Carousel

<div id="react-root"></div>

// Shared data and utilities for carousel example
// Supports both fixed-width and variable-width modes via a toggle

// =============================================================================
// Constants
// =============================================================================

export const ITEM_COUNT = 10_000;
export const DEFAULT_HEIGHT = 240;
export const ASPECT_RATIO = 260 / 320; // width / height ≈ 0.8125

// Color palette for cards
export const colors = [
  ["#667eea", "#764ba2"],
  ["#f093fb", "#f5576c"],
  ["#4facfe", "#00f2fe"],
  ["#43e97b", "#38f9d7"],
  ["#fa709a", "#fee140"],
  ["#a18cd1", "#fbc2eb"],
  ["#fccb90", "#d57eeb"],
  ["#e0c3fc", "#8ec5fc"],
  ["#f5576c", "#ff9a9e"],
  ["#667eea", "#00f2fe"],
];

export const emojis = [
  "🎵",
  "🎶",
  "🎸",
  "🥁",
  "🎹",
  "🎺",
  "🎻",
  "🎷",
  "🪗",
  "🪘",
];

export const categories = [
  "Photo",
  "Video",
  "Music",
  "Document",
  "Archive",
  "Code",
  "Design",
  "Text",
];

export const icons = ["📷", "🎬", "🎵", "📄", "📦", "💻", "🎨", "📝"];

// Width patterns — creates visual variety in variable-width mode
const widthPatterns = [120, 180, 240, 160, 200, 140, 220, 190];

// =============================================================================
// Data Generation
// =============================================================================

// Generate card items (used in both modes)
export const items = Array.from({ length: ITEM_COUNT }, (_, i) => {
  const color = colors[i % colors.length];
  const categoryIndex = i % categories.length;

  // Variable-width fields
  const baseWidth = widthPatterns[i % widthPatterns.length];
  const isFeatured = i % 17 === 0;
  const variableWidth = isFeatured ? baseWidth + 100 : baseWidth;

  return {
    id: i + 1,
    title: `Card ${i + 1}`,
    subtitle: `Item #${(i + 1).toLocaleString()}`,
    emoji: emojis[i % emojis.length],
    gradientStart: color[0],
    gradientEnd: color[1],
    // Variable-width extras
    category: categories[categoryIndex],
    icon: icons[categoryIndex],
    width: variableWidth,
    isFeatured,
  };
});

// =============================================================================
// Templates
// =============================================================================

// Fixed-width card template
const fixedTemplate = (item) => `
  <div class="card" style="background: linear-gradient(135deg, ${item.gradientStart} 0%, ${item.gradientEnd} 100%);">
    <div class="card-emoji">${item.emoji}</div>
    <div class="card-title">${item.title}</div>
    <div class="card-subtitle">${item.subtitle}</div>
  </div>
`;

// Variable-width card template
const variableTemplate = (item) => {
  const featuredClass = item.isFeatured ? " card--featured" : "";
  return `
    <div class="card${featuredClass}" style="background: linear-gradient(135deg, ${item.gradientStart} 0%, ${item.gradientEnd} 100%);">
      <div class="card-emoji">${item.icon}</div>
      <div class="card-content">
        <div class="card-title">${item.isFeatured ? `⭐ Featured #${item.id}` : item.title}</div>
        <div class="card-category">${item.category}</div>
        <div class="card-width">${item.width}px</div>
      </div>
      ${item.isFeatured ? '<div class="card-badge">Featured</div>' : ""}
    </div>
  `;
};

// Returns the correct template for the current mode
export function getTemplate(variableWidth) {
  return variableWidth ? variableTemplate : fixedTemplate;
}

// =============================================================================
// Config builder
// =============================================================================

// Build vlist config for the given mode, height, and gap.
// Gap is added to item dimensions so vlist spaces items correctly.
export function buildConfig(variableWidth, height = DEFAULT_HEIGHT, gap = 0) {
  const cardWidth = Math.round(height * ASPECT_RATIO);
  return {
    orientation: "horizontal",
    scroll: { wheel: true },
    ariaLabel: "Horizontal card carousel",
    item: {
      height,
      width: variableWidth
        ? (index) => items[index].width + gap
        : cardWidth + gap,
      template: getTemplate(variableWidth),
    },
    items,
  };
}

// =============================================================================
// Utilities
// =============================================================================

// Calculate stats
export function calculateStats(domNodes, total, variableWidth) {
  const saved = Math.round((1 - domNodes / total) * 100);

  if (variableWidth) {
    const widths = items.map((item) => item.width);
    const minWidth = Math.min(...widths);
    const maxWidth = Math.max(...widths);
    const avgWidth = Math.round(
      widths.reduce((a, b) => a + b, 0) / widths.length,
    );
    return { saved, minWidth, maxWidth, avgWidth };
  }

  return { saved };
}

// Detail panel HTML
export function getDetailHtml(item, index, variableWidth) {
  return `
    <div class="detail-card" style="background: linear-gradient(135deg, ${item.gradientStart} 0%, ${item.gradientEnd} 100%);">
      <div class="detail-card__emoji">${variableWidth ? item.icon : item.emoji}</div>
      <div class="detail-card__title">${item.title}</div>
    </div>
    <div class="detail-meta">
      <strong>${item.title}</strong>
      <span>Index ${index}${variableWidth ? ` · ${item.category} · ${item.width}px` : ` · ${item.subtitle}`}</span>
      ${item.isFeatured && variableWidth ? '<span class="detail-meta__badge">⭐ Featured</span>' : ""}
    </div>
  `;
}

// Format stats HTML
export function formatStatsHtml(domNodes, total, variableWidth) {
  const stats = calculateStats(domNodes, total, variableWidth);
  let html = `
    <span><strong>Total:</strong> ${total.toLocaleString()} items</span>
    <span><strong>DOM nodes:</strong> ${domNodes}</span>
    <span><strong>Memory saved:</strong> ${stats.saved}%</span>
  `;

  if (variableWidth && stats.minWidth != null) {
    html += `<span><strong>Width:</strong> ${stats.minWidth}–${stats.maxWidth}px (avg ${stats.avgWidth}px)</span>`;
  }

  return html;
}

/* Carousel Example — example-specific styles only
   Common styles (.container, h1, .description, .stats, footer, .split-*, .panel-*)
   are provided by example/example.css using shell.css design tokens. */

/* Center the list vertically in the split-main */
.split-main {
    display: flex;
    align-items: center;
    justify-content: center;
    height: 560px;
}

/* List container - full width, height set by JS
   --card-scale is set by JS (0–1) based on slider height
   --item-gap is set by JS (px) from the gap chips */
#list-container {
    --card-scale: 1;
    --item-gap: 8px;
    --item-radius: 12px;
    width: 100%;
    max-width: 100%;
    min-width: 0;
    height: auto;
    overflow: hidden;
    border-radius: var(--item-radius);
}

/* Override vlist defaults for horizontal cards */
#list-container .vlist {
    border: none !important;
    border-radius: var(--item-radius) !important;
    background: transparent;
    max-width: 100%;
    width: 100%;
    box-sizing: border-box;
}

#list-container .vlist-viewport {
    max-width: 100%;
    width: 100% !important;
}

#list-container .vlist-item {
    padding: 0 calc(var(--item-gap) / 2) !important;
    border: none !important;
    cursor: pointer;
    background-color: transparent;
}

/* ============================================================================
   Card
   ============================================================================ */

.card {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: calc(4px + 6px * var(--card-scale));
    width: 100%;
    height: 100%;
    border-radius: var(--item-radius);
    color: #fff;
    text-align: center;
    padding: calc(8px + 12px * var(--card-scale))
        calc(6px + 8px * var(--card-scale));
    position: relative;
    transition: box-shadow 0.15s ease-out;
}

.vlist-item:hover .card {
    box-shadow: 0 4px 16px rgba(0, 0, 0, 0.2);
}

/* Featured cards — variable-width mode */
.card--featured {
    border: 2px solid rgba(255, 255, 255, 0.3);
}

.card-emoji {
    font-size: 42px;
    line-height: 1;
    margin-bottom: 16px;
}

.card-content {
    display: flex;
    flex-direction: column;
    gap: 4px;
    width: 100%;
}

.card-title {
    font-weight: 600;
    font-size: calc(11px + 5px * var(--card-scale));
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    max-width: 100%;
}

.card-subtitle {
    font-size: calc(10px + 3px * var(--card-scale));
    opacity: 0.85;
    white-space: nowrap;
}

.card-category {
    font-size: calc(9px + 3px * var(--card-scale));
    opacity: 0.85;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.card-width {
    font-size: calc(8px + 3px * var(--card-scale));
    opacity: 0.7;
    font-family: monospace;
}

.card-badge {
    position: absolute;
    top: 6px;
    right: 6px;
    background: rgba(255, 255, 255, 0.25);
    backdrop-filter: blur(4px);
    padding: 2px 6px;
    border-radius: 10px;
    font-size: 8px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    line-height: 1.4;
}

/* ============================================================================
   Gap chip buttons
   ============================================================================ */

.ctrl-btn {
    padding: 6px 14px;
    border: 1px solid var(--border);
    border-radius: 6px;
    background: var(--bg-card);
    color: var(--text-muted);
    font-size: 13px;
    font-weight: 600;
    font-family: inherit;
    cursor: pointer;
    transition: all 0.15s ease;
    min-width: 36px;
    text-align: center;
}

.ctrl-btn:hover {
    border-color: var(--accent);
    color: var(--accent-text);
}

.ctrl-btn--active {
    background: var(--accent);
    color: white;
    border-color: var(--accent);
}

/* ============================================================================
   Toggle switch
   ============================================================================ */

.toggle {
    display: flex;
    align-items: center;
    cursor: pointer;
    user-select: none;
}

.toggle input {
    display: none;
}

.toggle-track {
    position: relative;
    width: 36px;
    height: 20px;
    border-radius: 10px;
    background: var(--border);
    transition: background 0.2s ease;
    flex-shrink: 0;
}

.toggle input:checked + .toggle-track {
    background: var(--accent, #667eea);
}

.toggle-track::after {
    content: "";
    position: absolute;
    top: 2px;
    left: 2px;
    width: 16px;
    height: 16px;
    border-radius: 50%;
    background: #fff;
    transition: transform 0.2s ease;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.2);
}

.toggle input:checked + .toggle-track::after {
    transform: translateX(16px);
}

/* ============================================================================
   Card Detail (panel preview)
   ============================================================================ */

.detail-card {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 8px;
    width: 100%;
    height: 120px;
    border-radius: 10px;
    color: #fff;
    text-align: center;
    padding: 16px 12px;
    margin-bottom: 8px;
}

.detail-card__emoji {
    font-size: 32px;
    line-height: 1;
}

.detail-card__title {
    font-weight: 600;
    font-size: 14px;
}

.detail-meta {
    display: flex;
    flex-direction: column;
    gap: 2px;
    font-size: 13px;
}

.detail-meta strong {
    font-weight: 600;
}

.detail-meta span {
    font-size: 12px;
    color: var(--text-muted);
}

.detail-meta__badge {
    font-size: 11px;
    color: var(--accent, #667eea);
    font-weight: 600;
}