Engal Sandhai

Engal Sandhai is a web-based, billing and realtime stock management system built for a college campus vegetable store.
It connects faculty buyers (~300 daily active users) with admin faculty (10 users) who manage daily stock and prices.
The system generates bills, accepts static-QR-based payments (faculty upload payment screenshots), decrements stock atomically, and provides realtime stock updates across connected clients.

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📌 Quick Summary

• Single-server, intranet-only web app for campus vegetable billing.
• Two roles:
  • Admin (5 faculty) → manage stock, prices, and orders.
  • Faculty (all others) → place orders, upload payment screenshot, receive bills.
• Payment flow:
  • Static QR is displayed on the bill.
  • Faculty uploads payment screenshot.
  • Admin verifies payment manually.
• Stock updates:
  • Stock decrements only when payment screenshot is uploaded.
  • Updates are processed atomically to prevent overselling.
• Realtime updates via WebSockets.

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🚀 Key Features

• 🔑 Role-based authentication (employee_id + password) with forced password reset option.
• 🛠️ Admin panel:
  • Add/update vegetables (photo, quantity, rate).
  • View & filter orders.
  • Verify/reject payments.
  • Revert stock when needed.
• 🛒 Buying panel:
  • Browse vegetables with stock, price, and photo.
  • Add to cart & place multi-item orders.
  • Bill page with static admin QR.
  • Upload payment screenshot.
• 🔐 Per-order session rule → automatic logout after successful payment upload.
• ⚡ Realtime updates:
  • Stock updates across all connected faculty.
  • New order notifications for admins.
• 🧮 Atomic multi-item order processing → no overselling.
• 🖼️ Local file storage for:
  • Vegetable photos.
  • Payment screenshots.
• 🪶 Lightweight, self-hosted stack → no paid cloud required.

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🏗️ Tech Stack & Architecture

Frontend

• ⚛️ React (Vite) + TypeScript
• 🎨 Tailwind CSS
• 🔄 React Router, Axios
• 🔔 WebSocket client

Backend

• 🔐 Firebase Authentication
• 📂 Firestore Database
• 📡 WebSockets for realtime updates

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📷 Workflow

1. Admin updates daily stock (vegetable name, qty, rate, photo).
2. Faculty places order → system generates bill with static QR.
3. Faculty uploads payment screenshot.
4. Stock decrements atomically after upload.
5. Admin verifies payment → order marked as completed.
6. Realtime notifications keep all clients updated.