"use client";

import React, { useCallback, useEffect, useMemo, useRef, useState } from "react";

type CardItem = {
  id: number;
  region: string;
  name: string;
  address: string;
  image: string;
};

interface HorizontalCardScrollerProps {
  items: CardItem[];
}

export default function HorizontalCardScroller({ items }: HorizontalCardScrollerProps) {
  const scrollRef = useRef<HTMLDivElement | null>(null);
  const trackRef = useRef<HTMLDivElement | null>(null);
  const [thumbWidth, setThumbWidth] = useState<number>(60);
  const [thumbLeft, setThumbLeft] = useState<number>(0);
  const [isDragging, setIsDragging] = useState<boolean>(false);
  const dragOffsetRef = useRef<number>(0);

  const CARD_WIDTH = 384;
  const CARD_GAP = 16; // Tailwind gap-4
  const SCROLL_STEP = CARD_WIDTH + CARD_GAP;

  const updateThumb = useCallback(() => {
    const scroller = scrollRef.current;
    const track = trackRef.current;
    if (!scroller || !track) return;

    const { scrollWidth, clientWidth, scrollLeft } = scroller;
    const trackWidth = track.clientWidth;
    if (scrollWidth <= 0 || trackWidth <= 0) return;

    const ratioVisible = Math.max(0, Math.min(1, clientWidth / scrollWidth));
    const newThumbWidth = Math.max(40, Math.round(trackWidth * ratioVisible));
    const maxThumbLeft = Math.max(0, trackWidth - newThumbWidth);
    const ratioPosition = scrollWidth === clientWidth ? 0 : scrollLeft / (scrollWidth - clientWidth);
    const newThumbLeft = Math.round(maxThumbLeft * ratioPosition);

    setThumbWidth(newThumbWidth);
    setThumbLeft(newThumbLeft);
  }, []);

  useEffect(() => {
    updateThumb();
    const el = scrollRef.current;
    if (!el) return;
    const onScroll = () => updateThumb();
    const onResize = () => updateThumb();
    el.addEventListener("scroll", onScroll);
    window.addEventListener("resize", onResize);
    return () => {
      el.removeEventListener("scroll", onScroll);
      window.removeEventListener("resize", onResize);
    };
  }, [updateThumb]);

  useEffect(() => {
    if (!isDragging) return;
    const onMove = (e: MouseEvent) => {
      const el = scrollRef.current;
      const track = trackRef.current;
      if (!el || !track) return;
      const rect = track.getBoundingClientRect();
      let x = e.clientX - rect.left - dragOffsetRef.current;
      x = Math.max(0, Math.min(x, rect.width - thumbWidth));
      setThumbLeft(x);
      const ratio = rect.width === thumbWidth ? 0 : x / (rect.width - thumbWidth);
      const targetScrollLeft = ratio * (el.scrollWidth - el.clientWidth);
      el.scrollLeft = targetScrollLeft;
    };
    const onUp = () => setIsDragging(false);
    window.addEventListener("mousemove", onMove);
    window.addEventListener("mouseup", onUp);
    return () => {
      window.removeEventListener("mousemove", onMove);
      window.removeEventListener("mouseup", onUp);
    };
  }, [isDragging, thumbWidth]);

  const handleThumbMouseDown = (e: React.MouseEvent<HTMLDivElement>) => {
    const rect = trackRef.current?.getBoundingClientRect();
    if (!rect) return;
    dragOffsetRef.current = e.clientX - rect.left - thumbLeft;
    setIsDragging(true);
    e.preventDefault();
  };

  const scrollByStep = (direction: 1 | -1) => {
    const el = scrollRef.current;
    if (!el) return;
    el.scrollBy({ left: direction * SCROLL_STEP, behavior: "smooth" });
  };

  return (
    <div className="relative h-[400px]">
      <div ref={scrollRef} className="scrollbar-hidden h-full overflow-x-auto overflow-y-hidden">
        <div className="flex h-full items-center gap-4">
          {items.map((card) => (
            <article key={card.id} className="flex-shrink-0 w-[384px] h-[324px] rounded-xl bg-white overflow-hidden shadow-sm p-2">
              <div className="grid grid-rows-[192px_116px] h-full">
                <div className="w-full h-[192px] overflow-hidden rounded-lg">
                  <img src={card.image} alt={card.name} className="w-full h-full object-cover" />
                </div>
                <div className="h-[116px] flex flex-col justify-center px-2">
                  <p className="text-sm text-neutral-600">{card.region}</p>
                  <p className="text-base font-semibold">{card.name}</p>
                  <p className="text-sm text-neutral-600">{card.address}</p>
                </div>
              </div>
            </article>
          ))}
        </div>
      </div>

      <div className="pointer-events-none absolute bottom-[20px] left-1/2 -translate-x-1/2 z-20 flex items-center gap-3">
        <button
          type="button"
          aria-label="이전"
          className="pointer-events-auto p-0 m-0 bg-transparent text-orange-500 hover:text-orange-600 focus:outline-none"
          onClick={() => scrollByStep(-1)}
        >
          <svg width="12" height="12" viewBox="0 0 12 12" fill="currentColor" aria-hidden="true">
            <polygon points="10,0 0,6 10,12" />
          </svg>
        </button>
        <div ref={trackRef} className="pointer-events-auto relative h-2 w-[30vw] rounded-full bg-orange-200/50">
          <div
            className="absolute top-0 h-2 rounded-full bg-orange-500"
            style={{ width: `${thumbWidth}px`, left: `${thumbLeft}px` }}
            onMouseDown={handleThumbMouseDown}
          />
        </div>
        <button
          type="button"
          aria-label="다음"
          className="pointer-events-auto p-0 m-0 bg-transparent text-orange-500 hover:text-orange-600 focus:outline-none"
          onClick={() => scrollByStep(1)}
        >
          <svg width="12" height="12" viewBox="0 0 12 12" fill="currentColor" aria-hidden="true">
            <polygon points="0,0 10,6 0,12" />
          </svg>
        </button>
      </div>
    </div>
  );
}