07Edge autoscroll — an rAF loop mapping edge distance into scroll speed

<main class="stage">
<div class="as">
  <p class="as__hint">Remaining distance to the edge is normalized and multiplied into per-frame scroll speed.</p>
  <div class="as__view" id="asView">
    <ul class="as__list" id="asList">
      <li class="as__row"><span class="as__txt">Packing</span></li>
      <li class="as__row"><span class="as__txt">Shipping</span></li>
      <li class="as__row"><span class="as__txt">Delivered</span></li>
      <li class="as__row"><span class="as__txt">Ticketing</span></li>
      <li class="as__row"><span class="as__txt">Confirmed</span></li>
      <li class="as__row"><span class="as__txt">Points</span></li>
      <li class="as__row"><span class="as__txt">Coupons</span></li>
      <li class="as__row"><span class="as__txt">Review ask</span></li>
      <li class="as__row"><span class="as__txt">Refunds</span></li>
    </ul>
  </div>
  <p class="as__meta"><b class="as__state" id="asState">speed 0px/s</b><span class="as__unit">480px per second</span></p>
</div>
</main>

@use "../../../../site/static/demo-tokens" as *;

$duration: 220ms;
$easing: cubic-bezier(.2,.8,.2,1);
$color: $subject-ink;

@include stage($stage-orange);

.as {
  width: 100%;
  max-width: 340px;
  display: flex;
  flex-direction: column;
  gap: $sp-2;
}

.as__hint {
  margin: 0;
  padding: 0 $sp-1;
  font-weight: 400;
  font-size: 11px;
  line-height: 1.4;
  color: $subject-ink;
}

.as__view {
  height: 160px;
  overflow-y: auto;
  padding: $sp-2;
  border-radius: $r-card;
  background: $subject-cream;
  box-shadow: $shadow-press;
}

.as__list {
  margin: 0;
  padding: 0;
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: $sp-1;
}

.as__row {
  padding: $sp-2;
  border-radius: $r-sm;
  background: $subject-blue-deep;
  color: $subject-cream;
  font-weight: 500;
  font-size: 12px;
  line-height: 1.3;
  touch-action: none;
  cursor: grab;
  will-change: transform;
}

.as__row--drag {
  cursor: grabbing;
  box-shadow: $shadow-raised;
}

.as__meta {
  margin: 0;
  padding: 0 $sp-1;
  display: flex;
  align-items: baseline;
  gap: $sp-1;
}

.as__state {
  font-weight: 700;
  font-size: 12px;
  color: $subject-ink;
}

.as__unit {
  font-weight: 400;
  font-size: 11px;
  color: $subject-ink;
}

@media (max-width: 340px) {
  .as { max-width: 260px; gap: $sp-1; }
  .as__hint { font-size: 10px; }
  .as__view { height: 76px; padding: $sp-1; }
  .as__row { font-size: 11px; padding: $sp-1; }
}

@media (prefers-reduced-motion: reduce) {
  .as__row {
    transition: none !important;
    transform: none !important;
  }
}

html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ff4d1f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.as {
  width: 100%;
  max-width: 340px;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.as__hint {
  margin: 0;
  padding: 0 4px;
  font-weight: 400;
  font-size: 11px;
  line-height: 1.4;
  color: #17141a;
}

.as__view {
  height: 160px;
  overflow-y: auto;
  padding: 8px;
  border-radius: 16px;
  background: #fff7e6;
  box-shadow: 0 6px 12px rgba(23, 20, 26, 0.32);
}

.as__list {
  margin: 0;
  padding: 0;
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.as__row {
  padding: 8px;
  border-radius: 8px;
  background: #0a4fe8;
  color: #fff7e6;
  font-weight: 500;
  font-size: 12px;
  line-height: 1.3;
  touch-action: none;
  cursor: grab;
  will-change: transform;
}

.as__row--drag {
  cursor: grabbing;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
}

.as__meta {
  margin: 0;
  padding: 0 4px;
  display: flex;
  align-items: baseline;
  gap: 4px;
}

.as__state {
  font-weight: 700;
  font-size: 12px;
  color: #17141a;
}

.as__unit {
  font-weight: 400;
  font-size: 11px;
  color: #17141a;
}

@media (max-width: 340px) {
  .as {
    max-width: 260px;
    gap: 4px;
  }
  .as__hint {
    font-size: 10px;
  }
  .as__view {
    height: 76px;
    padding: 4px;
  }
  .as__row {
    font-size: 11px;
    padding: 4px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .as__row {
    transition: none !important;
    transform: none !important;
  }
}

// 가장자리 자동 scroll(07) — 든 행을 옮기는 동안 포인터 y 를 scroll 상자(view) rect 와 비교해
// 위/아래 40px 밴드 안이면 가장자리까지 남은 거리를 0..1 로 정규화하고, 그 값에 최대 속도(480px per second)
// 를 곱해 매 rAF 프레임 scrollBy 로 스크롤한다. 밴드 밖이면 speed 0 — 정지.
(function () {
  var view = document.getElementById('asView');
  var list = document.getElementById('asList');
  var stateEl = document.getElementById('asState');
  if (!view || !list || !stateEl) return;

  var EDGE_PX = 40;
  var MAX_SPEED = 480; // px per second — 문구 "480px per second" 과 같은 값

  var drag = null;   // { row, offsetInRow }
  var lastT = 0;
  var raf = null;

  function rowsExcept(row) {
    return Array.prototype.slice.call(list.children).filter(function (r) { return r !== row; });
  }

  function flipInsert(row, target) {
    var siblings = rowsExcept(row);
    var first = siblings.map(function (s) { return s.getBoundingClientRect(); });
    list.insertBefore(row, target);
    siblings.forEach(function (s, i) {
      var r = s.getBoundingClientRect();
      var dy = first[i].top - r.top;
      if (dy !== 0) {
        s.style.transition = 'none';
        s.style.transform = 'translateY(' + dy + 'px)';
        requestAnimationFrame(function () {
          s.style.transition = 'transform 220ms cubic-bezier(.2,.8,.2,1)';
          s.style.transform = 'translateY(0)';
        });
      }
    });
  }

  function reflow(row, pointerY) {
    var siblings = rowsExcept(row);
    var target = null;
    for (var i = 0; i < siblings.length; i++) {
      var r = siblings[i].getBoundingClientRect();
      if (pointerY < r.top + r.height / 2) { target = siblings[i]; break; }
    }
    if (target === row.nextElementSibling) return;
    if (target === null && row === list.lastElementChild) return;
    flipInsert(row, target);
  }

  // 가장자리 거리 → 0..1 정규화 → 프레임당 스크롤량
  function edgeFactor(pointerY, viewRect) {
    var topDist = pointerY - viewRect.top;
    var botDist = viewRect.bottom - pointerY;
    if (topDist >= 0 && topDist < EDGE_PX) return -(1 - topDist / EDGE_PX);
    if (botDist >= 0 && botDist < EDGE_PX) return (1 - botDist / EDGE_PX);
    return 0;
  }

  function tick(now) {
    if (!drag) { raf = null; stateEl.textContent = 'speed 0px/s'; return; }
    var dt = lastT ? (now - lastT) / 1000 : 0;
    lastT = now;
    var viewRect = view.getBoundingClientRect();
    var f = edgeFactor(drag.pointerY, viewRect);
    var speed = f * MAX_SPEED;
    if (speed !== 0 && dt > 0) view.scrollBy(0, speed * dt);
    stateEl.textContent = 'speed ' + Math.round(Math.abs(speed)) + 'px/s';
    raf = requestAnimationFrame(tick);
  }

  function moveDrag(clientY) {
    if (!drag) return;
    drag.pointerY = clientY;
    var listRect = list.getBoundingClientRect();
    var ty = clientY - drag.offsetInRow - listRect.top - drag.row.offsetTop;
    drag.row.style.transform = 'translateY(' + ty.toFixed(1) + 'px)';
    reflow(drag.row, clientY);
  }

  function beginDrag(row, clientY) {
    var r = row.getBoundingClientRect();
    row.classList.add('as__row--drag');
    drag = { row: row, offsetInRow: clientY - r.top, pointerY: clientY };
    lastT = 0;
    if (!raf) raf = requestAnimationFrame(tick);
  }

  function endDrag() {
    if (!drag) return;
    var row = drag.row;
    drag = null;
    row.classList.remove('as__row--drag');
    row.style.transition = 'transform 220ms cubic-bezier(.2,.8,.2,1)';
    row.style.transform = 'translateY(0)';
    setTimeout(function () { row.style.transition = ''; }, 240);
  }

  function onDown(e) {
    var row = e.target.closest('.as__row');
    if (!row) return;
    stop();
    row.setPointerCapture(e.pointerId);
    beginDrag(row, e.clientY);
  }
  function onMove(e) { moveDrag(e.clientY); }
  function onUp() { endDrag(); }

  list.addEventListener('pointerdown', onDown);
  list.addEventListener('pointermove', onMove);
  list.addEventListener('pointerup', onUp);
  list.addEventListener('pointercancel', onUp);

  // 자동 시연 — 같은 함수를 합성 좌표로 호출해 위/아래 가장자리를 번갈아 지나가게 한다
  var playing = true;
  function stop() { playing = false; }
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;

  function loopOnce() {
    var vr = view.getBoundingClientRect();
    var row = list.children[3];
    beginDrag(row, vr.top + vr.height / 2);
    moveDrag(vr.bottom - 6);
    setTimeout(function () { if (drag) moveDrag(vr.top + 6); }, 520);
    setTimeout(function () { endDrag(); }, 980);
  }

  if (reduce) {
    view.scrollTop = 40;
  } else {
    loopOnce();
    setInterval(function () { if (playing) loopOnce(); }, 1700);
  }
})();

// DragAutoscroll — vanilla 판(run/336/demo/07-drag-autoscroll/index.html)
// 의 React 포트. 든 행을 옮기는 동안 포인터 y 를 스크롤 상자(view) rect 와 비교해
// 위/아래 40px 밴드 안이면 가장자리까지 남은 거리를 0..1 로 정규화하고, 그 값에 최대
// 속도(초당 480px)를 곱해 매 rAF 프레임 scrollBy 로 스크롤한다. 밴드 밖이면 속도 0 — 정지.
import { useEffect, useRef } from "react";
import styles from "./DragAutoscroll.module.scss";

export type DragAutoscrollProps = {
  duration?: string;
  easing?: string;
  color?: string;
};

const HINT = "가장자리까지 남은 거리를 정규화해 매 프레임 스크롤 속도에 곱합니다";
const ROW_TXT = ["배송 준비", "배송 중", "고객 인수", "티켓 발급", "문의 확정", "포인트 적립", "쿠폰 지급", "리뷰 요청", "환불 처리"];

type Box<T> = { current: T };
type DragState = { row: HTMLElement; offsetInRow: number; pointerY: number };

export default function DragAutoscroll({
  duration = "220ms",
  easing = "cubic-bezier(.2,.8,.2,1)",
  color = "#17141a"
}: DragAutoscrollProps) {
  const viewRef = useRef<HTMLDivElement | null>(null);
  const listRef = useRef<HTMLUListElement | null>(null);
  const stateRef = useRef<HTMLElement | null>(null);
  const rafRef = useRef(0) as Box<number>;

  useEffect(() => {
    const view = viewRef.current;
    const list = listRef.current;
    const stateEl = stateRef.current;
    if (!view || !list || !stateEl) return;

    const EDGE_PX = 40;
    const MAX_SPEED = 480; // px per second — 문구 "초당 480px" 과 같은 값

    let drag: DragState | null = null;
    let lastT = 0;
    let raf = 0;

    function rowsExcept(row: HTMLElement): HTMLElement[] {
      return Array.prototype.slice.call(list!.children).filter((r: HTMLElement) => r !== row);
    }

    function flipInsert(row: HTMLElement, target: HTMLElement | null): void {
      const siblings = rowsExcept(row);
      const first = siblings.map((s) => s.getBoundingClientRect());
      list!.insertBefore(row, target);
      siblings.forEach((s, i) => {
        const r = s.getBoundingClientRect();
        const dy = first[i].top - r.top;
        if (dy !== 0) {
          s.style.transition = "none";
          s.style.transform = "translateY(" + dy + "px)";
          requestAnimationFrame(() => {
            s.style.transition = "transform " + duration + " " + easing;
            s.style.transform = "translateY(0)";
          });
        }
      });
    }

    function reflow(row: HTMLElement, pointerY: number): void {
      const siblings = rowsExcept(row);
      let target: HTMLElement | null = null;
      for (let i = 0; i < siblings.length; i++) {
        const r = siblings[i].getBoundingClientRect();
        if (pointerY < r.top + r.height / 2) {
          target = siblings[i];
          break;
        }
      }
      if (target === row.nextElementSibling) return;
      if (target === null && row === list!.lastElementChild) return;
      flipInsert(row, target);
    }

    function edgeFactor(pointerY: number, viewRect: DOMRect): number {
      const topDist = pointerY - viewRect.top;
      const botDist = viewRect.bottom - pointerY;
      if (topDist >= 0 && topDist < EDGE_PX) return -(1 - topDist / EDGE_PX);
      if (botDist >= 0 && botDist < EDGE_PX) return 1 - botDist / EDGE_PX;
      return 0;
    }

    function tick(now: number): void {
      if (!drag) {
        raf = 0;
        stateEl!.textContent = "speed 0px/s";
        return;
      }
      const dt = lastT ? (now - lastT) / 1000 : 0;
      lastT = now;
      const viewRect = view!.getBoundingClientRect();
      const f = edgeFactor(drag.pointerY, viewRect);
      const speed = f * MAX_SPEED;
      if (speed !== 0 && dt > 0) view!.scrollBy(0, speed * dt);
      stateEl!.textContent = "speed " + Math.round(Math.abs(speed)) + "px/s";
      raf = requestAnimationFrame(tick);
      rafRef.current = raf;
    }

    function moveDrag(clientY: number): void {
      if (!drag) return;
      drag.pointerY = clientY;
      const listRect = list!.getBoundingClientRect();
      const ty = clientY - drag.offsetInRow - listRect.top - drag.row.offsetTop;
      drag.row.style.transform = "translateY(" + ty.toFixed(1) + "px)";
      reflow(drag.row, clientY);
    }

    function beginDrag(row: HTMLElement, clientY: number): void {
      const r = row.getBoundingClientRect();
      row.classList.add(styles.rowDrag);
      drag = { row, offsetInRow: clientY - r.top, pointerY: clientY };
      lastT = 0;
      if (!raf) {
        raf = requestAnimationFrame(tick);
        rafRef.current = raf;
      }
    }

    function endDrag(): void {
      if (!drag) return;
      const row = drag.row;
      drag = null;
      row.classList.remove(styles.rowDrag);
      row.style.transition = "transform 220ms cubic-bezier(.2,.8,.2,1)";
      row.style.transform = "translateY(0)";
      setTimeout(() => {
        row.style.transition = "";
      }, 240);
    }

    function onDown(e: PointerEvent): void {
      const row = (e.target as HTMLElement).closest("." + styles.row) as HTMLElement | null;
      if (!row) return;
      stop();
      row.setPointerCapture(e.pointerId);
      beginDrag(row, e.clientY);
    }
    function onMove(e: PointerEvent): void {
      moveDrag(e.clientY);
    }
    function onUp(): void {
      endDrag();
    }

    list.addEventListener("pointerdown", onDown as EventListener);
    list.addEventListener("pointermove", onMove as EventListener);
    list.addEventListener("pointerup", onUp as EventListener);
    list.addEventListener("pointercancel", onUp as EventListener);

    let playing = true;
    function stop(): void {
      playing = false;
    }
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;

    const timeouts: number[] = [];
    let intervalId = 0;

    function loopOnce(): void {
      const vr = view!.getBoundingClientRect();
      const row = list!.children[3] as HTMLElement;
      beginDrag(row, vr.top + vr.height / 2);
      moveDrag(vr.bottom - 6);
      timeouts.push(
        window.setTimeout(() => {
          if (drag) moveDrag(vr.top + 6);
        }, 520)
      );
      timeouts.push(window.setTimeout(endDrag, 980));
    }

    if (reduce) {
      view.scrollTop = 40;
    } else {
      loopOnce();
      intervalId = window.setInterval(() => {
        if (playing) loopOnce();
      }, 1700);
    }

    return () => {
      cancelAnimationFrame(rafRef.current);
      timeouts.forEach((t) => clearTimeout(t));
      if (intervalId) clearInterval(intervalId);
      list.removeEventListener("pointerdown", onDown as EventListener);
      list.removeEventListener("pointermove", onMove as EventListener);
      list.removeEventListener("pointerup", onUp as EventListener);
      list.removeEventListener("pointercancel", onUp as EventListener);
    };
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, []);

  return (
    <main className={styles.stage}>
      <div className={styles.as}>
        <p className={styles.hint}>{HINT}</p>
        <div className={styles.view} ref={viewRef}>
          <ul className={styles.list} ref={listRef}>
            {ROW_TXT.map((txt, i) => (
              <li key={i} className={styles.row}>
                <span>{txt}</span>
              </li>
            ))}
          </ul>
        </div>
        <p className={styles.meta}>
          <b className={styles.state} ref={stateRef} style={{ color }}>speed 0px/s</b>
          <span className={styles.unit}>초당 480px</span>
        </p>
      </div>
    </main>
  );
}