
const THEME_COLORS = [
  '#F7D9BF',
  '#CBF2D8',
  '#F5CDDE',
  '#F2ECCB',
  '#E2CBF2',
  '#CBD9F2',
];

type FeedItem = { content_id: string; text: string };

export default function HomeScreen() {
  const { t, i18n } = useTranslation();
  const isEnglish = i18n.language?.startsWith('en');
  const recoLang: 'en' | 'tc' = i18n.language?.toLowerCase().startsWith('zh') ? 'tc' : 'en';
  const navigation = useNavigation();
  const [index, setIndex] = useState(0);
  const [themeMode, setThemeModeState] = useState<ThemeMode>('scenery');
  const [themeOpen, setThemeOpen] = useState(false);
  const [profileOpen, setProfileOpen] = useState(false);
  const [profileName, setProfileName] = useState<string | undefined>(undefined);
  const [busy, setBusy] = useState(false);
  const [likeFilled, setLikeFilled] = useState(false);
  const [feedItems, setFeedItems] = useState<FeedItem[]>([]);
  const [isFetching, setIsFetching] = useState(false);

  // 解决语言切换时重复触发拉取/清空导致“文案不停跳动”的问题：
  // 用 ref 持有最新状态，避免 useCallback 依赖 feedItems/isFetching 造成函数 identity 变化 → effect 重复执行
  const feedItemsRef = useRef<FeedItem[]>([]);
  const isFetchingRef = useRef(false);
  useEffect(() => {
    feedItemsRef.current = feedItems;
  }, [feedItems]);
  useEffect(() => {
    isFetchingRef.current = isFetching;
  }, [isFetching]);

  // 动画相关 Shared Values
  const translateY = useSharedValue(0);
  const opacity = useSharedValue(1);
  const likeScale = useSharedValue(1);

  // 统一文案对象结构
  const currentFeed = useMemo(() => {
    if (feedItems.length > 0) {
      return feedItems;
    }
    return MOCK_CONTENT.map(item => ({
      content_id: item.id,
      text: t(item.textKey)
    }));
  }, [feedItems, t]);

  const item = useMemo(() => {
    const data = currentFeed[index % currentFeed.length];
    return {
      id: String(data.content_id),
      text: data.text
    };
  }, [currentFeed, index]);

  // 异步拉取新文案
  const fetchNewFeed = useCallback(async () => {
    if (isFetchingRef.current) return;
    isFetchingRef.current = true;
    setIsFetching(true);
    try {
      const scoringProfile = await getUserProfileScoring();
      if (!scoringProfile) return;

      const history = await getRecoFeedHistory();
      
      const { items, meta } = await fetchRecoFeed({
        k: 30,
        user_profile: scoringProfile,
        already_recommended_ids: history.already_recommended_ids,
        touched_or_viewed_ids: history.touched_or_viewed_ids,
      });

      if (items.length > 0) {
        const wasEmpty = feedItemsRef.current.length === 0;
        const newCache = {
          saved_at: new Date().toISOString(),
          lang: recoLang,
          items: items.map((x) => ({ content_id: x.content_id, text: x.text })),
          meta: meta as Record<string, unknown>,
        };
        await setRecoFeedCache(newCache);
        await recordRecoFeedServed(items.map((x) => x.content_id));
        setFeedItems(newCache.items.map((x) => ({ content_id: String(x.content_id), text: x.text })));
        // 如果当前是 mock 数据，切换到新数据的第一条
        if (wasEmpty) {
          setIndex(0);
        }
      }
    } catch (error) {
      console.error('Failed to fetch new feed:', error);
    } finally {
      isFetchingRef.current = false;
      setIsFetching(false);
    }
  }, [recoLang]);

  // 每次进入页面或页面获得焦点时刷新个人信息和缓存文案
  useFocusEffect(
    useCallback(() => {
      let cancelled = false;
      (async () => {
        const mode = await getThemeMode();
        const profile = await getUserProfile();
        const cache = await getRecoFeedCache();

        if (cancelled) return;
        setThemeModeState(mode);
        setProfileName(profile.name);
        
        // 语言切换时：旧语言缓存不复用，触发重新拉取
        if (cache && cache.items.length > 0 && (cache.lang ?? 'en') === recoLang) {
          setFeedItems(cache.items.map((x) => ({ content_id: String(x.content_id), text: x.text })));
        } else {
          // 语言不匹配或没有缓存：先清空回落到本地 mock（会立即随语言切换），再拉取对应语言的推荐文案
          setFeedItems([]);
          setIndex(0);
          fetchNewFeed();
        }
      })();
      return () => {
        cancelled = true;
      };
    }, [fetchNewFeed, recoLang])
  );

  const backgroundColor = useMemo(() => {
    if (themeMode === 'color') {
      const colorIndex = Math.floor(index / 10) % THEME_COLORS.length;
      return THEME_COLORS[colorIndex];
    }
    return '#F4D6C2'; // 风景模式下的默认底色（图片加载前显示）
  }, [themeMode, index]);

  // 计算当前应该显示的风景图索引（滑动 10 次切换一张）
  const natureImageIndex = useMemo(() => {
    return Math.floor(index / 10) % NATURE_IMAGES.length;
  }, [index]);

  const currentNatureImage = NATURE_IMAGES[natureImageIndex];

  useLayoutEffect(() => {
    navigation.setOptions({
      headerShadowVisible: false,
      // 为了让风景/颜色两种主题下“文案的视觉居中位置”一致，统一使用透明 Header
      // 颜色主题下 Header 透明也不会影响观感（背景就是纯色）
      headerStyle: { backgroundColor: 'transparent' },
      headerTransparent: true,
      headerRight: () => (
        <View style={styles.headerRight}>
          <CircleIconButton
            onPress={() => setThemeOpen(true)}
            accessibilityLabel={t('home.theme')}
          >
            <ThemeIcon width={18} height={18} />
          </CircleIconButton>
          <CircleIconButton
            onPress={() => setProfileOpen(true)}
            accessibilityLabel={t('home.profile')}
          >
            <MyIcon width={18} height={18} />
          </CircleIconButton>
        </View>
      ),
    });
  }, [backgroundColor, themeMode, navigation, t]);

  const textAnimatedStyle = useAnimatedStyle(() => ({
    transform: [{ translateY: translateY.value }],
    opacity: opacity.value,
  }));

  const likeAnimatedStyle = useAnimatedStyle(() => ({
    transform: [{ scale: likeScale.value }],
  }));

  // 切换到下一条文案的统一动画逻辑
  const triggerNextContent = useCallback(() => {
    if (busy) return;
    setBusy(true);

    // 1. 当前文案向上移动并消失
    translateY.value = withTiming(-40, { duration: 300, easing: Easing.out(Easing.quad) });
    opacity.value = withTiming(0, { duration: 300 }, (finished) => {
      if (finished) {
        // 2. 切换数据索引
        runOnJS(setIndex)(index + 1);
        runOnJS(setLikeFilled)(false);

        // 检查是否需要拉取新文案（当接近当前列表末尾时，例如还剩 5 条）
        if (index + 5 >= currentFeed.length && !isFetching) {
          runOnJS(fetchNewFeed)();
        }

        // 3. 准备下一条文案：先瞬移到下方 40pt
        translateY.value = 40;
        
        // 4. 下一条文案向上移动到原位并显现
        translateY.value = withTiming(0, { duration: 400, easing: Easing.out(Easing.back(1)) });
        opacity.value = withTiming(1, { duration: 400 }, (finished) => {
          if (finished) {
            runOnJS(setBusy)(false);
          }
        });
      }
    });
  }, [busy, index, currentFeed.length, isFetching, fetchNewFeed, translateY, opacity]);

  const lastTapRef = useRef<number>(0);
  
  // 使用 Ref 解决 PanResponder 闭包陷阱，确保手势回调能拿到最新的 state 和 function
  const handlersRef = useRef({ onPressLike, triggerNextContent });
  useEffect(() => {
    handlersRef.current = { onPressLike, triggerNextContent };
  }, [onPressLike, triggerNextContent]);

  // 使用系统自带的 PanResponder 代替第三方手势库
  const panResponder = useRef(
    PanResponder.create({
      onStartShouldSetPanResponder: () => true, // 允许开始捕获
      onMoveShouldSetPanResponder: (_, gestureState) => {
        // 只有当垂直滑动距离大于 20 时才接管位移手势
        return Math.abs(gestureState.dy) > 20;
      },
      onPanResponderRelease: (_, gestureState) => {
        const now = Date.now();
        const DOUBLE_TAP_DELAY = 300;

        // 1. 双击逻辑判定
        if (now - lastTapRef.current < DOUBLE_TAP_DELAY) {
          // 判定为双击
          if (Math.abs(gestureState.dx) < 10 && Math.abs(gestureState.dy) < 10) {
            runOnJS(handlersRef.current.onPressLike)();
            lastTapRef.current = 0; // 重置
            return;
          }
        }
        lastTapRef.current = now;

        // 2. 上滑逻辑判定
        if (gestureState.dy < -50) { // 上滑超过 50pt
          runOnJS(handlersRef.current.triggerNextContent)();
        }
      },
    })
  ).current;

  async function onPressLike() {
    if (busy) return;
    setLikeFilled(true);
    
    // 1. 获取当前日期
    const now = new Date();
    const dateStr = `${now.getFullYear()}.${String(now.getMonth() + 1).padStart(2, '0')}.${String(now.getDate()).padStart(2, '0')}`;

    // 2. 保存到收藏夹，包含当前背景信息
    const favItem = {
      favId: String(Date.now()), // 生成唯一 ID
      id: item.id,
      text: item.text,
      date: dateStr,
      themeMode: themeMode,
      background: themeMode === 'scenery' ? String(natureImageIndex) : backgroundColor,
    };
    console.log('Home: Triggering addFavorite', JSON.stringify(favItem));
    await addFavorite(favItem);

    // 3. 记录到后端 Reaction（喜欢）
    console.log('Home: Triggering setReaction', item.id);
    await setReaction(item.id, 'like');

    // 4. 爱心缩放动画
    likeScale.value = withSequence(
      withTiming(0.8, { duration: 100 }),
      withTiming(1.2, { duration: 150 }),
      withTiming(1, { duration: 100 }, (finished) => {
        if (finished) {
          console.log('Home: Like animation finished, triggering next content');
          runOnJS(triggerNextContent)();
        }
      })
    );
  }

  async function onSelectTheme(next: ThemeMode) {
    setThemeModeState(next);
    await setThemeMode(next);
    setThemeOpen(false);
  }

  return (
    <View style={[styles.container, { backgroundColor }]} {...panResponder.panHandlers}>
      {themeMode === 'scenery' && (
        <ImageBackground
          source={currentNatureImage}
          style={StyleSheet.absoluteFill}
          resizeMode="cover"
        />
      )}
      <Animated.View style={[styles.card, textAnimatedStyle, themeMode === 'scenery' && styles.sceneryCard]}>
        <Text style={[styles.text, isEnglish && styles.textEnglish, themeMode === 'scenery' && styles.sceneryText]}>
          {item.text}
        </Text>
      </Animated.View>

      <View style={styles.actions}>
        <Animated.View style={[styles.reactionButton, likeAnimatedStyle]}>
          <Pressable
            onPress={onPressLike}
            accessibilityRole="button"
            accessibilityLabel={t('home.like')}
            hitSlop={20}
            style={styles.reactionInner}
          >
            {likeFilled ? (
              <LikeFilledIcon width={35} height={36} style={{ color: '#EA6969' }} />
            ) : (
              <LikeIcon 
                width={35} 
                height={36} 
                style={{ color: themeMode === 'scenery' ? '#FFFFFF' : '#5E2A28' }}
              />
            )}
          </Pressable>
        </Animated.View>
      </View>

      <ThemeModal visible={themeOpen} mode={themeMode} onSelect={onSelectTheme} onClose={() => setThemeOpen(false)} />
      <ProfileModal
        visible={profileOpen}
        name={profileName}
        onClose={() => setProfileOpen(false)}
      />
    </View>
  );
}

function CircleIconButton({
  onPress,
  accessibilityLabel,
  children,
}: {
  onPress: () => void;
  accessibilityLabel: string;
  children: React.ReactNode;
}) {
  return (
    <Pressable
      onPress={onPress}
      hitSlop={10}
      accessibilityRole="button"
      accessibilityLabel={accessibilityLabel}
      style={styles.circleBtn}
    >
      {children}
    </Pressable>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    padding: 20,
    justifyContent: 'center',
    alignItems: 'center',
  },
  headerRight: {
    flexDirection: 'row',
    gap: 10,
    paddingRight: 10,
  },
  circleBtn: {
    width: 34,
    height: 34,
    borderRadius: 17,
    backgroundColor: 'rgba(255,255,255,0.75)',
    alignItems: 'center',
    justifyContent: 'center',
  },
  card: {
    position: 'absolute',
    top: 0,
    left: 0,
    right: 0,
    bottom: 0,
    justifyContent: 'center',
    alignItems: 'center',
    paddingHorizontal: 30,
    zIndex: 5, // 降低层级，防止遮挡底部按钮
  },
  text: {
    fontSize: 22,
    lineHeight: 32,
    color: '#5E2A28',
    fontWeight: '700',
    textAlign: 'center',
  },
  textEnglish: {
    fontFamily: 'STIXTwoText',
    // 英文字体观感更细一点，避免过粗
    fontWeight: '600',
  },
  sceneryCard: {
    // 风景模式下稍微收窄文案宽度，增加呼吸感
    paddingHorizontal: 50,
  },
  sceneryText: {
    color: '#FFFFFF',
    textShadowColor: 'rgba(0, 0, 0, 0.5)',
    textShadowOffset: { width: 0, height: 1 },
    textShadowRadius: 4,
  },
  actions: {
    position: 'absolute',
    bottom: SCREEN_HEIGHT * 0.16,
    left: 0,
    right: 0,
    flexDirection: 'row',
    justifyContent: 'center',
    zIndex: 20, // 提升层级，确保在最顶层可点击
  },
  reactionButton: {
    alignItems: 'center',
    justifyContent: 'center',
  },
  reactionInner: {
    alignItems: 'center',
    justifyContent: 'center',
  },
});
