defmodule FluentdForwarder.Handler do
  @moduledoc false

  @behaviour :ranch_protocol

  @type tag :: String.t
  @type time :: integer
  @type record :: map

  @callback format(tag, time, record) :: any

  use GenServer

  require Logger

  defstruct [:socket, :transport, :handler, pending: "", partial: nil]

  def start_link(ref, transport, opts) do
    GenServer.start_link(__MODULE__, {ref, transport, opts})
  end

  def init({ref, transport, opts}) do
    {:ok, %__MODULE__{transport: transport}, {:continue, {:handshake, ref}}}
  end

  def handle_continue({:handshake, ref}, %{transport: transport} = state) do
    {:ok, socket} = :ranch.handshake(ref)
    transport.setopts(socket, active: true)

    {:noreply, %{state | socket: socket}}
  end

  def handle_info({:tcp, _socket, data}, %{pending: pending} = state) do
    state =
      case Msgpax.unpack_slice(pending <> data) do
        {:ok, msg, pending} ->
          handle_msg(msg, %{state | pending: pending})

        {:error, _} ->
          %{state | pending: pending <> data}
      end

    {:noreply, state}
  end

  def handle_info({:tcp_closed, _socket}, state) do
    {:stop, :normal, state}
  end

  def handle_msg([tag, entries, option], state) when is_list(entries) do
    for [time, record] <- entries do
      handle_msg(tag, time, record, option, state)
    end
  end

  def handle_msg([tag, time, record, option], state) do
    handle_msg(tag, time, record, option, state)
  end

  def handle_msg(
        tag,
        time,
        %{
          "partial_message" => "true",
          "partial_id" => id,
          "partial_ordinal" => partial_ordinal,
          "partial_last" => partial_last,
          "log" => log
        } = record,
        option,
        %{partial: partial} = state
      ) do
    partial =
      case partial do
        nil ->
          {id, String.to_integer(partial_ordinal), log, time}

        {id, previous_ordinal, past_log, time} ->
          partial_ordinal = String.to_integer(partial_ordinal)

          log =
            if partial_ordinal == previous_ordinal + 1,
              do: past_log <> log,
              else: log

          {id, partial_ordinal, log, time}
      end

    partial =
      if partial_last == "true" do
        {_id, _partial_ordinal, log, time} = partial

        record =
          record
          |> Map.reject(fn {key, _} -> match?("partial_" <> _, key) end)
          |> Map.put("log", log)

        IO.inspect({tag, time, record, option})

        nil
      else
        partial
      end

    %{state | partial: partial}
  end

  def handle_msg(tag, time, record, option, state) do
    IO.inspect({tag, time, record, option})

    state
  end
end