import type { TextValue } from "./page.js";

/** Serialize Notion-as-Code date values for Apps property payloads. */
export function date(startDate: string, endDate?: string): TextValue {
	const start_date = parseIsoDate(startDate);
	const end_date = endDate === undefined ? undefined : parseIsoDate(endDate);
	if (end_date !== undefined && end_date < start_date) {
		throw new Error("Date range end must be on or after start.");
	}
	const value =
		end_date === undefined
			? { type: "date", start_date }
			: { type: "daterange", start_date, end_date };
	return [["‣", [["d", value]]]];
}

/** Serialize Notion-as-Code datetime values for Apps property payloads. */
export function datetime(value: { start: string; end?: string; timeZone?: string }): TextValue {
	const timeZone = value.timeZone ?? "UTC";
	try {
		new Intl.DateTimeFormat("en-US", { timeZone }).format();
	} catch {
		throw new Error("Invalid time zone: " + timeZone);
	}
	const start = parseIsoDatetime(value.start);
	const end = value.end === undefined ? undefined : parseIsoDatetime(value.end);
	if (end !== undefined && end.date + "T" + end.time < start.date + "T" + start.time) {
		throw new Error("Datetime range end must be on or after start.");
	}
	const dateValue =
		end === undefined
			? {
					type: "datetime",
					start_date: start.date,
					start_time: start.time,
					time_zone: timeZone,
				}
			: {
					type: "datetimerange",
					start_date: start.date,
					start_time: start.time,
					end_date: end.date,
					end_time: end.time,
					time_zone: timeZone,
				};
	return [["‣", [["d", dateValue]]]];
}

/** Validate a calendar date before serializing it. */
function parseIsoDate(value: string): string {
	const match = /^(\d{4})-(\d{2})-(\d{2})$/.exec(value);
	if (match === null) {
		throw new Error("Invalid ISO 8601 date: " + value + ". Expected format like 2024-01-15");
	}
	if (!isValidCalendarDate(match) || Number.isNaN(new Date(value).getTime())) {
		throw new Error("Invalid date: " + value);
	}
	return value;
}

/** Validate and split an ISO datetime before serializing it. */
function parseIsoDatetime(value: string): { date: string; time: string } {
	const match = /^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2})/.exec(value);
	if (match === null) {
		throw new Error(
			"Invalid ISO 8601 datetime: " +
				value +
				". Expected format like 2024-01-15T10:30 or 2024-01-15T10:30:00Z",
		);
	}
	if (
		!isValidCalendarDate(match) ||
		Number(match[4]) > 23 ||
		Number(match[5]) > 59 ||
		Number.isNaN(new Date(value).getTime())
	) {
		throw new Error("Invalid datetime: " + value);
	}
	return { date: value.slice(0, 10), time: value.slice(11, 16) };
}

/** Verify that parsed date components form a real calendar date. */
function isValidCalendarDate(match: RegExpExecArray): boolean {
	const year = Number(match[1] ?? "");
	const month = Number(match[2] ?? "");
	const day = Number(match[3] ?? "");
	const date = new Date(Date.UTC(year, month - 1, day));
	return (
		date.getUTCFullYear() === year &&
		date.getUTCMonth() === month - 1 &&
		date.getUTCDate() === day
	);
}