added rate-limiting fetch function

Author: commit111

app/templates/index.html

@@ -207,6 +207,27 @@ <h2>Ask Defang</h2>
             }
         });
 
+        async function rateLimitingFetch(url, options = {}) {
+            if (window.crypto && window.crypto.subtle) {
+                let bodyHash, nonceArray = new Uint32Array(1), nonce = 0;
+                const body = new TextEncoder().encode(options.body);
+                const bodyWithNonce = new Uint8Array(nonceArray.byteLength + body.byteLength);
+                bodyWithNonce.set(body, nonceArray.byteLength);
+
+                do {
+                    nonceArray[0] = ++nonce;
+                    bodyWithNonce.set(new Uint8Array(nonceArray.buffer));
+                    bodyHash = await crypto.subtle.digest('SHA-256', bodyWithNonce);
+                } while(new DataView(bodyHash).getUint32(0) > 0x50000);
+
+                options.headers = {
+                    ...options.headers,
+                    'X-Nonce': nonce
+                }
+                return fetch(url, options);
+            }
+        }
+
         function sendQuery() {
             const query = queryInput.value.trim();
             if (query === '') return;
@@ -228,7 +249,7 @@ <h2>Ask Defang</h2>
             sendButton.disabled = true;
 
             // Send query to server
-            fetch('/ask', {
+            rateLimitingFetch('/ask', {
                 method: 'POST',
                 headers: {
                     'Content-Type': 'application/json',