"use client";

import Image from "next/image";
import { useEffect, useMemo, useRef, useState } from "react";

type Slide = { src: string; alt?: string };

type Props = {
  slides: Slide[];
  className?: string;
  maxWidthClassName?: string;
  autoPlayMs?: number;
  imageHeightClassName?: string;
};

const PER_VIEW = 2;

export default function CaseImageSlider({
  slides,
  className = "",
  maxWidthClassName = "max-w-[700px]",
  autoPlayMs = 4500,
  imageHeightClassName = "h-[340px]",
}: Props) {
  const safeSlides = useMemo(() => slides.filter(Boolean), [slides]);

  const [page, setPage] = useState(0);
  const [dragging, setDragging] = useState(false);
  const [isHover, setIsHover] = useState(false);

  const startX = useRef(0);
  const deltaX = useRef(0);

  const pageCount = Math.ceil(safeSlides.length / PER_VIEW);
  const canSlide = pageCount > 1;

  const goTo = (nextPage: number) => {
    if (!canSlide) return;

    if (nextPage < 0) setPage(pageCount - 1);
    else if (nextPage >= pageCount) setPage(0);
    else setPage(nextPage);
  };

  const goNext = () => goTo(page + 1);
  const goPrev = () => goTo(page - 1);

  // ✅ 자동롤링 (hover 시 정지 포함)
  useEffect(() => {
    if (!canSlide || dragging || isHover) return;

    const timer = window.setInterval(() => {
      setPage((prev) => (prev + 1 >= pageCount ? 0 : prev + 1));
    }, autoPlayMs);

    return () => window.clearInterval(timer);
  }, [canSlide, dragging, isHover, pageCount, autoPlayMs]);

  // ✅ swipe
  const onPointerDown = (e: React.PointerEvent<HTMLDivElement>) => {
    if (!canSlide) return;

    setDragging(true);
    startX.current = e.clientX;
    deltaX.current = 0;
    e.currentTarget.setPointerCapture(e.pointerId);
  };

  const onPointerMove = (e: React.PointerEvent<HTMLDivElement>) => {
    if (!dragging) return;
    deltaX.current = e.clientX - startX.current;
  };

  const onPointerUp = () => {
    if (!dragging) return;

    setDragging(false);

    const threshold = 50;

    if (deltaX.current > threshold) goPrev();
    if (deltaX.current < -threshold) goNext();

    deltaX.current = 0;
  };

  if (!safeSlides.length) return null;

  return (
    <section className={className}>
      <div className={`mx-auto ${maxWidthClassName}`}>
        <div
          className="overflow-hidden select-none touch-pan-y cursor-grab active:cursor-grabbing"
          onMouseEnter={() => setIsHover(true)}   // ✅ hover 시작 → 정지
          onMouseLeave={() => setIsHover(false)}  // ✅ hover 끝 → 재시작
          onPointerDown={onPointerDown}
          onPointerMove={onPointerMove}
          onPointerUp={onPointerUp}
          onPointerCancel={onPointerUp}
        >
          <div
            className="flex transition-transform duration-500 ease-out"
            style={{
              transform: `translateX(-${page * 100}%)`,
            }}
          >
            {Array.from({ length: pageCount }).map((_, pageIndex) => {
              const pageSlides = safeSlides.slice(
                pageIndex * PER_VIEW,
                pageIndex * PER_VIEW + PER_VIEW
              );

              return (
                <div
                  key={pageIndex}
                  className="grid min-w-full grid-cols-2 gap-5"
                >
                  {pageSlides.map((slide, i) => (
                    <div
                      key={`${slide.src}-${i}`}
                      className={`relative ${imageHeightClassName} overflow-hidden rounded-[20px] bg-neutral-100`}
                    >
                      <Image
                        src={slide.src}
                        alt={slide.alt ?? `slide-${pageIndex * PER_VIEW + i + 1}`}
                        fill
                        className="object-cover"
                        sizes="(max-width: 768px) 50vw, 340px"
                        draggable={false}
                      />
                    </div>
                  ))}
                </div>
              );
            })}
          </div>
        </div>

        {/* 도트 */}
        {canSlide && (
          <div className="mt-5 flex items-center justify-center gap-[6px]">
            {Array.from({ length: pageCount }).map((_, i) => (
              <button
                key={i}
                type="button"
                onClick={() => setPage(i)}
                className={[
                  "h-[8px] w-[8px] rounded-full transition-all",
                  page === i ? "bg-[#18BCEB]" : "bg-[#D8DDE3]",
                ].join(" ")}
              />
            ))}
          </div>
        )}
      </div>
    </section>
  );
}