anagrams.exs

defmodule Dictionary do

  @name __MODULE__

  #########
  # External API

  def start_link, do:
    Agent.start_link(fn -> %{} end, name: @name)

  def add_words(words), do:
    Agent.update(@name, &do_add_words(&1, words))

  def anagrams_of(word), do: 
    Agent.get(@name, &Map.get(&1, signature_of(word)))

  ##########
  # Internal Implementation

  defp do_add_words(map, words), do:
    Enum.reduce(words, map, &add_one_word(&1, &2))

  defp add_one_word(word, map), do:
    Map.update(map, signature_of(word), [word], &[word|&1])


  defp signature_of(word), do:
    word |> to_charlist |> Enum.sort |> to_string

end

defmodule WordlistLoader do

  def load_from_files(file_names) do
    file_names
    |> Stream.map(fn name ->
                     Task.async(fn -> load_task(name) end)
                  end)
    |> Enum.map(&Task.await/1)
  end

  defp load_task(file_name) do
    File.stream!(file_name, [], :line)
    |> Enum.map(&String.strip/1)
    |> Dictionary.add_words
  end

end