Carousel

// Carousel — Vanilla JavaScript
// Horizontal scrolling with toggle between fixed and variable item widths.
// Uses split-layout + panel + shared footer stats (same pattern as basic).

import { vlist } from "vlist";
import { items, buildConfig, getDetailHtml, ASPECT_RATIO } from "../shared.js";
import { createStats } from "../../stats.js";

// Scale factor: maps height 200–500 → 0–1
const MIN_HEIGHT = 200;
const MAX_HEIGHT = 500;
function getScale(h) {
  return Math.max(0, Math.min(1, (h - MIN_HEIGHT) / (MAX_HEIGHT - MIN_HEIGHT)));
}

// =============================================================================
// State
// =============================================================================

let variableWidth = false;
let currentHeight = 240;
let currentGap = 8;
let currentRadius = 12;
let list = null;

// =============================================================================
// DOM references — panel
// =============================================================================

const toggleEl = document.getElementById("toggle-variable");
const sizeSlider = document.getElementById("size-slider");
const sizeValue = document.getElementById("size-value");
const gapButtons = document.getElementById("gap-buttons");
const radiusButtons = document.getElementById("radius-buttons");

const detailEl = document.getElementById("card-detail");
const listContainerEl = document.getElementById("list-container");

// =============================================================================
// DOM references — footer right side
// =============================================================================

const ftWidth = document.getElementById("ft-width");
const ftMode = document.getElementById("ft-mode");

// =============================================================================
// Stats — shared footer (progress, velocity, visible/total)
// =============================================================================

function getCurrentWidth() {
  return Math.round(currentHeight * ASPECT_RATIO);
}

const stats = createStats({
  getList: () => list,
  getTotal: () => items.length,
  getItemHeight: () => getCurrentWidth() + currentGap,
  container: "#list-container",
});

// =============================================================================
// Footer — right side (contextual)
// =============================================================================

function updateContext() {
  const w = getCurrentWidth();
  if (ftWidth) ftWidth.textContent = variableWidth ? "var" : w;
  if (ftMode) ftMode.textContent = variableWidth ? "variable" : "fixed";
}

// =============================================================================
// Create / Recreate list
// =============================================================================

function createList() {
  if (list) {
    list.destroy();
    list = null;
  }

  listContainerEl.innerHTML = "";
  listContainerEl.style.height = currentHeight + "px";
  listContainerEl.style.setProperty("--card-scale", getScale(currentHeight));
  listContainerEl.style.setProperty("--item-gap", currentGap + "px");
  listContainerEl.style.setProperty("--item-radius", currentRadius + "px");

  list = vlist({
    container: "#list-container",
    ...buildConfig(variableWidth, currentHeight, currentGap),
  }).build();

  list.on("range:change", stats.scheduleUpdate);
  list.on("scroll", stats.scheduleUpdate);
  list.on("velocity:change", ({ velocity }) => stats.onVelocity(velocity));

  list.on("item:click", ({ item, index }) => {
    showDetail(item, index);
  });

  stats.update();
  updateContext();
}

// =============================================================================
// Card detail (panel)
// =============================================================================

function showDetail(item, index) {
  if (detailEl) {
    detailEl.innerHTML = getDetailHtml(item, index, variableWidth);
  }
}

// =============================================================================
// Size slider
// =============================================================================

sizeSlider?.addEventListener("input", (e) => {
  currentHeight = parseInt(e.target.value, 10);
  if (sizeValue) sizeValue.textContent = currentHeight + "px";
  createList();
});

// =============================================================================
// Gap chips
// =============================================================================

gapButtons?.addEventListener("click", (e) => {
  const btn = e.target.closest("[data-gap]");
  if (!btn) return;

  const gap = parseInt(btn.dataset.gap, 10);
  if (gap === currentGap) return;
  currentGap = gap;

  gapButtons.querySelectorAll("button").forEach((b) => {
    b.classList.toggle("ctrl-btn--active", parseInt(b.dataset.gap) === gap);
  });

  createList();
});

// =============================================================================
// Radius chips
// =============================================================================

radiusButtons?.addEventListener("click", (e) => {
  const btn = e.target.closest("[data-radius]");
  if (!btn) return;

  const radius = parseInt(btn.dataset.radius, 10);
  if (radius === currentRadius) return;
  currentRadius = radius;

  radiusButtons.querySelectorAll("button").forEach((b) => {
    b.classList.toggle(
      "ctrl-btn--active",
      parseInt(b.dataset.radius) === radius,
    );
  });

  createList();
});

// =============================================================================
// Toggle — variable width
// =============================================================================

toggleEl?.addEventListener("change", (e) => {
  variableWidth = e.target.checked;
  createList();
});

// =============================================================================
// Scroll To — smooth navigation buttons
// =============================================================================

document.getElementById("btn-start")?.addEventListener("click", () => {
  list?.scrollToIndex(0, { align: "start", behavior: "smooth", duration: 600 });
});

document.getElementById("btn-center")?.addEventListener("click", () => {
  list?.scrollToIndex(Math.floor(items.length / 2), {
    align: "center",
    behavior: "smooth",
    duration: 800,
  });
});

document.getElementById("btn-end")?.addEventListener("click", () => {
  list?.scrollToIndex(items.length - 1, {
    align: "end",
    behavior: "smooth",
    duration: 600,
  });
});

// =============================================================================
// Init
// =============================================================================

createList();

<div class="container">
    <header>
        <h1>Carousel</h1>
        <p class="description">
            Pure vanilla JavaScript – no frameworks, no dependencies. A
            horizontal virtual list rendering 10,000 cards with
            <code>orientation: 'horizontal'</code> and
            <code>scroll.wheel: true</code>. Toggle
            <strong>variable width</strong> to switch between fixed-size cards
            and dynamic per-item widths. Only visible items are in the DOM.
        </p>
    </header>

    <div class="split-layout">
        <div class="split-main">
            <div id="list-container"></div>
        </div>

        <aside class="split-panel">
            <!-- Mode -->
            <section class="panel-section">
                <h3 class="panel-title">Mode</h3>

                <div class="panel-row">
                    <label class="panel-label">Size</label>
                    <span class="panel-value" id="size-value">240px</span>
                </div>
                <div class="panel-row">
                    <input
                        type="range"
                        id="size-slider"
                        class="panel-slider"
                        min="200"
                        max="500"
                        step="10"
                        value="240"
                    />
                </div>

                <div class="panel-row">
                    <label class="panel-label">Variable width</label>
                    <label class="toggle">
                        <input type="checkbox" id="toggle-variable" />
                        <span class="toggle-track"></span>
                    </label>
                </div>

                <div class="panel-row">
                    <label class="panel-label">Gap</label>
                    <div class="panel-btn-group" id="gap-buttons">
                        <button class="ctrl-btn" data-gap="0">0</button>
                        <button class="ctrl-btn" data-gap="4">4</button>
                        <button class="ctrl-btn ctrl-btn--active" data-gap="8">
                            8
                        </button>
                        <button class="ctrl-btn" data-gap="12">12</button>
                        <button class="ctrl-btn" data-gap="16">16</button>
                    </div>
                </div>

                <div class="panel-row">
                    <label class="panel-label">Radius</label>
                    <div class="panel-btn-group" id="radius-buttons">
                        <button class="ctrl-btn" data-radius="0">0</button>
                        <button class="ctrl-btn" data-radius="4">4</button>
                        <button class="ctrl-btn" data-radius="8">8</button>
                        <button
                            class="ctrl-btn ctrl-btn--active"
                            data-radius="12"
                        >
                            12
                        </button>
                        <button class="ctrl-btn" data-radius="16">16</button>
                    </div>
                </div>
            </section>

            <!-- Scroll To -->
            <section class="panel-section">
                <h3 class="panel-title">Scroll To</h3>

                <div class="panel-row">
                    <div class="panel-btn-group">
                        <button
                            id="btn-start"
                            class="panel-btn panel-btn--icon"
                            title="Start"
                        >
                            <i class="icon icon--back"></i>
                        </button>
                        <button
                            id="btn-center"
                            class="panel-btn panel-btn--icon"
                            title="Center"
                        >
                            <i class="icon icon--center"></i>
                        </button>
                        <button
                            id="btn-end"
                            class="panel-btn panel-btn--icon"
                            title="End"
                        >
                            <i class="icon icon--forward"></i>
                        </button>
                    </div>
                </div>
            </section>

            <!-- Card Detail -->
            <section class="panel-section">
                <h3 class="panel-title">Last clicked</h3>
                <div class="panel-detail" id="card-detail">
                    <span class="panel-detail__empty"
                        >Click a card to preview</span
                    >
                </div>
            </section>
        </aside>
    </div>

    <footer class="example-footer" id="example-footer">
        <div class="example-footer__left">
            <span class="example-footer__stat">
                <strong id="ft-progress">0%</strong>
            </span>
            <span class="example-footer__stat">
                <span id="ft-velocity">0.00</span> /
                <strong id="ft-velocity-avg">0.00</strong>
                <span class="example-footer__unit">px/ms</span>
            </span>
            <span class="example-footer__stat">
                <span id="ft-dom">0</span> /
                <strong id="ft-total">0</strong>
                <span class="example-footer__unit">items</span>
            </span>
        </div>
        <div class="example-footer__right">
            <span class="example-footer__stat">
                width <strong id="ft-width">260</strong
                ><span class="example-footer__unit">px</span>
            </span>
            <span class="example-footer__stat">
                mode <strong id="ft-mode">fixed</strong>
            </span>
        </div>
    </footer>
</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;
}