generate-ics.js

// Generates ICS file from `public/calendar.json`

const fs = require('fs')

const data = JSON.parse(fs.readFileSync('public/calendar.json', 'utf8'))
const icalendar = require('icalendar')

const ICalendar = icalendar.iCalendar

function generateICS() {
  const ical = new ICalendar()
  for (const event of generateEvents()) {
    ical.addComponent(event)
  }
  return ical.toString()

  function generateEvents() {
    const result = []
    for (const event of data) {
      const vEvent = new icalendar.VEvent(`${event.id}@thaiprogrammer-calendar`)
      let startDate
      let endDate

      if (event.time != null) {
        const total = event.time.length
        startDate = new Date(
          Date.UTC(
            event.start.year,
            event.start.month - 1,
            event.start.date,
            event.time[0].from.hour - 7,
            event.time[0].from.minute
          )
        )
        endDate = new Date(
          Date.UTC(
            event.start.year,
            event.start.month - 1,
            event.start.date,
            event.time[total - 1].to.hour - 7,
            event.time[total - 1].to.minute
          )
        )
        vEvent.setDate(startDate, endDate)
      } else {
        // Full day support hacked from https://github.com/tritech/node-icalendar/pull/43
        startDate = new Date(
          event.start.year,
          event.start.month - 1,
          event.start.date
        )
        endDate = new Date(
          event.end.year,
          event.end.month - 1,
          event.end.date + 1
        )
        const startProperty = vEvent.addProperty('DTSTART', startDate)
        startProperty.setParameter('VALUE', 'DATE')
        startProperty.type = 'DATE'
        const endProperty = vEvent.addProperty('DTEND', endDate)
        endProperty.setParameter('VALUE', 'DATE')
        endProperty.type = 'DATE'
      }
      vEvent.setSummary(event.title)
      vEvent.setLocation(event.location.title)
      const url = `https://calendar.thaiprogrammer.org/event/${event.id}`
      vEvent.addProperty('URL', url)
      vEvent.setDescription(
        `${event.summary}\n\n${event.description}\n\n${url}`
      )
      vEvent.addProperty('CATEGORIES', event.categories)
      vEvent.addProperty('TRANSP', 'OPAQUE')
      result.push(vEvent)
    }
    return result
  }
}

const ics = generateICS()
const path = `public/calendar.ics`
fs.writeFileSync(path, ics)

console.log('* Generated', path)