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A data first framework for building realtime applications

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riptide lib riptide uuid.ex
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lib/riptide/uuid.ex 

defmodule Riptide.UUID do

  @moduledoc false

  @forwards ~W(0 1 2 3 4 5 6 7 8 9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z a b c d e f g h i j k l m n o p q r s t u v w x y z)

  @forwards_inverse @forwards |> Enum.with_index() |> Enum.into(%{})

  @backwards @forwards |> Enum.reverse()

  @backwards_inverse @backwards |> Enum.with_index() |> Enum.into(%{})

  @base Enum.count(@forwards)

  @length 8

  @total @length + 12



  def descending(), do: descending_from(:os.system_time(:millisecond))

  def descending_from(time), do: generate(time, @backwards, @backwards)

  def descending_from(time, :uniform), do: generate(time, @backwards, ["0"])



  def ascending(), do: ascending_from(:os.system_time(:millisecond))

  def ascending_from(time), do: generate(time, @forwards, @forwards)

  def ascending_from(time, :uniform), do: generate(time, @forwards, ["0"])



  def generate(time, range, random) do

    time

    |> generate(range, random, @total, [])

    |> Enum.join()

  end



  # Random Part

  def generate(time, range, random, count, collect) when count > @length do

    collect = [Enum.random(random) | collect]

    generate(time, range, random, count - 1, collect)

  end



  # Time Part

  def generate(time, range, random, count, collect) when count > 0 do

    n = time |> rem(@base)

    collect = [Enum.at(range, n) | collect]

    generate(div(time, @base), range, random, count - 1, collect)

  end



  def generate(_time, _range, _random, _count, collect), do: collect



  def ascending_decode_time(key) do

    decode_time(@forwards_inverse, key)

  end



  def descending_decode_time(key) do

    decode_time(@backwards_inverse, key)

  end



  def decode_time(range, key) do

    decode_time(range, key, 0, 0)

  end



  def decode_time(_, _, value, count) when count === @length do

    value

  end



  def decode_time(range, <<head::utf8, tail::binary>>, collect, count) do

    value = Map.get(range, <<head>>)

    decode_time(range, tail, collect * @base + value, count + 1)

  end

end