const http = require('http')
const ical = require('ical')

function createEventEntry (event) {
  const content = document.createElement('p')
  const entry = document.createElement('div')
  const formatDate = Intl.DateTimeFormat('fr', { dateStyle: 'long', timeStyle: 'short' }).format
  const header = document.createElement('h3')

  content.innerHTML = event.location
  header.textContent = formatDate(event.date) + ' | ' + event.summary

  entry.className = 'event-entry'
  entry.setAttribute('entry-time', event.date.getTime())
  entry.appendChild(header)
  entry.appendChild(content)

  return entry
}

function createLoader (target) {
  const message = document.createElement('p')
  const spinner = document.createElement('div')
  const wrapper = document.createElement('div')

  wrapper.className = 'loader-wrapper'
  message.innerHTML = 'Chargement du calendrier...'

  wrapper.appendChild(spinner)
  wrapper.appendChild(message)

  target.insertBefore(wrapper, target.firstChild)
}

function sortEvents (events) {
  const sorted = []

  /* First extract the events. */
  Object.values(events).forEach(event => {
    if (event.type === 'VEVENT') {
      sorted.push({
        date: event.start,
        location: event.location,
        summary: event.summary
      })
    }
  })

  /* Then sort them out. */
  // TODO: Useless here. Should be done on callbacks below
  return sorted.sort((a, b) => { return a.date < b.date })
}

function loadEvents (cb) {
  http.request({
    host: 'www.ti-nuage.fr',
    path: '/donnees/calendrier.php'
  }, function (response) {
    let str = ''

    response.on('data', function (chunk) {
      str += chunk
    })

    response.on('end', function () {
      const events = sortEvents(ical.parseICS(str))
      cb(events)
    })
  }).end()
}

module.exports = {

  fill: function (target) {
    loadEvents(events => {
      events.forEach(event => {
        target.appendChild(createEventEntry(event))
      })
    })
  },

  mergeWithNews: function (target) {
    const blogElements = target.getElementsByClassName('blog-entry')
    const entries = {}

    const accumulate = function (index, item) {
      if (!entries.hasOwnProperty(index)) {
        entries[index] = []
      }
      entries[index].push(item)
    }

    for (let i = 0; i < blogElements.length; ++i) {
      const item = blogElements.item(i)
      accumulate(item.getAttribute('entry-time'), item)
    }

    createLoader(target)

    loadEvents(events => {
      const now = Date.now()
      const limitTime = now + (30 * 24 * 60 * 60 * 1000)

      target.innerHTML = ''

      /* Build calendar entries, keeping only the ones for the next 30 days */
      events.forEach(event => {
        const eventTime = event.date.getTime()

        console.log(event)
        if (eventTime >= now && eventTime < limitTime) {
          accumulate(eventTime, createEventEntry(event))
        }
      })

      Object.keys(entries).sort(function (a, b) { return a < b }).forEach(time => {
        entries[time].forEach(entry => { target.appendChild(entry) })
      })
    })
  }
}