[TASK] Make sure GET parameters from search and sorting are kept

theme/modules/product-list.module/module.html

@@ -116,6 +116,13 @@
 <div class="product-listing-module__search">
   <form action="{{ request.path }}" class="row-fluid">
     <input type="text" name="qd_name" value="{{ qd_name }}">
+    {% if request.query_dict %}
+      {% for key, value in request.query_dict.items() %}
+        {% if key != 'qd_name' %}
+          <input type="hidden" name="{{ key }}" value="{{ value }}">
+        {% endif %}
+      {% endfor %}
+    {% endif %}
     <button type="submit" class="btn-link btn-regular">{{ searchLabel }}</button>
   </form>
 </div>

theme/modules/product-list.module/module.js

@@ -15,8 +15,55 @@ function changeSorting (event) {
   }
 }
 
+function addEventListenerToFilters () {
+  document.addEventListener('DOMContentLoaded', function () {
+    function buildQueryString () {
+      const queryString = window.location.search
+      const urlParams = new URLSearchParams(queryString)
+      const params = {}
+      for (const [key, value] of urlParams.entries()) {
+        params[key] = value
+      }
+      let queryStringMerged = Object.keys(params)
+        .map(key => `${encodeURIComponent(key)}=${encodeURIComponent(params[key])}`)
+        .join('&')
+
+      if (queryStringMerged) {
+        queryStringMerged = '&' + queryStringMerged
+      }
+
+      return queryStringMerged
+    }
+
+    function appendToLinks (selector, queryString, excludeParams = []) {
+      const container = document.querySelector(selector)
+      const selects = container.getElementsByTagName('select')
+
+      const urlParams = new URLSearchParams(queryString)
+      excludeParams.forEach(param => urlParams.delete(param))
+      const filteredQueryString = urlParams.toString() ? '&' + urlParams.toString() : ''
+
+      for (let i = 0; i < selects.length; i++) {
+        const options = selects[i].getElementsByTagName('option')
+        for (let j = 0; j < options.length; j++) {
+          const currentHref = options[j].getAttribute('value')
+          if (currentHref.includes('?')) {
+            options[j].setAttribute('value', currentHref + filteredQueryString)
+          } else {
+            options[j].setAttribute('value', currentHref + '?' + filteredQueryString.substring(1))
+          }
+        }
+      }
+    }
+
+    const queryString = buildQueryString()
+    appendToLinks('.product-listing-module__sorting-filter', queryString, ['qd_sorting'])
+  })
+}
+
 function init () {
   addListener()
+  addEventListenerToFilters()
 }
 
 init()