tracks/app/models/stats/time_to_complete.rb

module Stats
  class TimeToComplete
    SECONDS_PER_DAY = 86_400

    attr_reader :actions

    def initialize(actions)
      @actions = actions
    end

    def avg
      @avg ||= to_days(sum / count)
    end

    def max
      @max ||= to_days(max_in_seconds)
    end

    def min
      @min ||= to_days(min_in_seconds)
    end

    def min_sec
      min_sec = arbitrary_day + min_in_seconds # convert to a datetime
      @min_sec = min_sec.strftime("%H:%M:%S")
      @min_sec = min.floor.to_s + " days " + @min_sec if min >= 1
      @min_sec
    end

    private

    def to_days(value)
      (value * 10 / SECONDS_PER_DAY).round / 10.0
    end

    def min_in_seconds
      @min_in_seconds ||= durations.min || 0
    end

    def max_in_seconds
      @max_in_seconds ||= durations.max || 0
    end

    def count
      actions.empty? ? 1 : actions.size
    end

    def durations
      @durations ||= actions.map do |r|
        (r.completed_at - r.created_at)
      end
    end

    def sum
      @sum ||= durations.inject(0) { |sum, d| sum + d }
    end

    def arbitrary_day
      @arbitrary_day ||= Time.utc(2000, 1, 1, 0, 0)
    end
  end
end