import React, { useState, useRef, useEffect, useCallback, memo } from 'react'
import {
    View,
    Text,
    StyleSheet,
    Dimensions,
    FlatList,
    Pressable,
    StatusBar as RNStatusBar,
    Platform,
} from 'react-native'
import { StatusBar } from 'expo-status-bar'
import { SafeAreaView } from 'react-native-safe-area-context'
import { Image, ImageLoadEventData } from 'expo-image'
import { useTranslation } from 'react-i18next'

import { SameStyleIcon, WhiteStarIcon } from '@/components/icon'
import { useRouter } from 'expo-router'
import { useTemplates, type TemplateDetail } from '@/hooks'
import LoadingState from '@/components/LoadingState'
import ErrorState from '@/components/ErrorState'
import PaginationLoader from '@/components/PaginationLoader'

const { width: screenWidth, height: screenHeight } = Dimensions.get('window')
const TAB_BAR_HEIGHT = 83

// 检查 URL 是否为视频格式
const isVideoUrl = (url: string): boolean => {
    const videoExtensions = ['.mp4', '.webm', '.mov', '.avi', '.mkv', '.m3u8']
    return videoExtensions.some(ext => url.toLowerCase().endsWith(ext))
}

// 统一的布局组件
const Layout = ({ children }: { children: React.ReactNode }) => (
    <SafeAreaView style={styles.container} edges={[]}>
        <StatusBar style="light" />
        <RNStatusBar barStyle="light-content" />
        {children}
    </SafeAreaView>
)

const EmptyState = () => (
    <Layout>
        <View style={styles.centerContainer}>
            <Text style={styles.messageText}>暂无视频模板</Text>
        </View>
    </Layout>
)

// 计算图片显示尺寸
const calculateImageSize = (
    imageSize: { width: number; height: number } | null,
    videoHeight: number
) => {
    if (!imageSize) return { width: screenWidth, height: videoHeight }

    const imageAspectRatio = imageSize.width / imageSize.height
    const screenAspectRatio = screenWidth / videoHeight

    return imageAspectRatio > screenAspectRatio
        ? { width: screenWidth, height: screenWidth / imageAspectRatio }
        : { width: videoHeight * imageAspectRatio, height: videoHeight }
}

export const VideoItem = memo(({ item, videoHeight }: { item: TemplateDetail; videoHeight: number }) => {
    const { t } = useTranslation()
    const router = useRouter()
    const [imageSize, setImageSize] = useState<{ width: number; height: number } | null>(null)

    const handleImageLoad = useCallback((event: ImageLoadEventData) => {
        const { source } = event
        if (source?.width && source?.height) {
            setImageSize({ width: source.width, height: source.height })
        }
    }, [])

    const handlePress = useCallback(() => {
        router.push({
            pathname: '/generateVideo' as any,
            params: { templateId: item.id },
        })
    }, [router, item.id])

    const imageStyle = calculateImageSize(imageSize, videoHeight)

    // 优先使用 WebP 格式（支持动画），回退到普通预览图
    const displayUrl = item.webpHighPreviewUrl || item.webpPreviewUrl || item.previewUrl

    return (
        <View style={[styles.videoContainer, { height: videoHeight }]}>
            <View style={styles.videoWrapper}>
                {displayUrl && (
                    <Image
                        source={{ uri: displayUrl }}
                        style={imageStyle}
                        contentFit="contain"
                        onLoad={handleImageLoad}
                    />
                )}
                <View style={styles.thumbnailContainer}>
                    <Image source={{ uri: item.coverImageUrl }} style={styles.thumbnail} contentFit="cover" />
                </View>
            </View>
            <Pressable style={styles.actionButtonLeft}>
                <WhiteStarIcon />
                <Text style={styles.actionButtonTextTitle}>{item.title}</Text>
            </Pressable>
            <Pressable style={styles.actionButtonRight} onPress={handlePress}>
                <SameStyleIcon />
                <Text style={styles.actionButtonText}>{t('video.makeSame')}</Text>
            </Pressable>
        </View>
    )
})

export default function VideoScreen() {
    const flatListRef = useRef<FlatList>(null)
    const videoHeight = screenHeight - TAB_BAR_HEIGHT
    const PAGE_SIZE = 10 // 每页10个数据
    const { templates, loading, error, execute, refetch, loadMore, hasMore } = useTemplates({
        sortBy: 'likeCount',
        sortOrder: 'desc',
        page: 1,
        limit: PAGE_SIZE,
    })

    useEffect(() => {
        execute()
    }, [execute])

    const handleRefresh = useCallback(async () => {
        await refetch()
    }, [refetch])

    const handleLoadMore = useCallback(() => {
        console.log('onEndReached triggered', { hasMore, loading, templatesLength: templates.length })
        if (!hasMore || loading) {
            console.log('LoadMore blocked', { hasMore, loading })
            return
        }
        console.log('Loading more...')
        loadMore()
    }, [hasMore, loading, loadMore, templates.length])

    const renderItem = useCallback(({ item }: { item: TemplateDetail }) => (
        <VideoItem item={item} videoHeight={videoHeight} />
    ), [videoHeight])

    const keyExtractor = useCallback((item: TemplateDetail) => item.id, [])

    const getItemLayout = useCallback((_: any, index: number) => ({
        length: videoHeight,
        offset: videoHeight * index,
        index,
    }), [videoHeight])

    // 过滤掉没有可用预览的 item
    const filteredTemplates = templates.filter((item: TemplateDetail) => {
        // 优先使用 WebP 格式（支持动画），回退到普通预览图
        const displayUrl = item.webpHighPreviewUrl || item.webpPreviewUrl || item.previewUrl

        // 只检查最终要显示的 URL 是否为视频格式
        const isDisplayVideo = displayUrl && isVideoUrl(displayUrl)

        // 有显示URL且不是视频格式才保留
        const shouldKeep = !!displayUrl && !isDisplayVideo

        console.log(`[VIDEO PAGE] Filtering ${item.title}:`, {
            webpHighPreviewUrl: item.webpHighPreviewUrl,
            webpPreviewUrl: item.webpPreviewUrl,
            previewUrl: item.previewUrl,
            displayUrl,
            isDisplayVideo,
            shouldKeep,
        })

        return shouldKeep
    })

    console.log('Video page state:', {
        templatesLength: templates.length,
        filteredTemplatesLength: filteredTemplates.length,
        loading,
        error,
        hasMore,
    })

    if (loading && templates.length === 0) {
        return (
            <Layout>
                <LoadingState color="#FFE500" message="加载中..." />
            </Layout>
        )
    }

    if (error && templates.length === 0) {
        return (
            <Layout>
                <ErrorState message="加载失败，请下拉刷新重试" onRetry={handleRefresh} />
            </Layout>
        )
    }

    if (!loading && filteredTemplates.length === 0) return <EmptyState />

    return (
        <Layout>
            <FlatList
                ref={flatListRef}
                data={filteredTemplates}
                renderItem={renderItem}
                keyExtractor={keyExtractor}
                getItemLayout={getItemLayout}
                pagingEnabled
                showsVerticalScrollIndicator={false}
                snapToInterval={videoHeight}
                snapToAlignment="start"
                decelerationRate="fast"
                onEndReached={handleLoadMore}
                onEndReachedThreshold={0.1}
                ListFooterComponent={loading ? <PaginationLoader color="#FFE500" /> : null}
                maxToRenderPerBatch={5}
                windowSize={7}
                initialNumToRender={3}
            />
        </Layout>
    )
}

const styles = StyleSheet.create({
    container: {
        flex: 1,
        backgroundColor: '#090A0B',
    },
    centerContainer: {
        flex: 1,
        alignItems: 'center',
        justifyContent: 'center',
        gap: 12,
    },
    messageText: {
        color: '#FFFFFF',
        fontSize: 14,
        textAlign: 'center',
    },
    videoContainer: {
        width: screenWidth,
        position: 'relative',
    },
    videoWrapper: {
        flex: 1,
        position: 'relative',
        alignItems: 'center',
        justifyContent: 'center',
    },
    thumbnailContainer: {
        position: 'absolute',
        left: 12,
        bottom: 80,
        width: 56,
        height: 56,
        borderRadius: 8,
        overflow: 'hidden',
        borderWidth: 2,
        borderColor: '#FFFFFF',
    },
    thumbnail: {
        width: '100%',
        height: '100%',
    },
    actionButtonLeft: {
        position: 'absolute',
        left: 12,
        bottom: 16,
        flexDirection: 'row',
        alignItems: 'center',
        gap: 4,
        paddingHorizontal: 6,
        paddingVertical: 8,
        backgroundColor: '#191B1F',
        borderRadius: 8,
        borderWidth: 1,
        borderColor: '#2F3134',
    },
    actionButtonRight: {
        position: 'absolute',
        right: 13,
        bottom: 13,
        flexDirection: 'column',
        alignItems: 'center',
    },
    actionButtonTextTitle: {
        color: '#F5F5F5',
        fontSize: 11,
    },
    actionButtonText: {
        color: '#CCCCCC',
        fontSize: 10,
        fontWeight: '500',
    },
})
