elixir_to_sys_config

#!/usr/bin/env elixir
# Convert an Elixir config.exs to an erlang sys.config
# 
# Usage:  elixir_to_sys_config config.exs > sys.config
#   First argument is the Elixir config.exs file
#   Writes to stdout
#   You probably want to set MIX_ENV accordingly
#
# 2015 by Dan Swain, dan.t.swain@gmail.com

defmodule ConfigConverter do
  @usage """
  USAGE: elixir_to_sys_config prod.exs > sys.config
  Generate Erlang-style sys.config from Elixir-style prod.exs
  """

  def convert([path]) do
    convert(path, File.exists?(path))
  end

  def convert(_) do
    {:error, @usage}
  end

  defp convert(path, false) do
    msg = "Error: Could not find #{inspect path}\n\n" <> @usage
    {:error, msg}
  end

  defp convert(path, true) do
    config = Mix.Config.read!(path)
    {:ok, :io_lib.format('~p.~n', [config]) |> List.to_string}
  end
end

case ConfigConverter.convert(System.argv) do
  {:ok, output} ->
    IO.puts output
  {:error, msg} ->
    IO.puts :stderr, msg
    System.halt(1)
end