fix: division by zero error #201

[JettChenT]

Fixes #201

Summary by CodeRabbit

• Bug Fixes
  • Improved search result ranking stability by addressing edge cases in the search scoring algorithm that could occur with certain document collections.

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2 Skipped Deployments

Project	Deployment	Review	Updated (UTC)
cmumaps	Skipped		Jan 17, 2026 9:31pm
cmumaps-visualizer	Skipped		Jan 17, 2026 9:31pm

[coderabbitai]

📝 Walkthrough

Walkthrough

Fixes a division by zero vulnerability in the BM25Term utility by applying Math.max(1, avgDl) to the denominator when calculating term frequency normalization, preventing invalid results when average document length approaches zero.

Changes

Cohort / File(s)	Summary
BM25 Division by Zero Prevention apps/server/src/utils/search/rank.ts	Modified tfPart calculation in BM25Term to guard against division by zero using Math.max(1, avgDl) in the denominator

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~7 minutes

Poem

🐰 A tiny math tweak saved the day,
When avgDl shrank away,
With Math.max, we stand tall,
No more zero division fall! ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and specifically summarizes the main change: fixing a division by zero error related to issue #201.
Linked Issues check	✅ Passed	The PR implements a fix for the division by zero issue by using Math.max(1, avgDl) in the denominator, directly addressing issue #201's acceptance criteria to resolve the issue.
Out of Scope Changes check	✅ Passed	All changes in rank.ts are focused on fixing the BM25Term division by zero issue specified in issue #201 with no extraneous modifications.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing touches

• 📝 Generate docstrings

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