defmodule ExRLP do
  @moduledoc """
  Elixir implementation of Ethereum's RLP (Recursive Length Prefix) encoding.
  """

  alias ExRLP.Decode
  alias ExRLP.Encode

  @type t :: any()

  @doc """
  Given an RLP structure (i.e. anything), returns the encoding as a binary.

  ## Examples

      iex> ExRLP.encode("dog")
      <<0x83, ?d, ?o, ?g>>

      iex> ExRLP.encode("dog", encoding: :hex)
      "83646f67"

      iex> ExRLP.encode(Enum.join(for _ <- 1..60, do: "A"))
      <<184, 60, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65>>

      iex> ExRLP.encode(["cat", "dog"])
      <<0xc8, 0x83, ?c, ?a, ?t, 0x83, ?d, ?o, ?g>>

      iex> ExRLP.encode("")
      <<0x80>>

      iex> ExRLP.encode([])
      <<0xc0>>

      iex> ExRLP.encode("\x0f")
      <<0x0f>>

      iex> ExRLP.encode(15)
      <<0x0f>>

      iex> ExRLP.encode(15_000_000_000_000_000_000_000_000_000_000_000)
      <<143, 2, 227, 142, 158, 4, 75, 160, 83, 84, 85, 150, 0, 0, 0, 0>>

      iex> ExRLP.encode(1024)
      <<0x82, 0x04, 0x00>>

      iex> ExRLP.encode("\x04\x00")
      <<0x82, 0x04, 0x00>>

      iex> ExRLP.encode([[],[[]],[[],[[]]]])
      <<0xc7, 0xc0, 0xc1, 0xc0, 0xc3, 0xc0, 0xc1, 0xc0>>

      iex> ExRLP.encode(for _ <- 1..60, do: [])
      <<248, 60, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192>>
  """
  @spec encode(t) :: binary()
  @spec encode(t, keyword()) :: binary()
  def encode(item, options \\ []) do
    Encode.encode(item, options)
  end

  @doc """
  Given an RLP-encoded string, returns a decoded RPL structure (which is an
  array of RLP structures or binaries).

  If stream (`[stream: true]`) is enabled, it will just decode the first rlp sequence

  ## Examples

      iex> ExRLP.decode(<<>>)
      ** (ExRLP.DecodeError) invalid rlp encoding

      iex> ExRLP.decode(<<0xc8, 0x83, ?c, ?a, ?t, 0x83, ?d, ?o, ?g>>)
      ["cat", "dog"]

      iex> ExRLP.decode(<<131, 99, 97, 116, 131, 99, 97, 116>>, stream: true)
      {"cat", <<131, 99, 97, 116>>}

      iex> ExRLP.decode(<<0x83, ?d, ?o, ?g>>)
      "dog"

      iex> ExRLP.decode("83646f67", encoding: :hex)
      "dog"

      iex> ExRLP.decode(<<184, 60, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65, 65>>)
      Enum.join(for _ <- 1..60, do: "A")

      iex> ExRLP.decode(<<198, 51, 132, 99, 111, 111, 108>>)
      ["3", "cool"]

      iex> ExRLP.decode(<<0x80>>)
      ""

      iex> ExRLP.decode(<<0xc0>>)
      []

      iex> ExRLP.decode(<<0x0f>>)
      <<0x0f>>

      iex> ExRLP.decode(<<0x82, 0x04, 0x00>>)
      "\x04\x00"

      iex> ExRLP.decode(<<0xc7, 0xc0, 0xc1, 0xc0, 0xc3, 0xc0, 0xc1, 0xc0>>)
      [[],[[]],[[],[[]]]]

      iex> ExRLP.decode(<<248, 60, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192, 192>>)
      for _ <- 1..60, do: []

      iex> ExRLP.decode(<<143, 2, 227, 142, 158, 4, 75, 160, 83, 84, 85, 150, 0, 0, 0, 0>>) |> :binary.decode_unsigned
      15_000_000_000_000_000_000_000_000_000_000_000

  """
  @spec decode(binary()) :: t
  @spec decode(binary(), keyword()) :: t() | {t(), binary()} | no_return()
  def decode(item, options \\ [encoding: :binary]) do
    Decode.decode(item, options)
  end
end