"use client";

import { useCallback, useEffect, useLayoutEffect, useRef, useState } from "react";
import type { GalleryImage } from "@/generated/prisma/client";
import { WaffleMenuImage } from "./WaffleMenuImage";

const INTERVAL_MS = 5000;
const MAX_VISIBLE = 3;
/** gap-3 = 0.75rem — garder aligné avec les classes Tailwind */
const GAP_PX = 12;

const SLIDE_EASE = "cubic-bezier(0.25, 0.46, 0.45, 0.94)";

type Props = {
  images: GalleryImage[];
};

/** Nombre de positions « première image à gauche » : 0 … len-3 → len-2 positions */
function positionCount(len: number) {
  return Math.max(0, len - 2);
}

export function GalleryCarousel({ images }: Props) {
  const viewportRef = useRef<HTMLDivElement>(null);
  const [startIndex, setStartIndex] = useState(0);
  const [paused, setPaused] = useState(false);
  const [metrics, setMetrics] = useState({ itemW: 0, step: 0 });

  const len = images.length;
  const positions = positionCount(len);

  useLayoutEffect(() => {
    const el = viewportRef.current;
    if (!el) return;

    function measure() {
      const node = viewportRef.current;
      if (!node) return;
      const w = node.clientWidth;
      if (w <= 0) return;
      const itemW = (w - 2 * GAP_PX) / MAX_VISIBLE;
      const step = itemW + GAP_PX;
      setMetrics((m) =>
        m.itemW === itemW && m.step === step ? m : { itemW, step }
      );
    }

    measure();
    const ro = new ResizeObserver(measure);
    ro.observe(el);
    return () => ro.disconnect();
  }, []);

  const advance = useCallback(() => {
    if (len <= MAX_VISIBLE || positions <= 1) return;
    setStartIndex((i) => (i + 1) % positions);
  }, [len, positions]);

  useEffect(() => {
    if (len <= MAX_VISIBLE || paused || positions <= 1) return undefined;
    const t = window.setInterval(advance, INTERVAL_MS);
    return () => window.clearInterval(t);
  }, [len, paused, positions, advance]);

  useEffect(() => {
    if (startIndex >= positions) setStartIndex(0);
  }, [startIndex, positions]);

  function goToPosition(i: number) {
    if (i < 0 || i >= positions || i === startIndex) return;
    setStartIndex(i);
  }

  if (len === 0) {
    return (
      <p className="rounded-3xl border border-dashed border-chocolat/20 bg-cream/50 px-6 py-12 text-center text-muted">
        Photos à venir — ajoutez-en depuis l’administration (section Galerie).
      </p>
    );
  }

  if (len <= MAX_VISIBLE) {
    const gridClass =
      len === 1
        ? "mx-auto grid max-w-md grid-cols-1 gap-3 sm:gap-4"
        : len === 2
          ? "mx-auto grid max-w-2xl grid-cols-2 gap-3 sm:gap-4"
          : "grid grid-cols-1 gap-3 sm:grid-cols-3 sm:gap-4";

    return (
      <div className={gridClass}>
        {images.map((img) => (
          <figure
            key={img.id}
            className="group relative aspect-square overflow-hidden rounded-3xl shadow-[0_10px_40px_-10px_rgba(61,43,31,0.2)]"
          >
            <div className="relative h-full w-full origin-center transition-transform duration-700 ease-[cubic-bezier(0.22,1,0.36,1)] will-change-transform group-hover:scale-[1.035]">
              <WaffleMenuImage src={img.imageUrl} alt={img.alt} />
            </div>
          </figure>
        ))}
      </div>
    );
  }

  const translateX = metrics.step > 0 ? -startIndex * metrics.step : 0;

  return (
    <div
      className="relative"
      onMouseEnter={() => setPaused(true)}
      onMouseLeave={() => setPaused(false)}
    >
      <div
        ref={viewportRef}
        className="overflow-hidden rounded-3xl"
      >
        <div
          className="flex flex-row flex-nowrap gap-3 will-change-transform"
          style={{
            transform: `translateX(${translateX}px)`,
            transition: `transform 650ms ${SLIDE_EASE}`,
          }}
        >
          {images.map((img) => (
            <div
              key={img.id}
              className="shrink-0"
              style={
                metrics.itemW > 0
                  ? { width: metrics.itemW, minWidth: metrics.itemW }
                  : { width: "calc((100% - 24px) / 3)", minWidth: "calc((100% - 24px) / 3)" }
              }
            >
              <figure className="group relative aspect-square overflow-hidden rounded-3xl shadow-[0_10px_40px_-10px_rgba(61,43,31,0.2)]">
                <div className="relative h-full w-full origin-center transition-transform duration-700 ease-[cubic-bezier(0.22,1,0.36,1)] will-change-transform group-hover:scale-[1.035]">
                  <WaffleMenuImage src={img.imageUrl} alt={img.alt} />
                </div>
              </figure>
            </div>
          ))}
        </div>
      </div>

      {positions > 1 ? (
        <div className="mt-6 flex flex-wrap justify-center gap-1.5">
          {Array.from({ length: positions }).map((_, i) => (
            <button
              key={`dot-${i}`}
              type="button"
              aria-label={`Position ${i + 1} sur ${positions}`}
              aria-current={i === startIndex}
              onClick={() => goToPosition(i)}
              className={`h-2 rounded-full transition-all duration-500 ease-out ${
                i === startIndex
                  ? "w-8 bg-gaufre"
                  : "w-2 bg-chocolat/30 hover:bg-chocolat/50"
              }`}
            />
          ))}
        </div>
      ) : null}
    </div>
  );
}