module Prosperity
  class Extractors::Change < Extractors::Base
    def self.key
      'change'
    end

    def to_a
      data = []

      period.each_period(start_time, end_time) do |start_time|
        if metric.sql?
          new = count_up_to_date_with_sql(start_time)
          last = count_up_to_date_with_sql(start_time - period.duration)
        elsif metric.ruby?
          new = metric.value_at.call(start_time, period)
          last = metric.value_at.call(start_time - period.duration, period)
        else
          new = aggregate.apply(scope.where("#{metric.group_by} < ?", start_time))
          last = aggregate.apply(scope.where("#{metric.group_by} < ?", start_time - period.duration))
        end

        change = if last && last > 0
                   ((new.to_f / last) - 1.0) * 100
                 else
                   0.0
                 end

        data << change
      end

      data
    end
  end
end