faker

defmodule Faker do
  @moduledoc """
  Main module to start application with some helper functions.
  """

  @doc """
  Starts Faker with default locale.
  """
  @spec start() :: :ok
  def start do
    :application.start(:faker)
  end

  @doc """
  Starts Faker with `lang` locale.
  """
  @spec start(atom) :: :ok
  def start(lang) when is_atom(lang) do
    :application.start(:faker)
    Faker.locale(lang)
    :ok
  end

  @doc """
  Internal function to format string.

  It replaces `"#"` to random number and `"?"` to random latin letter.
  """
  @spec format(String.t) :: String.t
  def format(str) when is_binary(str) do
    format(str, "")
  end

  defp format(<<"#" :: utf8, tail :: binary>>, acc) do
    format(tail, <<acc :: binary, "#{:crypto.rand_uniform(0, 10)}">>)
  end

  defp format(<<"?" :: utf8, tail :: binary>>, acc) do
    format(tail, <<acc :: binary, letter()>>)
  end

  defp format(<<other :: utf8, tail :: binary>>, acc) do
    format(tail, <<acc :: binary, other>>)
  end

  defp format("", acc) do
    acc
  end

  defp letter do
    alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'
    Enum.at(alphabet, :crypto.rand_uniform(0, Enum.count(alphabet)))
  end

  @doc """
  Returns application locale ready for module constract.
  """
  @spec mlocale() :: String.t
  def mlocale do
    String.capitalize(to_string(Faker.locale))
  end

  @doc """
  Returns application locale.
  """
  @spec locale() :: atom
  def locale do
    Application.get_env(:faker, :locale)
  end

  @doc """
  Sets application locale.
  """
  @spec locale(atom) :: :ok
  def locale(lang) when is_atom(lang) do
    Application.put_env(:faker, :locale, lang)
  end

  defmacro sampler(name, data) do
    count = Enum.count(data)
    mapped_data = data |> Enum.with_index |> Enum.into(%{}, fn({k, v}) -> {v, k} end) |> Macro.escape()

    quote do
      def unquote(name)() do
        unquote(mapped_data)
        |> Map.get(:crypto.rand_uniform(0, unquote(count)))
      end
    end
  end

  defmacro samplerp(name, data) do
    count = Enum.count(data)
    mapped_data = data |> Enum.with_index |> Enum.into(%{}, fn({k, v}) -> {v, k} end) |> Macro.escape()

    quote do
      defp unquote(name)() do
        unquote(mapped_data)
        |> Map.get(:crypto.rand_uniform(0, unquote(count)))
      end
    end
  end
end