import { GlassView, isLiquidGlassAvailable } from 'expo-glass-effect';
import { LinearGradient } from 'expo-linear-gradient';
import { useRouter } from 'expo-router';
import { StatusBar } from 'expo-status-bar';
import React, { useCallback, useEffect, useRef, useState } from 'react';
import {
  Animated,
  Easing,
  FlatList,
  Image,
  ImageSourcePropType,
  NativeScrollEvent,
  NativeSyntheticEvent,
  Pressable,
  StyleSheet,
  Text,
  TouchableOpacity,
  View,
  useWindowDimensions,
} from 'react-native';
import { SafeAreaView } from 'react-native-safe-area-context';

import { palette } from '@/constants/Colors';
import { ROUTES } from '@/constants/Routes';
import { STORAGE_KEYS } from '@/services/api';
import AsyncStorage from '@/utils/kvStore';

const ONBOARDING_COMPLETED_KEY = STORAGE_KEYS.onboardingCompleted;

type OnboardingSlide = {
  key: string;
  title: string;
  description: string;
  image: ImageSourcePropType;
};

const SLIDES: OnboardingSlide[] = [
  {
    key: 'statistics',
    title: '全方位健康数据追踪',
    description: '实时监测步数、心率、睡眠等多维度健康指标，助你全面了解身体状况。',
    image: require('@/assets/images/onboarding/statistic.png'),
  },
  {
    key: 'insights',
    title: '科学轻断食计划',
    description: '个性化断食方案，智能提醒与进度追踪，助你改善代谢，科学控脂。',
    image: require('@/assets/images/onboarding/fasting.jpg'),
  },
  {
    key: 'support',
    title: '健康挑战赛',
    description: '参与精选健康挑战，与好友一起打卡，保持每日运动动力。',
    image: require('@/assets/images/onboarding/challange.jpg'),
  },
];

export default function OnboardingScreen() {
  const router = useRouter();
  const { width } = useWindowDimensions();
  const [currentIndex, setCurrentIndex] = useState(0);
  const listRef = useRef<FlatList<OnboardingSlide>>(null);
  const indicatorAnim = useRef(SLIDES.map((_, index) => new Animated.Value(index === 0 ? 1 : 0))).current;
  const glassAvailable = isLiquidGlassAvailable();

  useEffect(() => {
    indicatorAnim.forEach((anim, index) => {
      Animated.timing(anim, {
        toValue: index === currentIndex ? 1 : 0,
        duration: 250,
        easing: Easing.out(Easing.quad),
        useNativeDriver: false,
      }).start();
    });
  }, [currentIndex, indicatorAnim]);

  const updateIndexFromScroll = useCallback(
    (event: NativeSyntheticEvent<NativeScrollEvent>) => {
      const offsetX = event.nativeEvent.contentOffset.x;
      const nextIndex = Math.round(offsetX / width);
      if (!Number.isNaN(nextIndex) && nextIndex !== currentIndex) {
        setCurrentIndex(nextIndex);
      }
    },
    [currentIndex, width],
  );

  const completeOnboarding = useCallback(async () => {
    await AsyncStorage.setItem(ONBOARDING_COMPLETED_KEY, 'true');
    router.replace(ROUTES.TAB_STATISTICS);
  }, [router]);

  const handleSkip = useCallback(() => {
    completeOnboarding();
  }, [completeOnboarding]);

  const handleNext = useCallback(() => {
    if (currentIndex < SLIDES.length - 1) {
      const nextIndex = currentIndex + 1;
      listRef.current?.scrollToOffset({ offset: nextIndex * width, animated: true });
      setCurrentIndex(nextIndex);
      return;
    }
    completeOnboarding();
  }, [completeOnboarding, currentIndex, width]);

  const renderSlide = useCallback(
    ({ item }: { item: OnboardingSlide }) => (
      <View style={[styles.slide, { width }]}>
        <Image source={item.image} style={styles.slideImage} />
      </View>
    ),
    [width],
  );

  const currentSlide = SLIDES[currentIndex];

  return (
    <SafeAreaView style={styles.safeArea}>
      <StatusBar style="dark" />
      <View style={styles.header}>
        <Pressable onPress={handleSkip} hitSlop={12}>
          <Text style={styles.skipText}>跳过</Text>
        </Pressable>
      </View>

      <View style={styles.carouselContainer}>
        <FlatList
          ref={listRef}
          data={SLIDES}
          horizontal
          keyExtractor={(item) => item.key}
          pagingEnabled
          decelerationRate="fast"
          bounces={false}
          showsHorizontalScrollIndicator={false}
          renderItem={renderSlide}
          onMomentumScrollEnd={updateIndexFromScroll}
        />
      </View>
      <View style={styles.body}>
        <View style={styles.indicatorContainer}>
          {SLIDES.map((slide, index) => {
            const animatedStyle = {
              width: indicatorAnim[index].interpolate({
                inputRange: [0, 1],
                outputRange: [8, 24],
              }),
              backgroundColor: indicatorAnim[index].interpolate({
                inputRange: [0, 1],
                outputRange: ['#D8D8D8', '#0066FF'],
              }),
            };
            return <Animated.View key={slide.key} style={[styles.indicatorDot, animatedStyle]} />;
          })}
        </View>

        <View style={styles.textContainer}>
          <Text style={styles.title}>{currentSlide.title}</Text>
          <Text style={styles.description}>{currentSlide.description}</Text>
        </View>

        <TouchableOpacity style={styles.primaryButtonWrapper} onPress={handleNext} activeOpacity={0.9}>
          {glassAvailable ? (
            <GlassView
              style={styles.primaryButtonGlass}
              glassEffectStyle="regular"
              tintColor="rgba(122, 90, 248, 0.25)"
              isInteractive
            >
              <LinearGradient
                colors={[palette.purple[600], palette.purple[400]]}
                start={{ x: 0, y: 0 }}
                end={{ x: 1, y: 1 }}
                style={styles.primaryButtonGradient}
              />
              <Text style={styles.primaryButtonText}>
                {currentIndex === SLIDES.length - 1 ? '开始使用' : '下一步'}
              </Text>
            </GlassView>
          ) : (
            <LinearGradient
              colors={[palette.purple[600], palette.purple[400]]}
              start={{ x: 0, y: 0 }}
              end={{ x: 1, y: 1 }}
              style={[styles.primaryButtonGlass, styles.primaryButtonFallback]}
            >
              <Text style={styles.primaryButtonText}>{currentIndex === SLIDES.length - 1 ? '开始使用' : '下一步'}</Text>
            </LinearGradient>
          )}
        </TouchableOpacity>
      </View>
    </SafeAreaView>
  );
}

const styles = StyleSheet.create({
  safeArea: {
    flex: 1,
    backgroundColor: '#FFFFFF',
  },
  header: {
    alignItems: 'flex-end',
    paddingHorizontal: 24,
    paddingTop: 12,
  },
  skipText: {
    fontSize: 16,
    color: '#666C7A',
    fontWeight: '500',
  },
  carouselContainer: {
    flex: 1,
    marginTop: 20,
    alignItems: 'center',
    justifyContent: 'center',
  },
  slide: {
    height: 'auto',
    justifyContent: 'center',
    alignItems: 'center',
  },
  slideImage: {
    width: '85%',
    height: '100%',
    resizeMode: 'cover',
  },
  body: {
    paddingHorizontal: 24,
    paddingBottom: 24,
  },
  indicatorContainer: {
    flexDirection: 'row',
    justifyContent: 'center',
    alignItems: 'center',
    marginVertical: 24,
    gap: 10,
  },
  indicatorDot: {
    height: 8,
    borderRadius: 4,
  },
  textContainer: {
    alignItems: 'center',
    marginBottom: 32,
  },
  title: {
    fontSize: 24,
    color: '#222532',
    fontWeight: '700',
    textAlign: 'center',
    marginBottom: 12,
  },
  description: {
    fontSize: 16,
    color: '#5C6373',
    textAlign: 'center',
    lineHeight: 22,
    paddingHorizontal: 8,
  },
  primaryButtonWrapper: {
    marginTop: 16,
  },
  primaryButtonGlass: {
    borderRadius: 24,
    paddingVertical: 16,
    alignItems: 'center',
    justifyContent: 'center',
    overflow: 'hidden',
    shadowColor: palette.purple[600],
    shadowOffset: { width: 0, height: 8 },
    shadowOpacity: 0.35,
    shadowRadius: 16,
    elevation: 6,
  },
  primaryButtonFallback: {
    borderRadius: 24,
  },
  primaryButtonGradient: {
    ...StyleSheet.absoluteFillObject,
  },
  primaryButtonText: {
    color: '#FFFFFF',
    fontSize: 18,
    fontWeight: '600',
  },
});