Horizontal scroll steps

import { useEffect, useRef, useState } from "react";
import { motion, useMotionValue, useMotionValueEvent, useScroll, useSpring, useTransform } from "framer-motion";

interface PinnedHorizontalScrollProps {
  title?: string;
  accent?: string;
  /** Suaviza el desplazamiento con un muelle. */
  smooth?: boolean;
  /** true: caja con scroll propio. false: se fija en la página mientras haces scroll. */
  contained?: boolean;
}

const STEPS = [
  { title: "Explore", text: "We listen before we draw the first line." },
  { title: "Sketch", text: "A hundred ideas on paper to land on three." },
  { title: "Prototype", text: "Something you can touch before Friday." },
  { title: "Polish", text: "The last few millimeters are the ones you notice." },
  { title: "Launch", text: "Ship, measure, and start again." },
];

export default function PinnedHorizontalScroll({
  title = "How we work",
  accent = "#6e56ff",
  smooth = true,
  contained = true,
}: PinnedHorizontalScrollProps) {
  const scroller = useRef<HTMLDivElement>(null);
  const target = useRef<HTMLDivElement>(null);
  const frame = useRef<HTMLDivElement>(null);
  const track = useRef<HTMLDivElement>(null);
  const items = useRef<(HTMLDivElement | null)[]>([]);
  const stops = useRef<number[]>([]);
  const distance = useMotionValue(0);
  const [active, setActive] = useState(0);
  const { scrollYProgress } = useScroll(
    contained
      ? { container: scroller, target, offset: ["start start", "end end"] }
      : { target, offset: ["start start", "end end"] },
  );
  const springy = useSpring(scrollYProgress, { stiffness: 160, damping: 30, restDelta: 0.0005 });
  const progress = smooth ? springy : scrollYProgress;
  const x = useTransform([progress, distance], ([p = 0, d = 0]: number[]) => {
    const s = stops.current;
    if (s.length < 2) return -p * d;
    const t = Math.min(s.length - 1, Math.max(0, p * (s.length - 1)));
    const i = Math.min(s.length - 2, Math.floor(t));
    const a = s[i] ?? 0;
    const b = s[i + 1] ?? a;
    const f = t - i;
    return -Math.min(d, a + (b - a) * f * f * (3 - 2 * f));
  });

  useMotionValueEvent(scrollYProgress, "change", (p) =>
    setActive(Math.min(STEPS.length - 1, Math.round(p * (STEPS.length - 1)))),
  );

  useEffect(() => {
    const measure = () => {
      if (!frame.current || !track.current) return;
      const first = items.current[0]?.offsetLeft ?? 0;
      stops.current = items.current.map((el) => (el ? el.offsetLeft - first : 0));
      distance.set(Math.max(0, track.current.scrollWidth - frame.current.clientWidth));
    };
    measure();
    const ro = new ResizeObserver(measure);
    if (frame.current) ro.observe(frame.current);
    if (track.current) ro.observe(track.current);
    return () => ro.disconnect();
  }, [distance]);

  const section = (
    <div ref={target} className={contained ? "relative h-[400%]" : "relative h-[400vh]"}>
      <div
        className={
          (contained ? "h-[25%]" : "h-screen") +
          " sticky top-0 flex flex-col justify-between overflow-hidden py-7 [container-type:inline-size]"
        }
      >
        <div className="flex items-baseline justify-between gap-4 px-7">
          <h3 className="text-[15px] font-semibold tracking-[-0.01em] text-[#1d1d1f] dark:text-[#f5f5f7]">{title}</h3>
          <span className="shrink-0 text-[13px] tabular-nums text-[#86868b]">
            {active + 1} de {STEPS.length}
          </span>
        </div>
        <div ref={frame} className="w-full">
          <motion.div ref={track} style={{ x }} className="flex w-max items-end gap-[7cqi] px-7">
            {STEPS.map((s, i) => (
              <motion.div
                key={s.title}
                ref={(el) => {
                  items.current[i] = el;
                }}
                animate={{ opacity: i === active ? 1 : 0.16 }}
                transition={{ duration: 0.45, ease: [0.25, 0.1, 0.25, 1] }}
                className="shrink-0"
              >
                <span className="block text-[13px] font-semibold tabular-nums" style={{ color: accent }}>
                  {String(i + 1).padStart(2, "0")}
                </span>
                <h4 className="mt-1 text-[clamp(56px,15cqi,132px)] font-semibold leading-[0.92] tracking-[-0.055em] text-[#1d1d1f] dark:text-[#f5f5f7]">
                  {s.title}
                </h4>
                <p className="mt-4 max-w-[24ch] text-[15px] leading-snug text-[#6e6e73] dark:text-[#a1a1a6]">{s.text}</p>
              </motion.div>
            ))}
          </motion.div>
        </div>
        <div className="mx-7 h-[2px] overflow-hidden rounded-full bg-black/[0.06] dark:bg-white/10">
          <motion.div style={{ scaleX: progress, background: accent }} className="h-full origin-left" />
        </div>
      </div>
    </div>
  );

  if (!contained) return <div className="bg-[#f5f5f7] dark:bg-black">{section}</div>;
  return (
    <div
      ref={scroller}
      className="relative h-[26rem] w-full overflow-y-auto rounded-3xl bg-[#f5f5f7] [scrollbar-width:none] dark:bg-black"
    >
      {section}
    </div>
  );
}