Consolidate prefersEphemeralSession availability check

Author: mdmathias

Source/AppAuth/iOS/OIDAuthorizationService+IOS.m

@@ -60,21 +60,38 @@ @implementation OIDAuthorizationService (IOS)
 + (id<OIDExternalUserAgentSession>)presentAuthorizationRequest:(OIDAuthorizationRequest *)request
                                                       callback:(OIDAuthorizationCallback)callback {
   return [self presentAuthorizationRequest:request
-                   prefersEphemeralSession:NO
+        prefersEphemeralSessionIfAvailable:NO
                                   callback:callback];
 }
 
 + (id<OIDExternalUserAgentSession>)presentAuthorizationRequest:(OIDAuthorizationRequest *)request
                                        prefersEphemeralSession:(BOOL)prefersEphemeralSession
                                                       callback:(OIDAuthorizationCallback)callback {
+  return [self presentAuthorizationRequest:request
+        prefersEphemeralSessionIfAvailable:prefersEphemeralSession
+                                  callback:callback];
+}
+
++ (id<OIDExternalUserAgentSession>)presentAuthorizationRequest:(OIDAuthorizationRequest *)request
+                            prefersEphemeralSessionIfAvailable:(BOOL)prefersEphemeralSession
+                                                      callback:(OIDAuthorizationCallback)callback {
   id<OIDExternalUserAgent> externalUserAgent;
+
+  if (@available(iOS 13, *)) {
 #if TARGET_OS_MACCATALYST
-  externalUserAgent = [[OIDExternalUserAgentCatalyst alloc]
-      initWithPrefersEphemeralSession:prefersEphemeralSession];
+    externalUserAgent = [[OIDExternalUserAgentCatalyst alloc]
+                            initWithPrefersEphemeralSession:prefersEphemeralSession];
+#else // TARGET_OS_MACCATALYST
+    externalUserAgent = [[OIDExternalUserAgentIOS alloc]
+                            initWithPrefersEphemeralSession:prefersEphemeralSession];
+#endif // TARGET_OS_MACCATALYST
+  } else {
+#if TARGET_OS_MACCATALYST
+    externalUserAgent = [[OIDExternalUserAgentCatalyst alloc] init];
 #else // TARGET_OS_MACCATALYST
-  externalUserAgent = [[OIDExternalUserAgentIOS alloc]
-      initWithPrefersEphemeralSession:prefersEphemeralSession];
+    externalUserAgent = [[OIDExternalUserAgentIOS alloc] init];
 #endif // TARGET_OS_MACCATALYST
+  }
   return [self presentAuthorizationRequest:request
                          externalUserAgent:externalUserAgent
                                   callback:callback];