Prevent Duplicate Event Registrations

[AYUSH-P-SINGH]

Closes issue #129

Description

This PR prevents duplicate event registrations by ensuring a user cannot register for the same event more than once using the same email address.

Changes made:

• Added a new POST /api/events/[id]/register API endpoint.
• Validates event ID, request body, email format, and event existence.
• Normalizes email addresses using trim().toLowerCase().
• Checks for existing registrations before creating a new booking.
• Returns 409 Conflict for duplicate registration attempts.
• Updated lib/actions/booking.actions.ts to maintain consistent duplicate-check logic.
• Handles MongoDB duplicate key (11000) errors gracefully.
• Revalidates relevant pages after successful registration.

Fixes #

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Type of Change

• Bug fix (non-breaking change which fixes an issue)

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How Has This Been Tested?

Manual testing

• Registered a new email for an event successfully.

• Attempted to register the same email again for the same event and verified that a 409 Conflict response was returned.

• Verified that the same email can register for different events.

• Verified email matching is case-insensitive (User@example.com and user@example.com are treated as the same).

• Confirmed the project compiles without TypeScript errors.

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Checklist

• My code follows the style guidelines of this project.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• My changes generate no new warnings or console errors.

Summary by CodeRabbit

• New Features

  • Added event registration support so users can submit an email to book an event.

• Bug Fixes

  • Improved duplicate booking handling to prevent the same email from registering for the same event twice.
  • Added clearer responses for invalid requests, missing events, and duplicate registrations.
  • Updated page refresh behavior so event and home pages stay in sync after a successful booking.

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[coderabbitai]

📝 Walkthrough

Walkthrough

Adds a POST REST endpoint at app/api/events/[id]/register/route.ts that validates the event ID and email, checks for duplicates, creates a booking, and revalidates cache. Updates createBooking in lib/actions/booking.actions.ts to proactively guard against duplicate bookings via an explicit pre-insert query.

Changes

Event Registration API and Booking Duplicate Guard

Layer / File(s)	Summary
createBooking duplicate guard lib/actions/booking.actions.ts	createBooking now queries for an existing Booking by eventId + normalized email before attempting insert, returning an early error; other functions (getBookingsByEventId, getBookingsCountByEventId, getBookingsByEmail) have formatting-only changes.
POST registration route app/api/events/[id]/register/route.ts	Adds the complete POST handler: validates id as ObjectId and email via regex, connects to DB, checks event existence, detects duplicate registrations, creates the booking, revalidates /events/${slug} and / paths, and returns structured JSON with status codes 201/400/404/409/500.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related issues

• [FEATURE] - Prevent Duplicate Event Registrations #129: This PR directly implements the duplicate event-registration prevention described in the issue, using eventId + email normalization checks in both the route handler and the createBooking action.

Possibly related PRs

• niharika-mente/DevEvent_Tracker#5: Touches createBooking duplicate-check logic in lib/actions/booking.actions.ts, the same function modified in this PR.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 20.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly matches the main change: preventing duplicate event registrations.
Description check	✅ Passed	The description covers the required summary, issue reference, change type, testing, and checklist well enough.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 2

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@app/api/events/`[id]/register/route.ts:
- Around line 13-109: The new POST registration route violates the repo pattern
and duplicates logic already handled by createBooking. Remove the
app/api/events/[id]/register route handler and move its validation and booking
flow into the existing createBooking server action in lib/actions/*.actions.ts,
including event lookup, email validation, duplicate checking, Booking.create,
and revalidatePath. Then update the client to call createBooking directly so
there is a single booking path and no divergent API route.
- Line 94: The catch in the route handler currently uses `error: any`, which
should be avoided; update the `register` route’s `catch` block to use `unknown`
instead, then narrow the value before accessing `.code` just like the server
action does. Keep the handling logic in the same `route.ts` handler, but add the
appropriate type guard or `instanceof`/property check so only narrowed errors
are read for `.code`.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 87d28dfb-1c4c-4a0e-a026-92356ef7cca3

📥 Commits

Reviewing files that changed from the base of the PR and between 8049abd and 5be8274.

⛔ Files ignored due to path filters (1)

• package-lock.json is excluded by !**/package-lock.json, !package-lock.json

📒 Files selected for processing (3)

• app/api/events/[id]/register/route.ts
• lib/actions/booking.actions.ts
• tsconfig.json

[TarunyaProgrammer]

LGTM! The defensive checks in the server action and the new registration API endpoint are very clean and well-structured. Thanks for handling the path revalidation and edge cases (like the unique index constraints) properly! 🚀