import { useState, useEffect, useCallback, memo } from 'react';
import { useParams, useNavigate } from 'react-router-dom';
import { motion, AnimatePresence } from 'framer-motion';
import { X, ChevronLeft, ChevronRight, Download } from 'lucide-react';
import { RowsPhotoAlbum } from 'react-photo-album';
import 'react-photo-album/rows.css';
import { getAlbumByName } from '../../../api/public/albums';

// 인디케이터 컴포넌트 - CSS transition 사용으로 JS 블로킹에 영향받지 않음
const LightboxIndicator = memo(function LightboxIndicator({ count, currentIndex, setLightbox }) {
    const translateX = -(currentIndex * 18) + 100 - 6;
    
    return (
        <div className="absolute bottom-6 left-1/2 -translate-x-1/2 overflow-hidden" style={{ width: '200px' }}>
            {/* 양옆 페이드 그라데이션 */}
            <div className="absolute inset-0 pointer-events-none z-10" style={{
                background: 'linear-gradient(to right, rgba(0,0,0,1) 0%, transparent 20%, transparent 80%, rgba(0,0,0,1) 100%)'
            }} />
            {/* 슬라이딩 컨테이너 - CSS transition으로 GPU 가속 */}
            <div 
                className="flex items-center gap-2 justify-center"
                style={{ 
                    width: `${count * 18}px`,
                    transform: `translateX(${translateX}px)`,
                    transition: 'transform 0.3s cubic-bezier(0.25, 0.46, 0.45, 0.94)'
                }}
            >
                {Array.from({ length: count }).map((_, i) => (
                    <button
                        key={i}
                        className={`rounded-full flex-shrink-0 transition-all duration-300 ${
                            i === currentIndex 
                                ? 'w-3 h-3 bg-white' 
                                : 'w-2.5 h-2.5 bg-white/40 hover:bg-white/60'
                        }`}
                        onClick={() => setLightbox(prev => ({ ...prev, index: i }))}
                    />
                ))}
            </div>
        </div>
    );
});

// CSS로 호버 효과 추가 + overflow 문제 수정 + 로드 애니메이션
const galleryStyles = `
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(20px) scale(0.95);
    }
    to {
        opacity: 1;
        transform: translateY(0) scale(1);
    }
}
.react-photo-album {
    overflow: visible !important;
}
.react-photo-album--row {
    overflow: visible !important;
}
.react-photo-album--photo {
    transition: transform 0.3s ease, filter 0.3s ease !important;
    cursor: pointer;
    overflow: visible !important;
}
.react-photo-album--photo:hover {
    transform: scale(1.05);
    filter: brightness(0.9);
    z-index: 10;
}
`;

function AlbumGallery() {
    const { name } = useParams();
    const navigate = useNavigate();
    const [album, setAlbum] = useState(null);
    const [photos, setPhotos] = useState([]);
    const [loading, setLoading] = useState(true);
    const [lightbox, setLightbox] = useState({ open: false, index: 0 });
    const [imageLoaded, setImageLoaded] = useState(false);
    const [slideDirection, setSlideDirection] = useState(0);
    const [preloadedImages] = useState(() => new Set()); // 프리로드된 이미지 URL 추적

    useEffect(() => {
        getAlbumByName(name)
            .then(data => {
                setAlbum(data);
                const allPhotos = [];
                
                if (data.conceptPhotos && typeof data.conceptPhotos === 'object') {
                    Object.entries(data.conceptPhotos).forEach(([concept, photos]) => {
                        photos.forEach(p => allPhotos.push({ 
                            // API에서 직접 제공하는 URL 및 크기 정보 사용
                            mediumUrl: p.medium_url,
                            originalUrl: p.original_url,
                            width: p.width || 800,
                            height: p.height || 1200,
                            title: concept,
                            members: p.members ? p.members.split(', ') : []
                        }));
                    });
                }
                
                setPhotos(allPhotos);
                setLoading(false);
            })
            .catch(error => {
                console.error('앨범 데이터 로드 오류:', error);
                setLoading(false);
            });
    }, [name]);

    // 라이트박스 열기
    const openLightbox = (index) => {
        setImageLoaded(false);
        setLightbox({ open: true, index });
    };

    // 라이트박스 닫기
    const closeLightbox = useCallback(() => {
        setLightbox(prev => ({ ...prev, open: false }));
    }, []);

    // 라이트박스 열릴 때 body 스크롤 숨기기
    useEffect(() => {
        if (lightbox.open) {
            document.documentElement.style.overflow = 'hidden';
            document.body.style.overflow = 'hidden';
        } else {
            document.documentElement.style.overflow = '';
            document.body.style.overflow = '';
        }
        return () => {
            document.documentElement.style.overflow = '';
            document.body.style.overflow = '';
        };
    }, [lightbox.open]);

    // 이전/다음 이미지
    const goToPrev = useCallback(() => {
        if (photos.length <= 1) return;
        setImageLoaded(false);
        setSlideDirection(-1);
        setLightbox(prev => ({
            ...prev,
            index: (prev.index - 1 + photos.length) % photos.length
        }));
    }, [photos.length]);

    const goToNext = useCallback(() => {
        if (photos.length <= 1) return;
        setImageLoaded(false);
        setSlideDirection(1);
        setLightbox(prev => ({
            ...prev,
            index: (prev.index + 1) % photos.length
        }));
    }, [photos.length]);

    // 다운로드
    const downloadImage = useCallback(async () => {
        const photo = photos[lightbox.index];
        if (!photo) return;
        
        try {
            const response = await fetch(photo.originalUrl);
            const blob = await response.blob();
            const url = window.URL.createObjectURL(blob);
            const link = document.createElement('a');
            link.href = url;
            link.download = `fromis9_${album?.title || 'photo'}_${String(lightbox.index + 1).padStart(2, '0')}.webp`;
            document.body.appendChild(link);
            link.click();
            document.body.removeChild(link);
            window.URL.revokeObjectURL(url);
        } catch (error) {
            console.error('다운로드 오류:', error);
        }
    }, [photos, lightbox.index, album?.title]);

    // 키보드 이벤트
    useEffect(() => {
        if (!lightbox.open) return;

        const handleKeyDown = (e) => {
            switch (e.key) {
                case 'ArrowLeft': goToPrev(); break;
                case 'ArrowRight': goToNext(); break;
                case 'Escape': closeLightbox(); break;
                default: break;
            }
        };

        window.addEventListener('keydown', handleKeyDown);
        return () => window.removeEventListener('keydown', handleKeyDown);
    }, [lightbox.open, goToPrev, goToNext, closeLightbox]);

    // 프리로딩 (이전/다음 2개씩) - 백그라운드에서 프리로드만
    useEffect(() => {
        if (!lightbox.open || photos.length <= 1) return;
        
        // 양옆 이미지 프리로드
        const indicesToPreload = [];
        for (let offset = -2; offset <= 2; offset++) {
            if (offset === 0) continue;
            const idx = (lightbox.index + offset + photos.length) % photos.length;
            indicesToPreload.push(idx);
        }
        
        indicesToPreload.forEach(idx => {
            const url = photos[idx].originalUrl;
            if (preloadedImages.has(url)) return;
            
            const img = new Image();
            img.onload = () => preloadedImages.add(url);
            img.src = url;
        });
    }, [lightbox.open, lightbox.index, photos, preloadedImages]);

    if (loading) {
        return (
            <motion.div 
                initial={{ opacity: 0 }}
                animate={{ opacity: 1 }}
                className="py-16 flex justify-center items-center min-h-[60vh]"
            >
                <div className="animate-spin rounded-full h-12 w-12 border-4 border-primary border-t-transparent"></div>
            </motion.div>
        );
    }

    return (
        <>
        <motion.div 
            initial={{ opacity: 0 }}
            animate={{ opacity: 1 }}
            transition={{ duration: 0.3 }}
            className="py-16"
        >
            <div className="px-24">
                {/* 브레드크럼 스타일 헤더 */}
                <div className="mb-8">
                    <div className="flex items-center gap-2 text-sm text-gray-500 mb-2">
                        <button 
                            onClick={() => navigate('/album')}
                            className="hover:text-primary transition-colors"
                        >
                            앨범
                        </button>
                        <span>/</span>
                        <button 
                            onClick={() => navigate(`/album/${name}`)}
                            className="hover:text-primary transition-colors"
                        >
                            {album?.title}
                        </button>
                        <span>/</span>
                        <span className="text-gray-700">컨셉 포토</span>
                    </div>
                    <h1 className="text-3xl font-bold">컨셉 포토</h1>
                    <p className="text-gray-500 mt-1">{photos.length}장의 사진</p>
                </div>

                {/* CSS 스타일 주입 */}
                <style>{galleryStyles}</style>
                
                {/* Justified 갤러리 - 동적 비율 + 호버 */}
                <RowsPhotoAlbum
                    photos={photos.map((photo, idx) => ({
                        src: photo.mediumUrl,
                        width: photo.width || 800,
                        height: photo.height || 1200,
                        key: idx.toString()
                    }))}
                    targetRowHeight={280}
                    spacing={16}
                    rowConstraints={{ singleRowMaxHeight: 400, minPhotos: 1 }}
                    onClick={({ index }) => openLightbox(index)}
                    componentsProps={{
                        image: { 
                            loading: 'lazy',
                            style: { borderRadius: '12px' }
                        }
                    }}
                />
            </div>
        </motion.div>

        {/* 라이트박스 */}
        <AnimatePresence>
        {lightbox.open && (
            <motion.div 
                initial={{ opacity: 0 }}
                animate={{ opacity: 1 }}
                exit={{ opacity: 0 }}
                transition={{ duration: 0.2 }}
                className="fixed inset-0 bg-black/95 z-50 overflow-scroll lightbox-no-scrollbar"
                style={{ scrollbarWidth: 'none', msOverflowStyle: 'none' }}
            >
                {/* 내부 컨테이너 - min-width, min-height 적용 (화면 줄여도 크기 유지, 스크롤) */}
                <div className="min-w-[1400px] min-h-[1200px] w-full h-full relative flex items-center justify-center">
                    {/* 상단 버튼들 */}
                    <div className="absolute top-6 right-6 flex gap-3 z-10">
                        <button 
                            className="text-white/70 hover:text-white transition-colors"
                            onClick={downloadImage}
                        >
                            <Download size={28} />
                        </button>
                        <button 
                            className="text-white/70 hover:text-white transition-colors"
                            onClick={closeLightbox}
                        >
                            <X size={32} />
                        </button>
                    </div>

                    {/* 카운터 */}
                    <div className="absolute top-6 left-6 text-white/70 text-sm z-10">
                        {lightbox.index + 1} / {photos.length}
                    </div>

                    {/* 이전 버튼 - margin으로 이미지와 간격 */}
                    {photos.length > 1 && (
                        <button 
                            className="absolute left-6 p-2 text-white/70 hover:text-white transition-colors z-10"
                            onClick={goToPrev}
                        >
                            <ChevronLeft size={48} />
                        </button>
                    )}

                    {/* 로딩 스피너 */}
                    {!imageLoaded && (
                        <div className="absolute inset-0 flex items-center justify-center">
                            <div className="animate-spin rounded-full h-12 w-12 border-4 border-white border-t-transparent"></div>
                        </div>
                    )}

                    {/* 이미지 + 컨셉 정보 */}
                    <div className="flex flex-col items-center mx-24">
                        <motion.img 
                            key={lightbox.index}
                            src={photos[lightbox.index]?.originalUrl}
                            alt="확대 이미지"
                            className={`max-w-[1100px] max-h-[900px] object-contain transition-opacity duration-200 ${imageLoaded ? 'opacity-100' : 'opacity-0'}`}
                            onLoad={() => setImageLoaded(true)}
                            initial={{ x: slideDirection * 100 }}
                            animate={{ x: 0 }}
                            transition={{ duration: 0.25, ease: 'easeOut' }}
                        />
                        {/* 컨셉 정보 + 멤버 */}
                        {imageLoaded && (
                            (() => {
                                const title = photos[lightbox.index]?.title;
                                const hasValidTitle = title && title.trim() && title !== 'Default';
                                const members = photos[lightbox.index]?.members;
                                const hasMembers = members && String(members).trim();
                                
                                if (!hasValidTitle && !hasMembers) return null;
                                
                                return (
                                    <div className="mt-6 flex flex-col items-center gap-2">
                                        {hasValidTitle && (
                                            <span className="px-4 py-2 bg-white/10 backdrop-blur-sm rounded-full text-white font-medium text-base">
                                                {title}
                                            </span>
                                        )}
                                        {hasMembers && (
                                            <div className="flex items-center gap-2">
                                                {String(members).split(',').map((member, idx) => (
                                                    <span key={idx} className="px-3 py-1.5 bg-primary/80 rounded-full text-white text-sm">
                                                        {member.trim()}
                                                    </span>
                                                ))}
                                            </div>
                                        )}
                                    </div>
                                );
                            })()
                        )}
                    </div>

                    {/* 다음 버튼 - margin으로 이미지와 간격 */}
                    {photos.length > 1 && (
                        <button 
                            className="absolute right-6 p-2 text-white/70 hover:text-white transition-colors z-10"
                            onClick={goToNext}
                        >
                            <ChevronRight size={48} />
                        </button>
                    )}

                    {/* 하단 점 인디케이터 - memo 컴포넌트로 분리 */}
                    <LightboxIndicator
                        count={photos.length}
                        currentIndex={lightbox.index}
                        setLightbox={setLightbox}
                    />
                </div>
            </motion.div>
        )}
        </AnimatePresence>
        </>
    );
}

export default AlbumGallery;