#
# Implementation from https://github.com/elixir-ecto/ecto/blob/v3.8.4/lib/ecto/uuid.ex
# Apache License 2.0 https://github.com/elixir-ecto/ecto/blob/master/LICENSE.md
#
defmodule Commanded.UUID do
  @moduledoc """
  Generate and format random, version 4 UUIDs.
  """

  @typedoc """
  A hex-encoded UUID string.
  """
  @type hex :: <<_::288>>

  @typedoc """
  A raw binary representation of a UUID.
  """
  @type raw :: <<_::128>>

  @doc """
  Generates a random, version 4 UUID.
  """
  @spec uuid4() :: hex()
  def uuid4, do: bingenerate() |> hex_encode()

  @doc """
  Converts a string representing a UUID into a raw binary.
  """
  @spec string_to_binary!(hex()) :: raw()
  def string_to_binary!(
        <<a1, a2, a3, a4, a5, a6, a7, a8, ?-, b1, b2, b3, b4, ?-, c1, c2, c3, c4, ?-, d1, d2, d3,
          d4, ?-, e1, e2, e3, e4, e5, e6, e7, e8, e9, e10, e11, e12>>
      ) do
    <<d(a1)::4, d(a2)::4, d(a3)::4, d(a4)::4, d(a5)::4, d(a6)::4, d(a7)::4, d(a8)::4, d(b1)::4,
      d(b2)::4, d(b3)::4, d(b4)::4, d(c1)::4, d(c2)::4, d(c3)::4, d(c4)::4, d(d1)::4, d(d2)::4,
      d(d3)::4, d(d4)::4, d(e1)::4, d(e2)::4, d(e3)::4, d(e4)::4, d(e5)::4, d(e6)::4, d(e7)::4,
      d(e8)::4, d(e9)::4, d(e10)::4, d(e11)::4, d(e12)::4>>
  end

  @spec binary_to_string!(raw()) :: hex()
  def binary_to_string!(<<_::128>> = raw_uuid) do
    hex_encode(raw_uuid)
  end

  defp bingenerate do
    <<u0::48, _::4, u1::12, _::2, u2::62>> = :crypto.strong_rand_bytes(16)
    <<u0::48, 4::4, u1::12, 2::2, u2::62>>
  end

  defp hex_encode(
         <<a1::4, a2::4, a3::4, a4::4, a5::4, a6::4, a7::4, a8::4, b1::4, b2::4, b3::4, b4::4,
           c1::4, c2::4, c3::4, c4::4, d1::4, d2::4, d3::4, d4::4, e1::4, e2::4, e3::4, e4::4,
           e5::4, e6::4, e7::4, e8::4, e9::4, e10::4, e11::4, e12::4>>
       ) do
    <<e(a1), e(a2), e(a3), e(a4), e(a5), e(a6), e(a7), e(a8), ?-, e(b1), e(b2), e(b3), e(b4), ?-,
      e(c1), e(c2), e(c3), e(c4), ?-, e(d1), e(d2), e(d3), e(d4), ?-, e(e1), e(e2), e(e3), e(e4),
      e(e5), e(e6), e(e7), e(e8), e(e9), e(e10), e(e11), e(e12)>>
  end

  @compile {:inline, d: 1}

  defp d(?0), do: 0
  defp d(?1), do: 1
  defp d(?2), do: 2
  defp d(?3), do: 3
  defp d(?4), do: 4
  defp d(?5), do: 5
  defp d(?6), do: 6
  defp d(?7), do: 7
  defp d(?8), do: 8
  defp d(?9), do: 9
  defp d(?A), do: 10
  defp d(?B), do: 11
  defp d(?C), do: 12
  defp d(?D), do: 13
  defp d(?E), do: 14
  defp d(?F), do: 15
  defp d(?a), do: 10
  defp d(?b), do: 11
  defp d(?c), do: 12
  defp d(?d), do: 13
  defp d(?e), do: 14
  defp d(?f), do: 15
  defp d(_), do: throw(:error)

  @compile {:inline, e: 1}

  defp e(0), do: ?0
  defp e(1), do: ?1
  defp e(2), do: ?2
  defp e(3), do: ?3
  defp e(4), do: ?4
  defp e(5), do: ?5
  defp e(6), do: ?6
  defp e(7), do: ?7
  defp e(8), do: ?8
  defp e(9), do: ?9
  defp e(10), do: ?a
  defp e(11), do: ?b
  defp e(12), do: ?c
  defp e(13), do: ?d
  defp e(14), do: ?e
  defp e(15), do: ?f
end