Support server-determined build expiration

ts/util/parseRemoteClientExpiration.ts

@@ -0,0 +1,33 @@
+import semver from 'semver';
+
+type RemoteVersion = {
+  'min-version': string;
+  iso8601: string;
+};
+
+export function parseRemoteClientExpiration(
+  remoteExpirationValue: string
+): number | null {
+  const remoteVersions = JSON.parse(remoteExpirationValue) || [];
+  const ourVersion = window.getVersion();
+
+  return remoteVersions.reduce(
+    (acc: number | null, remoteVersion: RemoteVersion) => {
+      const minVersion = remoteVersion['min-version'];
+      const { iso8601 } = remoteVersion;
+
+      if (semver.gt(minVersion, ourVersion)) {
+        const timestamp = new Date(iso8601).getTime();
+
+        if (!acc) {
+          return timestamp;
+        }
+
+        return timestamp < acc ? timestamp : acc;
+      }
+
+      return acc;
+    },
+    null
+  );
+}