import ICAL from "ical.js";
import type { CalendarEvent } from "@/lib/types";

export function parseICS(icsString: string): CalendarEvent[] {
	const jcalData = ICAL.parse(icsString);
	const comp = new ICAL.Component(jcalData);
	const vevents = comp.getAllSubcomponents("vevent");

	return vevents.map((v) => {
		const ev = new ICAL.Event(v);
		const isAllDay = ev.startDate.isDate;

		return {
			id: ev.uid || crypto.randomUUID(),
			title: ev.summary || "Untitled Event",
			description: ev.description || "",
			location: ev.location || "",
			url: v.getFirstPropertyValue("url") || undefined,
			start: ev.startDate.toJSDate().toISOString(),
			end: ev.endDate ? ev.endDate.toJSDate().toISOString() : undefined,
			allDay: isAllDay,
			createdAt: v.getFirstPropertyValue("dtstamp")
				? (v.getFirstPropertyValue("dtstamp") as ICAL.Time)
						.toJSDate()
						.toISOString()
				: undefined,
			lastModified: v.getFirstPropertyValue("last-modified")
				? (v.getFirstPropertyValue("last-modified") as ICAL.Time)
						.toJSDate()
						.toISOString()
				: undefined,
			recurrenceRule: v.getFirstPropertyValue("rrule")
				? (v.getFirstPropertyValue("rrule") as ICAL.Recur).toString()
				: undefined,
		};
	});
}

export function generateICS(events: CalendarEvent[]): string {
	const comp = new ICAL.Component(["vcalendar", [], []]);
	comp.addPropertyWithValue("version", "2.0");
	comp.addPropertyWithValue("prodid", "-//iCalPWA//EN");

	events.forEach((ev) => {
		const vevent = new ICAL.Component("vevent");
		vevent.addPropertyWithValue("uid", ev.id);
		vevent.addPropertyWithValue("summary", ev.title);
		if (ev.description)
			vevent.addPropertyWithValue("description", ev.description);
		if (ev.location) vevent.addPropertyWithValue("location", ev.location);
		if (ev.url) vevent.addPropertyWithValue("url", ev.url);

		// Start/End
		if (ev.allDay) {
			vevent.addPropertyWithValue(
				"dtstart",
				ICAL.Time.fromDateString(ev.start.split("T")[0]),
			);
			if (ev.end)
				vevent.addPropertyWithValue(
					"dtend",
					ICAL.Time.fromDateString(ev.end.split("T")[0]),
				);
		} else {
			vevent.addPropertyWithValue(
				"dtstart",
				ICAL.Time.fromJSDate(new Date(ev.start)),
			);
			if (ev.end)
				vevent.addPropertyWithValue(
					"dtend",
					ICAL.Time.fromJSDate(new Date(ev.end)),
				);
		}

		// Timestamps
		vevent.addPropertyWithValue(
			"dtstamp",
			ICAL.Time.fromJSDate(ev.createdAt ? new Date(ev.createdAt) : new Date()),
		);
		if (ev.lastModified) {
			vevent.addPropertyWithValue(
				"last-modified",
				ICAL.Time.fromJSDate(new Date(ev.lastModified)),
			);
		}

		// Recurrence
		if (ev.recurrenceRule) {
			vevent.addPropertyWithValue(
				"rrule",
				ICAL.Recur.fromString(ev.recurrenceRule),
			);
		}

		comp.addSubcomponent(vevent);
	});

	return comp.toString();
}