import { connectDB } from '../../utils/mongoose.js'
import Event from '../../models/event'

export default defineEventHandler(async (event) => {
  await connectDB()
  const member = await requireAuth(event)

  try {
    const events = await Event.find({
      'registrations.memberId': member._id,
      isCancelled: { $ne: true },
    })
      .select('title slug description startDate endDate location')
      .sort({ startDate: 1 })

    const ical = generateICalendar(events, member)

    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

    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')
}