headver Elixir implementation

headver.exs

# headver.exs - a headver implementation in Elixir. See https://github.com/line/headver.
#
# Run
#  $ elixir headver.exs --head=5 --build=23 --suffix=qa
#  5.2142.23+qa

Mix.install([
  {:timex, "~> 3.7"}
])

{options, _, _} =
  OptionParser.parse(System.argv(),
    strict: [
      head: :integer,
      build: :integer,
      suffix: :string
    ]
  )

head = Keyword.fetch!(options, :head)
build = Keyword.fetch!(options, :build)
suffix = Keyword.fetch!(options, :suffix)

{year, weeknumber} = Timex.iso_week(DateTime.utc_now())
yearweek = "#{rem(year, 100)}#{weeknumber}"

version = "#{head}.#{yearweek}.#{build}"

version =
  if String.length(suffix) != 0 do
    "#{version}+#{suffix}"
  else
    version
  end

IO.puts(version)