03A File That Flies Into the Tray

<main class="stage">
<div class="fl is-demo" id="flRoot">
  <button class="fl__btn" id="flBtn" type="button">
    <svg class="fl__icon" viewBox="0 0 24 24" aria-hidden="true"><path d="M12 4v11M6.5 10.5 12 16l5.5-5.5M5 20h14"/></svg>
    <span>Download</span>
  </button>
  <svg class="fl__file" id="flFile" viewBox="0 0 24 24" aria-hidden="true"><path d="M7 3h7l5 5v13H7zM14 3v5h5"/></svg>
  <div class="fl__tray" id="flTray" role="status"><span>Received</span><b id="flCount">0</b></div>
</div>
</main>

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

// 핵심: 파일은 JS 가 베지어 곡선 위 좌표를 계산해 transform 으로 옮긴다. 도착한 순간 트레이가 스프링으로 튄다.

$fly-face: $subject-lilac;
$fly-tray: $subject-sky;
$fly-land: $subject-mint;

@include stage($stage-paper);

.fl {
  position: relative;
  width: 240px;
  max-width: 100%;
  height: 164px;
}

.fl__btn {
  position: absolute;
  left: 20px;
  right: 20px;
  top: 0;
  box-sizing: border-box;
  height: 56px;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: $sp-3;
  border: 0;
  border-radius: $r-control;
  background: $fly-face;
  box-shadow: $shadow-press;
  color: $subject-ink;
  font-family: inherit;
  font-size: 18px;
  font-weight: 700;
  line-height: 24px;
  cursor: pointer;
}
.fl__btn:focus-visible { outline: 3px solid $subject-ink; outline-offset: 3px; }
.fl__icon {
  width: 24px;
  height: 24px;
  fill: none;
  stroke: currentColor;
  stroke-width: 2.5;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.fl__file {
  position: absolute;
  left: 0;
  top: 0;
  width: 28px;
  height: 28px;
  opacity: 0;
  fill: $stage-paper;
  stroke: $subject-ink;
  stroke-width: 2;
  stroke-linejoin: round;
  pointer-events: none;
}

.fl__tray {
  --h: 0;
  position: absolute;
  left: 0;
  right: 0;
  top: 92px;
  box-sizing: border-box;
  height: 56px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 $sp-6;
  border: 3px solid $subject-ink;
  border-top-width: 0;
  border-radius: 0 0 $r-card $r-card;
  background: color-mix(in srgb, #{$fly-tray}, #{$fly-land} calc(var(--h) * 100%));
  color: $subject-ink;
  font-size: 16px;
  font-weight: 700;
  line-height: 24px;
}
.fl__tray b { min-width: 3ch; text-align: right; font-variant-numeric: tabular-nums; }

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

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

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

.fl {
  position: relative;
  width: 240px;
  max-width: 100%;
  height: 164px;
}

.fl__btn {
  position: absolute;
  left: 20px;
  right: 20px;
  top: 0;
  box-sizing: border-box;
  height: 56px;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 12px;
  border: 0;
  border-radius: 12px;
  background: #b9a0ff;
  box-shadow: 0 6px 12px rgba(23, 20, 26, 0.32);
  color: #17141a;
  font-family: inherit;
  font-size: 18px;
  font-weight: 700;
  line-height: 24px;
  cursor: pointer;
}

.fl__btn:focus-visible {
  outline: 3px solid #17141a;
  outline-offset: 3px;
}

.fl__icon {
  width: 24px;
  height: 24px;
  fill: none;
  stroke: currentColor;
  stroke-width: 2.5;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.fl__file {
  position: absolute;
  left: 0;
  top: 0;
  width: 28px;
  height: 28px;
  opacity: 0;
  fill: #ffffff;
  stroke: #17141a;
  stroke-width: 2;
  stroke-linejoin: round;
  pointer-events: none;
}

.fl__tray {
  --h: 0;
  position: absolute;
  left: 0;
  right: 0;
  top: 92px;
  box-sizing: border-box;
  height: 56px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 24px;
  border: 3px solid #17141a;
  border-top-width: 0;
  border-radius: 0 0 16px 16px;
  background: color-mix(in srgb, #6ec8ff, #4cd4a6 calc(var(--h) * 100%));
  color: #17141a;
  font-size: 16px;
  font-weight: 700;
  line-height: 24px;
}

.fl__tray b {
  min-width: 3ch;
  text-align: right;
  font-variant-numeric: tabular-nums;
}

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

(function () {
  // 기법: 파일 아이콘은 2차 베지어 곡선 B(t) = (1-t)^2 P0 + 2(1-t)t P1 + t^2 P2 위를 날아간다.
  // 제어점 P1 을 옆으로 ARC_HEIGHT 만큼 밀어 활처럼 휘게 하고, 도착하면 트레이를 TRAY_BOUNCE 만큼 눌러 스프링으로 되돌린다.
  var FLY_MS = 700;
  var ARC_HEIGHT = 56;
  var TRAY_BOUNCE = 14;
  var TRAY_K = 180;
  var TRAY_DAMP = 10;
  var START_MS = 200;
  var CYCLE_MS = 2000;

  var root = document.getElementById('flRoot');
  var btn = document.getElementById('flBtn');
  var file = document.getElementById('flFile');
  var tray = document.getElementById('flTray');
  var countEl = document.getElementById('flCount');
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;

  var clock = 0;
  var flightStart = null;
  var count = 0;
  var ty = 0;
  var tv = 0;
  var lastCycle = -1;
  var t0 = null;
  var lastTs = null;

  function stopDemo() { root.classList.remove('is-demo'); }
  function ease(t) { return t < 0.5 ? 4 * t * t * t : 1 - Math.pow(-2 * t + 2, 3) / 2; }

  function geometry() {
    var w = root.clientWidth;
    var b = btn.offsetTop + btn.offsetHeight / 2;
    var tr = tray.offsetTop + tray.offsetHeight / 2;
    return { x: w / 2, y0: b, y2: tr };
  }

  function land() {
    count += 1;
    ty = TRAY_BOUNCE;
    tv = 0;
    flightStart = null;
  }

  function renderFile(now) {
    if (flightStart === null) { file.style.opacity = '0'; return; }
    var t = Math.min(1, (now - flightStart) / FLY_MS);
    var e = ease(t);
    var g = geometry();
    var cx = g.x + 2 * ARC_HEIGHT;
    var cy = (g.y0 + g.y2) / 2;
    var x = (1 - e) * (1 - e) * g.x + 2 * (1 - e) * e * cx + e * e * g.x;
    var y = (1 - e) * (1 - e) * g.y0 + 2 * (1 - e) * e * cy + e * e * g.y2;
    var rot = 28 * Math.sin(Math.PI * e);
    var sc = 1 - 0.45 * e;
    file.style.opacity = t > 0.9 ? String((1 - t) * 10) : '1';
    file.style.transform = 'translate(' + (x - 14).toFixed(1) + 'px,' + (y - 14).toFixed(1) + 'px) rotate(' + rot.toFixed(1) + 'deg) scale(' + sc.toFixed(3) + ')';
  }

  function renderTray() {
    tray.style.transform = 'translateY(' + ty.toFixed(2) + 'px)';
    tray.style.setProperty('--h', Math.max(0, Math.min(1, ty / TRAY_BOUNCE)).toFixed(3));
    countEl.textContent = String(count);
  }

  function activate() {
    stopDemo();
    if (reduce) { count += 1; renderTray(); return; }
    if (flightStart === null) flightStart = clock;
  }
  btn.addEventListener('click', activate);

  function tick(ts) {
    if (t0 === null) t0 = ts;
    clock = ts - t0;
    var dt = lastTs === null ? 0.016 : Math.min(0.05, (ts - lastTs) / 1000);
    lastTs = ts;
    if (root.classList.contains('is-demo') && clock >= START_MS) {
      var cyc = Math.floor((clock - START_MS) / CYCLE_MS);
      if (cyc > lastCycle) { lastCycle = cyc; count = 0; flightStart = START_MS + cyc * CYCLE_MS; }
    }
    if (flightStart !== null && clock - flightStart >= FLY_MS) land();
    var n = Math.ceil(dt / 0.008);
    var h = dt / n;
    for (var i = 0; i < n; i += 1) {
      tv += (-TRAY_K * ty - TRAY_DAMP * tv) * h;
      ty += tv * h;
    }
    renderFile(clock);
    renderTray();
    requestAnimationFrame(tick);
  }

  if (reduce) {
    stopDemo();
    renderTray();
  } else {
    requestAnimationFrame(tick);
  }
})();

// FlyTrayButton — vanilla 판(03-dlbtn-file-fly-tray) 의 React 포트.
// 파일 아이콘은 2차 베지어 곡선 위를 날고, 도착하면 트레이가 TRAY_BOUNCE 만큼 눌렸다가 스프링으로 돌아온다.
import { useEffect, useRef } from "react";
import styles from "./FlyTrayButton.module.scss";

const FLY_MS = 700;
const ARC_HEIGHT = 56;
const TRAY_BOUNCE = 14;
const TRAY_K = 180;
const TRAY_DAMP = 10;
const START_MS = 200;
const CYCLE_MS = 2000;

function ease(t: number): number {
  return t < 0.5 ? 4 * t * t * t : 1 - Math.pow(-2 * t + 2, 3) / 2;
}

export default function FlyTrayButton() {
  const rootRef = useRef<HTMLDivElement | null>(null);
  const btnRef = useRef<HTMLButtonElement | null>(null);
  const fileRef = useRef<SVGSVGElement | null>(null);
  const trayRef = useRef<HTMLDivElement | null>(null);
  const countRef = useRef<HTMLElement | null>(null);

  useEffect(() => {
    const root = rootRef.current;
    const btn = btnRef.current;
    const file = fileRef.current;
    const tray = trayRef.current;
    const countEl = countRef.current;
    if (!root || !btn || !file || !tray || !countEl) return;
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    let demo = !reduce;
    let clock = 0;
    let flightStart: number | null = null;
    let count = 0;
    let ty = 0;
    let tv = 0;
    let lastCycle = -1;
    let t0: number | null = null;
    let lastTs: number | null = null;
    let raf = 0;

    const land = (): void => { count += 1; ty = TRAY_BOUNCE; tv = 0; flightStart = null; };
    const renderFile = (now: number): void => {
      if (flightStart === null) { file.style.opacity = "0"; return; }
      const t = Math.min(1, (now - flightStart) / FLY_MS);
      const e = ease(t);
      const gx = root.clientWidth / 2;
      const y0 = btn.offsetTop + btn.offsetHeight / 2;
      const y2 = tray.offsetTop + tray.offsetHeight / 2;
      const cx = gx + 2 * ARC_HEIGHT;
      const cy = (y0 + y2) / 2;
      const x = (1 - e) * (1 - e) * gx + 2 * (1 - e) * e * cx + e * e * gx;
      const y = (1 - e) * (1 - e) * y0 + 2 * (1 - e) * e * cy + e * e * y2;
      const rot = 28 * Math.sin(Math.PI * e);
      const sc = 1 - 0.45 * e;
      file.style.opacity = t > 0.9 ? String((1 - t) * 10) : "1";
      file.style.transform = `translate(${(x - 14).toFixed(1)}px,${(y - 14).toFixed(1)}px) rotate(${rot.toFixed(1)}deg) scale(${sc.toFixed(3)})`;
    };
    const renderTray = (): void => {
      tray.style.transform = `translateY(${ty.toFixed(2)}px)`;
      tray.style.setProperty("--h", Math.max(0, Math.min(1, ty / TRAY_BOUNCE)).toFixed(3));
      countEl.textContent = String(count);
    };
    const activate = (): void => {
      demo = false;
      if (reduce) { count += 1; renderTray(); return; }
      if (flightStart === null) flightStart = clock;
    };
    btn.addEventListener("click", activate);

    function tick(ts: number): void {
      if (t0 === null) t0 = ts;
      clock = ts - t0;
      const dt = lastTs === null ? 0.016 : Math.min(0.05, (ts - lastTs) / 1000);
      lastTs = ts;
      if (demo && clock >= START_MS) {
        const cyc = Math.floor((clock - START_MS) / CYCLE_MS);
        if (cyc > lastCycle) { lastCycle = cyc; count = 0; flightStart = START_MS + cyc * CYCLE_MS; }
      }
      if (flightStart !== null && clock - flightStart >= FLY_MS) land();
      const n = Math.ceil(dt / 0.008);
      const h = dt / n;
      for (let i = 0; i < n; i += 1) {
        tv += (-TRAY_K * ty - TRAY_DAMP * tv) * h;
        ty += tv * h;
      }
      renderFile(clock);
      renderTray();
      raf = requestAnimationFrame(tick);
    }

    if (reduce) renderTray();
    else raf = requestAnimationFrame(tick);
    return () => {
      cancelAnimationFrame(raf);
      btn.removeEventListener("click", activate);
    };
  }, []);

  return (
    <main className={styles.stage}>
      <div className={styles.fl} ref={rootRef}>
        <button className={styles.fl__btn} type="button" ref={btnRef}>
          <svg className={styles.fl__icon} viewBox="0 0 24 24" aria-hidden="true">
            <path d="M12 4v11M6.5 10.5 12 16l5.5-5.5M5 20h14" />
          </svg>
          <span>내려받기</span>
        </button>
        <svg className={styles.fl__file} viewBox="0 0 24 24" aria-hidden="true" ref={fileRef}>
          <path d="M7 3h7l5 5v13H7zM14 3v5h5" />
        </svg>
        <div className={styles.fl__tray} role="status" ref={trayRef}>
          <span>받은 파일</span>
          <b ref={countRef}>0</b>
        </div>
      </div>
    </main>
  );
}