Add check config changes during WebUI

www/editor.html

@@ -29,39 +29,42 @@
 <br>
 <div id="config"></div>
 <script>
+    let dump;
+
     ace.config.set('basePath', 'https://cdnjs.cloudflare.com/ajax/libs/ace/1.24.1/');
     const editor = ace.edit('config', {
         mode: 'ace/mode/yaml',
     });
 
-    document.getElementById('save').addEventListener('click', () => {
+    document.getElementById('save').addEventListener('click', async () => {
-        fetch('api/config', {
+        let r = await fetch('api/config', {cache: 'no-cache'});
-            method: 'POST', body: editor.getValue()
+        if (r.ok && dump !== await r.text()) {
-        }).then(r => {
+            alert('Config was changed from another place. Refresh the page and make changes again');
+            return;
+        }
+
+        r = await fetch('api/config', {method: 'POST', body: editor.getValue()});
         if (r.ok) {
             alert('OK');
             fetch('api/exit?code=100', {method: 'POST'});
         } else {
-                r.text().then(alert);
+            alert(await r.text());
         }
     });
-    });
 
-    window.addEventListener('load', () => {
+    window.addEventListener('load', async () => {
-        fetch('api/config', {cache: 'no-cache'}).then(r => {
+        const r = await fetch('api/config', {cache: 'no-cache'});
         if (r.status === 410) {
             alert('Config file is not set');
         } else if (r.status === 404) {
             editor.setValue(''); // config file not exist
         } else if (r.ok) {
-                r.text().then(data => {
+            dump = await r.text();
-                    editor.setValue(data);
+            editor.setValue(dump);
-                });
         } else {
             alert(`Unknown error: ${r.statusText} (${r.status})`);
         }
     });
-    });
 </script>
 </body>
 </html>