cvut/sirius

# -*- encoding : utf-8 -*-
require 'role_playing'
require 'interpipe/interactor'
require 'icalendar'
require 'icalendar/tzinfo'
require 'url_helper'

##
# Converts {Event}'s collection to an ICalendar.
#
class FormatEventsIcal
  include RolePlaying::Context
  include Interpipe::Interactor

  def setup
    @calendar = Icalendar::Calendar.new
    @calendar.add_timezone timezone(Config.tz)
  end

  ##
  # Adds events to an ICalendar and convert it to a text representation.
  # @return [String] ICalendar as a string.
  def perform(events: [])
    @events = events.eager(:parallel, :course, :room).all

    @events.each do |e|
      @calendar.add_event IcalEvent(e).to_ical
    end
  end

  def timezone(tzid)
    tz = TZInfo::Timezone.get(tzid)
    tz.ical_timezone(DateTime.new 2014) # XXX it needs _some_ date; maybe current year should be used instead?
  end

  def results
    {ical: ical}
  end

  def ical
    @calendar.to_ical
  end
  alias_method :to_ical, :ical


  # Event to Icalendar::Event mapping.
  role :IcalEvent do
    include UrlHelper

     DEFAULT_LOCALE = 'cs'

    def ical_summary
      # FIXME: Add localized #{event_type}
      case event_type
      when 'exam', 'assessment'
        "#{course_id} #{localized_event_type}"
      when 'tutorial', 'lecture', 'laboratory'
        "#{course_id} #{sequence_number}. #{localized_event_type} (#{parallel})"
      when 'teacher_timetable_slot'
        "Nepojmenované #{localized_event_type}"
      else
        raise "Don't know how to format iCalendar summary for event with type: '#{event_type}'"
      end
    end

    def ical_description
      # Programování v Ruby (prof. Petr Skočdopole PhD., Ing. Karel Vomáčka)
      # TODO: remove hardcoded locale, map usernames
      # XXX: I don't like this chaining in particular; could we get some role or helper method?
      "#{course.name[DEFAULT_LOCALE]}"
    rescue
      nil
    end

    def ical_categories
      [course_id, localized_event_type].compact
    end

    # Maps {Event} attributes to {Icalendar::Event} object.
    # @return [Icalendar::Event]
    def to_ical
      Icalendar::Event.new.tap do |e|
        e.summary = (name && name[DEFAULT_LOCALE]) || ical_summary
        e.description = (note && note[DEFAULT_LOCALE]) || ical_description
        e.dtstart = Icalendar::Values::DateTime.new(starts_at, tzid: Config.tz)
        e.dtend = Icalendar::Values::DateTime.new(ends_at, tzid: Config.tz)
        e.location = room.to_s
        e.ip_class = 'PUBLIC'
        e.created = created_at
        e.last_modified = updated_at
        e.uid = "#{self.id}@#{Config.domain}"
        e.url = url_for "/events/#{self.id}"
        e.categories = ical_categories
      end
    end

    # TODO: extract hardcoded strings to config file
    EVENT_TYPE_TRANSLATIONS = {
      tutorial: 'cvičení'.freeze,
      lecture: 'přednáška'.freeze,
      laboratory: 'laboratoř'.freeze,
      assessment: 'zápočet'.freeze,
      teacher_timetable_slot: 'omezení učitele'.freeze,
      exam: 'zkouška'.freeze
    }

    def localized_event_type
      EVENT_TYPE_TRANSLATIONS[event_type.to_sym] if event_type
    end

  end

end