qwe.ex

defmodule Qwe do
  @formats ["{ISO}", "{ISOz}", "{RFC822}", "{RFC822z}", "{RFC1123}", "{RFC1123z}",
            "{RFC3339}", "{RFC3339z}", "{ANSIC}", "{UNIX}"]

  def parse(nil), do: {:error, "Input string does not match format!"}
  def parse(string) do
    try do
      acc = {:cont, {:error, "Input string does not match format!"}}
      reduced = Enumerable.reduce(@formats, acc, fn f, acc ->
        try do
          case Timex.DateFormat.parse(string, f) do
            {:ok, _} = ok -> {:suspend, ok}
            {:error, _} -> {:cont, acc}
          end
        rescue
          _ -> {:cont, acc}
        end
      end)

      parsed = case reduced do
        {_, parsed} -> parsed
        {_, parsed, _} -> parsed
      end

      case parsed do
        {:ok, date} ->
          date = Timex.Date.universal(date) |> Timex.Date.Convert.to_erlang_datetime
          {:ok, date}
        {:error, _} = error ->
          error
      end
    catch
      _, {:error, _} = error ->
        error
      _, error ->
        {:error, error}
    end
  end
end