Add nonblocking/asyn I/O operations

backend/tests/Notes.test.js

@@ -1,16 +1,18 @@
 import { describe, it, expect, vi, beforeEach } from 'vitest';
 import request from 'supertest';
+import { Readable } from 'node:stream';
 import app from '../app.js';
 
 vi.mock('../db/notes.dao.js', () => ({
   getAllNotes: vi.fn(),
+  streamAllNotes: vi.fn(),
 }));
 
 vi.mock('../services/clustering.service.js', () => ({
   clusterNotes: vi.fn(),
 }));
 
-import { getAllNotes } from '../db/notes.dao.js';
+import { getAllNotes, streamAllNotes } from '../db/notes.dao.js';
 import { clusterNotes } from '../services/clustering.service.js';
 
 const MOCK_NOTES = [
@@ -24,6 +26,8 @@ const MOCK_CLUSTERS = [
   { label: 'Export Problems', noteIds: ['note_003'] },
 ];
 
+const rowStream = (rows) => Readable.from(rows, { objectMode: true });
+
 describe('GET /v1/notes', () => {
 
   beforeEach(() => {
@@ -31,7 +35,7 @@ describe('GET /v1/notes', () => {
   });
 
   it('should return 200 and an array of notes', async () => {
-    getAllNotes.mockResolvedValue(MOCK_NOTES);
+    streamAllNotes.mockResolvedValue(rowStream(MOCK_NOTES));
 
     const res = await request(app).get('/v1/notes');
 
@@ -40,8 +44,26 @@ describe('GET /v1/notes', () => {
     expect(Array.isArray(res.body)).toBe(true);
   });
 
+  it('should send JSON incrementally rather than buffering the row set', async () => {
+    streamAllNotes.mockResolvedValue(rowStream(MOCK_NOTES));
+
+    const res = await request(app).get('/v1/notes');
+
+    expect(res.headers['content-type']).toMatch(/application\/json/);
+    expect(res.headers['content-length']).toBeUndefined();
+  });
+
+  it('should return an empty array when there are no notes', async () => {
+    streamAllNotes.mockResolvedValue(rowStream([]));
+
+    const res = await request(app).get('/v1/notes');
+
+    expect(res.status).toBe(200);
+    expect(res.body).toEqual([]);
+  });
+
   it('should return notes with expected properties', async () => {
-    getAllNotes.mockResolvedValue(MOCK_NOTES);
+    streamAllNotes.mockResolvedValue(rowStream(MOCK_NOTES));
 
     const res = await request(app).get('/v1/notes');
     const note = res.body[0];
@@ -55,7 +77,7 @@ describe('GET /v1/notes', () => {
   });
 
   it('should return 500 when the database query fails', async () => {
-    getAllNotes.mockRejectedValue(new Error('connection refused'));
+    streamAllNotes.mockRejectedValue(new Error('connection refused'));
 
     const res = await request(app).get('/v1/notes');
 
@@ -63,6 +85,19 @@ describe('GET /v1/notes', () => {
     expect(res.body).toHaveProperty('error');
     expect(res.body.error).toBe('Failed to load notes');
   });
+
+  it('should abort the response when the row stream fails mid-flight', async () => {
+    const failing = new Readable({
+      objectMode: true,
+      read() {
+        this.push(MOCK_NOTES[0]);
+        this.destroy(new Error('connection lost'));
+      },
+    });
+    streamAllNotes.mockResolvedValue(failing);
+
+    await expect(request(app).get('/v1/notes')).rejects.toThrow();
+  });
 });
 
 describe('POST /v1/notes/cluster', () => {
@@ -101,7 +136,22 @@ describe('POST /v1/notes/cluster', () => {
     await request(app).post('/v1/notes/cluster');
 
     expect(clusterNotes).toHaveBeenCalledOnce();
-    expect(clusterNotes).toHaveBeenCalledWith(MOCK_NOTES);
+    expect(clusterNotes).toHaveBeenCalledWith(
+      MOCK_NOTES,
+      expect.objectContaining({ signal: expect.any(AbortSignal) })
+    );
+  });
+
+  it('should pass a signal that is not aborted while the request is open', async () => {
+    getAllNotes.mockResolvedValue(MOCK_NOTES);
+    clusterNotes.mockImplementation(async (_notes, { signal }) => {
+      expect(signal.aborted).toBe(false);
+      return MOCK_CLUSTERS;
+    });
+
+    const res = await request(app).post('/v1/notes/cluster');
+
+    expect(res.status).toBe(200);
   });
 
   it('should return 500 when clusterNotes (API call) fails', async () => {