Route stats background mode through isolated daemon and defer in-app startup to live daemon (#58)

src/main/runtime/stats-server-routing.ts

@@ -0,0 +1,41 @@
+import type { BackgroundStatsServerState } from './stats-daemon';
+
+type EnsureStatsServerUrlDeps = {
+  currentPid: number;
+  readBackgroundState: () => BackgroundStatsServerState | null;
+  removeBackgroundState: () => void;
+  isProcessAlive: (pid: number) => boolean;
+  hasLocalStatsServer: () => boolean;
+  startLocalStatsServer: () => void;
+  getConfiguredPort: () => number;
+};
+
+function formatStatsServerUrl(port: number): string {
+  return `http://127.0.0.1:${port}`;
+}
+
+export type EnsureStatsServerUrlResult =
+  | { url: string; source: 'foreign' }
+  | { url: string; source: 'local' };
+
+export function createEnsureStatsServerUrlHandler(
+  deps: EnsureStatsServerUrlDeps,
+): () => EnsureStatsServerUrlResult {
+  return () => {
+    const state = deps.readBackgroundState();
+    if (!state) {
+      deps.removeBackgroundState();
+    } else if (state.pid === deps.currentPid && !deps.hasLocalStatsServer()) {
+      deps.removeBackgroundState();
+    } else if (!deps.isProcessAlive(state.pid)) {
+      deps.removeBackgroundState();
+    } else if (state.pid !== deps.currentPid) {
+      return { url: formatStatsServerUrl(state.port), source: 'foreign' };
+    }
+
+    if (!deps.hasLocalStatsServer()) {
+      deps.startLocalStatsServer();
+    }
+    return { url: formatStatsServerUrl(deps.getConfiguredPort()), source: 'local' };
+  };
+}