Prevent duplicate submissions on frontend

views/problem.ejs

@@ -221,6 +221,7 @@ if (contest) {
 <script src="/libs/ace/ace.js"></script>
 <script type="text/javascript">
 var editor = ace.edit("editor");
+var lastSubmitted = '';
 
 editor.setTheme("ace/theme/tomorrow");
 editor.getSession().setMode("ace/mode/" + $('#languages-menu .item.active').data('mode'));
@@ -233,9 +234,10 @@ editor.setShowPrintMargin(false);
 editor.renderer.updateFontSize();
 
 function submit_code() {
-  if (!editor.getValue().trim()) return false;
+  if (!editor.getValue().trim() || editor.getValue().trim() == lastSubmitted) return false;
   $('#submit_code input[name=language]').val($('#languages-menu .item.active').data('value'));
-  $('#submit_code input[name=code]').val(editor.getValue());
+  lastSubmitted = editor.getValue();
+  $('#submit_code input[name=code]').val(lastSubmitted);
   return true;
 }