add testurls

lib/utils.ts

@@ -1,3 +1,5 @@
+import { Platform } from "react-native";
+
 export function logger(...args: any[]) {
   console.log('Pushy: ', ...args);
 }
@@ -7,3 +9,25 @@ export function assertRelease() {
     throw new Error('react-native-update 只能在 RELEASE 版本中运行.');
   }
 }
+
+const ping =
+  Platform.OS === 'web'
+    ? Promise.resolve
+    : async (url: string) =>
+        Promise.race([
+          fetch(url, {
+            method: 'HEAD',
+          })
+            .then(({ status }) => (status === 200 ? url : null))
+            .catch(() => null),
+          new Promise(r => setTimeout(() => r(null), 2000)),
+        ]);
+
+const canUseGoogle = ping('https://www.google.com');
+
+export const testUrls = async (urls?: string[]) => {
+  if (!urls?.length || (await canUseGoogle)) {
+    return null;
+  }
+  return Promise.race(urls.map(ping)).catch(() => null);
+};