/**
 * Component: Similar Series Row
 * Documentation: documentation/frontend/components.md
 *
 * Horizontal scrollable carousel of similar series cards.
 * Desktop: left/right nav arrows. Mobile: drag-to-scroll.
 * Each card navigates to the series detail page.
 */

'use client';

import React, { useRef, useState, useEffect, useCallback } from 'react';
import Image from 'next/image';
import Link from 'next/link';
import { SimilarSeries } from '@/lib/hooks/useSeries';

interface SimilarSeriesRowProps {
  series: SimilarSeries[];
  currentSeriesTitle?: string;
  squareCovers?: boolean;
}

export function SimilarSeriesRow({ series, currentSeriesTitle, squareCovers = false }: SimilarSeriesRowProps) {
  const scrollRef = useRef<HTMLDivElement>(null);
  const [canScrollLeft, setCanScrollLeft] = useState(false);
  const [canScrollRight, setCanScrollRight] = useState(false);

  const checkScroll = useCallback(() => {
    const el = scrollRef.current;
    if (!el) return;
    setCanScrollLeft(el.scrollLeft > 4);
    setCanScrollRight(el.scrollLeft < el.scrollWidth - el.clientWidth - 4);
  }, []);

  useEffect(() => {
    checkScroll();
    const el = scrollRef.current;
    if (!el) return;
    el.addEventListener('scroll', checkScroll, { passive: true });
    const observer = new ResizeObserver(checkScroll);
    observer.observe(el);
    return () => {
      el.removeEventListener('scroll', checkScroll);
      observer.disconnect();
    };
  }, [checkScroll, series]);

  const scroll = (direction: 'left' | 'right') => {
    const el = scrollRef.current;
    if (!el) return;
    const scrollAmount = el.clientWidth * 0.7;
    el.scrollBy({
      left: direction === 'left' ? -scrollAmount : scrollAmount,
      behavior: 'smooth',
    });
  };

  if (series.length === 0) return null;

  return (
    <div className="space-y-3">
      <div className="flex items-center gap-3">
        <div className="w-1 h-6 bg-gradient-to-b from-emerald-500 to-teal-500 rounded-full" />
        <h2 className="text-xl sm:text-2xl font-bold text-gray-900 dark:text-gray-100">
          Similar Series
        </h2>
        <span className="text-sm text-gray-500 dark:text-gray-400">
          ({series.length})
        </span>
      </div>

      <div className="relative group">
        {/* Left arrow */}
        {canScrollLeft && (
          <button
            onClick={() => scroll('left')}
            className="hidden md:flex absolute left-0 top-1/2 -translate-y-1/2 -translate-x-3 z-10 w-10 h-10 bg-white dark:bg-gray-800 rounded-full shadow-lg items-center justify-center text-gray-600 dark:text-gray-300 hover:bg-gray-50 dark:hover:bg-gray-700 transition-all opacity-0 group-hover:opacity-100"
            aria-label="Scroll left"
          >
            <svg className="w-5 h-5" fill="none" stroke="currentColor" viewBox="0 0 24 24">
              <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M15 19l-7-7 7-7" />
            </svg>
          </button>
        )}

        {/* Scrollable row */}
        <div
          ref={scrollRef}
          className="flex gap-4 sm:gap-5 overflow-x-auto scrollbar-hide pb-2 scroll-smooth"
          style={{ scrollbarWidth: 'none', msOverflowStyle: 'none' }}
        >
          {series.map(s => (
            <Link
              key={s.asin}
              href={`/series/${s.asin}${currentSeriesTitle ? `?from=${encodeURIComponent(currentSeriesTitle)}` : ''}`}
              className="flex-shrink-0 w-20 sm:w-24 group/card outline-none focus-visible:ring-2 focus-visible:ring-emerald-500 rounded-xl"
            >
              {/* Cover */}
              <div className={`relative w-20 ${squareCovers ? 'h-20 sm:w-24 sm:h-24' : 'h-[120px] sm:w-24 sm:h-36'} rounded-lg overflow-hidden shadow-md shadow-black/15 dark:shadow-black/30 group-hover/card:shadow-lg group-hover/card:scale-[1.04] group-hover/card:-translate-y-0.5 transition-all duration-300`}>
                <Image
                  src={s.coverArtUrl || '/placeholder_cover.svg'}
                  alt=""
                  fill
                  className="object-cover"
                  sizes="96px"
                  onError={(e) => { (e.target as HTMLImageElement).src = '/placeholder_cover.svg'; }}
                />
              </div>

              {/* Title */}
              <p className="mt-2 text-xs sm:text-sm font-medium text-center text-gray-700 dark:text-gray-300 line-clamp-2 group-hover/card:text-emerald-600 dark:group-hover/card:text-emerald-400 transition-colors">
                {s.title}
              </p>
            </Link>
          ))}
        </div>

        {/* Right arrow */}
        {canScrollRight && (
          <button
            onClick={() => scroll('right')}
            className="hidden md:flex absolute right-0 top-1/2 -translate-y-1/2 translate-x-3 z-10 w-10 h-10 bg-white dark:bg-gray-800 rounded-full shadow-lg items-center justify-center text-gray-600 dark:text-gray-300 hover:bg-gray-50 dark:hover:bg-gray-700 transition-all opacity-0 group-hover:opacity-100"
            aria-label="Scroll right"
          >
            <svg className="w-5 h-5" fill="none" stroke="currentColor" viewBox="0 0 24 24">
              <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M9 5l7 7-7 7" />
            </svg>
          </button>
        )}

        {/* Fade edges */}
        {canScrollLeft && (
          <div className="hidden md:block absolute left-0 top-0 bottom-2 w-8 bg-gradient-to-r from-white dark:from-gray-900 to-transparent pointer-events-none z-[5]" />
        )}
        {canScrollRight && (
          <div className="hidden md:block absolute right-0 top-0 bottom-2 w-8 bg-gradient-to-l from-white dark:from-gray-900 to-transparent pointer-events-none z-[5]" />
        )}
      </div>
    </div>
  );
}

export function SimilarSeriesSkeleton({ squareCovers = false }: { squareCovers?: boolean }) {
  return (
    <div className="space-y-3 animate-pulse">
      <div className="flex items-center gap-3">
        <div className="w-1 h-6 bg-gray-300 dark:bg-gray-600 rounded-full" />
        <div className="h-7 w-40 bg-gray-200 dark:bg-gray-700 rounded-lg" />
      </div>
      <div className="flex gap-4 sm:gap-5 overflow-hidden">
        {Array.from({ length: 8 }).map((_, i) => (
          <div key={i} className="flex-shrink-0 w-20 sm:w-24" style={{ animationDelay: `${i * 50}ms` }}>
            <div className={`w-20 ${squareCovers ? 'h-20 sm:w-24 sm:h-24' : 'h-[120px] sm:w-24 sm:h-36'} rounded-lg bg-gradient-to-br from-gray-200 to-gray-300 dark:from-gray-700 dark:to-gray-800 relative overflow-hidden`}>
              <div className="absolute inset-0 -translate-x-full animate-[shimmer_2s_infinite] bg-gradient-to-r from-transparent via-white/20 to-transparent" />
            </div>
            <div className="mt-2 h-3 bg-gray-200 dark:bg-gray-700 rounded w-4/5 mx-auto" />
          </div>
        ))}
      </div>
    </div>
  );
}