rpcfn2.rb

require 'test/unit'


class ArrivalTime
  def convert_to_24h(time)
    if time =~ %r{(\d+):(\d+)pm$}
      h, m = "%02d" % ($1.to_i+12), $2
      "#{h}#{m}"
    elsif time =~ %r{(\d+):(\d+)am$}
      h = $1.to_i
      h = 0 if h == 12
      h, m = ("%02d" % h), $2
      "#{h}#{m}"
    end
  end

  def convert_from_24h(time)
    if time =~ %r{(\d\d)(\d\d)}
      h, m = $1.to_i, $2.to_i
      if h > 11
        am_or_pm = "pm"
        h = h - 12 
      else
        am_or_pm = "am"
      end
      "#{"%d" % h}:#{"%02d" % m}#{am_or_pm}"
    end
  end

  def average(times)
    first = times.first.to_i
    seconds = times.inject(0) do |sum, n| 
      convert_to_seconds(n) + sum 
    end / times.size
    convert_from_seconds(seconds)
  end

  def convert_to_seconds(time)
    if time =~ %r{^(\d\d)(\d\d)$}
      hour, minute = $1.to_i, $2.to_i
      (hour * 60 * 60) + (minute * 60)
    end
  end

  def convert_from_seconds(seconds)
    hours = seconds / (60 * 60)
    seconds = seconds - (hours * 60 * 60)
    minutes = seconds / 60
    "#{"%02d" % hours}#{"%02d" % minutes}"
  end

  def convert_and_average(times)
    converted_times = times.map do |time| 
      time = convert_to_24h(time)
    end

    average_time = average(converted_times)
    convert_from_24h(average_time)
  end
end

def average_time_of_day(times)
  arrival_time = ArrivalTime.new
  arrival_time.convert_and_average(times)
end

class ArrivalTimeTest < Test::Unit::TestCase

  def setup
    @arrival_time = ArrivalTime.new
  end
  def test_convert_time_to_24h

    assert_equal "2351", @arrival_time.convert_to_24h("11:51pm")
    assert_equal "1150", @arrival_time.convert_to_24h("11:50am")
    assert_equal "1000", @arrival_time.convert_to_24h("10:00am")
    assert_equal "0500", @arrival_time.convert_to_24h("5:00am")
  end

  def test_convert_24h_to_time
    assert_equal "11:51pm", @arrival_time.convert_from_24h("2351")
    assert_equal "11:50am", @arrival_time.convert_from_24h("1150")
    assert_equal "10:00am", @arrival_time.convert_from_24h("1000")
    assert_equal "5:00am", @arrival_time.convert_from_24h("0500")
  end

  def test_should_average_an_array_of_times_that_dont_cross_date_boundaries
    times = %w[1101 1107]
    assert_equal "1104", @arrival_time.average(times)

    times =%w[2142 2148]
    assert_equal "2145", @arrival_time.average(times)
  end

  def test_convert_time_to_seconds
    {"0005" => 300, "1306" => 47_160, "2237" => 81_420}.each_pair do |k,v|
      assert_equal v, @arrival_time.convert_to_seconds(k)
    end
  end

  def test_convert_seconds_to_time
    {"0005" => 300, "1306" => 47_160, "2237" => 81_420}.each_pair do |k,v|
      assert_equal k, @arrival_time.convert_from_seconds(v)
    end
  end

  def test_averaging_times_in_same_day
    assert_equal "6:51am", average_time_of_day(["6:41am", "6:51am", "7:01am"])
  end

  def test_averaging_times_across_a_date_boundary
    assert_equal "9:37am", average_time_of_day(["11:51pm", "11:56pm", "12:01am", "12:06am", "12:11am"])
  end
end