Gateway: fallback routes per host, for the laptop's VPN address

gateway/test/host.test.ts

@@ -0,0 +1,58 @@
+// A host with several routes connects through the first one that answers.
+import { afterEach, describe, expect, it } from "bun:test";
+import type { Server } from "bun";
+
+import { T3Host } from "../src/t3/host.ts";
+
+const ENVIRONMENT_ID = "env-laptop";
+let server: Server<undefined> | undefined;
+afterEach(() => server?.stop(true));
+
+/** Just enough of a T3 server: the descriptor, a ticket, config, and an empty shell snapshot. */
+function fakeT3() {
+  server = Bun.serve({
+    port: 0,
+    fetch(req, srv) {
+      const { pathname } = new URL(req.url);
+      if (pathname === "/.well-known/t3/environment") {
+        return Response.json({ environmentId: ENVIRONMENT_ID, label: "framework-gib", serverVersion: "0.1.5", orchestrationProtocolVersion: 2 });
+      }
+      if (pathname === "/api/auth/websocket-ticket/rpc") return Response.json({ ticket: "t" });
+      if (pathname === "/ws" && srv.upgrade(req)) return undefined;
+      return new Response("not found", { status: 404 });
+    },
+    websocket: {
+      message(ws, data) {
+        const frame = JSON.parse(String(data)) as { _tag: string; id: string; tag: string };
+        if (frame._tag !== "Request") return;
+        if (frame.tag === "server.getConfig") {
+          ws.send(JSON.stringify({ _tag: "Exit", requestId: frame.id, exit: { _tag: "Success", value: {} } }));
+        } else if (frame.tag === "orchestration.subscribeShell") {
+          const snapshot = { snapshotSequence: 1, projects: [], threads: [] };
+          ws.send(JSON.stringify({ _tag: "Chunk", requestId: frame.id, values: [{ kind: "snapshot", snapshot }] }));
+        }
+      },
+    },
+  });
+  return `http://localhost:${server.port}`;
+}
+
+describe("T3Host routes", () => {
+  it("falls back to the next route when the preferred one does not answer", async () => {
+    const working = fakeT3();
+    // Port 9 (discard) refuses connections, standing in for a LAN route that is down.
+    const host = new T3Host({ id: ENVIRONMENT_ID, label: "Laptop", urls: ["http://127.0.0.1:9", working], token: "x", environmentId: ENVIRONMENT_ID });
+    const online = new Promise<void>((resolve) => {
+      const check = setInterval(() => {
+        if (host.status === "online") {
+          clearInterval(check);
+          resolve();
+        }
+      }, 5);
+    });
+    host.start();
+    await online;
+    expect(host.url).toBe(working);
+    host.stop();
+  });
+});