add conditional check

packages/http/src/webauthn.ts

@@ -114,24 +114,49 @@ export async function getWebAuthnAssertion(
   payload: string,
   options?: TurnkeyCredentialRequestOptions
 ): Promise<string> {
-  const signingOptions = await getCredentialRequestOptions(payload, options);
-  const clientGetResult = await webauthnCredentialGet(signingOptions);
-  const assertion = clientGetResult.toJSON();
-
-  const stamp: TWebAuthnStamp = {
-    authenticatorData: assertion.response.authenticatorData,
-    clientDataJson: assertion.response.clientDataJSON,
-    credentialId: assertion.id,
-    signature: assertion.response.signature,
-  };
+  const supported = await isWebAuthnSupported();
+
+  if (supported) {
+    const signingOptions = await getCredentialRequestOptions(payload, options);
+    const clientGetResult = await webauthnCredentialGet(signingOptions);
+    const assertion = clientGetResult.toJSON();
+    const stamp: TWebAuthnStamp = {
+      authenticatorData: assertion.response.authenticatorData,
+      clientDataJson: assertion.response.clientDataJSON,
+      credentialId: assertion.id,
+      signature: assertion.response.signature,
+    };
+
+    return JSON.stringify(stamp);
+  }
 
-  return JSON.stringify(stamp);
+  throw new Error("webauthn is not supported by this browser");
 }
 
 export async function getWebAuthnAttestation(
   options: TurnkeyCredentialCreationOptions
 ): Promise<TAttestation> {
-  const res = await webauthnCredentialCreate(options);
+  const supported = await isWebAuthnSupported();
+
+  if (supported) {
+    const res = await webauthnCredentialCreate(options);
+
+    return toInternalAttestation(res.toJSON());
+  }
+
+  throw new Error("webauthn is not supported by this browser");
+}
+
+// For additional details see https://web.dev/articles/passkey-form-autofill#feature-detection
+async function isWebAuthnSupported(): Promise<boolean> {
+  if (
+    window.PublicKeyCredential &&
+    PublicKeyCredential.isConditionalMediationAvailable
+  ) {
+    const isCMA = await PublicKeyCredential.isConditionalMediationAvailable();
+
+    return isCMA;
+  }
 
-  return toInternalAttestation(res.toJSON());
+  return false;
 }