🧩 PlayStore Monitoring Server (Backend)

An automated backend service that monitors Google Play Store app listings by periodically capturing screenshots, storing metadata in a PostgreSQL database, and streaming real-time updates to connected clients using Server-Sent Events (SSE) — with zero manual refresh or polling.

---

🚀 Features

• ✅ Automated Play Store Screenshot Capture (via Playwright)
• ✅ Real-time Updates using Server-Sent Events (SSE)
• ✅ Prisma + PostgreSQL for structured data storage
• ✅ Express.js API serving JSON and static image assets
• ✅ Scheduled Cron Jobs for periodic screenshot capture
• ✅ CORS-enabled API for secure frontend communication
• ✅ Fully implemented in TypeScript

---

🧱 Tech Stack

Layer	Technology
Runtime	Node.js (≥18)
Framework	Express.js
ORM	Prisma
Database	PostgreSQL
Scheduler	node-cron
Screenshot Engine	Playwright (Chromium)
Realtime Transport	Server-Sent Events (SSE)
Language	TypeScript

---

📂 Project Structure

google-play-monitor-server/
├── .env
├── package.json
├── prisma/
│ ├── schema.prisma # Database schema definition
│ ├── migrations/ # Prisma migration history
│ └── migration_lock.toml
├── public/
│ └── screenshots/ # Saved screenshots by appId
├── src/
│ ├── index.ts # Server entrypoint + cron job
│ ├── lib/
│ │ └── prisma.ts # Prisma client instance
│ ├── routes/
│ │ ├── app.ts # Fetch registered apps
│ │ ├── screenshot.ts # Capture new screenshot
│ │ ├── screenshots.ts # Get screenshots by appId
│ │ └── events.ts # SSE live updates
│ └── services/
│ └── playwright.ts # Playwright capture logic
└── tsconfig.json

---

⚙️ Setup Instructions

1️⃣ Prerequisites

Ensure the following are installed on your machine:

• Node.js ≥ 18
• npm ≥ 9
• PostgreSQL (local or cloud)
• Playwright dependencies

Install missing Playwright system dependencies (Linux only):

npx playwright install-deps

2️⃣ Install Dependencies

npm install

3️⃣ Environment Variables

Create a .env file in the root directory with the following content:

DATABASE_URL="postgresql://user:password@localhost:5432/playstore_monitor"
PORT=4000

4️⃣ Initialize Database

Run Prisma migrations:

npx prisma migrate dev

5️⃣ Run the Server

Development mode (with hot reload):

npm run dev

Production build:

npm run build
npm start

---

🧠 System Overview

🕒 Automated Screenshot Capture

• A cron job runs every 12 hours (0 */12 * * *).
• It fetches all registered apps from the database.
• For each app:
  • Launches Playwright (Chromium).
  • Captures a full-page screenshot.
  • Saves the file under /public/screenshots/<appId>/.
  • Stores metadata (appId, imageUrl, capturedAt) in the database.
  • Broadcasts the update via SSE to all connected clients.

🧩 Data Model (Prisma Schema)

model App {
  appId        String       @id
  appName      String
  playStoreUrl String
  screenshots  Screenshot[]
}

model Screenshot {
  id          Int      @id @default(autoincrement())
  appId       String
  imageUrl    String
  fileName    String
  capturedAt  DateTime
  app         App      @relation(fields: [appId], references: [appId])
}

🟢 Live Updates (SSE)

When a new screenshot is captured, the backend broadcasts the event to all subscribed clients through /api/events.

Example SSE payload:

{
  "appId": "com.activision.callofduty.shooter",
  "appName": "Call of Duty Mobile",
  "imageUrl": "/public/screenshots/com.activision.callofduty.shooter/12345.png",
  "capturedAt": "2025-10-29T12:50:32.345Z"
}

📡 API Reference

| Action                 | Endpoint                  | Method      | Description                                          |
| :--------------------- | :------------------------ | :---------- | :--------------------------------------------------- |
| Add new app            | `/api/screenshot`         | `POST`      | Capture and save screenshot for given Play Store app |
| Get all apps           | `/api/apps`               | `GET`       | Retrieve list of monitored apps                      |
| Get screenshots by app | `/api/screenshots/:appId` | `GET`       | Fetch all screenshots for a specific app             |
| Real-time updates      | `/api/events`             | `GET (SSE)` | Receive live screenshot updates                      |

▶️ Example: Add a New App

Request

POST /api/screenshot
Content-Type: application/json

{
  "url": "https://play.google.com/store/apps/details?id=com.activision.callofduty.shooter",
  "appName": "Call of Duty Mobile"
}

Response

{
  "appName": "Call of Duty Mobile",
  "appId": "com.activision.callofduty.shooter",
  "url": "https://play.google.com/store/apps/details?id=com.activision.callofduty.shooter",
  "imagePath": "/public/screenshots/com.activision.callofduty.shooter/cod_1735603.png",
  "timestamp": "2025-10-30T14:50:32.345Z"
}

🧠 Key Logic Summary

| Task                   | File                         | Description                      |
| :--------------------- | :--------------------------- | :------------------------------- |
| Express App Setup      | `src/index.ts`               | Bootstraps app, routes, cron job |
| Capture App Screenshot | `src/routes/screenshot.ts`   | Handles POST `/api/screenshot`   |
| Fetch All Screenshots  | `src/routes/screenshots.ts`  | GET `/api/screenshots/:appId`    |
| Real-time Updates      | `src/routes/events.ts`       | SSE setup and broadcast logic    |
| Screenshot Logic       | `src/services/playwright.ts` | Headless Chromium capture        |
| Database Connection    | `src/lib/prisma.ts`          | Prisma client initialization     |

🧰 Developer Notes

• Screenshots are stored locally under public/screenshots/<appId>/.
• The API serves them statically via /public/... paths.
• SSE is used for simplicity — no WebSocket server needed.
• The frontend can subscribe to /api/events to receive updates.

🧭 Future Enhancements

• 🕓 Per-app “last updated” indicator
• 📊 Diff-viewer for screenshot comparison
• 🗑 Automated cleanup of old screenshots
• 🔐 Authentication & user management
• ⚙️ Configurable cron frequency via .env