use created_at as first due_at

1 files changed, 16 insertions, 5 deletions

diff --git a/src/lib/shared/routine-metrics.ts b/src/lib/shared/routine-metrics.ts
index 953a025..7758f27 100644
--- a/src/lib/shared/routine-metrics.ts
+++ b/src/lib/shared/routine-metrics.ts
@@ -92,10 +92,12 @@ export function computeRoutineState(
 	const period = periodMs(routine.frequencyDays);
 	// Calendar-day anchor: the period starts at midnight of the reference day,
 	// so any new calendar day past the frequency flips the routine to due.
+	// A never-done routine has no completed period: its creation day is its
+	// due date, so it ages exactly like a done one whose anchor is creation.
 	const due = reference
 		.toZonedDateTimeISO(UTC)
 		.startOfDay()
-		.add({ days: routine.frequencyDays })
+		.add({ days: lastDone === null ? 0 : routine.frequencyDays })
 		.toInstant();
 	const rawRatio = (now.epochMilliseconds - due.epochMilliseconds) / period;
 	const overdueRatio = Math.max(0, rawRatio);
@@ -141,11 +143,12 @@ function healthAtPoint(
 	reference: Temporal.Instant,
 	frequencyDays: number,
 	t: Temporal.Instant,
+	neverDone = false,
 ): number {
 	const due = reference
 		.toZonedDateTimeISO(UTC)
 		.startOfDay()
-		.add({ days: frequencyDays })
+		.add({ days: neverDone ? 0 : frequencyDays })
 		.toInstant();
 	const rawRatio =
 		(t.epochMilliseconds - due.epochMilliseconds) / periodMs(frequencyDays);
@@ -156,7 +159,8 @@ function healthAtPoint(
  * Daily health samples from the routine's creation to now: 100 right after a
  * completion, then a linear decay to 0 once two full periods are overdue
  * (sawtooth).
- * Each sample anchors on the latest completion at or before it (or creation).
+ * Each sample anchors on the latest completion at or before it (or creation,
+ * which is then itself the due date for a never-done routine).
  * Uses the routine's current frequency across the whole history.
  */
 export function computeHealthSeries(
@@ -183,7 +187,12 @@ export function computeHealthSeries(
 			reference = doneAt[nextCompletion];
 			nextCompletion++;
 		}
-		return healthAtPoint(reference, routine.frequencyDays, t);
+		return healthAtPoint(
+			reference,
+			routine.frequencyDays,
+			t,
+			nextCompletion === 0,
+		);
 	};
 
 	for (
@@ -250,7 +259,9 @@ export function computeProjectHealthSeries(
 			);
 			const anchor =
 				doneAt.length > 0 ? (maxInstant(doneAt) ?? now) : createdOrNow(r);
-			return sum + healthAtPoint(anchor, r.frequencyDays, t);
+			return (
+				sum + healthAtPoint(anchor, r.frequencyDays, t, doneAt.length === 0)
+			);
 		}, 0);
 		return Math.round(total / alive.length);
 	};