1 files changed, 59 insertions, 0 deletions
diff --git a/src/lib/shared/routine-metrics.ts b/src/lib/shared/routine-metrics.ts
index 2ac245e..99e5c56 100644
--- a/src/lib/shared/routine-metrics.ts
+++ b/src/lib/shared/routine-metrics.ts
@@ -84,6 +84,65 @@ export function computeHealthScore(states: { health: number }[]): number {
 	return Math.round(total / states.length);
 }
 
+export interface HealthPoint {
+	/** Epoch ms of the sample. */
+	at: number;
+	/** Health (0-100) at that instant. */
+	health: number;
+}
+
+/**
+ * Daily health samples from the routine's creation to now: 100 right after a
+ * completion, then a linear decay to 0 once a full period is overdue (sawtooth).
+ * Each sample anchors on the latest completion at or before it (or creation).
+ * Uses the routine's current frequency across the whole history.
+ */
+export function computeHealthSeries(
+	routine: RoutineInput,
+	completions: CompletionInput[],
+	now: number,
+): HealthPoint[] {
+	const createdMs = Date.parse(routine.createdAt);
+	const startMs = Number.isFinite(createdMs) ? createdMs : now;
+	const periodMs = routine.frequencyDays * DAY_MS;
+
+	const completionMs = completions
+		.filter((c) => c.routineId === routine.id)
+		.map((c) => Date.parse(c.doneAt))
+		.sort((a, b) => a - b);
+
+	const points: HealthPoint[] = [];
+	if (now <= startMs) {
+		return [{ at: now, health: 100 }];
+	}
+
+	// Reference anchor: latest completion at-or-before the sampled instant.
+	let refMs = startMs;
+	let nextCompletion = 0;
+	const sampleAt = (t: number): number => {
+		while (
+			nextCompletion < completionMs.length &&
+			completionMs[nextCompletion] <= t
+		) {
+			refMs = completionMs[nextCompletion];
+			nextCompletion++;
+		}
+		const dueMs = refMs + periodMs;
+		const rawRatio = (t - dueMs) / periodMs;
+		return Math.max(0, Math.round(100 - Math.max(0, rawRatio) * 100));
+	};
+
+	for (let t = startMs; t <= now; t += DAY_MS) {
+		points.push({ at: t, health: sampleAt(t) });
+	}
+
+	// Final unaligned sample so the curve ends at the present instant.
+	if (points[points.length - 1].at < now) {
+		points.push({ at: now, health: sampleAt(now) });
+	}
+	return points;
+}
+
 export function formatFrequency(days: number): string {
 	if (days === 1) return 'chaque jour';
 	if (days === 7) return 'chaque semaine';