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Contents
defmodule Meetup do
@moduledoc """
Calculate meetup dates.
"""
@type weekday ::
:monday
| :tuesday
| :wednesday
| :thursday
| :friday
| :saturday
| :sunday
@type schedule :: :first | :second | :third | :fourth | :last | :teenth
@doc """
Calculate a meetup date.
The schedule is in which week (1..4, last or "teenth") the meetup date should
fall.
"""
@spec meetup(pos_integer, pos_integer, weekday, schedule) :: :calendar.date()
def meetup(year, month, weekday, :last) do
start_day = :calendar.last_day_of_the_month(year, month) - 6
meetup_nth(year, month, start_day, weekday)
end
def meetup(year, month, weekday, schedule) do
meetup_nth(year, month, schedule_start(schedule), weekday)
end
defp meetup_nth(year, month, start_day, weekday) do
w = weekday_num(weekday)
case w - :calendar.day_of_the_week(year, month, start_day) do
n when n < 0 -> {year, month, start_day + n + 7}
n -> {year, month, start_day + n}
end
end
# Aliases for the day of week numbers from Erlang.
#
# Case matching is used because that's very fast in Elixir/Erlang.
defp weekday_num(:monday), do: 1
defp weekday_num(:tuesday), do: 2
defp weekday_num(:wednesday), do: 3
defp weekday_num(:thursday), do: 4
defp weekday_num(:friday), do: 5
defp weekday_num(:saturday), do: 6
defp weekday_num(:sunday), do: 7
defp schedule_start(:first), do: 1
defp schedule_start(:second), do: 8
defp schedule_start(:third), do: 15
defp schedule_start(:fourth), do: 22
defp schedule_start(:teenth), do: 13
end
Version data entries
69 entries across 69 versions & 1 rubygems