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

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

@@ -0,0 +1,86 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import { createEnsureStatsServerUrlHandler } from './stats-server-routing';
+
+function createHarness(options?: {
+  state?: { pid: number; port: number; startedAtMs: number } | null;
+  processAlive?: boolean;
+  localServerStarted?: boolean;
+}) {
+  const calls: string[] = [];
+  let localServerStarted = options?.localServerStarted ?? false;
+  const handler = createEnsureStatsServerUrlHandler({
+    currentPid: 100,
+    readBackgroundState: () => {
+      calls.push('readBackgroundState');
+      return options?.state ?? null;
+    },
+    removeBackgroundState: () => {
+      calls.push('removeBackgroundState');
+    },
+    isProcessAlive: () => {
+      calls.push('isProcessAlive');
+      return options?.processAlive ?? true;
+    },
+    hasLocalStatsServer: () => localServerStarted,
+    startLocalStatsServer: () => {
+      calls.push('startLocalStatsServer');
+      localServerStarted = true;
+    },
+    getConfiguredPort: () => 6969,
+  });
+
+  return {
+    calls,
+    handler,
+  };
+}
+
+test('stats server routing defers to a live background daemon from another process', () => {
+  const { calls, handler } = createHarness({
+    state: { pid: 200, port: 7979, startedAtMs: 1 },
+    processAlive: true,
+  });
+
+  assert.deepEqual(handler(), { url: 'http://127.0.0.1:7979', source: 'foreign' });
+  assert.deepEqual(calls, ['readBackgroundState', 'isProcessAlive']);
+});
+
+test('stats server routing clears dead daemon state and starts local server', () => {
+  const { calls, handler } = createHarness({
+    state: { pid: 200, port: 7979, startedAtMs: 1 },
+    processAlive: false,
+  });
+
+  assert.deepEqual(handler(), { url: 'http://127.0.0.1:6969', source: 'local' });
+  assert.deepEqual(calls, [
+    'readBackgroundState',
+    'isProcessAlive',
+    'removeBackgroundState',
+    'startLocalStatsServer',
+  ]);
+});
+
+test('stats server routing clears self-owned stale state and starts local server', () => {
+  const { calls, handler } = createHarness({
+    state: { pid: 100, port: 7979, startedAtMs: 1 },
+    processAlive: true,
+  });
+
+  assert.deepEqual(handler(), { url: 'http://127.0.0.1:6969', source: 'local' });
+  assert.deepEqual(calls, [
+    'readBackgroundState',
+    'removeBackgroundState',
+    'startLocalStatsServer',
+  ]);
+});
+
+test('stats server routing reuses a started local stats server', () => {
+  const { calls, handler } = createHarness({
+    state: null,
+    localServerStarted: true,
+  });
+
+  assert.deepEqual(handler(), { url: 'http://127.0.0.1:6969', source: 'local' });
+  assert.deepEqual(calls, ['readBackgroundState', 'removeBackgroundState']);
+});

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

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+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' };
+  };
+}