require 'rubygems'
require "active_support/all"

class TimeMath
  private_class_method :new

  TIME_COMPONENTS = [:add, :diff]

  def self.strftime(time_a, time_b)
    new(time_a, time_b, "strftime")
  end

  def self.realtime(time_a, time_b)
    new(time_a, time_b, "realtime")
  end

  def sum
    case @consumer
      when "strftime"
        strftime_sum
      when "realtime"
        # TODO
      else
        "Nothing here!"
    end
  end

  def diff
    case @consumer
      when "strftime"
        strftime_diff
      when "realtime"
        realtime_diff(@time_a, @time_b)
      else
        "Nothing here!"
    end
  end

  private

  def initialize(time_a, time_b, consumer)
    @time_a = time_a
    @time_b = time_b
    @consumer = consumer
  end

  def strftime_sum
    itime_a = convert_strftime(@time_a)
    itime_b = convert_strftime(@time_b)

    construct_strftime((itime_a + itime_b))
  end

  def strftime_diff
    itime_a = convert_strftime(@time_a)
    itime_b = convert_strftime(@time_b)

    time = itime_a - itime_b
    if time < 0
      construct_strftime(time * -1)
    else
      construct_strftime(time)
    end
  end

  def realtime_diff(time_a, time_b)
    time = (time_a - time_b).to_i.abs

    hr   = time / 3600
    min = (time % 3600) / 60
    sec = (time % 3600) % 60

    "#{hr.to_s.rjust(2, '0')}:#{min.to_s.rjust(2, '0')}:#{sec.to_s.rjust(2, '0')}"
  end

  def convert_strftime(strftime)
    time = strftime.split(":")
    (time[0].to_i * 3600) + (time[1].to_i * 60) + (time[2].to_i)
  end

  def construct_strftime(time)
    hr  = time / 3600
    min = (time % 3600) / 60
    sec = (time % 3600) % 60

    "#{hr.to_s.rjust(2, '0')}:#{min.to_s.rjust(2, '0')}:#{sec.to_s.rjust(2, '0')}"
  end
end