fix: remove duplicate merged code in registerForEvent and cancelRegistration

[Subha12125]

Closes #281

This PR removes mistakenly merged duplicate code from both registerForEvent and cancelRegistration, ensuring that only the correct, atomic logic remains and that event registration and cancellation workflows are reliable and safe for high-concurrency usage.

Changes Made

• Removed the broken first implementation in registerForEvent that used manual capacity checks, which could cause race conditions.
• Cleaned up unclosed or dangling else blocks and brackets that previously caused runtime errors and broken control flow.
• Retained only the atomic findOneAndUpdate implementation for capacity validation, providing robust handling of simultaneous requests.
• Fixed cancelRegistration logic, correcting the duplicate conflict and properly defining variables like eventDate.
• Restored the waitlist promotion logic so vacancies are refilled automatically when spots open up after cancellation.

Why These Changes Were Needed

Previously, two versions of the registration logic were merged together, resulting in unreachable code, errors in registration/cancellation, and reliability issues when multiple users tried to register at the same time. Cancellation was also broken due to missing variable definitions.

How It Was Fixed

• Deleted approximately 180 lines of redundant, buggy code, keeping only the atomic version.
• Prevented race conditions and handled duplicate registration errors gracefully (e.g., MongoDB error 11000).
• Triggered real-time dashboard updates using emitRegistrationCount().
• Ensured cancelled registrations are properly reused, preserving audit trails and avoiding database conflicts.

How to Test

1. Start the backend server using npm run dev.
2. Run a syntax check: node --check src/controllers/registrationController.js (no errors should appear).
3. Set an event capacity to 1, register a user, then attempt to register a second—the second should get "Event is full".
4. Cancel a registration and confirm that the event’s registeredCount is decremented in the database.

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Note:
Stage 1 may report a warning about use of a deprecated version of actions/github-script@v7 in the repo workflow, but this is unrelated to this PR’s changes.

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This version:

• Has a compliant title and sectioned, explicit description (well over 100 characters)
• Clearly explains the changes, rationale, and testing steps
• Includes a valid "Closes [BUG] Bug: registerForEvent function has duplicate/merged code blocks with broken control flow #281" line at the top

Next:
Update your pull request description and title as shown above—these changes will make the automated validation pass, assuming the PR is based on a feature branch and the linked issue (#281) is open and assigned to you.

[github-actions]

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[github-actions]

❌ PR Format Check — Failed — Please Fix Below

Hi @Subha12125! Please fix the issues below before your PR can proceed to mentor review.

❌ Must Fix Before Proceeding

❌ Issue #281 is not assigned to you (@Subha12125) — You must be assigned to the issue before submitting a PR.

Comment /assign on Issue #281 or ask a maintainer to assign it to you.

❌ Issue #281 is not assigned to you (@Subha12125) — You must be assigned to the issue before submitting a PR.

Comment /assign on Issue #281 or ask a maintainer to assign it to you.

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[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Refactors event registration and cancellation flows in registrationController to reduce duplication, improve consistency, and add clearer handling around capacity, refunds, and notifications.

Changes:

• Simplified registerForEvent with a single flow for QR generation, duplicate handling, live stats emission, and email sending.
• Hardened cancelRegistration with existence checks, past-event cancellation prevention, refund-policy handling, and waitlist promotion.
• Standardized formatting and logging/error messaging across the controller.

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[vercel]

@Subha12125 is attempting to deploy a commit to the anubhav12302387's projects Team on Vercel.

A member of the Team first needs to authorize it.

[Nitya-003]

@anubhavxdev Resolved the conflicts. Merge it.

[Subha12125]

@anubhavxdev I raised the PR , so why you assigned to others ????