refactor(health): move readiness status logic from controller to service

Author: programeryk

src/health/health.service.spec.ts

@@ -4,16 +4,18 @@ import { PrismaService } from 'src/prisma/prisma.service';
 
 describe('HealthService', () => {
   let service: HealthService;
+  const prismaMock = {
+    $queryRaw: jest.fn(),
+  };
 
   beforeEach(async () => {
+    jest.clearAllMocks();
     const module: TestingModule = await Test.createTestingModule({
       providers: [
         HealthService,
         {
           provide: PrismaService,
-          useValue: {
-            $queryRaw: jest.fn(),
-          },
+          useValue: prismaMock,
         },
       ],
     }).compile();
@@ -24,4 +26,24 @@ describe('HealthService', () => {
   it('should be defined', () => {
     expect(service).toBeDefined();
   });
+
+  it('returns 200 when database is reachable', async () => {
+    prismaMock.$queryRaw.mockResolvedValue(1);
+
+    const health = await service.getHealth();
+
+    expect(health.httpStatus).toBe(200);
+    expect(health.payload.status).toBe('ok');
+    expect(health.payload.services.database).toBe('up');
+  });
+
+  it('returns 503 when database check fails', async () => {
+    prismaMock.$queryRaw.mockRejectedValue(new Error('db down'));
+
+    const health = await service.getHealth();
+
+    expect(health.httpStatus).toBe(503);
+    expect(health.payload.status).toBe('degraded');
+    expect(health.payload.services.database).toBe('down');
+  });
 });

src/health/health.service.ts

@@ -1,23 +1,39 @@
-import { Injectable } from '@nestjs/common';
+import { HttpStatus, Injectable } from '@nestjs/common';
 import { PrismaService } from 'src/prisma/prisma.service';
 import packageJson from '../../package.json';
 
+export type HealthPayload = {
+  status: 'ok' | 'degraded';
+  timestamp: string;
+  uptime: number;
+  version: string;
+  services: {
+    database: 'up' | 'down';
+  };
+};
+
+export type HealthResult = {
+  httpStatus: number;
+  payload: HealthPayload;
+};
+
 @Injectable()
 export class HealthService {
   constructor(private prisma: PrismaService) {}
 
-  async getHealth() {
+  async getHealth(): Promise<HealthResult> {
     const timestamp = new Date().toISOString();
     const uptime = Math.floor(process.uptime());
     const version = packageJson.version;
-    let dbStatus = 'up';
+    let dbStatus: 'up' | 'down' = 'up';
 
     try {
       await this.prisma.$queryRaw`SELECT 1`;
     } catch {
       dbStatus = 'down';
     }
-    return {
+
+    const payload: HealthPayload = {
       status: dbStatus === 'up' ? 'ok' : 'degraded',
       timestamp,
       uptime,
@@ -26,5 +42,13 @@ export class HealthService {
         database: dbStatus,
       },
     };
+
+    return {
+      httpStatus:
+        payload.status === 'ok'
+          ? HttpStatus.OK
+          : HttpStatus.SERVICE_UNAVAILABLE,
+      payload,
+    };
   }
 }