07Tab content cross-fade

<main class="stage">
  <div class="pages is-demo">
    <div class="tabs">
      <span class="tab tab--on">General</span>
      <span class="tab">Security</span>
    </div>
    <section class="page page--a">
      <p class="page__body">Change language, theme, and notification frequency here</p>
    </section>
    <section class="page page--b">
      <p class="page__body">Change password and two-factor auth here</p>
    </section>
  </div>
</main>

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

// ── 변수 3개. 변형은 이것만 바꾼다 (값은 토큰에서 받는다) ──────
$duration: $dur-quick;
$easing: $ease-out;
$color: $subject-cream;

// ── 데모 무대 ───────────────────────────────
@include stage($stage-orange);

.pages { position: relative; width: min(300px, 88%); height: 150px; border-radius: $r-card; overflow: hidden; box-shadow: $shadow-raised; background: #fff; }
.tabs { position: absolute; top: 0; left: 0; right: 0; display: flex; gap: clamp(10px, 4vw, 16px); padding: clamp(10px, 4vw, 14px) clamp(12px, 5vw, 18px) 0; box-sizing: border-box; }
.tab { font-weight: 700; font-size: clamp(11px, 3.2vw, 13px); line-height: 1; font-family: inherit; color: $subject-ink; opacity: .4; padding-bottom: 8px; }
.tab--on { opacity: 1; color: $subject-ink; border-bottom: 2px solid $color; }
.page {
  position: absolute; left: 0; right: 0; bottom: 0; top: 40px; box-sizing: border-box;
  padding: clamp(12px, 5vw, 18px); display: flex; align-items: center;
}
.page__body { margin: 0; font-weight: 400; font-size: clamp(11px, 3.2vw, 13px); line-height: 1.5; font-family: inherit; color: $subject-ink; }

// 탭이 바뀌면 이전 콘텐츠는 사라지고 새 콘텐츠가 8px 위에서 겹쳐 내려온다.
.page--a { animation: tab-a $dur-loop $easing infinite; }
.page--b { animation: tab-b $dur-loop $easing infinite; opacity: 0; transform: translateY(8px); }

@keyframes tab-a {
  0%, 5% { opacity: 1; transform: translateY(0); }
  50% { opacity: 0; transform: translateY(-8px); }
  95%, 100% { opacity: 1; transform: translateY(0); }
}
@keyframes tab-b {
  0%, 5% { opacity: 0; transform: translateY(8px); }
  50% { opacity: 1; transform: translateY(0); }
  95%, 100% { opacity: 0; transform: translateY(8px); }
}

// ── 접근성: 움직임 줄이기 설정이면 최종 상태만 고정으로 ────────
@media (prefers-reduced-motion: reduce) {
  .page--a, .page--b { animation: none !important; }
  .page--a { opacity: 1; transform: translateY(0); }
  .page--b { opacity: 0; transform: translateY(0); }
}

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);
}

.pages {
  position: relative;
  width: min(300px, 88%);
  height: 150px;
  border-radius: 16px;
  overflow: hidden;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  background: #fff;
}

.tabs {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  display: flex;
  gap: clamp(10px, 4vw, 16px);
  padding: clamp(10px, 4vw, 14px) clamp(12px, 5vw, 18px) 0;
  box-sizing: border-box;
}

.tab {
  font-weight: 700;
  font-size: clamp(11px, 3.2vw, 13px);
  line-height: 1;
  font-family: inherit;
  color: #17141a;
  opacity: 0.4;
  padding-bottom: 8px;
}

.tab--on {
  opacity: 1;
  color: #17141a;
  border-bottom: 2px solid #fff7e6;
}

.page {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  top: 40px;
  box-sizing: border-box;
  padding: clamp(12px, 5vw, 18px);
  display: flex;
  align-items: center;
}

.page__body {
  margin: 0;
  font-weight: 400;
  font-size: clamp(11px, 3.2vw, 13px);
  line-height: 1.5;
  font-family: inherit;
  color: #17141a;
}

.page--a {
  animation: tab-a 2s ease-out infinite;
}

.page--b {
  animation: tab-b 2s ease-out infinite;
  opacity: 0;
  transform: translateY(8px);
}

@keyframes tab-a {
  0%, 5% {
    opacity: 1;
    transform: translateY(0);
  }
  50% {
    opacity: 0;
    transform: translateY(-8px);
  }
  95%, 100% {
    opacity: 1;
    transform: translateY(0);
  }
}
@keyframes tab-b {
  0%, 5% {
    opacity: 0;
    transform: translateY(8px);
  }
  50% {
    opacity: 1;
    transform: translateY(0);
  }
  95%, 100% {
    opacity: 0;
    transform: translateY(8px);
  }
}
@media (prefers-reduced-motion: reduce) {
  .page--a, .page--b {
    animation: none !important;
  }
  .page--a {
    opacity: 1;
    transform: translateY(0);
  }
  .page--b {
    opacity: 0;
    transform: translateY(0);
  }
}

import type { CSSProperties, ReactNode } from "react";
import styles from "./TabCrossfadeTransition.module.scss";

export type TabCrossfadeTransitionProps = {
  active: "a" | "b";
  tabA: ReactNode;
  tabB: ReactNode;
  panelA: ReactNode;
  panelB: ReactNode;
  /** 전환 시간 (기본 200ms) */
  duration?: number;
  easing?: string;
  color?: string;
  className?: string;
};

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };

export default function TabCrossfadeTransition({
  active,
  tabA,
  tabB,
  panelA,
  panelB,
  duration = 200,
  easing = "ease-out",
  color = "#fff7e6",
  className = "",
}: TabCrossfadeTransitionProps) {
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };
  return (
    <div className={`${styles.pages} ${className}`} style={vars} data-active={active}>
      <div className={styles.tabs}>
        <span className={styles.tab} data-on={active === "a"}>{tabA}</span>
        <span className={styles.tab} data-on={active === "b"}>{tabB}</span>
      </div>
      <section className={styles.panelA}>{panelA}</section>
      <section className={styles.panelB}>{panelB}</section>
    </div>
  );
}