allow pasting already generated link to generator

index.html

@@ -257,7 +257,15 @@
             (isValid ? document.querySelector('form') : document.querySelector('section')).classList.add('hidden');
         };
 
+        // when all apps can generate invite links internally, we may decide to remove on-site generator
+        // and instead show a page with instructions how to generate links in Delta Chat
         function textareaInput(inputData) {
+            // be idempotent: allow pasting a already generated invite-link to the generator (esp. if generated by the app)
+            if (inputData.startsWith('https://i.delta.chat/#')) {
+                inputData = inputData.replace(/https:\/\/i.delta.chat\/#/, '')
+                inputData = inputData.replace(/&/, '#')
+            }
+
             // '#' may be wrongly encoded to '%23' by Safari/iOS; convert it back. see issue #16
             if (inputData.indexOf('#') == -1) {
                 inputData = inputData.replace(/%23/, '#')