import { NextRequest, NextResponse } from 'next/server'
import { prisma } from '@/lib/db/prisma'
import { getCurrentUser } from '@/lib/auth'
import { canAccessWorkspace } from '@/lib/db/workspace-access'
import { format, addDays } from 'date-fns'

// GET /api/workspaces/[id]/calendar-feed
export async function GET(
  request: NextRequest,
  { params }: { params: { id: string } }
) {
  try {
    const workspaceId = params.id
    const token = request.nextUrl.searchParams.get('token')

    if (!token) {
      return NextResponse.json({ error: 'Missing token' }, { status: 401 })
    }

    // Find the calendar feed
    const feed = await prisma.calendarFeed.findUnique({
      where: { token }
    })

    if (!feed || feed.workspaceId !== workspaceId) {
      return NextResponse.json({ error: 'Invalid token' }, { status: 401 })
    }

    // Update last accessed
    await prisma.calendarFeed.update({
      where: { id: feed.id },
      data: { lastAccessedAt: new Date() }
    })

    // Fetch appointments
    const appointments = await prisma.appointment.findMany({
      where: {
        workspaceId,
        deletedAt: null,
        datetime: {
          gte: new Date(),
          lte: addDays(new Date(), feed.daysAhead)
        }
      },
      orderBy: { datetime: 'asc' }
    })

    // Generate ICS content
    const icsContent = generateICS(appointments, feed.includeMeds)

    // Return as ICS file
    return new NextResponse(icsContent, {
      headers: {
        'Content-Type': 'text/calendar; charset=utf-8',
        'Content-Disposition': `attachment; filename="nextstep-calendar-${workspaceId}.ics"`,
      },
    })
  } catch (error) {
    console.error('Failed to generate calendar feed:', error)
    return NextResponse.json(
      { error: 'Failed to generate calendar feed' },
      { status: 500 }
    )
  }
}

function generateICS(appointments: any[], includeMeds: boolean): string {
  const events = appointments.map(appt => {
    const start = new Date(appt.datetime)
    const end = new Date(start.getTime() + 60 * 60 * 1000) // 1 hour default

    return `
BEGIN:VEVENT
UID:${appt.id}@nextstep.app
DTSTART:${format(start, "yyyyMMdd'T'HHmmss")}
DTEND:${format(end, "yyyyMMdd'T'HHmmss")}
SUMMARY:${escapeICS(appt.title)}
${appt.location ? `LOCATION:${escapeICS(appt.location)}` : ''}
${appt.notes ? `DESCRIPTION:${escapeICS(appt.notes)}` : ''}
STATUS:CONFIRMED
END:VEVENT`
  }).join('')

  return `BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Next Step//Calendar//EN
CALSCALE:GREGORIAN
METHOD:PUBLISH
X-WR-CALNAME:Next Step Appointments
X-WR-TIMEZONE:Australia/Perth
${events}
END:VCALENDAR`
}

function escapeICS(str: string): string {
  return str
    .replace(/\\/g, '\\\\')
    .replace(/;/g, '\\;')
    .replace(/,/g, '\\,')
    .replace(/\n/g, '\\n')
}