1 files changed, 105 insertions, 0 deletions
diff --git a/src/lib/shared/routine-metrics.test.ts b/src/lib/shared/routine-metrics.test.ts
new file mode 100644
index 0000000..4a84eda
--- /dev/null
+++ b/src/lib/shared/routine-metrics.test.ts
@@ -0,0 +1,105 @@
+import { describe, it, expect } from 'vitest';
+import {
+	computeRoutineState,
+	computeHealthScore,
+	parseIntervalToDays,
+} from './routine-metrics';
+
+const DAY_MS = 24 * 60 * 60 * 1000;
+const CREATED = '2026-09-01T00:00:00.000Z';
+
+const routine = {
+	id: 1,
+	version: 1,
+	name: 'clean kitchen',
+	frequencyDays: 7,
+	createdAt: CREATED,
+};
+
+describe('computeRoutineState', () => {
+	it('is ok and healthy before the due date', () => {
+		const now = Date.parse(CREATED) + 3 * DAY_MS;
+		const state = computeRoutineState(routine, [], now);
+		expect(state.status).toBe('ok');
+		expect(state.overdueDays).toBe(0);
+		expect(state.health).toBe(100);
+		expect(state.dueAt).toBe(
+			new Date(Date.parse(CREATED) + 7 * DAY_MS).toISOString(),
+		);
+	});
+
+	it('uses the last completion as reference once done', () => {
+		const doneAt = new Date(Date.parse(CREATED) + 5 * DAY_MS).toISOString();
+		const now = Date.parse(doneAt) + 2 * DAY_MS;
+		const state = computeRoutineState(routine, [{ routineId: 1, doneAt }], now);
+		expect(state.lastDoneAt).toBe(doneAt);
+		expect(state.status).toBe('ok');
+	});
+
+	it('is due at exactly the frequency', () => {
+		const now = Date.parse(CREATED) + 7 * DAY_MS;
+		const state = computeRoutineState(routine, [], now);
+		expect(state.status).toBe('due');
+		expect(state.health).toBe(100);
+	});
+
+	it('is very urgent (veryLate) when two weeks old for a weekly routine', () => {
+		const now = Date.parse(CREATED) + 15 * DAY_MS;
+		const state = computeRoutineState(routine, [], now);
+		expect(state.status).toBe('veryLate');
+		expect(state.overdueDays).toBe(8);
+		expect(state.health).toBe(0);
+	});
+
+	it('is late when overdue by half a frequency', () => {
+		const now = Date.parse(CREATED) + 10.5 * DAY_MS;
+		const state = computeRoutineState(routine, [], now);
+		expect(state.status).toBe('late');
+	});
+
+	it('health of 75 means a quarter of the period overdue', () => {
+		const now = Date.parse(CREATED) + 7 * DAY_MS + 1.75 * DAY_MS;
+		const state = computeRoutineState(routine, [], now);
+		expect(state.health).toBe(75);
+	});
+});
+
+describe('parseIntervalToDays', () => {
+	it('converts units to days', () => {
+		expect(parseIntervalToDays('1d')).toBe(1);
+		expect(parseIntervalToDays('2w')).toBe(14);
+		expect(parseIntervalToDays('3m')).toBe(90);
+		expect(parseIntervalToDays('1y')).toBe(365);
+	});
+
+	it('accepts whitespace and uppercase', () => {
+		expect(parseIntervalToDays(' 2W ')).toBe(14);
+	});
+
+	it('rejects invalid input', () => {
+		expect(parseIntervalToDays('2')).toBeNull();
+		expect(parseIntervalToDays('w')).toBeNull();
+		expect(parseIntervalToDays('2x')).toBeNull();
+		expect(parseIntervalToDays('-1d')).toBeNull();
+		expect(parseIntervalToDays('')).toBeNull();
+	});
+});
+
+describe('computeHealthScore', () => {
+	it('is 100 with no routines', () => {
+		expect(computeHealthScore([])).toBe(100);
+	});
+
+	it('averages routine healths', () => {
+		const now = Date.parse(CREATED) + 8 * DAY_MS;
+		const a = computeRoutineState(routine, [], now); // overdue 1 day
+		const b = computeRoutineState(
+			routine,
+			[],
+			Date.parse(CREATED) + 3 * DAY_MS,
+		);
+		expect(computeHealthScore([a, b])).toBe(
+			Math.round((a.health + b.health) / 2),
+		);
+	});
+});