milestone 30: overview as a dashboard, explicit health contract, period aggregations

admin/src/features/overview/period.ts

@@ -0,0 +1,23 @@
+/**
+ * The period Overview is scoped to, as URL state.
+ *
+ * One home for the four values and for the rule that turns whatever the URL
+ * carried into one of them: the route validates with it and the picker offers
+ * exactly the same list, so a hand-typed `?period=90d` becomes the default
+ * instead of reaching the API as a parameter it answers 400 to.
+ */
+
+import type { Period } from "@/lib/types";
+
+export const PERIODS = ["1h", "24h", "7d", "30d"] as const satisfies readonly Period[];
+
+export const DEFAULT_PERIOD: Period = "24h";
+
+/**
+ * Undefined rather than the default for anything that is not one of the four,
+ * so an absent parameter and a nonsense one both leave a clean URL. The default
+ * is applied where the period is read, not written back into the address bar.
+ */
+export function parsePeriod(value: unknown): Period | undefined {
+	return PERIODS.find((period) => period === value);
+}