Cinta de titulares con inercia

import { Fragment, useRef } from "react";
import {
  motion,
  useAnimationFrame,
  useMotionValue,
  useReducedMotion,
  useScroll,
  useSpring,
  useTransform,
  useVelocity,
  type MotionValue,
} from "framer-motion";

interface ScrollVelocityMarqueeProps {
  /** Frases separadas por "·". */
  text?: string;
  accent?: string;
  /** Velocidad base, en % de la cinta por segundo. */
  speed?: number;
  /** true: caja con scroll propio. false: reacciona al scroll de la página. */
  contained?: boolean;
}

type RowStyle = "solid" | "band" | "ghost";
const ROWS: { look: RowStyle; direction: 1 | -1; start: number }[] = [
  { look: "ghost", direction: 1, start: -9 },
  { look: "solid", direction: -1, start: -6 },
  { look: "band", direction: 1, start: -14 },
  { look: "ghost", direction: -1, start: -5 },
];

const wrap = (min: number, max: number, v: number) => {
  const r = max - min;
  return ((((v - min) % r) + r) % r) + min;
};

function Row({
  items,
  speed,
  direction,
  factor,
  skew,
  look,
  start,
  accent,
}: {
  items: string[];
  speed: number;
  direction: 1 | -1;
  start: number;
  factor: MotionValue<number>;
  skew: MotionValue<number>;
  look: RowStyle;
  accent: string;
}) {
  const baseX = useMotionValue(start);
  const dir = useRef<number>(direction);
  const reduce = useReducedMotion();
  const x = useTransform(baseX, (v) => wrap(-25, 0, v) + "%");

  useAnimationFrame((_, delta) => {
    if (reduce) return;
    const f = factor.get();
    if (f < 0) dir.current = -direction;
    else if (f > 0) dir.current = direction;
    baseX.set(baseX.get() + dir.current * speed * (delta / 1000) * (1 + Math.abs(f)));
  });

  const text =
    look === "band"
      ? "text-[#0b0b0c]"
      : look === "ghost"
        ? "text-[#1d1d1f]/[0.13] dark:text-[#f5f5f7]/[0.16]"
        : "text-[#1d1d1f] dark:text-[#f5f5f7]";
  const dot = look === "band" ? "bg-[#0b0b0c]" : "bg-current opacity-30";

  return (
    <div
      className={"overflow-hidden whitespace-nowrap " + (look === "band" ? "py-[0.08em]" : "")}
      style={look === "band" ? { background: accent } : undefined}
    >
      <motion.div className="flex w-max" style={{ x, skewX: skew }}>
        {Array.from({ length: 4 }, (_, copy) => (
          <span
            key={copy}
            aria-hidden={copy > 0 ? true : undefined}
            className={
              "flex shrink-0 items-center text-[clamp(44px,17cqi,140px)] font-semibold leading-[1.02] tracking-[-0.045em] " +
              text
            }
          >
            {items.map((item, i) => (
              <Fragment key={i}>
                <span className="px-[0.18em]">{item}</span>
                <span className={"mx-[0.12em] h-[0.14em] w-[0.14em] shrink-0 rounded-full " + dot} />
              </Fragment>
            ))}
          </span>
        ))}
      </motion.div>
    </div>
  );
}

export default function ScrollVelocityMarquee({
  text = "Hecho a mano · Sin plantillas · Listo para lanzar",
  accent = "#d4ff3a",
  speed = 3,
  contained = true,
}: ScrollVelocityMarqueeProps) {
  const scroller = useRef<HTMLDivElement>(null);
  const { scrollY } = useScroll(contained ? { container: scroller } : {});
  const velocity = useVelocity(scrollY);
  const smooth = useSpring(velocity, { damping: 50, stiffness: 400 });
  const factor = useTransform(smooth, [0, 1000], [0, 5], { clamp: false });
  const skew = useTransform(smooth, [-2000, 2000], [-12, 12]);
  const items = text
    .split("·")
    .map((s) => s.trim())
    .filter(Boolean);

  const rows = (
    <div className="flex w-full flex-col gap-[1.5cqi] [container-type:inline-size]">
      {ROWS.map((r, i) => (
        <Row
          key={i}
          items={items}
          speed={speed}
          direction={r.direction}
          start={r.start}
          factor={factor}
          skew={skew}
          look={r.look}
          accent={accent}
        />
      ))}
    </div>
  );

  if (!contained) return <div className="w-full overflow-hidden py-10">{rows}</div>;
  return (
    <div
      ref={scroller}
      className="relative h-[28rem] w-full overflow-y-auto overflow-x-hidden rounded-3xl bg-[#fafafa] [scrollbar-width:none] dark:bg-[#0a0a0a]"
    >
      <div className="h-[500%]">
        <div className="sticky top-0 flex h-[20%] items-center overflow-hidden">{rows}</div>
      </div>
    </div>
  );
}