02Release-Velocity Swipe Verdict

<main class="stage">
<div class="vf is-demo" id="vf">
  <p class="vf__caption">Swipe verdict split by release speed</p>
  <div class="vf__scene" id="vfScene">
    <div class="vf__card" id="vfCard" tabindex="0" role="group" aria-roledescription="Swipe card">
      <p class="vf__label" id="vfLabel">Evening walk</p>
      <p class="vf__hint" id="vfHint">Speed 0.00 px/ms</p>
    </div>
    <button class="vf__btn vf__btn--nope" id="vfNope" type="button" aria-label="Dislike">✕</button>
    <button class="vf__btn vf__btn--like" id="vfLike" type="button" aria-label="Like">♥</button>
  </div>
  <p class="vf__status" id="vfStatus" aria-live="polite">Waiting</p>
</div>
</main>

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

// 값 하나: 놓는 순간 속도(px/ms)가 FLING_VELOCITY_MIN 을 넘지 못하면 카드는 날아가지 않는다.
// 드래그 중에는 SWIPE_ROTATE_LERP_RATIO(px 당 도) 만큼 살짝 기운다.

$duration: $dur-base;
$easing: $ease-out;
$color: $subject-orange-deep;

@include stage($stage-yellow);

.vf { display: grid; gap: $sp-2; justify-items: center; width: 100%; }
.vf__caption { margin: 0; font-size: 12px; font-weight: 600; color: $subject-ink; }

.vf__scene {
  position: relative;
  width: 220px;
  height: 190px;
  border-radius: $r-card;
  background: $subject-cream;
  display: grid;
  place-items: center;
  overflow: hidden;
}

.vf__card {
  position: relative;
  width: 160px;
  height: 180px;
  border-radius: $r-card;
  background: linear-gradient(160deg, $stage-orange, #e6d6cb);
  box-shadow: $shadow-raised;
  display: grid;
  gap: $sp-2;
  place-items: center;
  touch-action: none;
  cursor: grab;
  will-change: transform;
}
.vf__card:active { cursor: grabbing; }
.vf__card:focus-visible { outline: 2px solid $subject-blue-light; outline-offset: 3px; }

.vf__label { margin: 0; font-size: 14px; font-weight: 700; color: $subject-ink; padding: 0 $sp-3; text-align: center; }
.vf__hint { margin: 0; font-size: 10px; color: $subject-ink; opacity: .8; }

.vf__btn {
  position: absolute;
  bottom: $sp-3;
  width: 34px;
  height: 34px;
  border-radius: $r-pill;
  border: 0;
  background: $stage-paper;
  box-shadow: $shadow-press;
  font-size: 15px;
  line-height: 1;
  cursor: pointer;
  display: grid;
  place-items: center;
}
.vf__btn--nope { left: $sp-3; color: $error; }
.vf__btn--like { right: $sp-3; color: $subject-orange-deep; }
.vf__btn:focus-visible { outline: 2px solid $subject-blue-light; outline-offset: 2px; }

.vf__status { margin: 0; font-size: 11px; color: $subject-ink; font-weight: 600; }

@media (max-width: 340px) {
  .vf { gap: $sp-2; }
  .vf__scene { width: 150px; height: 108px; }
  .vf__card { width: 78px; height: 92px; gap: $sp-1; }
  .vf__label { font-size: 10px; padding: 0 $sp-1; }
  .vf__hint { display: none; }
  .vf__btn { width: 22px; height: 22px; font-size: 11px; bottom: $sp-1; }
  .vf__btn--nope { left: $sp-1; }
  .vf__btn--like { right: $sp-1; }
}

@media (prefers-reduced-motion: reduce) {
  .vf__card { transition: none; }
}

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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ffd23f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.vf {
  display: grid;
  gap: 8px;
  justify-items: center;
  width: 100%;
}

.vf__caption {
  margin: 0;
  font-size: 12px;
  font-weight: 600;
  color: #17141a;
}

.vf__scene {
  position: relative;
  width: 220px;
  height: 190px;
  border-radius: 16px;
  background: #fff7e6;
  display: grid;
  place-items: center;
  overflow: hidden;
}

.vf__card {
  position: relative;
  width: 160px;
  height: 180px;
  border-radius: 16px;
  background: linear-gradient(160deg, #ff4d1f, #e6d6cb);
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  display: grid;
  gap: 8px;
  place-items: center;
  touch-action: none;
  cursor: grab;
  will-change: transform;
}

.vf__card:active {
  cursor: grabbing;
}

.vf__card:focus-visible {
  outline: 2px solid #5b8cf8;
  outline-offset: 3px;
}

.vf__label {
  margin: 0;
  font-size: 14px;
  font-weight: 700;
  color: #17141a;
  padding: 0 12px;
  text-align: center;
}

.vf__hint {
  margin: 0;
  font-size: 10px;
  color: #17141a;
  opacity: 0.8;
}

.vf__btn {
  position: absolute;
  bottom: 12px;
  width: 34px;
  height: 34px;
  border-radius: 999px;
  border: 0;
  background: #ffffff;
  box-shadow: 0 6px 12px rgba(23, 20, 26, 0.32);
  font-size: 15px;
  line-height: 1;
  cursor: pointer;
  display: grid;
  place-items: center;
}

.vf__btn--nope {
  left: 12px;
  color: #c2361a;
}

.vf__btn--like {
  right: 12px;
  color: #c93000;
}

.vf__btn:focus-visible {
  outline: 2px solid #5b8cf8;
  outline-offset: 2px;
}

.vf__status {
  margin: 0;
  font-size: 11px;
  color: #17141a;
  font-weight: 600;
}

@media (max-width: 340px) {
  .vf {
    gap: 8px;
  }
  .vf__scene {
    width: 150px;
    height: 108px;
  }
  .vf__card {
    width: 78px;
    height: 92px;
    gap: 4px;
  }
  .vf__label {
    font-size: 10px;
    padding: 0 4px;
  }
  .vf__hint {
    display: none;
  }
  .vf__btn {
    width: 22px;
    height: 22px;
    font-size: 11px;
    bottom: 4px;
  }
  .vf__btn--nope {
    left: 4px;
  }
  .vf__btn--like {
    right: 4px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .vf__card {
    transition: none;
  }
}

(function () {
  "use strict";

  // 변형 3: 02 폴더에 SWIPE_ROTATE_LERP_RATIO 를 실재시킨다 — 드래그 중 카드가 이 비율로 살짝 기운다.
  var SWIPE_ROTATE_LERP_RATIO = 0.05; // deg per px
  var ROTATE_MAX_DEG = 14;
  // 값 하나: 놓는 순간의 Speed(px/ms)가 이 값을 넘지 못하면 카드는 날아가지 않는다.
  var FLING_VELOCITY_MIN = 0.42;
  var INERTIA_DECAY = 0.85;
  var SETTLE_RATE = 0.2;
  var EXIT_PX = 320;
  var CYCLE_S = 2;

  var root = document.getElementById("vf");
  var card = document.getElementById("vfCard");
  var label = document.getElementById("vfLabel");
  var hint = document.getElementById("vfHint");
  var status = document.getElementById("vfStatus");
  var btnLike = document.getElementById("vfLike");
  var btnNope = document.getElementById("vfNope");
  var reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;

  function seedRand(seed) {
    var s = seed >>> 0;
    return function () { s = (s * 1664525 + 1013904223) >>> 0; return s / 4294967296; };
  }
  function clamp(v, lo, hi) { return Math.max(lo, Math.min(hi, v)); }

  var CARDS = ["Evening walk", "Weekend café", "Home workout log", "Reading list", "Travel notes", "Morning routine"];
  var rand = seedRand(23);
  var idx = Math.floor(rand() * CARDS.length);

  var dragging = false;
  var startX = 0, lastX = 0, lastT = 0, vx = 0;
  var x = 0, phase = "idle", exitDir = 1;

  function setCard() { label.textContent = CARDS[idx % CARDS.length]; }
  setCard();

  function render() {
    var rot = clamp(x * SWIPE_ROTATE_LERP_RATIO, -ROTATE_MAX_DEG, ROTATE_MAX_DEG);
    card.style.transform = "translateX(" + x.toFixed(1) + "px) rotate(" + rot.toFixed(2) + "deg)";
  }

  function nextCard() {
    idx += 1; setCard();
    x = 0; vx = 0; phase = "idle";
    render();
    status.textContent = "Waiting";
  }

  function judge(velocity, dir) {
    root.classList.remove("is-demo");
    hint.textContent = "Speed " + Math.abs(velocity).toFixed(2) + " px/ms";
    var flung = Math.abs(velocity) >= FLING_VELOCITY_MIN;
    if (reduce) {
      if (flung) { status.textContent = dir > 0 ? "Marked as liked" : "Marked as disliked"; nextCard(); }
      else { x = 0; render(); status.textContent = "Below the release-speed threshold — snapped back"; phase = "idle"; }
      return;
    }
    if (flung) {
      phase = "exit"; exitDir = dir;
      status.textContent = dir > 0 ? "Marked as liked" : "Marked as disliked";
    } else {
      phase = "settle";
      status.textContent = "Below the release-speed threshold — snapped back";
    }
  }

  function startDrag(clientX) {
    root.classList.remove("is-demo");
    dragging = true;
    startX = clientX; lastX = clientX; lastT = performance.now(); vx = 0;
  }
  function moveDrag(clientX) {
    if (!dragging) return;
    var now = performance.now();
    var dt = Math.max(now - lastT, 1);
    vx = (clientX - lastX) / dt;
    lastX = clientX; lastT = now;
    x = clientX - startX;
    render();
  }
  function endDrag() {
    if (!dragging) return;
    dragging = false;
    judge(vx, x >= 0 ? 1 : -1);
  }

  card.addEventListener("pointerdown", function (e) { card.setPointerCapture(e.pointerId); startDrag(e.clientX); });
  card.addEventListener("pointermove", function (e) { moveDrag(e.clientX); });
  card.addEventListener("pointerup", endDrag);
  card.addEventListener("pointercancel", endDrag);

  function keyVerdict(dir) {
    root.classList.remove("is-demo");
    x = dir * 40; render();
    judge(dir * (FLING_VELOCITY_MIN + 0.15), dir);
  }
  card.addEventListener("keydown", function (e) {
    if (e.key === "ArrowRight") { e.preventDefault(); keyVerdict(1); }
    else if (e.key === "ArrowLeft") { e.preventDefault(); keyVerdict(-1); }
  });
  btnLike.addEventListener("click", function () { keyVerdict(1); });
  btnNope.addEventListener("click", function () { keyVerdict(-1); });

  function step(dt) {
    if (phase === "exit") {
      var speed = Math.max(Math.abs(vx), FLING_VELOCITY_MIN * 1.4);
      x += exitDir * speed * dt;
      render();
      if (Math.abs(x) > EXIT_PX) nextCard();
    } else if (phase === "settle") {
      x += vx * dt;
      vx *= INERTIA_DECAY;
      x += (0 - x) * SETTLE_RATE;
      render();
      if (Math.abs(x) < 0.5 && Math.abs(vx) < 0.01) { x = 0; phase = "idle"; render(); }
    }
  }

  // .is-demo 자동 시연: 실제 pointer 없이 x·judge() 를 같은 경로로 호출한다.
  var start = null, lastNow = 0, prevT = 0, synthPhase = "wait";
  function synth(t) {
    if (t > 0.45 && t < 0.7 && synthPhase === "wait") synthPhase = "weak";
    if (synthPhase === "weak") {
      var p = clamp((t - 0.45) / 0.25, 0, 1);
      x = p * 30; render();
      if (t >= 0.7) { synthPhase = "afterWeak"; judge(0.15, 1); }
    }
    if (t > 1.05 && t < 1.35 && synthPhase === "afterWeak") synthPhase = "strong";
    if (synthPhase === "strong") {
      var q = clamp((t - 1.05) / 0.3, 0, 1);
      x = q * 130; render();
      if (t >= 1.35) { synthPhase = "done"; judge(FLING_VELOCITY_MIN + 0.5, 1); }
    }
  }

  function loop(now) {
    if (start === null) { start = now; lastNow = now; lastT = now; }
    var dt = Math.min(now - lastNow, 48);
    lastNow = now;
    var t = ((now - start) / 1000) % CYCLE_S;
    if (t < prevT) synthPhase = "wait";
    prevT = t;
    if (!reduce && root.classList.contains("is-demo")) synth(t);
    if (!reduce) step(dt);
    requestAnimationFrame(loop);
  }
  requestAnimationFrame(loop);
})();

// VelocityFlingThresholdSwipeCard — vanilla 판(run/422/demo/02-swipe-deck-precision-velocity-fling-threshold/index.html) 의 React 포트.
// 값 하나: 놓는 순간 속도(px/ms) 가 FLING_VELOCITY_MIN 을 넘지 못하면 카드는 날아가지 않는다.
// 드래그 중에는 SWIPE_ROTATE_LERP_RATIO(px 당 도) 만큼 살짝 기운다.
import { useEffect, useRef, useState } from "react";
import type { PointerEvent as ReactPointerEvent } from "react";
import styles from "./VelocityFlingThresholdSwipeCard.module.scss";

type Box<T> = { current: T };

const SWIPE_ROTATE_LERP_RATIO = 0.05;
const ROTATE_MAX_DEG = 14;
const FLING_VELOCITY_MIN = 0.42;
const INERTIA_DECAY = 0.85;
const SETTLE_RATE = 0.2;
const EXIT_PX = 320;
const CYCLE_S = 2;
const CARDS = ["저녁 산책", "주말 카페", "홈트 기록", "독서 목록", "여행 메모", "아침 루틴"];

function seedRand(seed: number) {
  let s = seed >>> 0;
  return function (): number {
    s = (s * 1664525 + 1013904223) >>> 0;
    return s / 4294967296;
  };
}
function clamp(v: number, lo: number, hi: number): number {
  return Math.max(lo, Math.min(hi, v));
}

export default function VelocityFlingThresholdSwipeCard() {
  const cardRef = useRef<HTMLDivElement | null>(null);
  const xRef = useRef<number>(0) as Box<number>;
  const vxRef = useRef<number>(0) as Box<number>;
  const phaseRef = useRef<string>("idle") as Box<string>;
  const exitDirRef = useRef<number>(1) as Box<number>;
  const draggingRef = useRef<boolean>(false) as Box<boolean>;
  const startXRef = useRef<number>(0) as Box<number>;
  const lastXRef = useRef<number>(0) as Box<number>;
  const lastTRef = useRef<number>(0) as Box<number>;
  const idxRef = useRef<number>(Math.floor(seedRand(23)() * CARDS.length)) as Box<number>;
  const frameRef = useRef<number>(0) as Box<number>;
  const [label, setLabel] = useState(CARDS[idxRef.current % CARDS.length]);
  const [hint, setHint] = useState("속도 0.00 px/ms");
  const [status, setStatus] = useState("대기 중");
  const [demo, setDemo] = useState(true);
  const [reduce, setReduce] = useState(false);

  function render(): void {
    const card = cardRef.current;
    if (!card) return;
    const rot = clamp(xRef.current * SWIPE_ROTATE_LERP_RATIO, -ROTATE_MAX_DEG, ROTATE_MAX_DEG);
    card.style.transform = "translateX(" + xRef.current.toFixed(1) + "px) rotate(" + rot.toFixed(2) + "deg)";
  }

  function nextCard(): void {
    idxRef.current += 1;
    setLabel(CARDS[idxRef.current % CARDS.length]);
    xRef.current = 0; vxRef.current = 0; phaseRef.current = "idle";
    render();
    setStatus("대기 중");
  }

  function judge(velocity: number, dir: number): void {
    setDemo(false);
    setHint("속도 " + Math.abs(velocity).toFixed(2) + " px/ms");
    const flung = Math.abs(velocity) >= FLING_VELOCITY_MIN;
    if (reduce) {
      if (flung) { setStatus(dir > 0 ? "좋아요 처리됨" : "싫어요 처리됨"); nextCard(); }
      else { xRef.current = 0; render(); setStatus("기준 속도 미달 — 되돌아옴"); phaseRef.current = "idle"; }
      return;
    }
    if (flung) {
      phaseRef.current = "exit"; exitDirRef.current = dir;
      setStatus(dir > 0 ? "좋아요 처리됨" : "싫어요 처리됨");
    } else {
      phaseRef.current = "settle";
      setStatus("기준 속도 미달 — 되돌아옴");
    }
  }

  function startDrag(clientX: number): void {
    setDemo(false);
    draggingRef.current = true;
    startXRef.current = clientX; lastXRef.current = clientX; lastTRef.current = performance.now(); vxRef.current = 0;
  }
  function moveDrag(clientX: number): void {
    if (!draggingRef.current) return;
    const now = performance.now();
    const dt = Math.max(now - lastTRef.current, 1);
    vxRef.current = (clientX - lastXRef.current) / dt;
    lastXRef.current = clientX; lastTRef.current = now;
    xRef.current = clientX - startXRef.current;
    render();
  }
  function endDrag(): void {
    if (!draggingRef.current) return;
    draggingRef.current = false;
    judge(vxRef.current, xRef.current >= 0 ? 1 : -1);
  }

  function onPointerDown(e: ReactPointerEvent<HTMLDivElement>): void {
    e.currentTarget.setPointerCapture(e.pointerId);
    startDrag(e.clientX);
  }
  function onPointerMove(e: ReactPointerEvent<HTMLDivElement>): void { moveDrag(e.clientX); }
  function onPointerUp(): void { endDrag(); }

  function keyVerdict(dir: number): void {
    setDemo(false);
    xRef.current = dir * 40; render();
    judge(dir * (FLING_VELOCITY_MIN + 0.15), dir);
  }
  function onKeyDown(e: any): void {
    if (e.key === "ArrowRight") { e.preventDefault(); keyVerdict(1); }
    else if (e.key === "ArrowLeft") { e.preventDefault(); keyVerdict(-1); }
  }

  function step(dt: number): void {
    if (phaseRef.current === "exit") {
      const speed = Math.max(Math.abs(vxRef.current), FLING_VELOCITY_MIN * 1.4);
      xRef.current += exitDirRef.current * speed * dt;
      render();
      if (Math.abs(xRef.current) > EXIT_PX) nextCard();
    } else if (phaseRef.current === "settle") {
      xRef.current += vxRef.current * dt;
      vxRef.current *= INERTIA_DECAY;
      xRef.current += (0 - xRef.current) * SETTLE_RATE;
      render();
      if (Math.abs(xRef.current) < 0.5 && Math.abs(vxRef.current) < 0.01) { xRef.current = 0; phaseRef.current = "idle"; render(); }
    }
  }

  function synth(t: number, synthPhaseRef: Box<string>): void {
    if (t > 0.45 && t < 0.7 && synthPhaseRef.current === "wait") synthPhaseRef.current = "weak";
    if (synthPhaseRef.current === "weak") {
      const p = clamp((t - 0.45) / 0.25, 0, 1);
      xRef.current = p * 30; render();
      if (t >= 0.7) { synthPhaseRef.current = "afterWeak"; judge(0.15, 1); }
    }
    if (t > 1.05 && t < 1.35 && synthPhaseRef.current === "afterWeak") synthPhaseRef.current = "strong";
    if (synthPhaseRef.current === "strong") {
      const q = clamp((t - 1.05) / 0.3, 0, 1);
      xRef.current = q * 130; render();
      if (t >= 1.35) { synthPhaseRef.current = "done"; judge(FLING_VELOCITY_MIN + 0.5, 1); }
    }
  }

  useEffect(() => {
    setReduce(window.matchMedia("(prefers-reduced-motion: reduce)").matches);
  }, []);

  useEffect(() => {
    let start = 0, lastNow = 0, prevT = 0;
    const synthPhaseRef: Box<string> = { current: "wait" };
    function loop(now: number): void {
      if (start === 0) { start = now; lastNow = now; }
      const dt = Math.min(now - lastNow, 48);
      lastNow = now;
      const t = ((now - start) / 1000) % CYCLE_S;
      if (t < prevT) synthPhaseRef.current = "wait";
      prevT = t;
      if (!reduce && demo) synth(t, synthPhaseRef);
      if (!reduce) step(dt);
      frameRef.current = requestAnimationFrame(loop);
    }
    frameRef.current = requestAnimationFrame(loop);
    return () => cancelAnimationFrame(frameRef.current);
  }, [reduce, demo]);

  return (
    <main className={styles.stage}>
      <div className={styles.vf}>
        <p className={styles.caption}>놓는 속도로 갈리는 스와이프 판정</p>
        <div className={styles.scene}>
          <div
            className={styles.card}
            ref={cardRef}
            tabIndex={0}
            role="group"
            aria-roledescription="스와이프 카드"
            onPointerDown={onPointerDown}
            onPointerMove={onPointerMove}
            onPointerUp={onPointerUp}
            onKeyDown={onKeyDown}
          >
            <p className={styles.label}>{label}</p>
            <p className={styles.hint}>{hint}</p>
          </div>
          <button className={styles.btnNope} type="button" aria-label="싫어요" onClick={() => keyVerdict(-1)}>✕</button>
          <button className={styles.btnLike} type="button" aria-label="좋아요" onClick={() => keyVerdict(1)}>♥</button>
        </div>
        <p className={styles.status} aria-live="polite">{status}</p>
      </div>
    </main>
  );
}