Build for Ambula '26

### Project Overview Ambula Care is a full-stack, mobile-friendly healthcare web platform built using Next.js App Router (React 19, TypeScript), MongoDB (Mongoose), and Vanilla CSS (custom glassmorphic theme). It enables patients to search for doctors, choose slots from a 7-day calendar, fill out health summaries, and book appointments in under 45 seconds. It also provides doctors with a secure JWT-authenticated dashboard to log in, review patient records, log consultation diagnosis notes/prescriptions, and block slots for leave. ### Setup & Installation 1. Install node packages: npm install 2. Seed the database with mock doctors, 7 days of available slots, and doctor credentials: npx tsx src/scripts/seed.ts 3. Run the development server: npm run dev 4. Open the site locally at: http://localhost:3000 ### Test Credentials (Local & Live Site) - **Email**: doctor@ambula.com - **Password**: password123 (This account is linked to Dr. Amit Sharma) ### Concurrency Lock & Double-Booking Prevention To ensure 100% reliability under concurrent booking requests, we implemented an atomic lock mechanism at the query level instead of using heavy database transactions: - When a patient selects a slot, a temporary Booking is written in a 'pending' state. - We then run an atomic find-and-update operation on the Slot collection requiring its status to be exactly 'available': Slot.findOneAndUpdate({ _id: slotId, status: "available" }, { status: "booked", bookingId }) - If two bookings arrive simultaneously, MongoDB processes them sequentially. The first succeeds and locks the slot, while the second query matches 0 documents and returns null. - The losing thread deletes its pending booking and returns a 409 Conflict to the user, advising them to select the next slot. - You can run the concurrency test script to verify this (sends 5 simultaneous requests for the exact same slot): npx tsx src/scripts/test-concurrency.ts ### Mandatory Submission Statement "We prevented double-booking at the backend using a single-document atomic update query (`findOneAndUpdate`) matching the slot ID and requiring its status to be exactly 'available'; because single-document updates are processed sequentially and atomic by design in MongoDB, this acts as a lock that guarantees exactly one request modifies the slot state while all other concurrent requests are safely rejected."