03Social login — a button group that recomputes column count from how many providers there are

<main class="stage">
<section class="wrap" id="wrap">
  <p class="hint" id="hint">Out of 5 login methods, <span id="hintCount">2</span> shown</p>
  <div class="tick" id="tick" aria-hidden="true"><div class="tickBar" id="tickBar"></div></div>
  <div class="row" id="row" style="--cols:2">
    <button type="button" class="btn" id="btn0">
      <span class="icon iconCircle" aria-hidden="true"></span>
      <span class="label">Provider A</span>
    </button>
    <button type="button" class="btn" id="btn1">
      <span class="icon iconSquare" aria-hidden="true"></span>
      <span class="label">Provider B</span>
    </button>
    <button type="button" class="btn is-hidden" id="btn2">
      <span class="icon iconTriangle" aria-hidden="true"></span>
      <span class="label">Provider C</span>
    </button>
    <button type="button" class="btn is-hidden" id="btn3">
      <span class="icon iconDiamond" aria-hidden="true"></span>
      <span class="label">Provider D</span>
    </button>
    <button type="button" class="btn is-hidden" id="btn4">
      <span class="icon iconStar" aria-hidden="true"></span>
      <span class="label">Provider E</span>
    </button>
  </div>
</section>
</main>

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

$duration: $dur-loop;
$easing: $ease-out;
$color: $subject-ink;

@include stage($stage-orange);

.wrap {
  width: 100%;
  max-width: 380px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: $sp-3;
  text-align: center;
}

.hint {
  margin: 0;
  color: rgba($subject-ink, .72);
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  font-weight: 500;
  font-size: 11px;
}

.hint span {
  color: $subject-ink;
  font-weight: 700;
}

.tick {
  width: 100%;
  max-width: 120px;
  height: $sp-1;
  border-radius: $r-pill;
  background: rgba($subject-ink, .14);
  overflow: hidden;
}

.tickBar {
  --within: 0;
  width: 100%;
  height: 100%;
  border-radius: $r-pill;
  background: $subject-ink;
  transform: scaleX(var(--within, 0));
  transform-origin: left;
}

.row {
  --cols: 2;
  width: 100%;
  display: grid;
  grid-template-columns: repeat(var(--cols), 1fr);
  gap: $sp-2;
}

.btn {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: $sp-1;
  padding: $sp-2 $sp-1;
  border: 0;
  border-radius: $r-control;
  background: rgba($subject-ink, .08);
  cursor: default;
}

.btn.is-hidden {
  display: none;
}

.icon {
  width: $sp-4;
  height: $sp-4;
  animation: iconPulse $duration $easing infinite;
}

.iconCircle {
  border-radius: $r-pill;
  background: $subject-ink;
}

.iconSquare {
  border-radius: $r-xs;
  background: $subject-ink;
}

.iconTriangle {
  width: 0;
  height: 0;
  border-left: $sp-2 solid transparent;
  border-right: $sp-2 solid transparent;
  border-bottom: $sp-4 solid $subject-ink;
}

.iconDiamond {
  background: $subject-ink;
  border-radius: $r-xs;
  transform: rotate(45deg);
}

.iconStar {
  background: $subject-ink;
  clip-path: polygon(50% 0%, 61% 35%, 98% 35%, 68% 57%, 79% 91%, 50% 70%, 21% 91%, 32% 57%, 2% 35%, 39% 35%);
}

.label {
  color: $subject-ink;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  font-weight: 500;
  font-size: 10px;
}

@keyframes iconPulse {
  0%, 100% { opacity: .82; }
  50% { opacity: 1; }
}

@media (max-width: 340px) {
  .wrap { max-width: 280px; }
  .label { font-size: 9px; }
  .btn { padding: $sp-1; }
}

@media (prefers-reduced-motion: reduce) {
  .icon { animation: none; }
}

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);
}

.wrap {
  width: 100%;
  max-width: 380px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
  text-align: center;
}

.hint {
  margin: 0;
  color: rgba(23, 20, 26, 0.72);
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  font-weight: 500;
  font-size: 11px;
}

.hint span {
  color: #17141a;
  font-weight: 700;
}

.tick {
  width: 100%;
  max-width: 120px;
  height: 4px;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.14);
  overflow: hidden;
}

.tickBar {
  --within: 0;
  width: 100%;
  height: 100%;
  border-radius: 999px;
  background: #17141a;
  transform: scaleX(var(--within, 0));
  transform-origin: left;
}

.row {
  --cols: 2;
  width: 100%;
  display: grid;
  grid-template-columns: repeat(var(--cols), 1fr);
  gap: 8px;
}

.btn {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 4px;
  padding: 8px 4px;
  border: 0;
  border-radius: 12px;
  background: rgba(23, 20, 26, 0.08);
  cursor: default;
}

.btn.is-hidden {
  display: none;
}

.icon {
  width: 16px;
  height: 16px;
  animation: iconPulse 2s ease-out infinite;
}

.iconCircle {
  border-radius: 999px;
  background: #17141a;
}

.iconSquare {
  border-radius: 4px;
  background: #17141a;
}

.iconTriangle {
  width: 0;
  height: 0;
  border-left: 8px solid transparent;
  border-right: 8px solid transparent;
  border-bottom: 16px solid #17141a;
}

.iconDiamond {
  background: #17141a;
  border-radius: 4px;
  transform: rotate(45deg);
}

.iconStar {
  background: #17141a;
  clip-path: polygon(50% 0%, 61% 35%, 98% 35%, 68% 57%, 79% 91%, 50% 70%, 21% 91%, 32% 57%, 2% 35%, 39% 35%);
}

.label {
  color: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  font-weight: 500;
  font-size: 10px;
}

@keyframes iconPulse {
  0%, 100% {
    opacity: 0.82;
  }
  50% {
    opacity: 1;
  }
}
@media (max-width: 340px) {
  .wrap {
    max-width: 280px;
  }
  .label {
    font-size: 9px;
  }
  .btn {
    padding: 4px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .icon {
    animation: none;
  }
}

// 소셜 Log in(03) — 제공자 개수가 시나리오에 따라 바뀔 때 그리드 열 수를 재계산한다.
// 브랜드 로고·브랜드명 없이 순수 CSS 도형 아이콘 + 가상명("Provider A" 류)만 사용.
(function () {
  var row = document.getElementById('row');
  var hintCount = document.getElementById('hintCount');
  var tickBar = document.getElementById('tickBar');
  var btnIds = ['btn0', 'btn1', 'btn2', 'btn3', 'btn4'];
  var btns = btnIds.map(function (id) { return document.getElementById(id); });
  if (!row || !hintCount || !tickBar || btns.some(function (b) { return !b; })) return;
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;

  var COUNTS = [2, 3, 4, 5, 3];
  var STEP_MS = 400;
  var CYCLE_MS = COUNTS.length * STEP_MS;

  function colsFor(n) {
    return n <= 3 ? n : Math.ceil(n / 2);
  }

  function apply(t) {
    var tt = t % CYCLE_MS;
    var idx = Math.min(Math.max(Math.floor(tt / STEP_MS), 0), COUNTS.length - 1);
    var n = COUNTS[idx];
    var cols = colsFor(n);
    row.style.setProperty('--cols', String(cols));
    hintCount.textContent = String(n);
    btns.forEach(function (btn, i) {
      if (i < n) {
        btn.classList.remove('is-hidden');
      } else {
        btn.classList.add('is-hidden');
      }
    });
    // 다음 개수 전환까지 남은 구간을 매 프레임 다시 계산해 가는 줄(계산 한 겹) —
    // 그리드 재배치가 갑자기 튀지 않고 다음 변화가 다가옴을 예고한다.
    var within = (tt % STEP_MS) / STEP_MS;
    tickBar.style.setProperty('--within', within.toFixed(4));
  }

  if (reduce) {
    apply(0);
    return;
  }

  var start = null;
  function loop(ts) {
    if (start === null) start = ts;
    apply(ts - start);
    requestAnimationFrame(loop);
  }
  requestAnimationFrame(loop);
})();

import { useEffect, useRef } from "react";
import styles from "./SocialLogin.module.scss";

// 소셜 로그인 — 제공자 개수가 시나리오에 따라 바뀔 때 그리드 열 수를 재계산한다.
// 브랜드 로고·브랜드명 없이 순수 CSS 도형 아이콘 + 가상명("Provider A" 류)만 사용.
const COUNTS = [2, 3, 4, 5, 3];
const STEP_MS = 400;
const CYCLE_MS = COUNTS.length * STEP_MS;
const PROVIDERS = [
  { id: "btn0", icon: "iconCircle", label: "Provider A" },
  { id: "btn1", icon: "iconSquare", label: "Provider B" },
  { id: "btn2", icon: "iconTriangle", label: "Provider C" },
  { id: "btn3", icon: "iconDiamond", label: "Provider D" },
  { id: "btn4", icon: "iconStar", label: "Provider E" },
] as const;

function colsFor(n: number) {
  return n <= 3 ? n : Math.ceil(n / 2);
}

export default function SocialLogin() {
  const rowRef = useRef<HTMLDivElement>(null);
  const hintCountRef = useRef<HTMLSpanElement>(null);
  const tickBarRef = useRef<HTMLDivElement>(null);
  const btnRefs = [
    useRef<HTMLButtonElement>(null),
    useRef<HTMLButtonElement>(null),
    useRef<HTMLButtonElement>(null),
    useRef<HTMLButtonElement>(null),
    useRef<HTMLButtonElement>(null),
  ];

  useEffect(() => {
    const row = rowRef.current;
    const hintCount = hintCountRef.current;
    const tickBar = tickBarRef.current;
    const btns = btnRefs.map((r) => r.current);
    if (!row || !hintCount || !tickBar || btns.some((b) => !b)) return;
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;

    function apply(t: number) {
      const tt = t % CYCLE_MS;
      const idx = Math.min(Math.max(Math.floor(tt / STEP_MS), 0), COUNTS.length - 1);
      const n = COUNTS[idx];
      const cols = colsFor(n);
      row!.style.setProperty("--cols", String(cols));
      hintCount!.textContent = String(n);
      btns.forEach((btn, i) => {
        if (!btn) return;
        if (i < n) {
          btn.classList.remove(styles.isHidden);
        } else {
          btn.classList.add(styles.isHidden);
        }
      });
      // 다음 개수 전환까지 남은 구간을 매 프레임 다시 계산해 가는 줄(계산 한 겹) —
      // 그리드 재배치가 갑자기 튀지 않고 다음 변화가 다가옴을 예고한다.
      const within = (tt % STEP_MS) / STEP_MS;
      tickBar!.style.setProperty("--within", within.toFixed(4));
    }

    if (reduce) {
      apply(0);
      return;
    }

    let start: number | null = null;
    let raf = 0;
    function loop(ts: number) {
      if (start === null) start = ts;
      apply(ts - start);
      raf = requestAnimationFrame(loop);
    }
    raf = requestAnimationFrame(loop);
    return () => cancelAnimationFrame(raf);
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, []);

  return (
    <div className={styles.stage}>
      <section className={styles.wrap}>
        <p className={styles.hint}>
          로그인 방법 5개 중 <span ref={hintCountRef}>2</span>개 표시
        </p>
        <div className={styles.tick} aria-hidden="true">
          <div className={styles.tickBar} ref={tickBarRef} />
        </div>
        <div className={styles.row} ref={rowRef}>
          {PROVIDERS.map((p, i) => (
            <button
              type="button"
              className={i >= 2 ? `${styles.btn} ${styles.isHidden}` : styles.btn}
              ref={btnRefs[i]}
              key={p.id}
            >
              <span className={`${styles.icon} ${styles[p.icon]}`} aria-hidden="true" />
              <span className={styles.label}>{p.label}</span>
            </button>
          ))}
        </div>
      </section>
    </div>
  );
}