/**
 * Live file-input preview.
 * For every <input type="file" data-preview="CONTAINER_ID"> found on the page,
 * renders a list of selected files with thumbnails (images) or file-type icons
 * (PDFs, videos, archives…) and the filename + size.
 */
(() => {
  const ICON = {
    pdf:   '📄',
    video: '🎬',
    zip:   '🗜️',
    vtt:   '💬',
    image: '🖼️',
    other: '📎',
  };

  function iconFor(file) {
    const t = file.type;
    if (t.startsWith('image/'))      return ICON.image;
    if (t === 'application/pdf')     return ICON.pdf;
    if (t.startsWith('video/'))      return ICON.video;
    if (t === 'application/zip' || t === 'application/x-zip-compressed') return ICON.zip;
    if (file.name.endsWith('.vtt'))  return ICON.vtt;
    return ICON.other;
  }

  function humanSize(bytes) {
    if (bytes >= 1073741824) return `${(bytes / 1073741824).toFixed(2)} GB`;
    if (bytes >= 1048576)   return `${(bytes / 1048576).toFixed(2)} MB`;
    if (bytes >= 1024)      return `${(bytes / 1024).toFixed(1)} KB`;
    return `${bytes} B`;
  }

  function renderPreview(input, container) {
    container.innerHTML = '';
    const files = Array.from(input.files);
    if (!files.length) return;

    files.forEach((file) => {
      const item = document.createElement('div');
      item.className = 'fp-item';

      if (file.type.startsWith('image/')) {
        const img = document.createElement('img');
        img.className = 'fp-thumb';
        img.alt = file.name;
        const reader = new FileReader();
        reader.onload = (e) => { img.src = e.target.result; };
        reader.readAsDataURL(file);
        item.appendChild(img);
      } else {
        const icon = document.createElement('span');
        icon.className = 'fp-icon';
        icon.textContent = iconFor(file);
        item.appendChild(icon);
      }

      const meta = document.createElement('span');
      meta.className = 'fp-meta';
      meta.innerHTML =
        '<span class="fp-name">' + escHtml(file.name) + '</span>' +
        '<span class="fp-size">' + humanSize(file.size) + '</span>';
      item.appendChild(meta);

      container.appendChild(item);
    });
  }

  function escHtml(str) {
    return str
      .replace(/&/g, '&amp;')
      .replace(/</g, '&lt;')
      .replace(/>/g, '&gt;')
      .replace(/"/g, '&quot;');
  }

  function init() {
    document.querySelectorAll('input[type="file"][data-preview]').forEach((input) => {
      const containerId = input.getAttribute('data-preview');
      const container   = document.getElementById(containerId);
      if (!container) return;

      input.addEventListener('change', () => {
        renderPreview(input, container);
      });
    });
  }

  if (document.readyState === 'loading') {
    document.addEventListener('DOMContentLoaded', init);
  } else {
    init();
  }
})();