module IcalImporter
  class SingleEventBuilder
    attr_reader :event, :local_event

    def initialize(event)
      @event = RemoteEvent.new event
      @local_event = LocalEvent.new @event.event_attributes
    end

    # Get single-occurrence events built and get a lits of recurrence
    # events, these must be build last
    def build
      # handle recuring events
      @local_event.tap do |le|
        if @event.rrule.present?
          @rrule = @event.rrule.first # only support recurrence on one schedule
          # set out new event's basic rucurring properties
          le.attributes = recurrence_attributes

          set_date_exclusion
          frequency_set
        else # make sure we remove this if it changed
          le.attributes = non_recurrence_attributes
        end
      end
    end

    private

    def non_recurrence_attributes
      attributes = {
        :recur_interval => "none",
        :recur_interval_value => nil,
        :recur_end_date => nil
      }
      if !@local_event.all_day_event &&
        @event.start_date_time &&
        @event.end_date_time &&
        @event.start_date_time.day != @event.end_date_time.day # single event that spans multiple days
        attributes.merge({
          :recur_interval => "day",
          :recur_interval_value => 1,
          :recur_end_date => @event.end_date_time.end_of_day - 1.day,
          :all_day_event => true
        })
      end
      attributes
    end

    def recurrence_attributes
      {
        :recur_interval => recur_map[@rrule.frequency],
        :recur_interval_value => @rrule.interval || 1,
        :recur_end_date => @rrule.until.try(:to_datetime)
      }
    end

    def set_date_exclusion
      # set any date exclusions
      @local_event.date_exclusions = @event.exdate.flatten.map{|d| DateExclusion.new(d.to_datetime)}
    end

    def frequency_set
      # if bounded is an integer that's googles "recur X times"
      # if that's the case we try to figure out the date it should be by
      # multiplying this "X" times by the frequency that the event recurrs
      interval = @rrule.interval || 1
      case @rrule.frequency
      when "DAILY"
        @local_event.recur_end_date = @local_event.start_date_time + (@rrule.count * interval - 1).days if @rrule.count.is_a? Fixnum # convert X times to a date
      when "WEEKLY"
        if @rrule.value_ical.include?("BYDAY=")
          remote_days = @rrule.value_ical.split("BYDAY=").last.split(";WKST=").first.split(',')
          day_map.each do |abbr, day|
            @local_event.send "recur_week_#{day}=", remote_days.include?(abbr)
          end
        else
          remote_days = [@local_event.start_date_time.wday]
          wday_map.each do |abbr, day|
            @local_event.send "recur_week_#{day}=", remote_days.include?(abbr)
          end
        end
        # recurrence X times is probably broken - we can select multiple times in a week
        @local_event.recur_end_date = @local_event.start_date_time + ((@rrule.count * interval - 1) / remote_days.length).weeks if @rrule.count.is_a? Fixnum
      when "MONTHLY"
        @local_event.recur_month_repeat_by = (@rrule.value_ical =~ /BYDAY/) ? "day_of_week" : "day_of_month"
        @local_event.recur_end_date = @local_event.start_date_time + (@rrule.count * interval - 1).months if @rrule.count.is_a? Fixnum # convert X times to a date
      when "YEARLY"
        @local_event.recur_end_date = @local_event.start_date_time + (@rrule.count * interval - 1).years if @rrule.count.is_a? Fixnum # convert X times to a date
      end
    end

    def recur_map
      {
        "DAILY" => "day",
        "WEEKLY" => "week",
        "MONTHLY" => "month",
        "YEARLY" => "year"
      }
    end

    def day_map
      {
        "SU" => "sunday",
        "MO" => "monday",
        "TU" => "tuesday",
        "WE" => "wednesday",
        "TH" => "thursday",
        "FR" => "friday",
        "SA" => "saturday"
      }
    end

    def wday_map
      {
        0 => "sunday",
        1 => "monday",
        2 => "tuesday",
        3 => "wednesday",
        4 => "thursday",
        5 => "friday",
        6 => "saturday"
      }
    end
  end
end