08Picker Whose Value Sets a Heatmap Cell's Intensity

<main class="stage">
<figure class="hm is-demo" id="hm">
  <div class="hm__head">
    <span class="hm__title">Selected cell brightness</span>
    <span class="hm__stat" aria-hidden="true"><b class="hm__n" id="hm-val">62</b>%</span>
  </div>

  <div class="hm__zone">
    <div class="hm__grid" id="grid" role="img" aria-label="A 9-cell heatmap; the large cell at the top left is the selected cell, and its brightness recomputes to match the value's ratio. The other 8 cells stay at their previous ratio.">
      <div class="hm__cell hm__cell--hero" id="hero"></div>
    </div>
  </div>

  <div class="hm__track" id="track">
    <span class="hm__rail" aria-hidden="true"></span>
    <button class="hm__grab" id="grab" type="button" role="slider" aria-orientation="horizontal"
            aria-label="Choose selected cell's value" aria-valuemin="0" aria-valuemax="100"
            aria-valuenow="62" aria-valuetext="Selected cell 62%">
      <svg class="hm__ic" viewBox="0 0 256 256" aria-hidden="true"><g fill="currentColor"><rect x="40" y="40" width="176" height="176" rx="16" opacity=".2"/><path d="M200 32H56a24 24 0 0 0-24 24v144a24 24 0 0 0 24 24h144a24 24 0 0 0 24-24V56a24 24 0 0 0-24-24m8 168a8 8 0 0 1-8 8H56a8 8 0 0 1-8-8V56a8 8 0 0 1 8-8h144a8 8 0 0 1 8 8Z"/></g></svg>
    </button>
  </div>

  <p class="hm__hint">Drag on the bar or press the arrow keys and the selected cell's brightness recomputes.</p>

  <div class="sr">
    <span aria-live="polite" id="hm-live"></span>
    <ul id="hm-legend"></ul>
  </div>
</figure>
</main>

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

// 히트맵 셀 밝기 피커 — 선택 셀 값(0~100)을 드래그·키보드로 정하면, 그 값을 정해둔
// 최대값(100)으로 나눈 비율을 배경색 알파(밝기)로 바꿔 선택 셀(왼쪽 위 큰 칸)만 매 프레임
// 다시 칠한다. 나머지 8칸은 고정 비율로 처음 한 번만 칠하고 이후 손대지 않는다. 값은
// 관성 lerp 로 목표를 뒤따른다.
// CSS @keyframes 는 0개(값이 매 프레임 실수로 바뀌어 선언형으로 못 담는다, 398-01~07 과 같은 이유).
// picker-graph-heatmap-cell-count(JS, N)가 고정 눈금 칸 수를, picker-graph-heatmap-max-value(JS, MAX_V)가
// 정해둔 최대값을 정한다.

$duration: $dur-loop;
$easing: $ease-lerp-settle;
$color: $subject-blue;

@include stage($stage-paper);

.sr {
  position: absolute; width: 1px; height: 1px; overflow: hidden;
  clip-path: inset(50%); white-space: nowrap;
}

.hm {
  box-sizing: border-box;
  width: min(424px, 92vw);
  margin: 0; padding: $sp-3;
  display: flex; flex-direction: column; gap: $sp-2;
  border-radius: $r-card;
  background: $stage-paper;
  border: 1px solid rgba($subject-ink, .10);
  box-shadow: $shadow-raised;
  color: $subject-ink;
}

.hm__head { display: flex; align-items: baseline; justify-content: flex-end; gap: $sp-2; padding: 0 $sp-1; }
.hm__title { font-size: 13px; line-height: 18px; font-weight: 800; letter-spacing: .02em; margin-right: auto; }
.hm__stat { font-size: 12px; line-height: 18px; font-weight: 800; font-variant-numeric: tabular-nums; color: rgba($subject-ink, .62); }
.hm__n { color: $subject-blue-deep; }

.hm__zone { padding: 0 $sp-1; }
.hm__grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-template-rows: repeat(3, 1fr);
  grid-auto-flow: dense;
  gap: 4px;
  height: 116px;
}
.hm__cell { border-radius: $r-xs; }
.hm__cell--hero {
  grid-column: 1 / span 2;
  grid-row: 1 / span 2;
  border-radius: $r-sm;
  box-shadow: inset 0 0 0 2px rgba($subject-ink, .12);
}

.hm__track {
  position: relative;
  height: 24px;
  margin: 0 $sp-1;
  border-radius: $r-pill;
  background: mix($subject-blue, $stage-paper, 14%);
}
.hm__rail {
  position: absolute; left: $sp-3; right: $sp-3; top: 50%;
  height: 3px; transform: translateY(-50%);
  border-radius: $r-pill;
  background: rgba($subject-ink, .18);
}
.hm__grab {
  position: absolute; top: 50%; left: 50%;
  width: 26px; height: 26px;
  margin: 0; padding: 0; border: 0; border-radius: 50%;
  display: grid; place-items: center;
  background: $subject-blue-deep;
  color: $stage-paper;
  transform: translate(-50%, -50%);
  cursor: ew-resize;
  touch-action: none;
}
.hm__grab:focus-visible { outline: 2px solid $subject-blue-deep; outline-offset: 2px; }
.hm__ic { width: 13px; height: 13px; }

.hm__hint { margin: 0; padding: 0 $sp-1; font-size: 11px; line-height: 16px; color: rgba($subject-ink, .62); }

@media (max-width: 340px) {
  .hm { padding: $sp-2; gap: $sp-1; }
  .hm__hint { display: none; }
  .hm__title { font-size: 12px; line-height: 16px; }
  .hm__stat { font-size: 11px; line-height: 16px; }
  .hm__grid { height: 108px; }
  .hm__grab { width: 22px; height: 22px; }
}

@media (prefers-reduced-motion: reduce) {
  .hm.is-still .hm__cell--hero { transition: none !important; }
}

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);
}

.sr {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip-path: inset(50%);
  white-space: nowrap;
}

.hm {
  box-sizing: border-box;
  width: min(424px, 92vw);
  margin: 0;
  padding: 12px;
  display: flex;
  flex-direction: column;
  gap: 8px;
  border-radius: 16px;
  background: #ffffff;
  border: 1px solid rgba(23, 20, 26, 0.1);
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  color: #17141a;
}

.hm__head {
  display: flex;
  align-items: baseline;
  justify-content: flex-end;
  gap: 8px;
  padding: 0 4px;
}

.hm__title {
  font-size: 13px;
  line-height: 18px;
  font-weight: 800;
  letter-spacing: 0.02em;
  margin-right: auto;
}

.hm__stat {
  font-size: 12px;
  line-height: 18px;
  font-weight: 800;
  font-variant-numeric: tabular-nums;
  color: rgba(23, 20, 26, 0.62);
}

.hm__n {
  color: #0a4fe8;
}

.hm__zone {
  padding: 0 4px;
}

.hm__grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-template-rows: repeat(3, 1fr);
  grid-auto-flow: dense;
  gap: 4px;
  height: 116px;
}

.hm__cell {
  border-radius: 4px;
}

.hm__cell--hero {
  grid-column: 1/span 2;
  grid-row: 1/span 2;
  border-radius: 8px;
  box-shadow: inset 0 0 0 2px rgba(23, 20, 26, 0.12);
}

.hm__track {
  position: relative;
  height: 24px;
  margin: 0 4px;
  border-radius: 999px;
  background: rgb(88.5803921569%, 91.9843137255%, 99.5058823529%);
}

.hm__rail {
  position: absolute;
  left: 12px;
  right: 12px;
  top: 50%;
  height: 3px;
  transform: translateY(-50%);
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.18);
}

.hm__grab {
  position: absolute;
  top: 50%;
  left: 50%;
  width: 26px;
  height: 26px;
  margin: 0;
  padding: 0;
  border: 0;
  border-radius: 50%;
  display: grid;
  place-items: center;
  background: #0a4fe8;
  color: #ffffff;
  transform: translate(-50%, -50%);
  cursor: ew-resize;
  touch-action: none;
}

.hm__grab:focus-visible {
  outline: 2px solid #0a4fe8;
  outline-offset: 2px;
}

.hm__ic {
  width: 13px;
  height: 13px;
}

.hm__hint {
  margin: 0;
  padding: 0 4px;
  font-size: 11px;
  line-height: 16px;
  color: rgba(23, 20, 26, 0.62);
}

@media (max-width: 340px) {
  .hm {
    padding: 8px;
    gap: 4px;
  }
  .hm__hint {
    display: none;
  }
  .hm__title {
    font-size: 12px;
    line-height: 16px;
  }
  .hm__stat {
    font-size: 11px;
    line-height: 16px;
  }
  .hm__grid {
    height: 108px;
  }
  .hm__grab {
    width: 22px;
    height: 22px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .hm.is-still .hm__cell--hero {
    transition: none !important;
  }
}

// 실제 동작: pointerdown/move/up 과 keydown 이 Selected cell Value(0~100)을 바꾸면, 그 값을 정해둔
// 최대값(100)으로 나눈 비율을 배경색 알파(밝기)로 바꿔 Selected cell(왼쪽 위 큰 칸)만 매 프레임
// 다시 칠한다. 나머지 8칸은 고정 Ratio(RATIOS)로 처음 한 번만 칠하고 이후 손대지 않는다
// ("이전 Ratio 그대로 남는다"). CSS @keyframes 없음(값이 매 프레임 실수로 바뀌어 선언형으로
// 못 담는다, 398-01~07 과 같은 이유).
var root = document.getElementById('hm');
var track = document.getElementById('track');
var grab = document.getElementById('grab');
var grid = document.getElementById('grid');
var hero = document.getElementById('hero');
var valEl = document.getElementById('hm-val');
var live = document.getElementById('hm-live');
var legend = document.getElementById('hm-legend');

var N = 8;                      // picker-graph-heatmap-cell-count — 고정 눈금 칸 수
var MAX_V = 100;                // picker-graph-heatmap-max-value — 정해둔 최대값
var LERP_RATE = 0.22;
var AUTO_PERIOD = 2.0;
var STEP = 5;
var R = 10, G = 79, B = 232;    // $subject-blue-deep

var RATIOS = [];
for (var ri = 0; ri < N; ri++) {
  RATIOS.push(Math.min(0.85, 0.15 + 0.55 * Math.abs(Math.sin(ri * 1.9 + 0.4))));
}

var value = 62;
var current = 62;
var manual = false;
var autoT = 0;
var lastTs = 0;
var trackRect = null;
var rafId = 0;

function reduced() {
  return window.matchMedia && window.matchMedia('(prefers-reduced-motion: reduce)').matches;
}

function colorFor(ratio) {
  var a = 0.12 + ratio * 0.82;
  return 'rgba(' + R + ',' + G + ',' + B + ',' + a.toFixed(3) + ')';
}

function buildStatic() {
  var legendHtml = '';
  for (var i = 0; i < N; i++) {
    var cell = document.createElement('div');
    cell.className = 'hm__cell';
    cell.style.background = colorFor(RATIOS[i]);
    grid.appendChild(cell);
    legendHtml += '<li>Fixed cell ' + (i + 1) + ': ' + Math.round(RATIOS[i] * 100) + '%</li>';
  }
  legend.innerHTML = legendHtml;
}

function paint() {
  var ratio = current / MAX_V;
  hero.style.background = colorFor(ratio);
  var rv = Math.round(current);
  valEl.textContent = String(rv);
  grab.style.left = value + '%';
  grab.setAttribute('aria-valuenow', String(Math.round(value)));
  grab.setAttribute('aria-valuetext', 'Selected cell ' + Math.round(value) + '%');
}

function announce() {
  live.textContent = 'Selected cell ' + Math.round(current) + '% recomputed';
}

function setValue(v, isManual) {
  value = Math.max(0, Math.min(MAX_V, v));
  if (isManual) { manual = true; root.classList.remove('is-demo'); }
}

function fromPointer(clientX) {
  if (!trackRect) trackRect = track.getBoundingClientRect();
  var ratio = (clientX - trackRect.left) / trackRect.width;
  setValue(ratio * MAX_V, true);
}

function reflectNow() { current = value; paint(); announce(); }

function onDown(e) {
  trackRect = track.getBoundingClientRect();
  if (grab.setPointerCapture) { try { grab.setPointerCapture(e.pointerId); } catch (err) {} }
  fromPointer(e.clientX);
  if (reduced()) reflectNow();
}
function onMove(e) { fromPointer(e.clientX); if (reduced()) reflectNow(); }
function onUp() { announce(); }
function onTrackDown(e) { trackRect = track.getBoundingClientRect(); fromPointer(e.clientX); if (reduced()) reflectNow(); }

function onKey(e) {
  var map = { ArrowLeft: -STEP, ArrowDown: -STEP, ArrowRight: STEP, ArrowUp: STEP };
  if (e.key === 'Home') { setValue(0, true); e.preventDefault(); }
  else if (e.key === 'End') { setValue(MAX_V, true); e.preventDefault(); }
  else if (map[e.key] !== undefined) { setValue(value + map[e.key], true); e.preventDefault(); }
  else { return; }
  if (reduced()) reflectNow();
}

function onResize() { trackRect = track.getBoundingClientRect(); if (reduced()) paint(); }

function autoStep(dt) {
  autoT += dt;
  var omega = 2 * Math.PI / AUTO_PERIOD;
  value = 50 + 46 * Math.sin(autoT * omega);
}

function frame(ts) {
  if (!lastTs) lastTs = ts;
  var dt = Math.min(0.05, (ts - lastTs) / 1000);
  lastTs = ts;
  if (!manual) autoStep(dt);
  current += (value - current) * LERP_RATE;
  paint();
  rafId = requestAnimationFrame(frame);
}

buildStatic();

grab.addEventListener('pointerdown', onDown);
grab.addEventListener('pointermove', onMove);
grab.addEventListener('pointerup', onUp);
grab.addEventListener('keydown', onKey);
track.addEventListener('pointerdown', onTrackDown);
window.addEventListener('resize', onResize);

if (reduced()) {
  root.classList.add('is-still');
  current = value;
  paint();
} else {
  paint();
  rafId = requestAnimationFrame(frame);
}

// HeatmapCellIntensity — vanilla 판(run/398/demo/08-picker-graph-heatmap-cell-intensity/index.html) 의
// React 포트. 선택 셀 값을 정해둔 최대값으로 나눈 비율을 배경색의 밝기로 바꿔, 선택 셀(왼쪽
// 위 큰 칸)만 매 프레임 다시 칠한다. 나머지 고정 칸은 처음 한 번만 칠하고 이후 손대지 않는다.
import { useEffect, useRef } from "react";
import styles from "./HeatmapCellIntensity.module.scss";

type Box<T> = { current: T };
type KeyEvt = { key: string; preventDefault(): void };
type PtrEvt = { clientX: number; pointerId: number };

const N = 8;                    // picker-graph-heatmap-cell-count — 고정 눈금 칸 수
const MAX_V = 100;              // picker-graph-heatmap-max-value — 정해둔 최대값
const LERP_RATE = 0.22;
const AUTO_PERIOD = 2.0;
const STEP = 5;
const CR = 10, CG = 79, CB = 232; // $subject-blue-deep

const RATIOS: number[] = [];
for (let ri = 0; ri < N; ri++) {
  RATIOS.push(Math.min(0.85, 0.15 + 0.55 * Math.abs(Math.sin(ri * 1.9 + 0.4))));
}

function colorFor(ratio: number): string {
  const a = 0.12 + ratio * 0.82;
  return "rgba(" + CR + "," + CG + "," + CB + "," + a.toFixed(3) + ")";
}

export default function HeatmapCellIntensity() {
  const rootRef = useRef<HTMLElement | null>(null);
  const trackRef = useRef<HTMLDivElement | null>(null);
  const grabRef = useRef<HTMLButtonElement | null>(null);
  const heroRef = useRef<HTMLDivElement | null>(null);
  const valRef = useRef<HTMLElement | null>(null);
  const liveRef = useRef<HTMLSpanElement | null>(null);

  const value = useRef(62) as Box<number>;
  const current = useRef(62) as Box<number>;
  const manual = useRef(false) as Box<boolean>;
  const autoT = useRef(0) as Box<number>;
  const lastTs = useRef(0) as Box<number>;
  const trackRect = useRef<DOMRect | null>(null) as Box<DOMRect | null>;
  const rafId = useRef(0) as Box<number>;

  function reduced(): boolean {
    return window.matchMedia("(prefers-reduced-motion: reduce)").matches;
  }

  function paint(): void {
    const ratio = current.current / MAX_V;
    if (heroRef.current) heroRef.current.style.background = colorFor(ratio);
    const rv = Math.round(current.current);
    if (valRef.current) valRef.current.textContent = String(rv);
    const grab = grabRef.current;
    if (grab) {
      grab.style.left = value.current + "%";
      grab.setAttribute("aria-valuenow", String(Math.round(value.current)));
      grab.setAttribute("aria-valuetext", "선택 셀 " + Math.round(value.current) + "%");
    }
  }

  function announce(): void {
    if (liveRef.current) liveRef.current.textContent = "선택 셀 " + Math.round(current.current) + "%로 다시 계산됨";
  }

  function setValue(v: number, isManual: boolean): void {
    value.current = Math.max(0, Math.min(MAX_V, v));
    if (isManual) {
      manual.current = true;
      rootRef.current?.classList.remove("is-demo");
    }
  }

  function fromPointer(clientX: number): void {
    if (!trackRect.current && trackRef.current) trackRect.current = trackRef.current.getBoundingClientRect();
    const rect = trackRect.current;
    if (!rect) return;
    const ratio = (clientX - rect.left) / rect.width;
    setValue(ratio * MAX_V, true);
  }

  function reflectNow(): void {
    current.current = value.current;
    paint();
    announce();
  }

  function onDown(e: PtrEvt): void {
    if (trackRef.current) trackRect.current = trackRef.current.getBoundingClientRect();
    const grab = grabRef.current;
    if (grab && typeof grab.setPointerCapture === "function") {
      try { grab.setPointerCapture(e.pointerId); } catch { /* 캡처 실패는 치명적이지 않다 */ }
    }
    fromPointer(e.clientX);
    if (reduced()) reflectNow();
  }
  function onMove(e: PtrEvt): void {
    fromPointer(e.clientX);
    if (reduced()) reflectNow();
  }
  function onUp(): void {
    announce();
  }
  function onTrackDown(e: PtrEvt): void {
    if (trackRef.current) trackRect.current = trackRef.current.getBoundingClientRect();
    fromPointer(e.clientX);
    if (reduced()) reflectNow();
  }

  function onKey(e: KeyEvt): void {
    const map: Record<string, number> = { ArrowLeft: -STEP, ArrowDown: -STEP, ArrowRight: STEP, ArrowUp: STEP };
    if (e.key === "Home") { setValue(0, true); e.preventDefault(); }
    else if (e.key === "End") { setValue(MAX_V, true); e.preventDefault(); }
    else if (map[e.key] !== undefined) { setValue(value.current + map[e.key], true); e.preventDefault(); }
    else { return; }
    if (reduced()) reflectNow();
  }

  function onResize(): void {
    if (trackRef.current) trackRect.current = trackRef.current.getBoundingClientRect();
    if (reduced()) paint();
  }

  function autoStep(dt: number): void {
    autoT.current += dt;
    const omega = (2 * Math.PI) / AUTO_PERIOD;
    value.current = 50 + 46 * Math.sin(autoT.current * omega);
  }

  function frame(ts: number): void {
    if (!lastTs.current) lastTs.current = ts;
    const dt = Math.min(0.05, (ts - lastTs.current) / 1000);
    lastTs.current = ts;
    if (!manual.current) autoStep(dt);
    current.current += (value.current - current.current) * LERP_RATE;
    paint();
    rafId.current = requestAnimationFrame(frame);
  }

  useEffect(() => {
    window.addEventListener("resize", onResize);
    if (reduced()) {
      rootRef.current?.classList.add("is-still");
      reflectNow();
    } else {
      paint();
      rafId.current = requestAnimationFrame(frame);
    }
    return () => {
      window.removeEventListener("resize", onResize);
      cancelAnimationFrame(rafId.current);
    };
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, []);

  return (
    <main className={styles.stage}>
      <figure className={styles.hm + " is-demo"} ref={rootRef}>
        <div className={styles.head}>
          <span className={styles.title}>선택 셀 밝기</span>
          <span className={styles.stat} aria-hidden="true"><b className={styles.n} ref={valRef}>62</b>%</span>
        </div>

        <div className={styles.zone}>
          <div
            className={styles.grid}
            role="img"
            aria-label="9칸 히트맵, 왼쪽 위 큰 칸이 선택 셀이고 값 비율만큼 밝기가 다시 계산된다. 나머지 8칸은 이전 비율 그대로 남는다"
          >
            <div className={styles.cell + " " + styles.hero} ref={heroRef} />
            {RATIOS.map((r, i) => (
              <div key={i} className={styles.cell} style={{ background: colorFor(r) }} />
            ))}
          </div>
        </div>

        <div className={styles.track} ref={trackRef} onPointerDown={onTrackDown}>
          <span className={styles.rail} aria-hidden="true" />
          <button
            className={styles.grab}
            ref={grabRef}
            type="button"
            role="slider"
            aria-orientation="horizontal"
            aria-label="선택 셀 값 고르기"
            aria-valuemin={0}
            aria-valuemax={MAX_V}
            aria-valuenow={62}
            aria-valuetext="선택 셀 62%"
            onPointerDown={onDown}
            onPointerMove={onMove}
            onPointerUp={onUp}
            onKeyDown={onKey}
          >
            <svg className={styles.ic} viewBox="0 0 256 256" aria-hidden="true">
              <g fill="currentColor">
                <rect x={40} y={40} width={176} height={176} rx={16} opacity={0.2} />
                <path d="M200 32H56a24 24 0 0 0-24 24v144a24 24 0 0 0 24 24h144a24 24 0 0 0 24-24V56a24 24 0 0 0-24-24m8 168a8 8 0 0 1-8 8H56a8 8 0 0 1-8-8V56a8 8 0 0 1 8-8h144a8 8 0 0 1 8 8Z" />
              </g>
            </svg>
          </button>
        </div>

        <p className={styles.hint}>막대를 드래그하거나 화살표키를 누르면 선택 셀의 밝기가 다시 계산됩니다</p>

        <div className={styles.sr}>
          <span aria-live="polite" ref={liveRef} />
          <ul>
            {RATIOS.map((r, i) => (
              <li key={i}>고정 칸 {i + 1}: {Math.round(r * 100)}%</li>
            ))}
          </ul>
        </div>
      </figure>
    </main>
  );
}