// QR render helper. Scans for any element with data-qr="<text>" and renders
// a Kazuhiko Arase qrcode-generator QR into it as inline <img>. Size is
// controlled via data-qr-size="N" (px square, default 96). Error-correction
// level via data-qr-ec="L|M|Q|H" (default M).
//
// The qrcode-generator lib (loaded before this script) exposes a global
// `qrcode()` factory: typeNumber 0 = auto, ec = 'L'|'M'|'Q'|'H'.
(function () {
  function render(el) {
    var text = el.getAttribute('data-qr') || '';
    if (!text) return;
    if (el.dataset.qrRendered === '1') return;
    var size = parseInt(el.getAttribute('data-qr-size') || '96', 10);
    var ec   = el.getAttribute('data-qr-ec') || 'M';
    try {
      var qr = qrcode(0, ec);
      qr.addData(text);
      qr.make();
      // createImgTag(cellSize, margin)
      // 4-cell margin keeps the QR scannable per spec; cell size derived from
      // requested pixel size and module count.
      var modules = qr.getModuleCount();
      var cellSize = Math.max(1, Math.floor(size / (modules + 8)));
      el.innerHTML = qr.createImgTag(cellSize, 4);
      el.dataset.qrRendered = '1';
      el.title = 'Scan: ' + text;
    } catch (e) {
      el.textContent = '[QR error]';
    }
  }

  function scan() {
    var nodes = document.querySelectorAll('[data-qr]');
    for (var i = 0; i < nodes.length; i++) render(nodes[i]);
  }

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