Show time since done or lateness instead of the last-done date

2 files changed, 91 insertions, 0 deletions

diff --git a/src/lib/shared/routine-metrics.test.ts b/src/lib/shared/routine-metrics.test.ts
index 88d0498..7f4d656 100644
--- a/src/lib/shared/routine-metrics.test.ts
+++ b/src/lib/shared/routine-metrics.test.ts
@@ -4,6 +4,7 @@ import {
 	computeHealthScore,
 	computeHealthSeries,
 	computeProjectHealthSeries,
+	formatDoneAge,
 	type HealthPoint,
 } from './routine-metrics';
 const CREATED = '2026-09-01T00:00:00.000Z';
@@ -240,6 +241,69 @@ describe('computeRoutineState (quota)', () => {
 	});
 });
 
+describe('daysSinceDone', () => {
+	it('is null when the routine was never done', () => {
+		const state = computeRoutineState(routine, [], plusDays(created, 3));
+		expect(state.daysSinceDone).toBeNull();
+	});
+
+	it('counts whole UTC calendar days since the last completion', () => {
+		const state = computeRoutineState(
+			routine,
+			[{ routineId: 1, doneAt: '2026-09-07T20:00:00.000Z' }],
+			Temporal.Instant.from('2026-09-10T08:00:00.000Z'),
+		);
+		expect(state.daysSinceDone).toBe(3); // not 2: calendar days, not 24h chunks
+	});
+
+	it('is 0 for a completion earlier the same calendar day', () => {
+		const state = computeRoutineState(
+			routine,
+			[{ routineId: 1, doneAt: '2026-09-10T08:00:00.000Z' }],
+			Temporal.Instant.from('2026-09-10T20:00:00.000Z'),
+		);
+		expect(state.daysSinceDone).toBe(0);
+	});
+
+	it('clamps a future-dated completion to 0', () => {
+		const state = computeRoutineState(
+			routine,
+			[{ routineId: 1, doneAt: '2026-09-12T08:00:00.000Z' }],
+			Temporal.Instant.from('2026-09-10T20:00:00.000Z'),
+		);
+		expect(state.daysSinceDone).toBe(0);
+	});
+});
+
+describe('formatDoneAge', () => {
+	it('shows the lateness once a day past due, even when never done', () => {
+		expect(formatDoneAge({ daysSinceDone: null, overdueDays: 3 })).toBe(
+			'3 jours de retard',
+		);
+		expect(formatDoneAge({ daysSinceDone: 10, overdueDays: 1 })).toBe(
+			'1 jour de retard',
+		);
+		expect(formatDoneAge({ daysSinceDone: 10, overdueDays: 3 })).toBe(
+			'3 jours de retard',
+		);
+	});
+
+	it('shows the time since done while the deadline is still ahead', () => {
+		expect(formatDoneAge({ daysSinceDone: null, overdueDays: 0 })).toBe(
+			'jamais fait',
+		);
+		expect(formatDoneAge({ daysSinceDone: 0, overdueDays: 0 })).toBe(
+			"fait aujourd'hui",
+		);
+		expect(formatDoneAge({ daysSinceDone: 1, overdueDays: 0 })).toBe(
+			'fait hier',
+		);
+		expect(formatDoneAge({ daysSinceDone: 5, overdueDays: 0 })).toBe(
+			'fait il y a 5 jours',
+		);
+	});
+});
+
 describe('computeHealthSeries', () => {
 	it('decays from 100 at creation to 0 two periods overdue when never done', () => {
 		const now = plusDays(created, 22);
diff --git a/src/lib/shared/routine-metrics.ts b/src/lib/shared/routine-metrics.ts
index d3c1470..4417539 100644
--- a/src/lib/shared/routine-metrics.ts
+++ b/src/lib/shared/routine-metrics.ts
@@ -38,6 +38,15 @@ function maxInstant(instants: Temporal.Instant[]): Temporal.Instant | null {
 	);
 }
 
+/** Whole UTC-calendar days from an instant to now, floored at 0. */
+function daysAgo(then: Temporal.Instant, now: Temporal.Instant): number {
+	const days = then
+		.toZonedDateTimeISO(UTC)
+		.toPlainDate()
+		.until(now.toZonedDateTimeISO(UTC).toPlainDate()).days;
+	return Math.max(0, days);
+}
+
 function parseCompletions(
 	routineId: number,
 	completions: CompletionInput[],
@@ -75,6 +84,8 @@ export interface RoutineState {
 	/** Spec text, as stored. */
 	frequency: string;
 	lastDoneAt: string | null;
+	/** Whole UTC-calendar days since lastDoneAt (null when never done). */
+	daysSinceDone: number | null;
 	/** When the pending obligation must be done (window end for quotas). */
 	dueAt: string;
 	/** Days past dueAt (0 while the deadline is still ahead). */
@@ -131,6 +142,7 @@ export function computeRoutineState(
 		name: routine.name,
 		frequency: routine.frequency,
 		lastDoneAt: lastDone !== null ? iso(lastDone) : null,
+		daysSinceDone: lastDone !== null ? daysAgo(lastDone, now) : null,
 		dueAt: iso(due),
 		overdueDays: Math.floor(overdueRatio * days),
 		overdueRatio,
@@ -223,6 +235,7 @@ function quotaState(
 		name: routine.name,
 		frequency: routine.frequency,
 		lastDoneAt: lastDone !== null ? iso(lastDone) : null,
+		daysSinceDone: lastDone !== null ? daysAgo(lastDone, now) : null,
 		dueAt: iso(due),
 		overdueDays: Math.max(
 			0,
@@ -396,3 +409,17 @@ export const STATUS_LABELS: Record<RoutineStatus, string> = {
 	late: 'En retard',
 	veryLate: 'Très en retard',
 };
+
+/** Meta stamp next to the frequency: lateness past due, else time since done. */
+export function formatDoneAge(
+	state: Pick<RoutineState, 'daysSinceDone' | 'overdueDays'>,
+): string {
+	if (state.overdueDays > 0) {
+		const n = state.overdueDays;
+		return `${n} jour${n > 1 ? 's' : ''} de retard`;
+	}
+	if (state.daysSinceDone === null) return 'jamais fait';
+	if (state.daysSinceDone === 0) return "fait aujourd'hui";
+	if (state.daysSinceDone === 1) return 'fait hier';
+	return `fait il y a ${state.daysSinceDone} jours`;
+}