refactor: establish local frontend workspace boundaries

OpenSpec change: evolve-frontend-stack

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

@@ -0,0 +1,46 @@
+type IncomePeriod = { from: string; to: string };
+type IncomeForm = IncomePeriod;
+
+const datePattern = /^\d{4}-\d{2}-\d{2}$/;
+
+function formatDraftDate(value: string): string {
+	const [year, month, day] = value.split("-");
+	return `${day}.${month}.${year}`;
+}
+
+function parseDraftDate(value: string): string | null {
+	if (!/^\d{2}\.\d{2}\.\d{4}$/.test(value)) return null;
+	const [day, month, year] = value.split(".");
+	const date = `${year}-${month}-${day}`;
+	return isDate(date) ? date : null;
+}
+
+function isDate(value: string): boolean {
+	if (!datePattern.test(value)) return false;
+	const parsed = new Date(`${value}T00:00:00Z`);
+	return (
+		Number.isFinite(parsed.valueOf()) &&
+		parsed.toISOString().slice(0, 10) === value
+	);
+}
+
+function moscowDate(value: Date): string {
+	const parts = new Intl.DateTimeFormat("en-CA", {
+		timeZone: "Europe/Moscow",
+		year: "numeric",
+		month: "2-digit",
+		day: "2-digit",
+	}).formatToParts(value);
+	const part = (type: string) =>
+		parts.find((item) => item.type === type)?.value;
+	return `${part("year")}-${part("month")}-${part("day")}`;
+}
+
+export {
+	formatDraftDate,
+	type IncomeForm,
+	type IncomePeriod,
+	isDate,
+	moscowDate,
+	parseDraftDate,
+};