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

export default defineEventHandler(async (event) => {
  try {
    await connectDB()
    
    const id = getRouterParam(event, 'id')
    
    if (!id) {
      throw createError({
        statusCode: 400,
        statusMessage: 'Series ID is required'
      })
    }
    
    // Fetch all events in this series
    const events = await Event.find({ 
      'series.id': id, 
      'series.isSeriesEvent': true 
    })
      .sort({ 'series.position': 1, startDate: 1 })
      .select('-registrations')
      .lean()
    
    if (events.length === 0) {
      throw createError({
        statusCode: 404,
        statusMessage: 'Event series not found'
      })
    }
    
    // Get series metadata from the first event
    const seriesInfo = events[0].series
    
    // Calculate series statistics
    const now = new Date()
    const completedEvents = events.filter(e => e.endDate < now).length
    const upcomingEvents = events.filter(e => e.startDate > now).length
    const ongoingEvents = events.filter(e => e.startDate <= now && e.endDate >= now).length
    
    const firstEventDate = events[0].startDate
    const lastEventDate = events[events.length - 1].endDate
    
    // Return series with additional metadata
    return {
      id: id,
      title: seriesInfo.title,
      description: seriesInfo.description,
      type: seriesInfo.type,
      totalEvents: seriesInfo.totalEvents,
      startDate: firstEventDate,
      endDate: lastEventDate,
      events: events.map(e => ({
        ...e,
        id: e._id.toString()
      })),
      statistics: {
        totalEvents: events.length,
        completedEvents,
        upcomingEvents,
        ongoingEvents,
        isOngoing: firstEventDate <= now && lastEventDate >= now,
        isUpcoming: firstEventDate > now,
        isCompleted: lastEventDate < now,
        totalRegistrations: events.reduce((sum, e) => sum + (e.registrations?.length || 0), 0)
      }
    }
  } catch (error) {
    console.error('Error fetching event series:', error)
    if (error.statusCode) throw error
    
    throw createError({
      statusCode: 500,
      statusMessage: 'Failed to fetch event series'
    })
  }
})