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gnat

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A nats client in pure elixir. Resilience, Performance, Ease-of-Use.

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gnat lib gnat parser.ex
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lib/gnat/parser.ex 

defmodule Gnat.Parser do

  require Logger

  # states: waiting, reading_message

  defstruct [

    partial: "",

    state: :waiting,

  ]



  def new, do: %Gnat.Parser{}



  def parse(parser, data) do

    data = parser.partial <> data

    parser = %{parser | partial: ""}

    parse(parser, data, [])

  end



  def parse(parser, "", parsed), do: {parser, Enum.reverse(parsed)}

  def parse(parser, bytes, parsed) do

    case  :binary.match(bytes, "\r\n") do

      {index, 2} ->

        {command, "\r\n"<>rest} = String.split_at(bytes, index)

        case parse_command(command, rest) do

          :partial_message ->

            parser = %{parser | partial: bytes}

            parse(parser, "", parsed)

          {message, rest} ->

            parse(parser, rest, [message | parsed])

        end

      :nomatch ->

        parse(%{parser | partial: bytes}, "", parsed)

    end

  end



  defp parse_command(command, body) do

    [operation | details] = String.split(command)

    operation

    |> String.upcase

    |> parse_command(details, body)

  end



  defp parse_command("PING", _, body), do: {:ping, body}

  defp parse_command("PONG", _, body), do: {:pong, body}

  defp parse_command("MSG", [topic, sidstr, sizestr], body), do: parse_command("MSG", [topic, sidstr, nil, sizestr], body)

  defp parse_command("MSG", [topic, sidstr, reply_to, sizestr], body) do

    sid = String.to_integer(sidstr)

    bytesize = String.to_integer(sizestr)

    if byte_size(body) >= (bytesize + 2) do

      << message :: binary-size(bytesize), "\r\n", rest :: binary >> = body

      {{:msg, topic, sid, reply_to, message}, rest}

    else

      :partial_message

    end

  end

  defp parse_command("INFO", options, body) do

    {{:info, Poison.Parser.parse!(options, keys: :atoms)}, body}

  end

end