angelikatyborska's solution to Meetup on the Ruby track

Instructions

Test suite

Solution

Note:

This solution was written on an old version of Exercism. The tests below might not correspond to the solution code, and the exercise may have changed since this code was written.

Calculate the date of meetups.

Typically meetups happen on the same day of the week. In this exercise, you will take a description of a meetup date, and return the actual meetup date.

Examples of general descriptions are:

The first Monday of January 2017
The third Tuesday of January 2017
The wednesteenth of January 2017
The last Thursday of January 2017

The descriptors you are expected to parse are: first, second, third, fourth, fifth, last, monteenth, tuesteenth, wednesteenth, thursteenth, friteenth, saturteenth, sunteenth

Note that "monteenth", "tuesteenth", etc are all made up words. There was a meetup whose members realized that there are exactly 7 numbered days in a month that end in '-teenth'. Therefore, one is guaranteed that each day of the week (Monday, Tuesday, ...) will have exactly one date that is named with '-teenth' in every month.

Given examples of a meetup dates, each containing a month, day, year, and descriptor calculate the date of the actual meetup. For example, if given "The first Monday of January 2017", the correct meetup date is 2017/1/2.

For installation and learning resources, refer to the exercism help page.

For running the tests provided, you will need the Minitest gem. Open a terminal window and run the following command to install minitest:

gem install minitest

If you would like color output, you can require 'minitest/pride' in the test file, or note the alternative instruction, below, for running the test file.

Run the tests from the exercise directory using the following command:

ruby meetup_test.rb

To include color from the command line:

ruby -r minitest/pride meetup_test.rb

Source

Jeremy Hinegardner mentioned a Boulder meetup that happens on the Wednesteenth of every month https://twitter.com/copiousfreetime

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

meetup_test.rb

require 'minitest/autorun'
require_relative 'meetup'

# Common test data version: 1.0.0 fe9630e
class MeetupTest < Minitest::Test
  def test_monteenth_of_may_2013
    # skip
    assert_equal Date.new(2013, 5, 13),
      Meetup.new(5, 2013).day(:monday, :teenth)
  end

  def test_monteenth_of_august_2013
    skip
    assert_equal Date.new(2013, 8, 19),
      Meetup.new(8, 2013).day(:monday, :teenth)
  end

  def test_monteenth_of_september_2013
    skip
    assert_equal Date.new(2013, 9, 16),
      Meetup.new(9, 2013).day(:monday, :teenth)
  end

  def test_tuesteenth_of_march_2013
    skip
    assert_equal Date.new(2013, 3, 19),
      Meetup.new(3, 2013).day(:tuesday, :teenth)
  end

  def test_tuesteenth_of_april_2013
    skip
    assert_equal Date.new(2013, 4, 16),
      Meetup.new(4, 2013).day(:tuesday, :teenth)
  end

  def test_tuesteenth_of_august_2013
    skip
    assert_equal Date.new(2013, 8, 13),
      Meetup.new(8, 2013).day(:tuesday, :teenth)
  end

  def test_wednesteenth_of_january_2013
    skip
    assert_equal Date.new(2013, 1, 16),
      Meetup.new(1, 2013).day(:wednesday, :teenth)
  end

  def test_wednesteenth_of_february_2013
    skip
    assert_equal Date.new(2013, 2, 13),
      Meetup.new(2, 2013).day(:wednesday, :teenth)
  end

  def test_wednesteenth_of_june_2013
    skip
    assert_equal Date.new(2013, 6, 19),
      Meetup.new(6, 2013).day(:wednesday, :teenth)
  end

  def test_thursteenth_of_may_2013
    skip
    assert_equal Date.new(2013, 5, 16),
      Meetup.new(5, 2013).day(:thursday, :teenth)
  end

  def test_thursteenth_of_june_2013
    skip
    assert_equal Date.new(2013, 6, 13),
      Meetup.new(6, 2013).day(:thursday, :teenth)
  end

  def test_thursteenth_of_september_2013
    skip
    assert_equal Date.new(2013, 9, 19),
      Meetup.new(9, 2013).day(:thursday, :teenth)
  end

  def test_friteenth_of_april_2013
    skip
    assert_equal Date.new(2013, 4, 19),
      Meetup.new(4, 2013).day(:friday, :teenth)
  end

  def test_friteenth_of_august_2013
    skip
    assert_equal Date.new(2013, 8, 16),
      Meetup.new(8, 2013).day(:friday, :teenth)
  end

  def test_friteenth_of_september_2013
    skip
    assert_equal Date.new(2013, 9, 13),
      Meetup.new(9, 2013).day(:friday, :teenth)
  end

  def test_saturteenth_of_february_2013
    skip
    assert_equal Date.new(2013, 2, 16),
      Meetup.new(2, 2013).day(:saturday, :teenth)
  end

  def test_saturteenth_of_april_2013
    skip
    assert_equal Date.new(2013, 4, 13),
      Meetup.new(4, 2013).day(:saturday, :teenth)
  end

  def test_saturteenth_of_october_2013
    skip
    assert_equal Date.new(2013, 10, 19),
      Meetup.new(10, 2013).day(:saturday, :teenth)
  end

  def test_sunteenth_of_may_2013
    skip
    assert_equal Date.new(2013, 5, 19),
      Meetup.new(5, 2013).day(:sunday, :teenth)
  end

  def test_sunteenth_of_june_2013
    skip
    assert_equal Date.new(2013, 6, 16),
      Meetup.new(6, 2013).day(:sunday, :teenth)
  end

  def test_sunteenth_of_october_2013
    skip
    assert_equal Date.new(2013, 10, 13),
      Meetup.new(10, 2013).day(:sunday, :teenth)
  end

  def test_first_monday_of_march_2013
    skip
    assert_equal Date.new(2013, 3, 4),
      Meetup.new(3, 2013).day(:monday, :first)
  end

  def test_first_monday_of_april_2013
    skip
    assert_equal Date.new(2013, 4, 1),
      Meetup.new(4, 2013).day(:monday, :first)
  end

  def test_first_tuesday_of_may_2013
    skip
    assert_equal Date.new(2013, 5, 7),
      Meetup.new(5, 2013).day(:tuesday, :first)
  end

  def test_first_tuesday_of_june_2013
    skip
    assert_equal Date.new(2013, 6, 4),
      Meetup.new(6, 2013).day(:tuesday, :first)
  end

  def test_first_wednesday_of_july_2013
    skip
    assert_equal Date.new(2013, 7, 3),
      Meetup.new(7, 2013).day(:wednesday, :first)
  end

  def test_first_wednesday_of_august_2013
    skip
    assert_equal Date.new(2013, 8, 7),
      Meetup.new(8, 2013).day(:wednesday, :first)
  end

  def test_first_thursday_of_september_2013
    skip
    assert_equal Date.new(2013, 9, 5),
      Meetup.new(9, 2013).day(:thursday, :first)
  end

  def test_first_thursday_of_october_2013
    skip
    assert_equal Date.new(2013, 10, 3),
      Meetup.new(10, 2013).day(:thursday, :first)
  end

  def test_first_friday_of_november_2013
    skip
    assert_equal Date.new(2013, 11, 1),
      Meetup.new(11, 2013).day(:friday, :first)
  end

  def test_first_friday_of_december_2013
    skip
    assert_equal Date.new(2013, 12, 6),
      Meetup.new(12, 2013).day(:friday, :first)
  end

  def test_first_saturday_of_january_2013
    skip
    assert_equal Date.new(2013, 1, 5),
      Meetup.new(1, 2013).day(:saturday, :first)
  end

  def test_first_saturday_of_february_2013
    skip
    assert_equal Date.new(2013, 2, 2),
      Meetup.new(2, 2013).day(:saturday, :first)
  end

  def test_first_sunday_of_march_2013
    skip
    assert_equal Date.new(2013, 3, 3),
      Meetup.new(3, 2013).day(:sunday, :first)
  end

  def test_first_sunday_of_april_2013
    skip
    assert_equal Date.new(2013, 4, 7),
      Meetup.new(4, 2013).day(:sunday, :first)
  end

  def test_second_monday_of_march_2013
    skip
    assert_equal Date.new(2013, 3, 11),
      Meetup.new(3, 2013).day(:monday, :second)
  end

  def test_second_monday_of_april_2013
    skip
    assert_equal Date.new(2013, 4, 8),
      Meetup.new(4, 2013).day(:monday, :second)
  end

  def test_second_tuesday_of_may_2013
    skip
    assert_equal Date.new(2013, 5, 14),
      Meetup.new(5, 2013).day(:tuesday, :second)
  end

  def test_second_tuesday_of_june_2013
    skip
    assert_equal Date.new(2013, 6, 11),
      Meetup.new(6, 2013).day(:tuesday, :second)
  end

  def test_second_wednesday_of_july_2013
    skip
    assert_equal Date.new(2013, 7, 10),
      Meetup.new(7, 2013).day(:wednesday, :second)
  end

  def test_second_wednesday_of_august_2013
    skip
    assert_equal Date.new(2013, 8, 14),
      Meetup.new(8, 2013).day(:wednesday, :second)
  end

  def test_second_thursday_of_september_2013
    skip
    assert_equal Date.new(2013, 9, 12),
      Meetup.new(9, 2013).day(:thursday, :second)
  end

  def test_second_thursday_of_october_2013
    skip
    assert_equal Date.new(2013, 10, 10),
      Meetup.new(10, 2013).day(:thursday, :second)
  end

  def test_second_friday_of_november_2013
    skip
    assert_equal Date.new(2013, 11, 8),
      Meetup.new(11, 2013).day(:friday, :second)
  end

  def test_second_friday_of_december_2013
    skip
    assert_equal Date.new(2013, 12, 13),
      Meetup.new(12, 2013).day(:friday, :second)
  end

  def test_second_saturday_of_january_2013
    skip
    assert_equal Date.new(2013, 1, 12),
      Meetup.new(1, 2013).day(:saturday, :second)
  end

  def test_second_saturday_of_february_2013
    skip
    assert_equal Date.new(2013, 2, 9),
      Meetup.new(2, 2013).day(:saturday, :second)
  end

  def test_second_sunday_of_march_2013
    skip
    assert_equal Date.new(2013, 3, 10),
      Meetup.new(3, 2013).day(:sunday, :second)
  end

  def test_second_sunday_of_april_2013
    skip
    assert_equal Date.new(2013, 4, 14),
      Meetup.new(4, 2013).day(:sunday, :second)
  end

  def test_third_monday_of_march_2013
    skip
    assert_equal Date.new(2013, 3, 18),
      Meetup.new(3, 2013).day(:monday, :third)
  end

  def test_third_monday_of_april_2013
    skip
    assert_equal Date.new(2013, 4, 15),
      Meetup.new(4, 2013).day(:monday, :third)
  end

  def test_third_tuesday_of_may_2013
    skip
    assert_equal Date.new(2013, 5, 21),
      Meetup.new(5, 2013).day(:tuesday, :third)
  end

  def test_third_tuesday_of_june_2013
    skip
    assert_equal Date.new(2013, 6, 18),
      Meetup.new(6, 2013).day(:tuesday, :third)
  end

  def test_third_wednesday_of_july_2013
    skip
    assert_equal Date.new(2013, 7, 17),
      Meetup.new(7, 2013).day(:wednesday, :third)
  end

  def test_third_wednesday_of_august_2013
    skip
    assert_equal Date.new(2013, 8, 21),
      Meetup.new(8, 2013).day(:wednesday, :third)
  end

  def test_third_thursday_of_september_2013
    skip
    assert_equal Date.new(2013, 9, 19),
      Meetup.new(9, 2013).day(:thursday, :third)
  end

  def test_third_thursday_of_october_2013
    skip
    assert_equal Date.new(2013, 10, 17),
      Meetup.new(10, 2013).day(:thursday, :third)
  end

  def test_third_friday_of_november_2013
    skip
    assert_equal Date.new(2013, 11, 15),
      Meetup.new(11, 2013).day(:friday, :third)
  end

  def test_third_friday_of_december_2013
    skip
    assert_equal Date.new(2013, 12, 20),
      Meetup.new(12, 2013).day(:friday, :third)
  end

  def test_third_saturday_of_january_2013
    skip
    assert_equal Date.new(2013, 1, 19),
      Meetup.new(1, 2013).day(:saturday, :third)
  end

  def test_third_saturday_of_february_2013
    skip
    assert_equal Date.new(2013, 2, 16),
      Meetup.new(2, 2013).day(:saturday, :third)
  end

  def test_third_sunday_of_march_2013
    skip
    assert_equal Date.new(2013, 3, 17),
      Meetup.new(3, 2013).day(:sunday, :third)
  end

  def test_third_sunday_of_april_2013
    skip
    assert_equal Date.new(2013, 4, 21),
      Meetup.new(4, 2013).day(:sunday, :third)
  end

  def test_fourth_monday_of_march_2013
    skip
    assert_equal Date.new(2013, 3, 25),
      Meetup.new(3, 2013).day(:monday, :fourth)
  end

  def test_fourth_monday_of_april_2013
    skip
    assert_equal Date.new(2013, 4, 22),
      Meetup.new(4, 2013).day(:monday, :fourth)
  end

  def test_fourth_tuesday_of_may_2013
    skip
    assert_equal Date.new(2013, 5, 28),
      Meetup.new(5, 2013).day(:tuesday, :fourth)
  end

  def test_fourth_tuesday_of_june_2013
    skip
    assert_equal Date.new(2013, 6, 25),
      Meetup.new(6, 2013).day(:tuesday, :fourth)
  end

  def test_fourth_wednesday_of_july_2013
    skip
    assert_equal Date.new(2013, 7, 24),
      Meetup.new(7, 2013).day(:wednesday, :fourth)
  end

  def test_fourth_wednesday_of_august_2013
    skip
    assert_equal Date.new(2013, 8, 28),
      Meetup.new(8, 2013).day(:wednesday, :fourth)
  end

  def test_fourth_thursday_of_september_2013
    skip
    assert_equal Date.new(2013, 9, 26),
      Meetup.new(9, 2013).day(:thursday, :fourth)
  end

  def test_fourth_thursday_of_october_2013
    skip
    assert_equal Date.new(2013, 10, 24),
      Meetup.new(10, 2013).day(:thursday, :fourth)
  end

  def test_fourth_friday_of_november_2013
    skip
    assert_equal Date.new(2013, 11, 22),
      Meetup.new(11, 2013).day(:friday, :fourth)
  end

  def test_fourth_friday_of_december_2013
    skip
    assert_equal Date.new(2013, 12, 27),
      Meetup.new(12, 2013).day(:friday, :fourth)
  end

  def test_fourth_saturday_of_january_2013
    skip
    assert_equal Date.new(2013, 1, 26),
      Meetup.new(1, 2013).day(:saturday, :fourth)
  end

  def test_fourth_saturday_of_february_2013
    skip
    assert_equal Date.new(2013, 2, 23),
      Meetup.new(2, 2013).day(:saturday, :fourth)
  end

  def test_fourth_sunday_of_march_2013
    skip
    assert_equal Date.new(2013, 3, 24),
      Meetup.new(3, 2013).day(:sunday, :fourth)
  end

  def test_fourth_sunday_of_april_2013
    skip
    assert_equal Date.new(2013, 4, 28),
      Meetup.new(4, 2013).day(:sunday, :fourth)
  end

  def test_last_monday_of_march_2013
    skip
    assert_equal Date.new(2013, 3, 25),
      Meetup.new(3, 2013).day(:monday, :last)
  end

  def test_last_monday_of_april_2013
    skip
    assert_equal Date.new(2013, 4, 29),
      Meetup.new(4, 2013).day(:monday, :last)
  end

  def test_last_tuesday_of_may_2013
    skip
    assert_equal Date.new(2013, 5, 28),
      Meetup.new(5, 2013).day(:tuesday, :last)
  end

  def test_last_tuesday_of_june_2013
    skip
    assert_equal Date.new(2013, 6, 25),
      Meetup.new(6, 2013).day(:tuesday, :last)
  end

  def test_last_wednesday_of_july_2013
    skip
    assert_equal Date.new(2013, 7, 31),
      Meetup.new(7, 2013).day(:wednesday, :last)
  end

  def test_last_wednesday_of_august_2013
    skip
    assert_equal Date.new(2013, 8, 28),
      Meetup.new(8, 2013).day(:wednesday, :last)
  end

  def test_last_thursday_of_september_2013
    skip
    assert_equal Date.new(2013, 9, 26),
      Meetup.new(9, 2013).day(:thursday, :last)
  end

  def test_last_thursday_of_october_2013
    skip
    assert_equal Date.new(2013, 10, 31),
      Meetup.new(10, 2013).day(:thursday, :last)
  end

  def test_last_friday_of_november_2013
    skip
    assert_equal Date.new(2013, 11, 29),
      Meetup.new(11, 2013).day(:friday, :last)
  end

  def test_last_friday_of_december_2013
    skip
    assert_equal Date.new(2013, 12, 27),
      Meetup.new(12, 2013).day(:friday, :last)
  end

  def test_last_saturday_of_january_2013
    skip
    assert_equal Date.new(2013, 1, 26),
      Meetup.new(1, 2013).day(:saturday, :last)
  end

  def test_last_saturday_of_february_2013
    skip
    assert_equal Date.new(2013, 2, 23),
      Meetup.new(2, 2013).day(:saturday, :last)
  end

  def test_last_sunday_of_march_2013
    skip
    assert_equal Date.new(2013, 3, 31),
      Meetup.new(3, 2013).day(:sunday, :last)
  end

  def test_last_sunday_of_april_2013
    skip
    assert_equal Date.new(2013, 4, 28),
      Meetup.new(4, 2013).day(:sunday, :last)
  end

  def test_last_wednesday_of_february_2012
    skip
    assert_equal Date.new(2012, 2, 29),
      Meetup.new(2, 2012).day(:wednesday, :last)
  end

  def test_last_wednesday_of_december_2014
    skip
    assert_equal Date.new(2014, 12, 31),
      Meetup.new(12, 2014).day(:wednesday, :last)
  end

  def test_last_sunday_of_february_2015
    skip
    assert_equal Date.new(2015, 2, 22),
      Meetup.new(2, 2015).day(:sunday, :last)
  end

  def test_first_friday_of_december_2012
    skip
    assert_equal Date.new(2012, 12, 7),
      Meetup.new(12, 2012).day(:friday, :first)
  end

  # Problems in exercism evolve over time, as we find better ways to ask
  # questions.
  # The version number refers to the version of the problem you solved,
  # not your solution.
  #
  # Define a constant named VERSION inside of the top level BookKeeping
  # module, which may be placed near the end of your file.
  #
  # In your file, it will look like this:
  #
  # module BookKeeping
  #   VERSION = 1 # Where the version number matches the one in the test.
  # end
  #
  # If you are curious, read more about constants on RubyDoc:
  # http://ruby-doc.org/docs/ruby-doc-bundle/UsersGuide/rg/constants.html

  def test_bookkeeping
    skip
    assert_equal 1, BookKeeping::VERSION
  end
end

require 'date'

class Meetup
  ORDINALS = %i(first second third fourth)
  WEEKDAYS = Date::DAYNAMES.map { |dayname| dayname.downcase.to_sym }

  def initialize(month, year)
    @month = Date.new(year, month)
  end

  def day(weekday, ordinal)
    start, order =
      case ordinal
      when :last
        [end_of_month, :desc]
      when :teenth
        [thirteenth, :asc]
      else
        [week(ordinal), :asc]
      end

    nearest_weekday(start, weekday, order)
  end

  private

  def nearest_weekday(start, weekday, order = :asc)
    divisor = order == :desc ? -7 : 7
    day_difference = WEEKDAYS.index(weekday) - start.wday
    start + day_difference.divmod(divisor)[1]
  end

  def end_of_month
    (@month >> 1) - 1
  end

  def thirteenth
    @month + 12
  end

  def week(ordinal)
    @month + 7 * ORDINALS.index(ordinal)
  end
end

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angelikatyborska's solution

to Meetup in the Ruby Track