Initial setup for new frontend.

server/types/shared.ts

@@ -0,0 +1,45 @@
+// Types shared with the client.
+
+export function isObject(arg: unknown): arg is object {
+    return arg !== null && typeof arg === "object";
+}
+
+export type Version = string;
+
+export function isVersion(arg: unknown): arg is Version {
+    // Should be good enough for now.
+    return typeof arg === "string";
+}
+
+export type NodeStatistics = {
+    registered: number;
+    withVPN: number;
+    withCoords: number;
+    monitoring: {
+        active: number;
+        pending: number;
+    };
+};
+
+export function isNodeStatistics(arg: unknown): arg is NodeStatistics {
+    if (!isObject(arg)) {
+        return false;
+    }
+    const stats = arg as NodeStatistics;
+    return (
+        typeof stats.registered === "number" &&
+        typeof stats.withVPN === "number" &&
+        typeof stats.withCoords === "number" &&
+        typeof stats.monitoring === "object" &&
+        typeof stats.monitoring.active === "number" &&
+        typeof stats.monitoring.pending === "number"
+    );
+}
+
+export interface Statistics {
+    nodes: NodeStatistics;
+}
+
+export function isStatistics(arg: unknown): arg is Statistics {
+    return isObject(arg) && isNodeStatistics((arg as Statistics).nodes);
+}