JaeHyoLee's solution to Meetup on the Lua track

Instructions

Test suite

Solution

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.

Running the tests

To run the tests, run the command busted from within the exercise directory.

Further information

For more detailed information about the Lua track, including how to get help if you're having trouble, please visit the exercism.io Lua language page.

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_spec.lua

local meetup = require 'meetup'

describe('meetup', function()
  it('monteenth of May 2013', function()
    assert.are.equal(13, meetup({
      year = 2013,
      month = 5,
      week = 'teenth',
      day = 'Monday'
    }))
  end)

  it('monteenth of August 2013', function()
    assert.are.equal(19, meetup({
      year = 2013,
      month = 8,
      week = 'teenth',
      day = 'Monday'
    }))
  end)

  it('monteenth of September 2013', function()
    assert.are.equal(16, meetup({
      year = 2013,
      month = 9,
      week = 'teenth',
      day = 'Monday'
    }))
  end)

  it('tuesteenth of March 2013', function()
    assert.are.equal(19, meetup({
      year = 2013,
      month = 3,
      week = 'teenth',
      day = 'Tuesday'
    }))
  end)

  it('tuesteenth of April 2013', function()
    assert.are.equal(16, meetup({
      year = 2013,
      month = 4,
      week = 'teenth',
      day = 'Tuesday'
    }))
  end)

  it('tuesteenth of August 2013', function()
    assert.are.equal(13, meetup({
      year = 2013,
      month = 8,
      week = 'teenth',
      day = 'Tuesday'
    }))
  end)

  it('wednesteenth of January 2013', function()
    assert.are.equal(16, meetup({
      year = 2013,
      month = 1,
      week = 'teenth',
      day = 'Wednesday'
    }))
  end)

  it('wednesteenth of February 2013', function()
    assert.are.equal(13, meetup({
      year = 2013,
      month = 2,
      week = 'teenth',
      day = 'Wednesday'
    }))
  end)

  it('wednesteenth of June 2013', function()
    assert.are.equal(19, meetup({
      year = 2013,
      month = 6,
      week = 'teenth',
      day = 'Wednesday'
    }))
  end)

  it('thursteenth of May 2013', function()
    assert.are.equal(16, meetup({
      year = 2013,
      month = 5,
      week = 'teenth',
      day = 'Thursday'
    }))
  end)

  it('thursteenth of June 2013', function()
    assert.are.equal(13, meetup({
      year = 2013,
      month = 6,
      week = 'teenth',
      day = 'Thursday'
    }))
  end)

  it('thursteenth of September 2013', function()
    assert.are.equal(19, meetup({
      year = 2013,
      month = 9,
      week = 'teenth',
      day = 'Thursday'
    }))
  end)

  it('friteenth of April 2013', function()
    assert.are.equal(19, meetup({
      year = 2013,
      month = 4,
      week = 'teenth',
      day = 'Friday'
    }))
  end)

  it('friteenth of August 2013', function()
    assert.are.equal(16, meetup({
      year = 2013,
      month = 8,
      week = 'teenth',
      day = 'Friday'
    }))
  end)

  it('friteenth of September 2013', function()
    assert.are.equal(13, meetup({
      year = 2013,
      month = 9,
      week = 'teenth',
      day = 'Friday'
    }))
  end)

  it('saturteenth of February 2013', function()
    assert.are.equal(16, meetup({
      year = 2013,
      month = 2,
      week = 'teenth',
      day = 'Saturday'
    }))
  end)

  it('saturteenth of April 2013', function()
    assert.are.equal(13, meetup({
      year = 2013,
      month = 4,
      week = 'teenth',
      day = 'Saturday'
    }))
  end)

  it('saturteenth of October 2013', function()
    assert.are.equal(19, meetup({
      year = 2013,
      month = 10,
      week = 'teenth',
      day = 'Saturday'
    }))
  end)

  it('sunteenth of May 2013', function()
    assert.are.equal(19, meetup({
      year = 2013,
      month = 5,
      week = 'teenth',
      day = 'Sunday'
    }))
  end)

  it('sunteenth of June 2013', function()
    assert.are.equal(16, meetup({
      year = 2013,
      month = 6,
      week = 'teenth',
      day = 'Sunday'
    }))
  end)

  it('sunteenth of October 2013', function()
    assert.are.equal(13, meetup({
      year = 2013,
      month = 10,
      week = 'teenth',
      day = 'Sunday'
    }))
  end)

  it('first Monday of March 2013', function()
    assert.are.equal(4, meetup({
      year = 2013,
      month = 3,
      week = 'first',
      day = 'Monday'
    }))
  end)

  it('first Monday of April 2013', function()
    assert.are.equal(1, meetup({
      year = 2013,
      month = 4,
      week = 'first',
      day = 'Monday'
    }))
  end)

  it('first Tuesday of May 2013', function()
    assert.are.equal(7, meetup({
      year = 2013,
      month = 5,
      week = 'first',
      day = 'Tuesday'
    }))
  end)

  it('first Tuesday of June 2013', function()
    assert.are.equal(4, meetup({
      year = 2013,
      month = 6,
      week = 'first',
      day = 'Tuesday'
    }))
  end)

  it('first Wednesday of July 2013', function()
    assert.are.equal(3, meetup({
      year = 2013,
      month = 7,
      week = 'first',
      day = 'Wednesday'
    }))
  end)

  it('first Wednesday of August 2013', function()
    assert.are.equal(7, meetup({
      year = 2013,
      month = 8,
      week = 'first',
      day = 'Wednesday'
    }))
  end)

  it('first Thursday of September 2013', function()
    assert.are.equal(5, meetup({
      year = 2013,
      month = 9,
      week = 'first',
      day = 'Thursday'
    }))
  end)

  it('first Thursday of October 2013', function()
    assert.are.equal(3, meetup({
      year = 2013,
      month = 10,
      week = 'first',
      day = 'Thursday'
    }))
  end)

  it('first Friday of November 2013', function()
    assert.are.equal(1, meetup({
      year = 2013,
      month = 11,
      week = 'first',
      day = 'Friday'
    }))
  end)

  it('first Friday of December 2013', function()
    assert.are.equal(6, meetup({
      year = 2013,
      month = 12,
      week = 'first',
      day = 'Friday'
    }))
  end)

  it('first Saturday of January 2013', function()
    assert.are.equal(5, meetup({
      year = 2013,
      month = 1,
      week = 'first',
      day = 'Saturday'
    }))
  end)

  it('first Saturday of February 2013', function()
    assert.are.equal(2, meetup({
      year = 2013,
      month = 2,
      week = 'first',
      day = 'Saturday'
    }))
  end)

  it('first Sunday of March 2013', function()
    assert.are.equal(3, meetup({
      year = 2013,
      month = 3,
      week = 'first',
      day = 'Sunday'
    }))
  end)

  it('first Sunday of April 2013', function()
    assert.are.equal(7, meetup({
      year = 2013,
      month = 4,
      week = 'first',
      day = 'Sunday'
    }))
  end)

  it('second Monday of March 2013', function()
    assert.are.equal(11, meetup({
      year = 2013,
      month = 3,
      week = 'second',
      day = 'Monday'
    }))
  end)

  it('second Monday of April 2013', function()
    assert.are.equal(8, meetup({
      year = 2013,
      month = 4,
      week = 'second',
      day = 'Monday'
    }))
  end)

  it('second Tuesday of May 2013', function()
    assert.are.equal(14, meetup({
      year = 2013,
      month = 5,
      week = 'second',
      day = 'Tuesday'
    }))
  end)

  it('second Tuesday of June 2013', function()
    assert.are.equal(11, meetup({
      year = 2013,
      month = 6,
      week = 'second',
      day = 'Tuesday'
    }))
  end)

  it('second Wednesday of July 2013', function()
    assert.are.equal(10, meetup({
      year = 2013,
      month = 7,
      week = 'second',
      day = 'Wednesday'
    }))
  end)

  it('second Wednesday of August 2013', function()
    assert.are.equal(14, meetup({
      year = 2013,
      month = 8,
      week = 'second',
      day = 'Wednesday'
    }))
  end)

  it('second Thursday of September 2013', function()
    assert.are.equal(12, meetup({
      year = 2013,
      month = 9,
      week = 'second',
      day = 'Thursday'
    }))
  end)

  it('second Thursday of October 2013', function()
    assert.are.equal(10, meetup({
      year = 2013,
      month = 10,
      week = 'second',
      day = 'Thursday'
    }))
  end)

  it('second Friday of November 2013', function()
    assert.are.equal(8, meetup({
      year = 2013,
      month = 11,
      week = 'second',
      day = 'Friday'
    }))
  end)

  it('second Friday of December 2013', function()
    assert.are.equal(13, meetup({
      year = 2013,
      month = 12,
      week = 'second',
      day = 'Friday'
    }))
  end)

  it('second Saturday of January 2013', function()
    assert.are.equal(12, meetup({
      year = 2013,
      month = 1,
      week = 'second',
      day = 'Saturday'
    }))
  end)

  it('second Saturday of February 2013', function()
    assert.are.equal(9, meetup({
      year = 2013,
      month = 2,
      week = 'second',
      day = 'Saturday'
    }))
  end)

  it('second Sunday of March 2013', function()
    assert.are.equal(10, meetup({
      year = 2013,
      month = 3,
      week = 'second',
      day = 'Sunday'
    }))
  end)

  it('second Sunday of April 2013', function()
    assert.are.equal(14, meetup({
      year = 2013,
      month = 4,
      week = 'second',
      day = 'Sunday'
    }))
  end)

  it('third Monday of March 2013', function()
    assert.are.equal(18, meetup({
      year = 2013,
      month = 3,
      week = 'third',
      day = 'Monday'
    }))
  end)

  it('third Monday of April 2013', function()
    assert.are.equal(15, meetup({
      year = 2013,
      month = 4,
      week = 'third',
      day = 'Monday'
    }))
  end)

  it('third Tuesday of May 2013', function()
    assert.are.equal(21, meetup({
      year = 2013,
      month = 5,
      week = 'third',
      day = 'Tuesday'
    }))
  end)

  it('third Tuesday of June 2013', function()
    assert.are.equal(18, meetup({
      year = 2013,
      month = 6,
      week = 'third',
      day = 'Tuesday'
    }))
  end)

  it('third Wednesday of July 2013', function()
    assert.are.equal(17, meetup({
      year = 2013,
      month = 7,
      week = 'third',
      day = 'Wednesday'
    }))
  end)

  it('third Wednesday of August 2013', function()
    assert.are.equal(21, meetup({
      year = 2013,
      month = 8,
      week = 'third',
      day = 'Wednesday'
    }))
  end)

  it('third Thursday of September 2013', function()
    assert.are.equal(19, meetup({
      year = 2013,
      month = 9,
      week = 'third',
      day = 'Thursday'
    }))
  end)

  it('third Thursday of October 2013', function()
    assert.are.equal(17, meetup({
      year = 2013,
      month = 10,
      week = 'third',
      day = 'Thursday'
    }))
  end)

  it('third Friday of November 2013', function()
    assert.are.equal(15, meetup({
      year = 2013,
      month = 11,
      week = 'third',
      day = 'Friday'
    }))
  end)

  it('third Friday of December 2013', function()
    assert.are.equal(20, meetup({
      year = 2013,
      month = 12,
      week = 'third',
      day = 'Friday'
    }))
  end)

  it('third Saturday of January 2013', function()
    assert.are.equal(19, meetup({
      year = 2013,
      month = 1,
      week = 'third',
      day = 'Saturday'
    }))
  end)

  it('third Saturday of February 2013', function()
    assert.are.equal(16, meetup({
      year = 2013,
      month = 2,
      week = 'third',
      day = 'Saturday'
    }))
  end)

  it('third Sunday of March 2013', function()
    assert.are.equal(17, meetup({
      year = 2013,
      month = 3,
      week = 'third',
      day = 'Sunday'
    }))
  end)

  it('third Sunday of April 2013', function()
    assert.are.equal(21, meetup({
      year = 2013,
      month = 4,
      week = 'third',
      day = 'Sunday'
    }))
  end)

  it('fourth Monday of March 2013', function()
    assert.are.equal(25, meetup({
      year = 2013,
      month = 3,
      week = 'fourth',
      day = 'Monday'
    }))
  end)

  it('fourth Monday of April 2013', function()
    assert.are.equal(22, meetup({
      year = 2013,
      month = 4,
      week = 'fourth',
      day = 'Monday'
    }))
  end)

  it('fourth Tuesday of May 2013', function()
    assert.are.equal(28, meetup({
      year = 2013,
      month = 5,
      week = 'fourth',
      day = 'Tuesday'
    }))
  end)

  it('fourth Tuesday of June 2013', function()
    assert.are.equal(25, meetup({
      year = 2013,
      month = 6,
      week = 'fourth',
      day = 'Tuesday'
    }))
  end)

  it('fourth Wednesday of July 2013', function()
    assert.are.equal(24, meetup({
      year = 2013,
      month = 7,
      week = 'fourth',
      day = 'Wednesday'
    }))
  end)

  it('fourth Wednesday of August 2013', function()
    assert.are.equal(28, meetup({
      year = 2013,
      month = 8,
      week = 'fourth',
      day = 'Wednesday'
    }))
  end)

  it('fourth Thursday of September 2013', function()
    assert.are.equal(26, meetup({
      year = 2013,
      month = 9,
      week = 'fourth',
      day = 'Thursday'
    }))
  end)

  it('fourth Thursday of October 2013', function()
    assert.are.equal(24, meetup({
      year = 2013,
      month = 10,
      week = 'fourth',
      day = 'Thursday'
    }))
  end)

  it('fourth Friday of November 2013', function()
    assert.are.equal(22, meetup({
      year = 2013,
      month = 11,
      week = 'fourth',
      day = 'Friday'
    }))
  end)

  it('fourth Friday of December 2013', function()
    assert.are.equal(27, meetup({
      year = 2013,
      month = 12,
      week = 'fourth',
      day = 'Friday'
    }))
  end)

  it('fourth Saturday of January 2013', function()
    assert.are.equal(26, meetup({
      year = 2013,
      month = 1,
      week = 'fourth',
      day = 'Saturday'
    }))
  end)

  it('fourth Saturday of February 2013', function()
    assert.are.equal(23, meetup({
      year = 2013,
      month = 2,
      week = 'fourth',
      day = 'Saturday'
    }))
  end)

  it('fourth Sunday of March 2013', function()
    assert.are.equal(24, meetup({
      year = 2013,
      month = 3,
      week = 'fourth',
      day = 'Sunday'
    }))
  end)

  it('fourth Sunday of April 2013', function()
    assert.are.equal(28, meetup({
      year = 2013,
      month = 4,
      week = 'fourth',
      day = 'Sunday'
    }))
  end)

  it('last Monday of March 2013', function()
    assert.are.equal(25, meetup({
      year = 2013,
      month = 3,
      week = 'last',
      day = 'Monday'
    }))
  end)

  it('last Monday of April 2013', function()
    assert.are.equal(29, meetup({
      year = 2013,
      month = 4,
      week = 'last',
      day = 'Monday'
    }))
  end)

  it('last Tuesday of May 2013', function()
    assert.are.equal(28, meetup({
      year = 2013,
      month = 5,
      week = 'last',
      day = 'Tuesday'
    }))
  end)

  it('last Tuesday of June 2013', function()
    assert.are.equal(25, meetup({
      year = 2013,
      month = 6,
      week = 'last',
      day = 'Tuesday'
    }))
  end)

  it('last Wednesday of July 2013', function()
    assert.are.equal(31, meetup({
      year = 2013,
      month = 7,
      week = 'last',
      day = 'Wednesday'
    }))
  end)

  it('last Wednesday of August 2013', function()
    assert.are.equal(28, meetup({
      year = 2013,
      month = 8,
      week = 'last',
      day = 'Wednesday'
    }))
  end)

  it('last Thursday of September 2013', function()
    assert.are.equal(26, meetup({
      year = 2013,
      month = 9,
      week = 'last',
      day = 'Thursday'
    }))
  end)

  it('last Thursday of October 2013', function()
    assert.are.equal(31, meetup({
      year = 2013,
      month = 10,
      week = 'last',
      day = 'Thursday'
    }))
  end)

  it('last Friday of November 2013', function()
    assert.are.equal(29, meetup({
      year = 2013,
      month = 11,
      week = 'last',
      day = 'Friday'
    }))
  end)

  it('last Friday of December 2013', function()
    assert.are.equal(27, meetup({
      year = 2013,
      month = 12,
      week = 'last',
      day = 'Friday'
    }))
  end)

  it('last Saturday of January 2013', function()
    assert.are.equal(26, meetup({
      year = 2013,
      month = 1,
      week = 'last',
      day = 'Saturday'
    }))
  end)

  it('last Saturday of February 2013', function()
    assert.are.equal(23, meetup({
      year = 2013,
      month = 2,
      week = 'last',
      day = 'Saturday'
    }))
  end)

  it('last Sunday of March 2013', function()
    assert.are.equal(31, meetup({
      year = 2013,
      month = 3,
      week = 'last',
      day = 'Sunday'
    }))
  end)

  it('last Sunday of April 2013', function()
    assert.are.equal(28, meetup({
      year = 2013,
      month = 4,
      week = 'last',
      day = 'Sunday'
    }))
  end)

  it('last Wednesday of February 2012', function()
    assert.are.equal(29, meetup({
      year = 2012,
      month = 2,
      week = 'last',
      day = 'Wednesday'
    }))
  end)

  it('last Wednesday of December 2014', function()
    assert.are.equal(31, meetup({
      year = 2014,
      month = 12,
      week = 'last',
      day = 'Wednesday'
    }))
  end)

  it('last Sunday of February 2015', function()
    assert.are.equal(22, meetup({
      year = 2015,
      month = 2,
      week = 'last',
      day = 'Sunday'
    }))
  end)

  it('first Friday of December 2012', function()
    assert.are.equal(7, meetup({
      year = 2012,
      month = 12,
      week = 'first',
      day = 'Friday'
    }))
  end)
end)

local dayTable = {Sunday = 1, Monday = 2, Tuesday = 3, Wednesday = 4, Thursday = 5, Friday = 6, Saturday = 7}
local weekTable = {first = 1, second = 2, third = 3, fourth = 4, last = 5, teenth = 2}
local days_in_month = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }

local function is_leap_year(year)
  return year % 4 == 0 and (year % 100 ~= 0 or year % 400 == 0)
end

local function get_days_in_month(month, year)
  if month == 2 and is_leap_year(year) then
    return 29
  else
    return days_in_month[month]
  end
end

local function meetup_date(input)
  local date
  local time = os.time{year=input.year, month=input.month, day=1}
  local startingDay = os.date("%A", time)
  local dayDiff = dayTable[input.day] - dayTable[startingDay] + 1

  if dayDiff > 0 then
    date = dayDiff + (weekTable[input.week]-1) * 7
  else
    date = dayDiff + (weekTable[input.week]) * 7
  end

  if input.week == 'teenth' then
    if date < 13 then date = date + 7
    elseif date > 19 then date = date - 7 end
  end

  if date > get_days_in_month(input.month, input.year) then
    date = date - 7
  end
  return date
end

return meetup_date

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