refactor(calculate): extract isStreakAlive helper

Author: shambavi2007

lib/calculate.test.ts

@@ -1,5 +1,5 @@
 import { describe, it, expect } from 'vitest';
-import { calculateStreak, calculateMonthlyStats } from './calculate';
+import { calculateStreak, calculateMonthlyStats, isStreakAlive } from './calculate';
 import type { ContributionCalendar } from '../types';
 
 // Turns a flat array of daily counts into the ContributionCalendar shape,
@@ -259,6 +259,28 @@ describe('calculateStreak — timezone awareness', () => {
   });
 });
 
+describe('isStreakAlive', () => {
+  it('returns true when both today and yesterday have contributions', () => {
+    expect(isStreakAlive({ contributionCount: 1 }, { contributionCount: 1 })).toBe(true);
+  });
+
+  it('returns true when only today has contributions', () => {
+    expect(isStreakAlive({ contributionCount: 1 }, { contributionCount: 0 })).toBe(true);
+  });
+
+  it('returns true when only yesterday has contributions', () => {
+    expect(isStreakAlive({ contributionCount: 0 }, { contributionCount: 1 })).toBe(true);
+  });
+
+  it('returns false when both today and yesterday have zero contributions', () => {
+    expect(isStreakAlive({ contributionCount: 0 }, { contributionCount: 0 })).toBe(false);
+  });
+
+  it('returns false when yesterday is null and today has no contributions', () => {
+    expect(isStreakAlive({ contributionCount: 0 }, null)).toBe(false);
+  });
+});
+
 describe('calculateMonthlyStats', () => {
   it('calculates monthly stats correctly when both months have commits', () => {
     const calendar = {

lib/calculate.ts

@@ -50,6 +50,12 @@ const stats = calculateStreak(
   new Date('2026-05-25T10:00:00Z')
 );
 */
+export function isStreakAlive(
+  today: { contributionCount: number },
+  yesterday: { contributionCount: number } | null
+): boolean {
+  return today.contributionCount > 0 || (yesterday?.contributionCount ?? 0) > 0;
+}
 
 export function calculateStreak(
   calendar: ContributionCalendar,
@@ -98,9 +104,9 @@ export function calculateStreak(
   // If I committed today, the streak is alive.
   // If I haven't committed today, but I committed yesterday,
   // the streak is STILL alive (Grace Period).
-  const isStreakAlive = today.contributionCount > 0 || (yesterday?.contributionCount ?? 0) > 0;
+  const streakAlive = isStreakAlive(today, yesterday);
 
-  if (isStreakAlive) {
+  if (streakAlive) {
     // Count backwards from the first day that has a contribution
     // starting from either today or yesterday.
     let i = today.contributionCount > 0 ? todayIndex : todayIndex - 1;