{# ── Shared row-selection behaviour for bulk-action list pages ────────────────
   Included by the issues and inspections list templates (classic + modern).
   Generic on purpose — it keys off classes/attributes, not page-specific ids,
   so both pages share one implementation:

     .bulk-check       one per row  (name=issue_ids / inspection_ids)
     .bulk-check-all   the header select-all box
     .bulk-count       element whose text becomes the selected count
     [data-bulk-action] submit buttons, disabled while nothing is selected
     [data-bulk-confirm] optional confirm text, count substituted for {n}

   Guarding the submit on a zero selection matters: the browser would happily
   POST an empty id list, and the route would flash "No issues selected" after
   a full page round trip.
#}
<script>
(function () {
  'use strict';

  var boxes  = Array.prototype.slice.call(document.querySelectorAll('.bulk-check'));
  var all    = document.querySelector('.bulk-check-all');
  var counts = Array.prototype.slice.call(document.querySelectorAll('.bulk-count'));
  var btns   = Array.prototype.slice.call(document.querySelectorAll('[data-bulk-action]'));
  if (!boxes.length) return;

  function selected() {
    return boxes.filter(function (b) { return b.checked; });
  }

  function sync() {
    var n = selected().length;
    counts.forEach(function (el) { el.textContent = n; });
    btns.forEach(function (b) { b.disabled = (n === 0); });
    if (all) {
      all.checked       = (n > 0 && n === boxes.length);
      // Distinguishes "some" from "none"/"all" in the header box.
      all.indeterminate = (n > 0 && n < boxes.length);
    }
  }

  boxes.forEach(function (b) { b.addEventListener('change', sync); });

  if (all) {
    all.addEventListener('change', function () {
      boxes.forEach(function (b) { b.checked = all.checked; });
      sync();
    });
  }

  // Shift-click selects the range from the last clicked box — the usual
  // convention, and the difference between ticking 3 boxes and 40.
  var lastIndex = null;
  boxes.forEach(function (b, i) {
    b.addEventListener('click', function (e) {
      if (e.shiftKey && lastIndex !== null) {
        var lo = Math.min(lastIndex, i), hi = Math.max(lastIndex, i);
        for (var j = lo; j <= hi; j++) { boxes[j].checked = b.checked; }
        sync();
      }
      lastIndex = i;
    });
  });

  btns.forEach(function (btn) {
    btn.addEventListener('click', function (e) {
      var n = selected().length;
      if (n === 0) { e.preventDefault(); return; }
      var msg = btn.getAttribute('data-bulk-confirm');
      if (msg && !window.confirm(msg.replace('{n}', n) + '\n\n' + n + ' selected.')) {
        e.preventDefault();
      }
    });
  });

  sync();
}());
</script>