defmodule AshDoubleEntry.ULID do
  @moduledoc """
  An Ash type for ULID strings.
  """

  use Ash.Type

  @typedoc """
  A hex-encoded ULID string.
  """
  @type t :: <<_::208>>

  @doc """
  The underlying schema type.
  """
  def storage_type, do: :binary

  @doc """
  Casts a string to ULID.
  """
  def cast_input(nil, _), do: {:ok, nil}

  def cast_input(<<_::bytes-size(16)>> = value, constraints) do
    case encode(value) do
      {:ok, encoded} -> cast_input(encoded, constraints)
      :error -> :error
    end
  end

  def cast_input(<<_::bytes-size(26)>> = value, _) do
    if valid?(value) do
      {:ok, value}
    else
      :error
    end
  end

  def cast_input(_, _), do: :error

  @doc """
  Converts a Crockford Base32 encoded ULID into a binary.
  """
  def dump_to_native(nil, _), do: {:ok, nil}
  def dump_to_native(<<_::bytes-size(26)>> = encoded, _), do: decode(encoded)
  def dump_to_native(_, _), do: :error

  @doc """
  Converts a binary ULID into a Crockford Base32 encoded string.
  """
  def cast_stored(nil, _), do: {:ok, nil}
  def cast_stored(<<_::unsigned-size(128)>> = bytes, _), do: encode(bytes)
  def cast_stored(_, _), do: :error

  @doc false
  def autogenerate, do: generate()

  @doc """
  Generates a Crockford Base32 encoded ULID.

  If a value is provided for `timestamp`, the generated ULID will be for the provided timestamp.
  Otherwise, a ULID will be generated for the current time.

  Arguments:

  * `timestamp`: A Unix timestamp with millisecond precision.
  """
  def generate(timestamp \\ System.system_time(:millisecond))

  def generate(%DateTime{} = datetime) do
    datetime
    |> DateTime.to_unix(:millisecond)
    |> generate()
  end

  def generate(timestamp) do
    {:ok, ulid} = encode(bingenerate(timestamp))
    ulid
  end

  @doc """
  Generates a Crockford Base32 encoded ULID, guaranteed to sort equal to or after any other ULID generated for the same timestamp.

  Do not use this for storage, only for generating comparators, i.e "balance as of a given ulid".

  If a value is provided for `timestamp`, the generated ULID will be for the provided timestamp.
  Otherwise, a ULID will be generated for the current time.

  Arguments:

  * `timestamp`: A Unix timestamp with millisecond precision.
  """
  def generate_last(timestamp \\ System.system_time(:millisecond))

  def generate_last(%DateTime{} = datetime) do
    datetime
    |> DateTime.to_unix(:millisecond)
    |> generate_last()
  end

  def generate_last(timestamp) do
    {:ok, ulid} = encode(bingenerate_last(timestamp))
    ulid
  end

  @doc """
  Generates a binary ULID.

  If a value is provided for `timestamp`, the generated ULID will be for the provided timestamp.
  Otherwise, a ULID will be generated for the current time.

  Arguments:

  * `timestamp`: A Unix timestamp with millisecond precision.
  """
  def bingenerate(timestamp \\ System.system_time(:millisecond)) do
    <<timestamp::unsigned-size(48), :crypto.strong_rand_bytes(10)::binary>>
  end

  @doc """
  Generates a binary ULID.

  Do not use this for storage, only for generating comparators, i.e "balance as of a given ulid".

  If a value is provided for `timestamp`, the generated ULID will be for the provided timestamp.
  Otherwise, a ULID will be generated for the current time.

  Arguments:

  * `timestamp`: A Unix timestamp with millisecond precision.
  """
  def bingenerate_last(timestamp \\ System.system_time(:millisecond)) do
    <<timestamp::unsigned-size(48), 255, 255, 255, 255, 255, 255, 255, 255, 255, 255>>
  end

  @doc false
  def encode(
        <<b1::3, b2::5, b3::5, b4::5, b5::5, b6::5, b7::5, b8::5, b9::5, b10::5, b11::5, b12::5,
          b13::5, b14::5, b15::5, b16::5, b17::5, b18::5, b19::5, b20::5, b21::5, b22::5, b23::5,
          b24::5, b25::5, b26::5>>
      ) do
    <<e(b1), e(b2), e(b3), e(b4), e(b5), e(b6), e(b7), e(b8), e(b9), e(b10), e(b11), e(b12),
      e(b13), e(b14), e(b15), e(b16), e(b17), e(b18), e(b19), e(b20), e(b21), e(b22), e(b23),
      e(b24), e(b25), e(b26)>>
  catch
    :error -> :error
  else
    encoded -> {:ok, encoded}
  end

  def encode(_), do: :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
  defp e(16), do: ?G
  defp e(17), do: ?H
  defp e(18), do: ?J
  defp e(19), do: ?K
  defp e(20), do: ?M
  defp e(21), do: ?N
  defp e(22), do: ?P
  defp e(23), do: ?Q
  defp e(24), do: ?R
  defp e(25), do: ?S
  defp e(26), do: ?T
  defp e(27), do: ?V
  defp e(28), do: ?W
  defp e(29), do: ?X
  defp e(30), do: ?Y
  defp e(31), do: ?Z

  defp decode(
         <<c1::8, c2::8, c3::8, c4::8, c5::8, c6::8, c7::8, c8::8, c9::8, c10::8, c11::8, c12::8,
           c13::8, c14::8, c15::8, c16::8, c17::8, c18::8, c19::8, c20::8, c21::8, c22::8, c23::8,
           c24::8, c25::8, c26::8>>
       ) do
    <<d(c1)::3, d(c2)::5, d(c3)::5, d(c4)::5, d(c5)::5, d(c6)::5, d(c7)::5, d(c8)::5, d(c9)::5,
      d(c10)::5, d(c11)::5, d(c12)::5, d(c13)::5, d(c14)::5, d(c15)::5, d(c16)::5, d(c17)::5,
      d(c18)::5, d(c19)::5, d(c20)::5, d(c21)::5, d(c22)::5, d(c23)::5, d(c24)::5, d(c25)::5,
      d(c26)::5>>
  catch
    :error -> :error
  else
    decoded -> {:ok, decoded}
  end

  defp decode(_), do: :error

  @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(?G), do: 16
  defp d(?H), do: 17
  defp d(?J), do: 18
  defp d(?K), do: 19
  defp d(?M), do: 20
  defp d(?N), do: 21
  defp d(?P), do: 22
  defp d(?Q), do: 23
  defp d(?R), do: 24
  defp d(?S), do: 25
  defp d(?T), do: 26
  defp d(?V), do: 27
  defp d(?W), do: 28
  defp d(?X), do: 29
  defp d(?Y), do: 30
  defp d(?Z), do: 31
  defp d(_), do: throw(:error)

  defp valid?(
         <<c1::8, c2::8, c3::8, c4::8, c5::8, c6::8, c7::8, c8::8, c9::8, c10::8, c11::8, c12::8,
           c13::8, c14::8, c15::8, c16::8, c17::8, c18::8, c19::8, c20::8, c21::8, c22::8, c23::8,
           c24::8, c25::8, c26::8>>
       ) do
    v(c1) && v(c2) && v(c3) && v(c4) && v(c5) && v(c6) && v(c7) && v(c8) && v(c9) && v(c10) &&
      v(c11) && v(c12) && v(c13) &&
      v(c14) && v(c15) && v(c16) && v(c17) && v(c18) && v(c19) && v(c20) && v(c21) && v(c22) &&
      v(c23) && v(c24) && v(c25) && v(c26)
  end

  defp valid?(_), do: false

  @compile {:inline, v: 1}

  defp v(?0), do: true
  defp v(?1), do: true
  defp v(?2), do: true
  defp v(?3), do: true
  defp v(?4), do: true
  defp v(?5), do: true
  defp v(?6), do: true
  defp v(?7), do: true
  defp v(?8), do: true
  defp v(?9), do: true
  defp v(?A), do: true
  defp v(?B), do: true
  defp v(?C), do: true
  defp v(?D), do: true
  defp v(?E), do: true
  defp v(?F), do: true
  defp v(?G), do: true
  defp v(?H), do: true
  defp v(?J), do: true
  defp v(?K), do: true
  defp v(?M), do: true
  defp v(?N), do: true
  defp v(?P), do: true
  defp v(?Q), do: true
  defp v(?R), do: true
  defp v(?S), do: true
  defp v(?T), do: true
  defp v(?V), do: true
  defp v(?W), do: true
  defp v(?X), do: true
  defp v(?Y), do: true
  defp v(?Z), do: true
  defp v(_), do: false
end