From 8c346769464e586f194d8dfff1e655ec941c3590 Mon Sep 17 00:00:00 2001
From: kolaente <k@knt.li>
Date: Mon, 8 Jun 2026 15:16:46 +0200
Subject: [PATCH] feat(time-tracking): extract the smart-fill start computation

---
 .../src/helpers/time/smartFillStart.test.ts   | 47 +++++++++++++++++++
 frontend/src/helpers/time/smartFillStart.ts   | 20 ++++++++
 2 files changed, 67 insertions(+)
 create mode 100644 frontend/src/helpers/time/smartFillStart.test.ts
 create mode 100644 frontend/src/helpers/time/smartFillStart.ts

diff --git a/frontend/src/helpers/time/smartFillStart.test.ts b/frontend/src/helpers/time/smartFillStart.test.ts
new file mode 100644
index 000000000..e623125cf
--- /dev/null
+++ b/frontend/src/helpers/time/smartFillStart.test.ts
@@ -0,0 +1,47 @@
+import {describe, it, expect} from 'vitest'
+
+import {smartFillStart} from './smartFillStart'
+import type {ITimeEntry} from '@/modelTypes/ITimeEntry'
+
+function entry(startTime: Date, endTime: Date | null): ITimeEntry {
+	return {
+		id: 1,
+		userId: 1,
+		taskId: 0,
+		projectId: 0,
+		startTime,
+		endTime,
+		comment: '',
+		created: startTime,
+		updated: startTime,
+		maxPermission: null,
+	}
+}
+
+describe('smartFillStart', () => {
+	const now = new Date('2026-06-07T15:30:00')
+
+	it('continues from the latest entry end time', () => {
+		const entries = [
+			entry(new Date('2026-06-07T09:00:00'), new Date('2026-06-07T10:00:00')),
+			entry(new Date('2026-06-07T11:00:00'), new Date('2026-06-07T12:30:00')),
+		]
+		expect(smartFillStart(entries, '09:00', now)).toEqual(new Date('2026-06-07T12:30:00'))
+	})
+
+	it('ignores still-running entries (no end) when picking the latest end', () => {
+		const entries = [
+			entry(new Date('2026-06-07T09:00:00'), new Date('2026-06-07T10:00:00')),
+			entry(new Date('2026-06-07T13:00:00'), null),
+		]
+		expect(smartFillStart(entries, '09:00', now)).toEqual(new Date('2026-06-07T10:00:00'))
+	})
+
+	it('falls back to the default start time on the current day when there are no entries', () => {
+		expect(smartFillStart([], '08:15', now)).toEqual(new Date('2026-06-07T08:15:00'))
+	})
+
+	it('falls back to 09:00 when no default is configured', () => {
+		expect(smartFillStart([], '', now)).toEqual(new Date('2026-06-07T09:00:00'))
+	})
+})
diff --git a/frontend/src/helpers/time/smartFillStart.ts b/frontend/src/helpers/time/smartFillStart.ts
new file mode 100644
index 000000000..c131c1d0e
--- /dev/null
+++ b/frontend/src/helpers/time/smartFillStart.ts
@@ -0,0 +1,20 @@
+import type {ITimeEntry} from '@/modelTypes/ITimeEntry'
+
+// The smart-clock start time: continue from the most recent entry's end so
+// consecutive entries don't overlap or leave gaps; with no completed entry to
+// continue from, fall back to the user's configured default start (HH:MM) on
+// the given day.
+export function smartFillStart(recentEntries: ITimeEntry[], defaultStart: string, now: Date): Date {
+	const lastEnd = recentEntries
+		.map(entry => entry.endTime)
+		.filter((end): end is Date => end !== null)
+		.sort((a, b) => b.getTime() - a.getTime())[0]
+	if (lastEnd !== undefined) {
+		return new Date(lastEnd)
+	}
+
+	const [hours, minutes] = (defaultStart || '09:00').split(':').map(Number)
+	const start = new Date(now)
+	start.setHours(hours || 0, minutes || 0, 0, 0)
+	return start
+}