refs #15903 [master-v5] browser-cached lightbox forms

* uses JS to cache form inputs during modal lifetime
* ignore input fields for passwords for better security

themes/finc/js/lightbox_form_cache.js

+'use strict';
+
+document.addEventListener('DOMContentLoaded', function () {
+  if (typeof sessionStorage === 'undefined' || typeof MutationObserver !== 'function') {
+    return;
+  }
+
+  const cache = sessionStorage;
+  const cacheKeyPrefix = 'lightbox_form_';
+
+  function clearCache() {
+    (new Array(cache.length)).fill().map((_, index) => cache.key(index))
+      .forEach(key => cache.removeItem(key));
+  }
+
+  const modal = document.querySelector('#modal .modal-body');
+  const config = {attributes: false, childList: true, subtree: false};
+
+  const observer = new MutationObserver(function () {
+    const form = modal.querySelector('form:not([data-non-cached])');
+    if (!form) {
+      return;
+    }
+
+    form.addEventListener('submit', clearCache);
+    const cacheKeyBase = Array.from(form.attributes).map(attr => attr.value);
+    const cacheKey = cacheKeyPrefix + btoa(cacheKeyBase.join());
+
+    const inputs = Array.from(form.querySelectorAll('input:not([type=password])'));
+    JSON.parse(cache.getItem(cacheKey) || '[]').forEach(function (value, index) {
+      inputs[index].value = value;
+    });
+
+    modal.querySelectorAll('a:not([data-reset-forms])').forEach(function (link) {
+      link.onclick = function () {
+        var cachedItems = JSON.stringify(inputs.map(input => input.value));
+        cache.setItem(cacheKey, cachedItems);
+      };
+    });
+  });
+
+  clearCache();
+  document.addEventListener('VuFind.lightbox.closed', clearCache);
+  observer.observe(modal, config);
+});

themes/finc/theme.config.php

@@ -4,6 +4,7 @@ return [
     'js' => [
         'openurl.js',
         'check_item_statuses.js',
+        'lightbox_form_cache.js',
     ],
     'helpers' => [
         'aliases' => [