defmodule Munge do
  @moduledoc """
  `Munge` helps process and reshape complex records.
  """

  # def good({:ok, response}), do: response
  def good({key, response} = source, guard) when is_list(guard),
    do: (if (key in guard), do: response, else: raise(Munge.ResponseError, response: source))
  def good({key, response}, guard \\ :ok) when guard == key, do: response
  def good({key, response} = source, _), do: raise(Munge.ResponseError, response: source)

  @doc """
  From an enum of maps, group the maps by the values on a chosen key.
  """
  def group_by(records, key) when is_binary(key) do
    records |> Enum.reduce(%{}, fn record, groupings ->
      group = record |> Map.get(key)
      groupings |> Map.update(group, [record], fn prior -> [record | prior] end)
    end)
  end

  # @doc """
  # From a generic enum of terms,
  # group the terms by some &closure/1 on each term.
  # """
  # def group_by(records, closure) when is_function(closure) do
  #   records
  # end
end