defmodule DaProductApp.TCP.Handler do
  @behaviour :ranch_protocol
  require Logger

  @timeout 30_000
  @socket_opts [packet: 2, active: false]  # ISO8583 typically uses length-prefixed messages

  # Ranch 2.1-compatible start_link
  def start_link(ref, transport, _opts) do
    Task.start_link(__MODULE__, :handle, [ref, transport])
  end

  def handle(ref, transport) do
    # 1. Handshake and socket acquisition with error handling
    case :ranch.handshake(ref) do
      {:ok, socket} ->
        Logger.info("New TCP connection accepted")
        set_socket_opts(socket, transport)
        loop(socket, transport)

      {:error, reason} ->
        Logger.error("Handshake failed: #{inspect(reason)}")
        exit(:handshake_failed)
    end
  end

  defp set_socket_opts(socket, transport) do
    case transport.setopts(socket, @socket_opts) do
      :ok -> :ok
      {:error, reason} ->
        Logger.error("Socket options failed: #{inspect(reason)}")
        transport.close(socket)
        exit(:socket_options_failed)
    end
  end

  defp loop(socket, transport) do
    case transport.recv(socket, 0, @timeout) do
      {:ok, data} ->
        Logger.debug("Received data: #{inspect(data)}")
        process_data(socket, transport, data)
        loop(socket, transport)

      {:error, :timeout} ->
        Logger.info("Connection timeout")
        transport.close(socket)

      {:error, reason} ->
        Logger.warn("Connection error: #{inspect(reason)}")
        transport.close(socket)
    end
  end

  defp process_data(socket, transport, data) do
        Logger.debug("Received data process data: #{inspect(data)}")
    # Add your ISO8583 parsing and business logic here
    response = <<0, 4>> <> "ACK"  # Sample ISO8583 response
    case transport.send(socket, response) do
      :ok -> Logger.debug("Response sent successfully")
      {:error, reason} -> Logger.error("Failed to send response: #{inspect(reason)}")
    end
  end
end