Add vanilla JavaScript implementation for single radio selection in payment options

- Introduced a new self-invoking function to handle radio button selection without jQuery.
- Implemented visibility check for radio buttons and their labels.
- Added a MutationObserver to monitor changes in the payment options section and trigger selection accordingly.
- Included a fallback mechanism to ensure the selection function runs periodically.

themes/leo_gstore/assets/js/custom.js

@@ -1179,4 +1179,51 @@ $(document).ready(function () {
 
 		localStorage.removeItem('selectedSize')
 	}
-})
+});
+
+// WERSJA BEZ jQuery
+(() => {
+  const isVisible = (el) => {
+    if (!el) return false;
+    const s = getComputedStyle(el);
+    if (s.display === 'none' || s.visibility === 'hidden' || s.opacity === '0') return false;
+    const r = el.getBoundingClientRect();
+    return !!(r.width || r.height || el.getClientRects().length);
+  };
+
+  const findRadios = () => {
+    const container = document.querySelector('#checkout-payment-step .payment-options, .payment-options');
+    if (!container) return [];
+    return [...container.querySelectorAll('input[name="payment-option"][type="radio"]')]
+      .filter(r => !r.disabled && isVisible(r.closest('.payment-option') || r));
+  };
+
+  const selectSingle = () => {
+    const radios = findRadios();
+    if (radios.length === 1 && !radios[0].checked) {
+      const r = radios[0];
+      const label = document.querySelector(`label[for="${r.id}"]`);
+      label ? label.click() : (r.checked = true, r.dispatchEvent(new Event('change', {bubbles:true})));
+    }
+  };
+
+  // start
+  selectSingle();
+
+  // obserwator zmian sekcji płatności
+  const target = document.querySelector('#checkout-payment-step') || document.body;
+  const observer = new MutationObserver((muts) => {
+    if (muts.some(m =>
+      (m.target?.closest?.('.payment-options')) ||
+      [...m.addedNodes].some(n => n.nodeType === 1 && (n.matches?.('.payment-options') || n.querySelector?.('.payment-options')))
+    )) {
+      clearTimeout(observer._t);
+      observer._t = setTimeout(selectSingle, 60);
+    }
+  });
+  observer.observe(target, { childList: true, subtree: true, attributes: true, attributeFilter: ['class','style'] });
+
+  // lekki fallback
+  let tries = 0;
+  const iv = setInterval(() => { selectSingle(); if (++tries > 20) clearInterval(iv); }, 500);
+})();