Add exit node selection to the clients

server/lib/exitNodes/calculateExitNodeWeight.ts

@@ -0,0 +1,40 @@
+import { db, sites, clients } from "@server/db";
+import { and, eq, count } from "drizzle-orm";
+
+// (MAX_CONNECTIONS - current_connections) / MAX_CONNECTIONS)
+// higher = more desirable
+// like saying, this node has x% of its capacity left
+export async function calculateExitNodeWeight(
+    exitNodeId: number,
+    maxConnections: number | null | undefined
+): Promise<number | null> {
+    if (maxConnections === null || maxConnections === undefined) {
+        return 1;
+    }
+
+    const [[siteConnections], [clientConnections]] = await Promise.all([
+        db
+            .select({ count: count() })
+            .from(sites)
+            .where(
+                and(eq(sites.exitNodeId, exitNodeId), eq(sites.online, true))
+            ),
+        db
+            .select({ count: count() })
+            .from(clients)
+            .where(
+                and(
+                    eq(clients.exitNodeId, exitNodeId),
+                    eq(clients.online, true)
+                )
+            )
+    ]);
+
+    const currentConnections = siteConnections.count + clientConnections.count;
+
+    if (currentConnections >= maxConnections) {
+        return null;
+    }
+
+    return (maxConnections - currentConnections) / maxConnections;
+}