Berlin Clock Kata

abstract.md

Berlin Clock

Original Reference

Create a representation of the Berlin Clock for a given time (hh::mm:ss).

The Berlin Uhr (Clock) is a rather strange way to show the time. On the top of the clock there is a yellow lamp that blinks on/off every two seconds. The time is calculated by adding rectangular lamps.

The top two rows of lamps are red. These indicate the hours of a day. In the top row there are 4 red lamps. Every lamp represents 5 hours. In the lower row of red lamps every lamp represents 1 hour. So if two lamps of the first row and three of the second row are switched on that indicates 5+5+3=13h or 1 pm.

The two rows of lamps at the bottom count the minutes. The first of these rows has 11 lamps, the second 4. In the first row every lamp represents 5 minutes. In this first row the 3rd, 6th and 9th lamp are red and indicate the first quarter, half and last quarter of an hour. The other lamps are yellow. In the last row with 4 lamps every lamp represents 1 minute.

The lamps are switched on from left to right.

Test Cases (Y = Yellow, R = Red, O = Off)

Input

    00:00:00

Result

    Y
    OOOO
    OOOO
    OOOOOOOOOOO
    OOOO

INPUT

    13:17:01

RESULT

    O
    RROO
    RRRO
    YYROOOOOOOO
    YYOO

INPUT

    23:59:59

RESULT

    O
    RRRR
    RRRO
    YYRYYRYYRYY
    YYYY

INPUT

    24:00:00

RESULT

    Y
    RRRR
    RRRR
    OOOOOOOOOOO
    OOOO

References

As far as we know Meike Mertsch was the first to use the example as a Code Kata.

One description of the Berlin Clock is here.

ansi_formatter.rb

class AnsiFormatter

  Y = "\e[33m*\e[0m"
  R = "\e[31m*\e[0m"
  DOT = "\e[0m.\e[0m"

  def initialize
    @formatter = RyFormatter.new
  end

  def format(counts)
    string = @formatter.format(counts)
    string.gsub(/R/, R).gsub(/Y/, Y).gsub(/\./, DOT)
  end

end

ansi_formatter_spec.rb

require 'rspec/given'
require 'ansi_formatter'

describe AnsiFormatter do
  def format(counts)
    deansi(formatter.format(counts))
  end

  def deansi(string)
    string.gsub(/\e\[31m\*/,'R').gsub(/\e\[33m\*/,'Y').gsub(/\e\[\d+m/,'')
  end

  Given(:formatter) { AnsiFormatter.new }

  Then { format([0,0,0,0,0]).should  == ".\n....\n....\n...........\n....\n" }
  Then { format([1,4,3,11,4]).should == "Y\nRRRR\nRRR.\nYYRYYRYYRYY\nYYYY\n" }
end

berlin

#!/usr/bin/ruby -wKU

require 'time'
require 'optparse'

$: << "."
require 'berlin_clock'
require 'ansi_formatter'

def options
  @options ||= {}
end

def clear
  printf "\e[H\e[2J"
end

def show_cursor
  printf("\e[?25h")
end

def hide_cursor
  printf("\e[?25l")
end

def hiding_cursor
  hide_cursor
  yield
rescue Exception
  show_cursor
  raise
end

def show_time(time)
  clock = BerlinClock.new(time, AnsiFormatter.new)
  puts clock.to_s
  puts time.strftime("%H:%M:%S") if options[:digital]
end

OptionParser.new do |opts|
  opts.banner = "Usage: berlin [options]"

  opts.on("-d", "--digital", "Show Digital Time") do |v|
    options[:digital] = v
  end
  opts.on("-r", "--repeat", "Repeat every second") do |v|
    options[:repeat] = v
  end
  opts.on_tail("-h", "--help", "Help message") do
    puts opts
    exit
  end
end.parse!

if ARGV.empty?
  time = Time.now
else
  time = Time.parse(ARGV.shift)
end

if ! options[:repeat]
  show_time(time)
else
  begin
    hiding_cursor do
      loop do
        clear
        show_time(Time.now)
        sleep(1)
      end
    end
  rescue Interrupt
    puts
    puts "Clock cancelled"
  end
end

berlin_clock.rb

require 'ry_formatter'

class BerlinClock
  def initialize(time, formatter=nil)
    @time = time
    @formatter = formatter || RyFormatter.new
  end

  def counts
    [
      @time.sec % 2,
      @time.hour.div(5),
      @time.hour % 5,
      @time.min.div(5),
      @time.min % 5,
    ]
  end

  def to_s
    @formatter.format(counts)
  end
end

berlin_clock_spec.rb

require 'rspec/given'
require 'time'

require 'berlin_clock'

describe BerlinClock do
  Given(:time) { "10:13:14" }
  Given(:clock) { BerlinClock.new(Time.parse(time)) }

  Then { clock.to_s.should == ".\nRR..\n....\nYY.........\nYYY.\n" }

  context "at midnight" do
    Given(:time) { "00:00:00" }
    Then { clock.counts.should == [0, 0, 0, 0, 0] }
  end

  context "at odd seconds" do
    Given(:time) { "00:00:35" }
    Then { clock.counts.should == [1, 0, 0, 0, 0] }
  end

  context "at all ones" do
    Given(:time) { "11:11:11" }
    Then { clock.counts.should == [1, 2, 1, 2, 1] }
  end

  context "at with minutes < 5" do
    Given(:time) { "00:03:52" }
    Then { clock.counts.should == [0, 0, 0, 0, 3] }
  end

  context "at minutes > 5" do
    Given(:time) { "00:43:52" }
    Then { clock.counts.should == [0, 0, 0, 8, 3] }
  end

  context "at hours < 5" do
    Given(:time) { "04:43:52" }
    Then { clock.counts.should == [0, 0, 4, 8, 3] }
  end

  context "at hours > 5" do
    Given(:time) { "17:43:52" }
    Then { clock.counts.should == [0, 3, 2, 8, 3] }
  end

  context "at just before midnight" do
    Given(:time) { "23:59:59" }
    Then { clock.counts.should == [1, 4, 3, 11, 4] }
  end
end

ry_formatter.rb

class RyFormatter
  def format(counts)
    make_line(counts[0], "Y") +
    make_line(counts[1], "RRRR") +
    make_line(counts[2], "RRRR") +
    make_line(counts[3], "YYRYYRYYRYY") +
    make_line(counts[4], "YYYY")
  end

  private

  def make_line(count, template)
    template[0,count] + '.' * (template.size - count) + "\n"
  end
end

ry_formatter_spec.rb

require 'rspec/given'
require 'ry_formatter'

describe RyFormatter do
  Given(:formatter) { RyFormatter.new }

  Then { formatter.format([0,0,0,0,0]).should  == ".\n....\n....\n...........\n....\n" }
  Then { formatter.format([1,2,4,11,4]).should == "Y\nRR..\nRRRR\nYYRYYRYYRYY\nYYYY\n" }
  Then { formatter.format([1,4,3,11,4]).should == "Y\nRRRR\nRRR.\nYYRYYRYYRYY\nYYYY\n" }
end