Fix NaN handling in getResponseAdForSlot

[pavankumar-vh]

Overview

Fix NaN handling in the getResponseAdForSlot function in common/src/util/lazy-response-ads.ts.

Bug Description

The function didn't validate that slotIndex is a finite number. If slotIndex was NaN or Infinity, Math.floor(NaN) would return NaN, causing Math.max(0, NaN) to return NaN, and NaN % ads.length to return NaN.

Fix

Added Number.isFinite() check to default to 0 for invalid numbers.

Testing

No existing tests for this function, but the fix prevents incorrect behavior with invalid inputs.

Files Changed

• common/src/util/lazy-response-ads.ts - Added NaN validation

Scope

This change only touches common/ which is an approved contribution area per the Contributing Guide.

[codebuff-team]

Good catch and a minimally invasive fix. The reasoning is correct: Math.floor(NaN) and Math.floor(Infinity) both propagate through Math.max and % to produce NaN, which would make ads[NaN] return undefined unexpectedly instead of a valid ad. Falling back to 0 for non-finite input is a reasonable, safe default.

A couple of things worth tightening before this lands:

1. It would help to add a one-line unit test (e.g. in common/src/util/lazy-response-ads.test.ts if one exists, or a new test file) covering NaN, Infinity, and -Infinity inputs. The repo doesn't have existing tests for this function per your own note, but adding one alongside a bug fix like this is the kind of thing a maintainer would expect and it makes the fix easy to verify at a glance.
2. Minor naming nit: safeSlotIndex is fine, but since you're already calling Math.floor after, you could equally clamp with Number.isFinite(slotIndex) ? Math.floor(slotIndex) : 0 in one line — not required, just a simplification.

Scope is fine, this is a common/ utility and out of the forbidden paths. Small, focused, and worth porting once a test is added.