Add new players chart route

[tudddorrr]

No description provided.

[claude]

PR Review: Add new players chart route

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Code Quality and Best Practices

🟡 Duplicated logic — calculateChange extracted but not consolidated

src/lib/math/calculateChange.ts introduces a shared calculateChange utility, but src/routes/protected/event/common.ts already has an identical inline implementation:

// event/common.ts (existing, unchanged)
function calculateChange(count: number, lastEvent: EventData | undefined): number {
  const previousCount = lastEvent?.count ?? 0
  if (previousCount === 0) return count
  return (count - previousCount) / previousCount
}

The extracted utility is never used to replace this existing duplicate. Either update event/common.ts to import from the shared utility, or leave the extraction for a separate refactor PR — but the current state leaves two diverged implementations.

🟡 fillDateGaps is also duplicated

new-players.ts has its own fillDateGaps that mirrors the one in event/common.ts with only minor structural differences (flat list vs. grouped by series name). This is the same pattern and deserves the same treatment — either reuse/generalize the existing one or acknowledge the duplication.

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Potential Bugs or Issues

🔵 calculateChange return type is semantically inconsistent

When prevCount === 0, the function returns newCount (an absolute count), but otherwise returns a ratio. This means the change field carries different units depending on the data. The test at line 257 codifies this behaviour (expect(twoDaysAgoData.change).toBe(2)), but consumers of this API will need to handle the special case. If this is intentional, a comment in the utility explaining the convention would prevent future confusion.

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Performance, Security, Test Coverage

No issues found.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.73%. Comparing base (29b0c15) to head (50de8a6).
⚠️ Report is 2 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #834      +/-   ##
===========================================
+ Coverage    95.69%   95.73%   +0.03%     
===========================================
  Files          379      382       +3     
  Lines         5919     5950      +31     
  Branches       766      770       +4     
===========================================
+ Hits          5664     5696      +32     
  Misses         149      149              
+ Partials       106      105       -1     

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