fix: add stats server node fallback

backlog/tasks/task-238.5 - Split-immersion-tracker-query-layer-into-focused-read-model-modules.md

@@ -1,9 +1,11 @@
 ---
 id: TASK-238.5
 title: Split immersion tracker query layer into focused read-model modules
-status: To Do
-assignee: []
+status: Done
+assignee:
+  - codex
 created_date: '2026-03-26 20:49'
+updated_date: '2026-03-27 00:00'
 labels:
   - tech-debt
   - stats
@@ -29,10 +31,10 @@ priority: medium
 ## Acceptance Criteria
 
 <!-- AC:BEGIN -->
-- [ ] #1 Query responsibilities are grouped into focused modules such as library/session detail, vocabulary/kanji detail, and maintenance/cleanup helpers.
-- [ ] #2 The stats server and immersion tracker service depend on stable exported query surfaces instead of one monolithic file.
-- [ ] #3 The refactor preserves current SQL behavior and existing statistics outputs.
-- [ ] #4 Existing stats/immersion tests still pass, with added focused coverage where extraction creates new seams.
+- [x] #1 Query responsibilities are grouped into focused modules such as library/session detail, vocabulary/kanji detail, and maintenance/cleanup helpers.
+- [x] #2 The stats server and immersion tracker service depend on stable exported query surfaces instead of one monolithic file.
+- [x] #3 The refactor preserves current SQL behavior and existing statistics outputs.
+- [x] #4 Existing stats/immersion tests still pass, with added focused coverage where extraction creates new seams.
 <!-- AC:END -->
 
 ## Implementation Plan
@@ -43,3 +45,17 @@ priority: medium
 3. Keep SQL ownership close to the domain module that consumes it; avoid a giant `queries/` dump with no structure.
 4. Verify with the maintained stats/immersion test lane plus `bun run typecheck`.
 <!-- SECTION:PLAN:END -->
+
+## Implementation Notes
+
+<!-- SECTION:NOTES:BEGIN -->
+Split the monolithic query surface into focused read-model modules for sessions, trends, lexical data, library lookups, and maintenance helpers. Updated the service and test imports to use the new module boundaries.
+
+Verification: `bun run typecheck` passed. Focused query and stats-server tests passed, including the `stats-server.test.ts` coverage around the new Bun fallback path.
+<!-- SECTION:NOTES:END -->
+
+## Final Summary
+
+<!-- SECTION:FINAL_SUMMARY:BEGIN -->
+Extracted the immersion-tracker query layer into smaller read-model modules and kept the compatibility barrel in place so existing call sites can transition cleanly. Added focused coverage and verified the refactor with typecheck plus targeted tests.
+<!-- SECTION:FINAL_SUMMARY:END -->

changes/2026-03-27-stats-server-runtime-fallback.md

@@ -0,0 +1,5 @@
+type: fixed
+area: stats
+
+- Fixed stats startup so the immersion tracker can run when `Bun.serve` is unavailable.
+- Stats server now falls back to a Node `http` listener in Electron/runtime paths that do not expose Bun.

src/core/services/__tests__/stats-server.test.ts

@@ -1160,4 +1160,30 @@ describe('stats server API routes', () => {
       bun.Bun.serve = originalServe;
     }
   });
+
+  it('falls back to node:http when Bun.serve is unavailable', () => {
+    type BunRuntime = {
+      Bun: {
+        serve?: (options: { fetch: unknown; port: number; hostname: string }) => {
+          stop: () => void;
+        };
+      };
+    };
+
+    const bun = globalThis as typeof globalThis & BunRuntime;
+    const originalServe = bun.Bun.serve;
+    bun.Bun.serve = undefined;
+
+    try {
+      const server = startStatsServer({
+        port: 0,
+        staticDir: fs.mkdtempSync(path.join(os.tmpdir(), 'subminer-stats-server-node-')),
+        tracker: createMockTracker(),
+      });
+
+      server.close();
+    } finally {
+      bun.Bun.serve = originalServe;
+    }
+  });
 });

src/core/services/stats-server.ts

@@ -1,5 +1,6 @@
 import { Hono } from 'hono';
 import type { ImmersionTrackerService } from './immersion-tracker-service.js';
+import { createServer, type IncomingMessage, type ServerResponse } from 'node:http';
 import { basename, extname, resolve, sep } from 'node:path';
 import { readFileSync, existsSync, statSync } from 'node:fs';
 import { MediaGenerator } from '../../media-generator.js';
@@ -171,6 +172,10 @@ type BunRuntime = {
   };
 };
 
+type NodeRuntimeHandle = {
+  stop: () => void;
+};
+
 const STATS_STATIC_CONTENT_TYPES: Record<string, string> = {
   '.css': 'text/css; charset=utf-8',
   '.gif': 'image/gif',
@@ -197,7 +202,9 @@ function buildAnkiNotePreview(
   return {
     word: getPreferredNoteFieldValue(fields, [getConfiguredWordFieldName(ankiConfig)]),
     sentence: getPreferredNoteFieldValue(fields, [getConfiguredSentenceFieldName(ankiConfig)]),
-    translation: getPreferredNoteFieldValue(fields, [getConfiguredTranslationFieldName(ankiConfig)]),
+    translation: getPreferredNoteFieldValue(fields, [
+      getConfiguredTranslationFieldName(ankiConfig),
+    ]),
   };
 }
 
@@ -241,6 +248,82 @@ function createStatsStaticResponse(staticDir: string, requestPath: string): Resp
   });
 }
 
+async function readNodeRequestBody(req: IncomingMessage): Promise<Buffer> {
+  const chunks: Buffer[] = [];
+  for await (const chunk of req) {
+    chunks.push(typeof chunk === 'string' ? Buffer.from(chunk) : Buffer.from(chunk));
+  }
+  return Buffer.concat(chunks);
+}
+
+async function createNodeRequest(req: IncomingMessage): Promise<Request> {
+  const host = req.headers.host ?? '127.0.0.1';
+  const url = new URL(req.url ?? '/', `http://${host}`);
+  const headers = new Headers();
+  for (const [name, value] of Object.entries(req.headers)) {
+    if (value === undefined) continue;
+    if (Array.isArray(value)) {
+      headers.set(name, value.join(', '));
+    } else {
+      headers.set(name, value);
+    }
+  }
+
+  const method = req.method ?? 'GET';
+  const body = method === 'GET' || method === 'HEAD' ? undefined : await readNodeRequestBody(req);
+  const init: RequestInit = {
+    method,
+    headers,
+  };
+  if (body !== undefined && body.length > 0) {
+    init.body = new Uint8Array(body);
+  }
+  return new Request(url, init);
+}
+
+async function writeNodeResponse(
+  res: ServerResponse<IncomingMessage>,
+  response: Response,
+): Promise<void> {
+  res.statusCode = response.status;
+  res.statusMessage = response.statusText;
+  response.headers.forEach((value, key) => {
+    res.setHeader(key, value);
+  });
+
+  if (!response.body) {
+    res.end();
+    return;
+  }
+
+  const body = Buffer.from(await response.arrayBuffer());
+  res.end(body);
+}
+
+function startNodeStatsServer(app: StatsApp, port: number): NodeRuntimeHandle {
+  const server = createServer((req, res) => {
+    void (async () => {
+      try {
+        const response = await app.fetch(await createNodeRequest(req));
+        await writeNodeResponse(res, response);
+      } catch {
+        if (!res.headersSent) {
+          res.statusCode = 500;
+        }
+        res.end('Internal Server Error');
+      }
+    })();
+  });
+
+  server.listen(port, '127.0.0.1');
+
+  return {
+    stop: () => {
+      server.close();
+    },
+  };
+}
+
 export function createStatsApp(
   tracker: ImmersionTrackerService,
   options?: {
@@ -672,7 +755,11 @@ export function createStatsApp(
         method: 'POST',
         headers: { 'Content-Type': 'application/json' },
         signal: AbortSignal.timeout(ANKI_CONNECT_FETCH_TIMEOUT_MS),
-        body: JSON.stringify({ action: 'notesInfo', version: 6, params: { notes: resolvedNoteIds } }),
+        body: JSON.stringify({
+          action: 'notesInfo',
+          version: 6,
+          params: { notes: resolvedNoteIds },
+        }),
       });
       const result = (await response.json()) as {
         result?: Array<{ noteId: number; fields: Record<string, { value: string }> }>;
@@ -1016,11 +1103,14 @@ export function startStatsServer(config: StatsServerConfig): { close: () => void
     resolveAnkiNoteId: config.resolveAnkiNoteId,
   });
 
-  const server = (globalThis as typeof globalThis & BunRuntime).Bun.serve({
-    fetch: app.fetch,
-    port: config.port,
-    hostname: '127.0.0.1',
-  });
+  const bunServe = (globalThis as typeof globalThis & Partial<BunRuntime>).Bun?.serve;
+  const server = bunServe
+    ? bunServe({
+        fetch: app.fetch,
+        port: config.port,
+        hostname: '127.0.0.1',
+      })
+    : startNodeStatsServer(app, config.port);
 
   return {
     close: () => {