refactor: enforce frontend view model boundaries

src/pages/account-income/model/period.ts

@@ -7,12 +7,14 @@ const datePattern = /^\d{4}-\d{2}-\d{2}$/;
 
 function formatDraftDate(value: string): string {
 	const [year, month, day] = value.split("-", DATE_PART_COUNT);
+
 	return `${day}.${month}.${year}`;
 }
 
 function isDate(value: string): boolean {
 	if (!datePattern.test(value)) return false;
 	const parsed = new Date(`${value}T00:00:00Z`);
+
 	return (
 		Number.isFinite(parsed.valueOf())
 		&& parsed.toISOString().slice(0, ISO_DATE_LENGTH) === value
@@ -26,19 +28,27 @@ function moscowDate(value: Date): string {
 		timeZone: "Europe/Moscow",
 		year: "numeric",
 	}).formatToParts(value);
+
 	const part = (type: string) =>
 		parts.find(item => item.type === type)?.value;
+
 	return `${part("year")}-${part("month")}-${part("day")}`;
 }
 
 function parseDraftDate(value: string): null | string {
-	if (!/^\d{2}\.\d{2}\.\d{4}$/.test(value)) return /* eslint-disable-line unicorn/no-null -- Mantine date fields use null for an incomplete or invalid date. */ null;
+	if (!/^\d{2}\.\d{2}\.\d{4}$/.test(value))
+		// eslint-disable-next-line unicorn/no-null -- Mantine date fields use null for an incomplete or invalid date.
+		return null;
 	const [day, month, year] = value.split(".", DATE_PART_COUNT);
 	const date = `${year}-${month}-${day}`;
-	return isDate(date) ? date : /* eslint-disable-line unicorn/no-null -- Mantine date fields use null for an incomplete or invalid date. */ null;
+
+	return isDate(date)
+		? date
+		: null; // eslint-disable-line unicorn/no-null -- Mantine date fields use null for an incomplete or invalid date.
 }
 
-export { formatDraftDate,
+export {
+	formatDraftDate,
 	type IncomePeriod as IncomeForm,
 	type IncomePeriod,
 	isDate,