02Threshold gauge

<main class="stage">
  <section class="tg is-demo" id="tg" aria-label="Threshold gauge">
    <header class="tg__head">
      <p class="tg__title">Threshold gauge</p>
      <p class="tg__attr"><code>threshold: [0, 0.25, 0.5, 1]</code></p>
    </header>
    <div class="tg__body">
      <div class="tg__view" id="tg-view" tabindex="0" role="region" aria-label="Target viewport — try scrolling">
        <div class="tg__track" id="tg-track">
          <p class="tg__lead">The target rises from below</p>
          <div class="tg__target" id="tg-target">
            <b>Target element</b>
            <span>How much of its height is in view</span>
          </div>
        </div>
      </div>
      <div class="tg__panel">
        <p class="tg__read" aria-live="polite">
          <b class="tg__numcur" id="tg-num">0.00</b>
          <span class="tg__nums" aria-hidden="true"><b>0.00</b><b>0.25</b><b>0.50</b><b>1.00</b></span>
        </p>
        <div class="tg__gauge" aria-hidden="true">
          <i class="tg__fill" id="tg-fill"></i>
          <i class="tg__tick tg__tick--0"></i>
          <i class="tg__tick tg__tick--25"></i>
          <i class="tg__tick tg__tick--50"></i>
          <i class="tg__tick tg__tick--100"></i>
        </div>
        <p class="tg__scale" aria-hidden="true"><span class="tg__s0">0</span><span class="tg__s25">0.25</span><span class="tg__s50">0.5</span><span class="tg__s100">1</span></p>
        <p class="tg__candt">Threshold candidates</p>
        <div class="tg__cands" id="tg-cands">
          <button type="button" class="tg__cand" data-th="0" aria-pressed="false">0</button>
          <button type="button" class="tg__cand is-on" data-th="0.25" aria-pressed="true">0.25</button>
          <button type="button" class="tg__cand" data-th="0.5" aria-pressed="false">0.5</button>
          <button type="button" class="tg__cand" data-th="1" aria-pressed="false">1</button>
        </div>
        <p class="tg__lightline">
          <span class="tg__led" id="tg-led" aria-hidden="true"></span>
          <span class="tg__state">
            <b class="tg__stcur" id="tg-state">Waiting</b>
            <span class="tg__sts" aria-hidden="true"><b>Waiting</b><b>Threshold reached</b></span>
          </span>
        </p>
      </div>
    </div>
    <footer class="tg__foot">The observer reports only when a threshold is crossed</footer>
  </section>
</main>

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

// 임계값 게이지 — intersectionRatio 를 게이지 막대(scaleX) 와 숫자로 실측해 보여준다
// 관찰자는 threshold 후보를 지날 때만 보고하므로 숫자·게이지·불은 계단(steps 컷)으로 갱신하고
// 타깃 카드의 진입 움직임만 이징(transform) 으로 분리한다 — 유령 프레임 방지
$duration: $dur-loop;
$easing: $ease-spring;
$color: $subject-blue;

@include stage($stage-ink);

.tg {
  box-sizing: border-box;
  width: min(430px, 100%);
  border-radius: $r-card;
  background: $subject-cream;
  color: $subject-ink;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  overflow: hidden;
  box-shadow: $shadow-raised;
}

.tg__head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: $sp-2;
  padding: $sp-2 $sp-3;
}
.tg__title {
  margin: 0;
  font-size: 13px;
  font-weight: 800;
  line-height: 1.3;
}
.tg__attr {
  margin: 0;
  font-size: 10px;
  line-height: 1.3;
  color: rgba($subject-ink, .72);
  code { font-family: "Consolas", "Menlo", monospace; }
}

.tg__body {
  display: grid;
  grid-template-columns: 1fr 188px;
  gap: $sp-3;
  padding: 0 $sp-3 $sp-2;
}

.tg__view {
  box-sizing: border-box;
  height: 158px;
  overflow-y: auto;
  padding: 0 $sp-2;
  outline: none;
  background: rgba($subject-ink, .05);
  border: 1px solid rgba($subject-ink, .14);
  border-radius: $r-sm;
}
.tg__track {
  position: relative; // 안내 문구를 절대 위치로 띄워 줄이 바뀌어도 타깃 위치가 흔들리지 않게 한다
  padding-top: $sp-2;
  padding-bottom: $sp-6; // 스크롤 여유
}
.tg__lead {
  position: absolute;
  top: $sp-2;
  left: $sp-2;
  right: $sp-2;
  margin: 0;
  font-size: 11px;
  font-weight: 700;
  line-height: 14px;
  color: rgba($subject-ink, .72);
}
.tg__target {
  margin-top: 150px; // 타깃 top 이 뷰포트 바닥(158px = 8 + 150) 에 딱 닿게 — 진입 전 intersectionRatio 0
  box-sizing: border-box;
  height: 88px; // 0.25 배수(22·44·88) 로 잡아 임계값 통과 거리가 정수가 되게 한다
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: $sp-1;
  padding: $sp-2 $sp-3;
  border-radius: $r-control;
  background: $subject-blue-deep;
  color: $subject-cream;
  b { font-size: 14px; font-weight: 800; line-height: 1.3; }
  span { font-size: 10px; font-weight: 700; line-height: 1.3; }
}

.tg__panel { display: flex; flex-direction: column; }
.tg__read {
  position: relative;
  height: 32px;
  margin: 0;
}
.tg__numcur,
.tg__nums b {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  font-size: 22px;
  font-weight: 800;
  line-height: 1;
  font-variant-numeric: tabular-nums;
}
.tg__nums { display: none; }
.tg__nums b { opacity: 0; }
.tg.is-demo .tg__nums { display: block; }
.tg.is-demo .tg__numcur { visibility: hidden; } // 미리보기 동안엔 계단 레이어가 값을 보여준다

.tg__gauge {
  position: relative;
  height: 10px;
  margin-top: $sp-2;
  border-radius: $r-pill;
  background: rgba($subject-ink, .14);
}
.tg__fill {
  position: absolute;
  inset: 0;
  border-radius: $r-pill;
  background: $color;
  transform: scaleX(0);
  transform-origin: left center; // 채움 막대 — 시작 변에서 자란다 (붙는 지점이 있는 요소 예외)
}
.tg__tick {
  position: absolute;
  top: -3px;
  width: 2px;
  height: 16px;
  border-radius: $r-pill;
  background: rgba($subject-ink, .35);
}
.tg__tick--0 { left: 0; }
.tg__tick--25 { left: 25%; }
.tg__tick--50 { left: 50%; transform: translateX(-1px); }
.tg__tick--100 { left: 100%; transform: translateX(-2px); }
.tg__scale {
  position: relative;
  height: 12px;
  margin: $sp-1 0 0;
  font-size: 9px;
  font-weight: 700;
  line-height: 12px;
  color: rgba($subject-ink, .72);
}
.tg__scale span { position: absolute; }
.tg__s0 { left: 0; }
.tg__s25 { left: 25%; }
.tg__s50 { left: 50%; transform: translateX(-50%); }
.tg__s100 { left: 100%; transform: translateX(-100%); }

.tg__candt {
  margin: $sp-2 0 0;
  font-size: 10px;
  font-weight: 700;
  line-height: 1.3;
  color: rgba($subject-ink, .72);
}
.tg__cands {
  display: flex;
  gap: $sp-1;
  margin-top: $sp-1;
}
.tg__cand {
  flex: 1 1 auto;
  padding: $sp-1 0;
  border: 1px solid rgba($subject-ink, .25);
  border-radius: $r-xs;
  background: none;
  color: rgba($subject-ink, .72);
  font-family: inherit;
  font-size: 11px;
  font-weight: 700;
  line-height: 1.3;
  cursor: pointer;
}
.tg__cand.is-on {
  border-color: $subject-ink;
  background: $subject-ink;
  color: $subject-cream;
}
// 후보 칩의 두 얼굴 — 미리보기 키프레임도 같은 값을 쓰도록 믹스인으로 한 곳에 둔다
@mixin cand-off {
  border-color: rgba($subject-ink, .25);
  background-color: transparent;
  color: rgba($subject-ink, .72);
}
@mixin cand-on {
  border-color: $subject-ink;
  background-color: $subject-ink;
  color: $subject-cream;
}
.tg__lightline {
  display: flex;
  align-items: center;
  gap: $sp-2;
  margin: $sp-2 0 0;
}
.tg__led {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: rgba($subject-ink, .18);
}
.tg__led.is-on { background: $subject-orange-deep; }
.tg__state {
  position: relative;
  flex: 1 1 auto; // 라벨 칸이 남은 폭을 다 가져간다 — 절대 배치된 컷 레이어가 설 자리
  min-width: 0;
  white-space: nowrap; // 「임계값 도달」이 여러 줄로 쪼개지지 않게
  font-size: 11px;
  font-weight: 700;
  line-height: 1.3;
}
.tg__stcur { font-weight: 700; }
.tg__stcur.is-on { color: $subject-orange-deep; }
.tg__sts { display: none; }
.tg__sts b {
  position: absolute;
  left: 0;
  top: 0;
  opacity: 0;
}
.tg__sts b:last-child { color: $subject-orange-deep; }
.tg.is-demo .tg__sts { display: block; position: absolute; inset: 0; }
.tg.is-demo .tg__stcur { visibility: hidden; } // 미리보기 동안엔 컷 레이어가 상태 글자를 보여준다

.tg__foot {
  padding: $sp-2 $sp-3;
  border-top: 1px solid rgba($subject-ink, .12);
  font-size: 10px;
  font-weight: 700;
  line-height: 1.3;
  color: rgba($subject-ink, .72);
}

// 미리보기 — 스크롤 대신 트랙을 올리고, 숫자·게이지·불은 임계값 통과 순간(30·42·58%) 에 계단으로 갱신한다
.tg.is-demo {
  .tg__track {
    animation-name: tg-flow;
    animation-duration: $duration;
    animation-timing-function: $easing;
    animation-iteration-count: infinite;
  }
  .tg__nums b {
    animation-duration: $duration;
    animation-timing-function: steps(1, end);
    animation-iteration-count: infinite;
  }
  .tg__nums b:nth-child(1) { animation-name: tg-n1; }
  .tg__nums b:nth-child(2) { animation-name: tg-n2; }
  .tg__nums b:nth-child(3) { animation-name: tg-n3; }
  .tg__nums b:nth-child(4) { animation-name: tg-n4; }
  .tg__fill {
    animation-name: tg-fill;
    animation-duration: $duration;
    animation-timing-function: steps(1, end);
    animation-iteration-count: infinite;
  }
  .tg__led {
    animation-name: tg-led;
    animation-duration: $duration;
    animation-timing-function: steps(1, end);
    animation-iteration-count: infinite;
  }
  .tg__sts b {
    animation-duration: $duration;
    animation-timing-function: steps(1, end);
    animation-iteration-count: infinite;
  }
  .tg__sts b:nth-child(1) { animation-name: tg-st1; }
  .tg__sts b:nth-child(2) { animation-name: tg-st2; }
  // 미리보기 동안엔 활성 후보도 같이 걷는다 — 어느 프레임을 잘라도 강조된 후보와 표시된 비율이 같은 값이다
  .tg__cand.is-on { @include cand-off; } // 정적 선택(0.25) 은 잠시 내려놓는다
  .tg__cand {
    animation-duration: $duration;
    animation-timing-function: steps(1, end);
    animation-iteration-count: infinite;
  }
  .tg__cand:nth-child(1) { animation-name: tg-c1; }
  .tg__cand:nth-child(2) { animation-name: tg-c2; }
  .tg__cand:nth-child(3) { animation-name: tg-c3; }
  .tg__cand:nth-child(4) { animation-name: tg-c4; }
}

@keyframes tg-flow {
  0%, 12% { transform: translateY(0); }
  30% { transform: translateY(-22px); }   // 타깃 22px 진입 — 0.25 통과
  42% { transform: translateY(-44px); }   // 0.50 통과
  58% { transform: translateY(-88px); }   // 1.00 통과 (완전 진입)
  66%, 100% { transform: translateY(-110px); } // 도달 상태로 끝까지 — 재시작은 0% 점프
}
@keyframes tg-n1 { 0% { opacity: 1; } 30%, 100% { opacity: 0; } }
@keyframes tg-n2 { 0% { opacity: 0; } 30% { opacity: 1; } 42%, 100% { opacity: 0; } }
@keyframes tg-n3 { 0% { opacity: 0; } 42% { opacity: 1; } 58%, 100% { opacity: 0; } }
@keyframes tg-n4 { 0% { opacity: 0; } 58%, 100% { opacity: 1; } }
@keyframes tg-fill {
  0%, 12% { transform: scaleX(0); }
  30% { transform: scaleX(.25); }
  42% { transform: scaleX(.5); }
  58%, 100% { transform: scaleX(1); }
}
@keyframes tg-led {
  0% { background: rgba($subject-ink, .18); }
  30%, 100% { background: $subject-orange-deep; } // 첫 후보를 지난 순간 점등, 이후로는 계속 도달 상태
}
// 후보 강조 — 숫자·게이지와 같은 시각(30·42·58%) 에 다음 후보로 넘어간다
@keyframes tg-c1 { 0% { @include cand-on; } 30%, 100% { @include cand-off; } }
@keyframes tg-c2 { 0% { @include cand-off; } 30% { @include cand-on; } 42%, 100% { @include cand-off; } }
@keyframes tg-c3 { 0% { @include cand-off; } 42% { @include cand-on; } 58%, 100% { @include cand-off; } }
@keyframes tg-c4 { 0% { @include cand-off; } 58%, 100% { @include cand-on; } }
@keyframes tg-st1 {
  0% { opacity: 1; }
  30%, 100% { opacity: 0; }
}
@keyframes tg-st2 {
  0% { opacity: 0; }
  30%, 100% { opacity: 1; }
}

@media (max-width: 340px) {
  .tg__head { padding: $sp-1 $sp-2; }
  .tg__body { grid-template-columns: 1fr 148px; gap: $sp-2; padding: 0 $sp-2 $sp-1; }
  .tg__view { height: 112px; }
  .tg__target { margin-top: 104px; }
  .tg__read { height: 26px; }
  .tg__numcur, .tg__nums b { font-size: 18px; }
  .tg__gauge { margin-top: $sp-1; }
  .tg__candt { margin-top: $sp-1; }
  .tg__lightline { margin-top: $sp-1; }
  .tg__foot { padding: $sp-1 $sp-2; }
}

@media (prefers-reduced-motion: reduce) {
  .tg.is-demo .tg__track,
  .tg.is-demo .tg__nums b,
  .tg.is-demo .tg__fill,
  .tg.is-demo .tg__led,
  .tg.is-demo .tg__sts b,
  .tg.is-demo .tg__cand { animation: none !important; }
  .tg.is-demo .tg__cand.is-on { @include cand-on; } // 정지 상태에선 정적 선택(0.25) 이 그대로 보인다
  .tg.is-demo .tg__nums,
  .tg.is-demo .tg__sts { display: none !important; }
  .tg.is-demo .tg__numcur,
  .tg.is-demo .tg__stcur { visibility: visible !important; } // 정지 상태에서도 숫자·상태가 보인다
}

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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.tg {
  box-sizing: border-box;
  width: min(430px, 100%);
  border-radius: 16px;
  background: #fff7e6;
  color: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  overflow: hidden;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
}

.tg__head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 8px;
  padding: 8px 12px;
}

.tg__title {
  margin: 0;
  font-size: 13px;
  font-weight: 800;
  line-height: 1.3;
}

.tg__attr {
  margin: 0;
  font-size: 10px;
  line-height: 1.3;
  color: rgba(23, 20, 26, 0.72);
}
.tg__attr code {
  font-family: "Consolas", "Menlo", monospace;
}

.tg__body {
  display: grid;
  grid-template-columns: 1fr 188px;
  gap: 12px;
  padding: 0 12px 8px;
}

.tg__view {
  box-sizing: border-box;
  height: 158px;
  overflow-y: auto;
  padding: 0 8px;
  outline: none;
  background: rgba(23, 20, 26, 0.05);
  border: 1px solid rgba(23, 20, 26, 0.14);
  border-radius: 8px;
}

.tg__track {
  position: relative;
  padding-top: 8px;
  padding-bottom: 24px;
}

.tg__lead {
  position: absolute;
  top: 8px;
  left: 8px;
  right: 8px;
  margin: 0;
  font-size: 11px;
  font-weight: 700;
  line-height: 14px;
  color: rgba(23, 20, 26, 0.72);
}

.tg__target {
  margin-top: 150px;
  box-sizing: border-box;
  height: 88px;
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: 4px;
  padding: 8px 12px;
  border-radius: 12px;
  background: #0a4fe8;
  color: #fff7e6;
}
.tg__target b {
  font-size: 14px;
  font-weight: 800;
  line-height: 1.3;
}
.tg__target span {
  font-size: 10px;
  font-weight: 700;
  line-height: 1.3;
}

.tg__panel {
  display: flex;
  flex-direction: column;
}

.tg__read {
  position: relative;
  height: 32px;
  margin: 0;
}

.tg__numcur,
.tg__nums b {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  font-size: 22px;
  font-weight: 800;
  line-height: 1;
  font-variant-numeric: tabular-nums;
}

.tg__nums {
  display: none;
}

.tg__nums b {
  opacity: 0;
}

.tg.is-demo .tg__nums {
  display: block;
}

.tg.is-demo .tg__numcur {
  visibility: hidden;
}

.tg__gauge {
  position: relative;
  height: 10px;
  margin-top: 8px;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.14);
}

.tg__fill {
  position: absolute;
  inset: 0;
  border-radius: 999px;
  background: #2f6df6;
  transform: scaleX(0);
  transform-origin: left center;
}

.tg__tick {
  position: absolute;
  top: -3px;
  width: 2px;
  height: 16px;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.35);
}

.tg__tick--0 {
  left: 0;
}

.tg__tick--25 {
  left: 25%;
}

.tg__tick--50 {
  left: 50%;
  transform: translateX(-1px);
}

.tg__tick--100 {
  left: 100%;
  transform: translateX(-2px);
}

.tg__scale {
  position: relative;
  height: 12px;
  margin: 4px 0 0;
  font-size: 9px;
  font-weight: 700;
  line-height: 12px;
  color: rgba(23, 20, 26, 0.72);
}

.tg__scale span {
  position: absolute;
}

.tg__s0 {
  left: 0;
}

.tg__s25 {
  left: 25%;
}

.tg__s50 {
  left: 50%;
  transform: translateX(-50%);
}

.tg__s100 {
  left: 100%;
  transform: translateX(-100%);
}

.tg__candt {
  margin: 8px 0 0;
  font-size: 10px;
  font-weight: 700;
  line-height: 1.3;
  color: rgba(23, 20, 26, 0.72);
}

.tg__cands {
  display: flex;
  gap: 4px;
  margin-top: 4px;
}

.tg__cand {
  flex: 1 1 auto;
  padding: 4px 0;
  border: 1px solid rgba(23, 20, 26, 0.25);
  border-radius: 4px;
  background: none;
  color: rgba(23, 20, 26, 0.72);
  font-family: inherit;
  font-size: 11px;
  font-weight: 700;
  line-height: 1.3;
  cursor: pointer;
}

.tg__cand.is-on {
  border-color: #17141a;
  background: #17141a;
  color: #fff7e6;
}

.tg__lightline {
  display: flex;
  align-items: center;
  gap: 8px;
  margin: 8px 0 0;
}

.tg__led {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: rgba(23, 20, 26, 0.18);
}

.tg__led.is-on {
  background: #c93000;
}

.tg__state {
  position: relative;
  flex: 1 1 auto;
  min-width: 0;
  white-space: nowrap;
  font-size: 11px;
  font-weight: 700;
  line-height: 1.3;
}

.tg__stcur {
  font-weight: 700;
}

.tg__stcur.is-on {
  color: #c93000;
}

.tg__sts {
  display: none;
}

.tg__sts b {
  position: absolute;
  left: 0;
  top: 0;
  opacity: 0;
}

.tg__sts b:last-child {
  color: #c93000;
}

.tg.is-demo .tg__sts {
  display: block;
  position: absolute;
  inset: 0;
}

.tg.is-demo .tg__stcur {
  visibility: hidden;
}

.tg__foot {
  padding: 8px 12px;
  border-top: 1px solid rgba(23, 20, 26, 0.12);
  font-size: 10px;
  font-weight: 700;
  line-height: 1.3;
  color: rgba(23, 20, 26, 0.72);
}

.tg.is-demo .tg__track {
  animation-name: tg-flow;
  animation-duration: 2s;
  animation-timing-function: cubic-bezier(0.2, 0.8, 0.2, 1);
  animation-iteration-count: infinite;
}
.tg.is-demo .tg__nums b {
  animation-duration: 2s;
  animation-timing-function: steps(1, end);
  animation-iteration-count: infinite;
}
.tg.is-demo .tg__nums b:nth-child(1) {
  animation-name: tg-n1;
}
.tg.is-demo .tg__nums b:nth-child(2) {
  animation-name: tg-n2;
}
.tg.is-demo .tg__nums b:nth-child(3) {
  animation-name: tg-n3;
}
.tg.is-demo .tg__nums b:nth-child(4) {
  animation-name: tg-n4;
}
.tg.is-demo .tg__fill {
  animation-name: tg-fill;
  animation-duration: 2s;
  animation-timing-function: steps(1, end);
  animation-iteration-count: infinite;
}
.tg.is-demo .tg__led {
  animation-name: tg-led;
  animation-duration: 2s;
  animation-timing-function: steps(1, end);
  animation-iteration-count: infinite;
}
.tg.is-demo .tg__sts b {
  animation-duration: 2s;
  animation-timing-function: steps(1, end);
  animation-iteration-count: infinite;
}
.tg.is-demo .tg__sts b:nth-child(1) {
  animation-name: tg-st1;
}
.tg.is-demo .tg__sts b:nth-child(2) {
  animation-name: tg-st2;
}
.tg.is-demo .tg__cand.is-on {
  border-color: rgba(23, 20, 26, 0.25);
  background-color: transparent;
  color: rgba(23, 20, 26, 0.72);
}
.tg.is-demo .tg__cand {
  animation-duration: 2s;
  animation-timing-function: steps(1, end);
  animation-iteration-count: infinite;
}
.tg.is-demo .tg__cand:nth-child(1) {
  animation-name: tg-c1;
}
.tg.is-demo .tg__cand:nth-child(2) {
  animation-name: tg-c2;
}
.tg.is-demo .tg__cand:nth-child(3) {
  animation-name: tg-c3;
}
.tg.is-demo .tg__cand:nth-child(4) {
  animation-name: tg-c4;
}

@keyframes tg-flow {
  0%, 12% {
    transform: translateY(0);
  }
  30% {
    transform: translateY(-22px);
  }
  42% {
    transform: translateY(-44px);
  }
  58% {
    transform: translateY(-88px);
  }
  66%, 100% {
    transform: translateY(-110px);
  }
}
@keyframes tg-n1 {
  0% {
    opacity: 1;
  }
  30%, 100% {
    opacity: 0;
  }
}
@keyframes tg-n2 {
  0% {
    opacity: 0;
  }
  30% {
    opacity: 1;
  }
  42%, 100% {
    opacity: 0;
  }
}
@keyframes tg-n3 {
  0% {
    opacity: 0;
  }
  42% {
    opacity: 1;
  }
  58%, 100% {
    opacity: 0;
  }
}
@keyframes tg-n4 {
  0% {
    opacity: 0;
  }
  58%, 100% {
    opacity: 1;
  }
}
@keyframes tg-fill {
  0%, 12% {
    transform: scaleX(0);
  }
  30% {
    transform: scaleX(0.25);
  }
  42% {
    transform: scaleX(0.5);
  }
  58%, 100% {
    transform: scaleX(1);
  }
}
@keyframes tg-led {
  0% {
    background: rgba(23, 20, 26, 0.18);
  }
  30%, 100% {
    background: #c93000;
  }
}
@keyframes tg-c1 {
  0% {
    border-color: #17141a;
    background-color: #17141a;
    color: #fff7e6;
  }
  30%, 100% {
    border-color: rgba(23, 20, 26, 0.25);
    background-color: transparent;
    color: rgba(23, 20, 26, 0.72);
  }
}
@keyframes tg-c2 {
  0% {
    border-color: rgba(23, 20, 26, 0.25);
    background-color: transparent;
    color: rgba(23, 20, 26, 0.72);
  }
  30% {
    border-color: #17141a;
    background-color: #17141a;
    color: #fff7e6;
  }
  42%, 100% {
    border-color: rgba(23, 20, 26, 0.25);
    background-color: transparent;
    color: rgba(23, 20, 26, 0.72);
  }
}
@keyframes tg-c3 {
  0% {
    border-color: rgba(23, 20, 26, 0.25);
    background-color: transparent;
    color: rgba(23, 20, 26, 0.72);
  }
  42% {
    border-color: #17141a;
    background-color: #17141a;
    color: #fff7e6;
  }
  58%, 100% {
    border-color: rgba(23, 20, 26, 0.25);
    background-color: transparent;
    color: rgba(23, 20, 26, 0.72);
  }
}
@keyframes tg-c4 {
  0% {
    border-color: rgba(23, 20, 26, 0.25);
    background-color: transparent;
    color: rgba(23, 20, 26, 0.72);
  }
  58%, 100% {
    border-color: #17141a;
    background-color: #17141a;
    color: #fff7e6;
  }
}
@keyframes tg-st1 {
  0% {
    opacity: 1;
  }
  30%, 100% {
    opacity: 0;
  }
}
@keyframes tg-st2 {
  0% {
    opacity: 0;
  }
  30%, 100% {
    opacity: 1;
  }
}
@media (max-width: 340px) {
  .tg__head {
    padding: 4px 8px;
  }
  .tg__body {
    grid-template-columns: 1fr 148px;
    gap: 8px;
    padding: 0 8px 4px;
  }
  .tg__view {
    height: 112px;
  }
  .tg__target {
    margin-top: 104px;
  }
  .tg__read {
    height: 26px;
  }
  .tg__numcur, .tg__nums b {
    font-size: 18px;
  }
  .tg__gauge {
    margin-top: 4px;
  }
  .tg__candt {
    margin-top: 4px;
  }
  .tg__lightline {
    margin-top: 4px;
  }
  .tg__foot {
    padding: 4px 8px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .tg.is-demo .tg__track,
  .tg.is-demo .tg__nums b,
  .tg.is-demo .tg__fill,
  .tg.is-demo .tg__led,
  .tg.is-demo .tg__sts b,
  .tg.is-demo .tg__cand {
    animation: none !important;
  }
  .tg.is-demo .tg__cand.is-on {
    border-color: #17141a;
    background-color: #17141a;
    color: #fff7e6;
  }
  .tg.is-demo .tg__nums,
  .tg.is-demo .tg__sts {
    display: none !important;
  }
  .tg.is-demo .tg__numcur,
  .tg.is-demo .tg__stcur {
    visibility: visible !important;
  }
}

// Threshold gauge — 관찰자는 임계값 후보를 지날 때만 값을 보고한다
// 그래서 숫자와 게이지는 연속이 아니라 계단으로 갱신된다 (이것이 이 데모의 주제다)
var root = document.getElementById('tg');
var view = document.getElementById('tg-view');
var target = document.getElementById('tg-target');
var numEl = document.getElementById('tg-num');
var fill = document.getElementById('tg-fill');
var led = document.getElementById('tg-led');
var stateEl = document.getElementById('tg-state');
var cands = document.getElementById('tg-cands');
var selected = 0.25;
var lastRatio = 0;
var lastIn = false;
var started = false;

function paint(ratio, isIn) {
  numEl.textContent = ratio.toFixed(2);
  fill.style.transform = 'scaleX(' + ratio + ')';
  var on = isIn && ratio >= selected - 0.01;
  led.classList.toggle('is-on', on);
  stateEl.textContent = on ? 'Threshold reached' : 'Waiting';
  stateEl.classList.toggle('is-on', on);
}
function start() {
  if (started) return;
  started = true;
  root.classList.remove('is-demo');
  var io = new IntersectionObserver(function (entries) {
    entries.forEach(function (entry) {
      lastRatio = entry.intersectionRatio;
      lastIn = entry.isIntersecting;
      paint(lastRatio, lastIn);
    });
  }, { root: view, threshold: [0, 0.25, 0.5, 1] });
  io.observe(target);
}
view.addEventListener('scroll', start, { passive: true });
view.addEventListener('pointerdown', start);
view.addEventListener('keydown', function (e) {
  if (e.key === 'ArrowDown' || e.key === 'ArrowUp' || e.key === ' ') start();
});
cands.addEventListener('click', function (e) {
  var btn = e.target.closest('.tg__cand');
  if (!btn) return;
  start();
  selected = parseFloat(btn.getAttribute('data-th'));
  var all = cands.querySelectorAll('.tg__cand');
  for (var i = 0; i < all.length; i++) {
    var on = all[i] === btn;
    all[i].classList.toggle('is-on', on);
    all[i].setAttribute('aria-pressed', on ? 'true' : 'false');
  }
  paint(lastRatio, lastIn);
});

import { useEffect, useRef, useState } from "react";
import type { CSSProperties } from "react";
import styles from "./ThresholdGauge.module.scss";

export type ThresholdGaugeProps = {
  title?: string;
  attr?: string;
  lead?: string;
  targetTitle?: string;
  targetSub?: string;
  viewLabel?: string;
  groupLabel?: string;
  candidatesLabel?: string;
  waiting?: string;
  reached?: string;
  foot?: string;
  /** 격자 미리보기용 2초 자동 루프. 사람이 손대면 꺼진다 */
  demo?: boolean;
  duration?: number;
  easing?: string;
  color?: string;
};

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };
// ambient 가 얇아 DOM 요소 타입을 못 쓴다 — 필요한 꼴만 로컬 타입으로 선언
type Box<T> = { current: T };
type KeyEvt = { key: string };
type ClickEvt = { target: { closest: (s: string) => HTMLElement | null } };

const CANDIDATES = [0, 0.25, 0.5, 1];
const NUM_LAYERS = ["0.00", "0.25", "0.50", "1.00"];

export default function ThresholdGauge({
  title = "임계값 게이지",
  attr = "threshold: [0, 0.25, 0.5, 1]",
  lead = "타깃이 아래에서 올라옵니다",
  targetTitle = "타깃 요소",
  targetSub = "높이의 몇 %가 들어왔나",
  viewLabel = "타깃 뷰포트 — 스크롤해 보세요",
  groupLabel = "임계값 게이지",
  candidatesLabel = "임계값 후보",
  waiting = "대기",
  reached = "임계값 도달",
  foot = "임계값을 지날 때만 관찰자가 알려줍니다",
  demo = true,
  duration = 2000,
  easing = "cubic-bezier(.2, .8, .2, 1)",
  color = "#2f6df6",
}: ThresholdGaugeProps) {
  const [live, setLive] = useState(demo);
  const [ratio, setRatio] = useState(0);
  const [on, setOn] = useState(false);
  const [selected, setSelected] = useState(0.25);
  const viewRef = useRef<HTMLDivElement>(null) as unknown as Box<HTMLDivElement | null>;
  const targetRef = useRef<HTMLDivElement>(null) as unknown as Box<HTMLDivElement | null>;
  const selRef = useRef(0.25) as unknown as Box<number>;
  const inRef = useRef(false) as unknown as Box<boolean>;
  const ratioRef = useRef(0) as unknown as Box<number>;

  useEffect(() => {
    if (live) return;
    const view = viewRef.current;
    const target = targetRef.current;
    if (!view || !target) return;
    // 관찰자는 임계값 후보를 지날 때만 보고한다 — 숫자·게이지는 계단으로 갱신된다
    const io = new IntersectionObserver(
      (entries) => {
        entries.forEach((entry) => {
          const r = entry.intersectionRatio;
          ratioRef.current = r;
          inRef.current = entry.isIntersecting;
          setRatio(r);
          setOn(entry.isIntersecting && r >= selRef.current - 0.01);
        });
      },
      { root: view, threshold: [0, 0.25, 0.5, 1] }
    );
    io.observe(target);
    return () => io.disconnect();
  }, [live]);

  const pick = (e: ClickEvt) => {
    const btn = e.target.closest("button");
    if (!btn) return;
    setLive(false);
    const v = parseFloat(btn.getAttribute("data-th") || "0");
    selRef.current = v;
    setSelected(v);
    setOn(inRef.current && ratioRef.current >= v - 0.01);
  };

  const vars: Vars = {
    "--duration": `${duration}ms`,
    "--easing": easing,
    "--color": color,
  };

  return (
    <section
      className={`${styles.tg} ${live ? styles.isDemo : ""}`}
      style={vars}
      aria-label={groupLabel}
    >
      <header className={styles.head}>
        <p className={styles.title}>{title}</p>
        <p className={styles.attr}><code>{attr}</code></p>
      </header>
      <div className={styles.body}>
        <div
          className={styles.view}
          ref={viewRef as unknown as Box<HTMLDivElement>}
          onScroll={() => setLive(false)}
          onPointerDown={() => setLive(false)}
          onKeyDown={(e: KeyEvt) => {
            if (e.key === "ArrowDown" || e.key === "ArrowUp" || e.key === " ") setLive(false);
          }}
          tabIndex={0}
          role="region"
          aria-label={viewLabel}
        >
          <div className={styles.track}>
            <p className={styles.lead}>{lead}</p>
            <div className={styles.target} ref={targetRef as unknown as Box<HTMLDivElement>}>
              <b>{targetTitle}</b>
              <span>{targetSub}</span>
            </div>
          </div>
        </div>
        <div className={styles.panel}>
          <p className={styles.read} aria-live="polite">
            {live ? null : (
              <b className={styles.numcur}>{ratio.toFixed(2)}</b>
            )}
            {live ? (
              <span className={styles.nums} aria-hidden="true">
                {NUM_LAYERS.map((n) => (<b key={n}>{n}</b>))}
              </span>
            ) : null}
          </p>
          <div className={styles.gauge} aria-hidden="true">
            <i
              className={styles.fill}
              style={live ? undefined : { transform: `scaleX(${ratio})` }}
            />
            <i className={`${styles.tick} ${styles.tick0}`}></i>
            <i className={`${styles.tick} ${styles.tick25}`}></i>
            <i className={`${styles.tick} ${styles.tick50}`}></i>
            <i className={`${styles.tick} ${styles.tick100}`}></i>
          </div>
          <p className={styles.scale} aria-hidden="true">
            <span className={styles.s0}>0</span>
            <span className={styles.s25}>0.25</span>
            <span className={styles.s50}>0.5</span>
            <span className={styles.s100}>1</span>
          </p>
          <p className={styles.candt}>{candidatesLabel}</p>
          <div className={styles.cands} onClick={pick}>
            {CANDIDATES.map((v) => (
              <button
                type="button"
                key={v}
                className={`${styles.cand} ${selected === v ? styles.isOn : ""}`}
                data-th={v}
                aria-pressed={selected === v ? "true" : "false"}
              >
                {v}
              </button>
            ))}
          </div>
          <p className={styles.lightline}>
            <span className={styles.led} aria-hidden="true" />
            <span className={styles.state}>
              {live ? (
                <span className={styles.sts} aria-hidden="true">
                  <b>{waiting}</b>
                  <b className={styles.stOn}>{reached}</b>
                </span>
              ) : (
                <b className={`${styles.stcur} ${on ? styles.stcurOn : ""}`}>
                  {on ? reached : waiting}
                </b>
              )}
            </span>
          </p>
        </div>
      </div>
      <footer className={styles.foot}>{foot}</footer>
    </section>
  );
}