import ICAL from 'ical.js'

const clouds = {
  KLUB_RESEAU: 'klub-reseau',
  ELEVES_ENS: 'eleves-ens'
}

const calendars = {
  '5WrcagPPARQ3BD87': {
    cloud: clouds.KLUB_RESEAU,
    name: 'Club réseau',
    color: null
  },
  TFEAKjAgNFQZpNjo: {
    cloud: clouds.KLUB_RESEAU,
    name: 'hackENS',
    color: null
  },
  LLWm8qK9iC5YGrrR: {
    cloud: clouds.ELEVES_ENS,
    name: 'Délégation Générale',
    short_name: 'DG',
    color: null
  }
}

export const calendarTree = {
  'Clubs COF': {
    'Club réseau': {},
    hackENS: {}
  },
  COF: {
    BDA: {
      Philharmonie: {}
    },
    AG: {}
  },
  BDS: {},
  'Délégation Générale': {}
}

const calendarIds = Object.keys(calendars)

function mkCalendarUrl(id, { cloud }) {
  return `/cal/${cloud}/${id}/?export&accept=jcal`
}

function fetchCalendar(id, cal) {
  return fetch(mkCalendarUrl(id, cal), { credentials: 'omit' })
    .then(resp => resp.json())
    .catch(err => console.error(err))
}

class Calendar {
  constructor(id, calendar) {
    const metadata = calendars[id]
    this.name = metadata.name
    this.color = metadata.color || calendar[1][4][3]
    this.events = calendar[2]
      .filter(item => item[0] === 'vevent')
      .map(item => this._parse_vevent(item[1]))
  }

  _parse_vevent(vevent) {
    const event = {}
    vevent.forEach(elt => {
      event[elt[0]] = elt[3]
    })
    return event
  }
}

function fcEventFromjCalEvent(cal) {
  return function (evt) {
    const start = new Date(evt.dtstart)
    const end = new Date(evt.dtend)
    const fcEvent = {
      title: `${cal.name}: ${evt.summary}`,
      start: evt.dtstart,
      end: evt.dtend,
      color: cal.color,
      duration: end - start // in ms
    }

    if (evt.description) {
      fcEvent.description = evt.description
    }

    if (evt.location) {
      fcEvent.location = evt.location
    }

    if (evt.rrule) {
      const { freq, byday, interval } = evt.rrule
      fcEvent.rrule = {
        freq,
        byweekday: byday,
        dtstart: evt.dtstart
      }

      if (interval) {
        fcEvent.rrule.interval = interval
      }
    }

    return fcEvent
  }
}

function mkEventsFromCalendar(id, cal) {
  return fetchCalendar(id, cal).then(calendar => {
    if (calendar[0] !== 'vcalendar') return
    const cal = new Calendar(id, calendar)
    return cal.events.map(fcEventFromjCalEvent(cal))
  })
}

export function mkEvent(title, start, duration, ...rest) {
  start = new Date(start)
  const end = new Date(start)
  end.setMinutes(start.getMinutes() + duration)
  return {
    title,
    start,
    end,
    ...rest
  }
}

// TODO: move to FullCalendar custom fetcher to control start&end.
export function refreshEvents(selectedCalendars) {
  return Promise.all(
    calendarIds
      .filter(id =>
        selectedCalendars ? selectedCalendars.includes(calendars[id].name) : true
      )
      .map(id => mkEventsFromCalendar(id, calendars[id]))
  )
}