import Event from "../../models/event";
import Member from "../../models/member";

export default defineEventHandler(async (event) => {
  const query = getQuery(event);
  const { memberId } = query;

  if (!memberId) {
    throw createError({
      statusCode: 400,
      statusMessage: "Member ID is required",
    });
  }

  try {
    // Verify member exists
    const member = await Member.findById(memberId);
    if (!member) {
      throw createError({
        statusCode: 404,
        statusMessage: "Member not found",
      });
    }

    // Find all events where the user is registered
    const events = await Event.find({
      "registrations.memberId": memberId,
      isCancelled: { $ne: true },
    })
      .select("title slug description startDate endDate location")
      .sort({ startDate: 1 });

    // Generate iCal format
    const ical = generateICalendar(events, member);

    // Set headers for calendar subscription (not download)
    setHeader(event, "Content-Type", "text/calendar; charset=utf-8");
    setHeader(event, "Cache-Control", "no-cache, no-store, must-revalidate");
    setHeader(event, "Pragma", "no-cache");
    setHeader(event, "Expires", "0");

    return ical;
  } catch (error) {
    console.error("Error generating calendar:", error);

    if (error.statusCode) {
      throw error;
    }

    throw createError({
      statusCode: 500,
      statusMessage: "Failed to generate calendar",
    });
  }
});

function generateICalendar(events, member) {
  const now = new Date();
  const timestamp = now
    .toISOString()
    .replace(/[-:]/g, "")
    .replace(/\.\d{3}/, "");

  let ical = [
    "BEGIN:VCALENDAR",
    "VERSION:2.0",
    "PRODID:-//Ghost Guild//Events Calendar//EN",
    "CALSCALE:GREGORIAN",
    "METHOD:PUBLISH",
    "X-WR-CALNAME:Ghost Guild - My Events",
    "X-WR-TIMEZONE:UTC",
    "X-WR-CALDESC:Your registered Ghost Guild events",
    "REFRESH-INTERVAL;VALUE=DURATION:PT1H",
    "X-PUBLISHED-TTL:PT1H",
  ];

  events.forEach((evt) => {
    const eventStart = new Date(evt.startDate);
    const eventEnd = new Date(evt.endDate);

    const dtstart = eventStart
      .toISOString()
      .replace(/[-:]/g, "")
      .replace(/\.\d{3}/, "");
    const dtend = eventEnd
      .toISOString()
      .replace(/[-:]/g, "")
      .replace(/\.\d{3}/, "");
    const dtstamp = timestamp;

    // Clean description for iCal format
    const description = (evt.description || "")
      .replace(/\n/g, "\\n")
      .replace(/,/g, "\\,");

    const eventUrl = `https://ghostguild.org/events/${evt.slug || evt._id}`;

    ical.push("BEGIN:VEVENT");
    ical.push(`UID:${evt._id}@ghostguild.org`);
    ical.push(`DTSTAMP:${dtstamp}`);
    ical.push(`DTSTART:${dtstart}`);
    ical.push(`DTEND:${dtend}`);
    ical.push(`SUMMARY:${evt.title}`);
    ical.push(`DESCRIPTION:${description}\\n\\nView event: ${eventUrl}`);
    ical.push(`LOCATION:${evt.location || "Online"}`);
    ical.push(`URL:${eventUrl}`);
    ical.push(`STATUS:CONFIRMED`);
    ical.push("END:VEVENT");
  });

  ical.push("END:VCALENDAR");

  return ical.join("\r\n");
}