Auto refresh feature on public scoreboards

#12
#13

app/views/contests/_selectors.html.slim

@@ -1,15 +1,3 @@
-javascript:
-  function updateParams() {
-    categorySelectEl = document.getElementById('categories');
-    offlineInputEl = document.getElementById('offline');
-    if (categorySelectEl && !offlineInputEl) {
-      window.location.replace(`/public/#{@contest.slug}?category=${categorySelectEl.value}`);
-    } else if (!categorySelectEl) {
-      window.location.replace(`/public/#{@contest.slug}?hide_offline=${offlineInputEl.checked}`);
-    } else {
-      window.location.replace(`/public/#{@contest.slug}?category=${categorySelectEl.value}&hide_offline=${offlineInputEl.checked}`);
-    }
-  }
 - if @contest.categories.size > 0
   .row
     .col
@@ -17,29 +5,29 @@ javascript:
         option value=-1
           = t("contests.scoreboard.all_categories")
         - @contest.categories.each do |category|
-          option value=category.id
-            = category.name
+          - if @category == category.id.to_s
+            option value=category.id selected=true
+              = category.name
+          - else
+            option value=category.id
+              = category.name
       javascript:
-        categorySelectEl = document.getElementById('categories');
-        urlParams = new URLSearchParams(window.location.search);
-        selectedCategory = urlParams.get('category');
-        Array.from(categorySelectEl.children).forEach((option) => {
-          if (option.value == selectedCategory) option.selected = true;
-        });
-        categorySelectEl.addEventListener('change', (e) => {
-          updateParams();
+        document.getElementById('categories').addEventListener('change', (e) => {
+          addParam('category', e.target.value);
         })
 - if @contest.offline_form && @contest.puzzles.length < 2
   .row
     .col
-      input type="checkbox" id="offline" style="padding: 5px;"
+      - if @hide_offline
+        input type="checkbox" id="offline" style="padding: 5px;" checked=true
+      - else
+        input type="checkbox" id="offline" style="padding: 5px;"
       label for="offline"
         .ms-2
           = t("contests.scoreboard.hide_offline")
       javascript:
-        offlineInputEl = document.getElementById('offline');
-        urlParams = new URLSearchParams(window.location.search);
-        offlineInputEl.checked = urlParams.get('hide_offline') == "true";
-        offlineInputEl.addEventListener('change', (e) => {
-          updateParams();
+        document.getElementById('offline').addEventListener('change', (e) => {
+          console.log('changed');
+          if (e.target.checked) addParam('hide_offline', e.target.checked);
+          else removeParam('hide_offline');
         })