defmodule ACS.Session do
  use GenServer
  use Prometheus.Metric
  require Logger

  @moduledoc """

    The actual ACS-CPE session is handled here. A session is initiated
    when an Inform arrives, therefore the init function takes a parsed
    Inform request as an argument.

    We let the supervisor handle the main session handler, and then we
    register new sessions with the session_begins method

  """

  @doc """

    For the supervisor.

    Ths supervisors starts the sessions from start_child

  """
  def start_link(session_module,
        session_id: session_id,
        device_id: device_id,
        message: message,
        fun: fun
      ) do
    Logger.debug(
      "ACS.Session start_link(#{inspect(session_id)},#{inspect(device_id)}) with function"
    )

    Gauge.inc(name: :acs_ex_nof_sessions, labels: [device_id.product_class])
    GenServer.start_link(__MODULE__, [session_module, session_id, device_id, message, fun])
  end

  def start_link(session_module,
        session_id: session_id,
        device_id: device_id,
        message: message
      ) do
    Logger.debug("ACS.Session start_link(#{inspect(session_id)},#{inspect(device_id)})")
    Gauge.inc(name: :acs_ex_nof_sessions, labels: [device_id.product_class])
    GenServer.start_link(__MODULE__, [session_module, session_id, device_id, message, nil])
  end

  # API

  @doc """

    when stuff is sent into this session, like CWMP messages
    or other stuff.

  """
  def process_message(session_id, message) do
    try do
      timeout =
        case Application.fetch_env(:acs_ex, :session_timeout) do
          {:ok, to} -> to
          :error -> 30000
        end

      GenServer.call(via_tuple(session_id), {:process_message, [session_id, message]}, timeout)
    catch
      # timeout comes as :exit, reason.
      :exit, reason ->
        case reason do
          # Generate fault response? Or maybee just end the session by returning ""
          {:timeout, _} ->
            # Will it depend on the state of things?
            msg = hd(message)

            CWMP.Protocol.Generator.generate(
              %CWMP.Protocol.Messages.Header{id: msg.header.id},
              %CWMP.Protocol.Messages.Fault{
                faultcode: "Server",
                faultstring: "CWMP fault",
                detail: %CWMP.Protocol.Messages.FaultStruct{
                  code: "8002",
                  string: "Internal error"
                }
              }
            )

          {what, ever} ->
            {what, ever}
        end
    end
  end

  @doc """

  When something non-Inform'ish is sent into the session we need to find and verify the
  session.

  """
  def verify_session(session_id, remote_host) do
    try do
      timeout =
        case Application.fetch_env(:acs_ex, :session_timeout) do
          {:ok, to} -> to
          :error -> 30000
        end

      case GenServer.call(via_tuple(session_id), {:verify_remotehost, [remote_host]}, timeout) do
        {:noproc, _} -> false
        host_verify_result -> host_verify_result
      end
    catch
      # timeout comes as :exit, reason.
      :exit, _reason -> false
    end
  end

  @doc """

    Script message. This means the a scripting process wants a response to a request
    we just put the request in the plug queue and answer no_reply here.

  """
  def script_command(device_id, command) do
    # put it into the script_element
    Logger.debug("API script_command called...#{inspect(device_id)}, #{inspect(command)}")

    try do
      timeout =
        case Application.fetch_env(:acs_ex, :script_timeout) do
          {:ok, to} -> to
          :error -> 2000
        end

      Logger.debug("API script_command got timeout value: #{timeout}")
      GenServer.call(via_tuple(device_id), {:script_command, [command]}, timeout)
    catch
      :exit, reason ->
        case reason do
          # reply with timeout
          {:timeout, _} ->
            Logger.debug("API script_command timeout occured!")
            {:error, "timeout"}

          {what, ever} ->
            Logger.debug("Whatever occured #{inspect(what)}, #{inspect(ever)}")
            {what, ever}
        end
    end
  end

  defp takeover_session(session_id, tries \\ 5)

  defp takeover_session(_session_id, 0), do: {:error, "Could not take over session"}

  defp takeover_session(session_id, tries) do
    case :gproc.reg_or_locate({:n, :l, {:session_id, session_id}}) do
      {other, _} when other == self() ->
        :ok

      {other, _} ->
        ref = Process.monitor(other)
        # TODO: Maybe send a poison pill?
        Process.exit(other, :kill)

        receive do
          {:DOWN, _ref, :process, _other, _} -> takeover_session(session_id, tries - 1)
        after
          1000 ->
            Process.demonitor(ref, [:flush])
            takeover_session(session_id, tries - 1)
        end
    end
  end

  # SERVER

  def init([script_module, session_id, device_id, message, fun]) do
    # This should only be called when the Plug gets an Inform, it this up
    # to me to check, or the caller? I will assume caller.

    # This conn.body_params must be a parsed Inform, if not - ignore
    # Queue the response in the plug_element, so that it can be popped with next response
    # InformResponse into the plug queue

    Logger.metadata(serial: device_id.serial_number, sessionid: session_id)
    gspid = self()
    # TODO: Should be "first inform encountered", not just hd
    sspid =
      spawn_link(__MODULE__, :session_prestart, [
        gspid,
        script_module,
        device_id,
        hd(message.entries),
        session_id,
        fun
      ])

    # Start session script process, save pid to state
    case takeover_session(session_id) do
      :ok ->
        Process.flag(:trap_exit, true)

        {:ok,
         %{
           device_id: device_id,
           session_id: session_id,
           script_element: nil,
           plug_element: nil,
           unmatched_incomming_list: [],
           sspid: sspid,
           cwmp_version: message.cwmp_version
         }}

      _ ->
        {:stop, "Could not take over session"}
    end
  end

  @doc """

  Used for :trap_exit

  1. signal with reply/2 that this is over
  2. kill me?

  """
  def handle_info({:EXIT, _pid, _reason}, state) do
    ## Session Script is done.
    Logger.debug("Script system exited.")

    case state.plug_element do
      nil ->
        Logger.debug(
          "Session script exited, and we have no waiting plug, leave the plug some time to end session"
        )

      pe ->
        # Waiting plug, we have to tell it to stop by sending {204,""}
        Logger.debug(
          "Waiting plug when SS ends, just tell it to stop, which in turn will kill me (the session)"
        )

        GenServer.reply(pe.from, {204, ""})
    end

    {:noreply, %{state | plug_element: nil, script_element: nil, sspid: nil}, 5000}
  end

  def handle_info(:timeout, state) do
    # Kill self...
    Logger.warn("Session died due to timeout")
    # Update the Prometheus metrics
    Counter.inc(name: :acs_ex_dead_sessions, labels: [state.device_id.product_class])
    {:stop, :timeout, state}
  end

  def handle_info(message, state) do
    Logger.error("Unhandled handle_info(#{inspect(message)}, #{inspect(state)})")
  end

  def terminate(reason, state) do
    Logger.debug("Session terminate called: #{inspect(reason)}, #{inspect(state)}")
    Gauge.dec(name: :acs_ex_nof_sessions, labels: [state.device_id.product_class])
    :normal
  end

  def handle_call({:script_command, [command]}, from, state) do
    Logger.debug("handle_call(:script_command, [#{inspect(command)}])")

    case state.plug_element do
      %{message: _msg, from: plug_from, state: :waiting} ->
        # A plug is waiting when a scripting function has not ended, and the plug is ready for more requests
        # meaning it received "" from a CPE indicating that the CPE has nothing more. We keep waiting
        # because the scripting system is supposed to introduce new reqeusts, that is its purpose, and
        # as long as it is not dead, we must expect more.
        Logger.debug(
          "Session Script discovered a waiting plug. Sending scripted command at once!"
        )

        case gen_request(command.method, command.args, "script", state.cwmp_version) do
          {:ok, {id, req}} ->
            GenServer.reply(plug_from, {200, req})

            {:noreply,
             %{
               state
               | plug_element: nil,
                 script_element: %{command: command, from: from, state: :sent, id: id}
             }}

          {:error, msg} ->
            # some error should be returned to "from" who is the SS
            {:reply, {:error, msg}, %{state | script_element: nil}}
        end

      _ ->
        Logger.debug(
          "No known plug_element, meaning no plug is waiting, so store script command in state"
        )

        # Just put the command in the script element, we wont affect the plug queue until the
        # session reaches the "what now?" stage (empty request from device)
        case state.script_element do
          nil ->
            {:noreply,
             %{state | script_element: %{command: command, from: from, state: :unhandled}}}

          _ ->
            Logger.error("Unable to handle multiple scripting commands at the time.")
            {:reply, :error, state}
        end
    end
  end

  @doc """
  :verify_remotehost - verifies the remote_host by comparing it to the one in the state.device_id

  :process_message - Processes a message from the plug. message is the CWMP.Protocol version of
  the parsed request sent into the plug.
  """
  def handle_call({:verify_remotehost, [remote_host]}, _from, state) do
    {:reply, state.device_id.ip == remote_host, state}
  end

  def handle_call({:process_message, [session_id, message]}, from, state) do
    Logger.debug("handle_call(:process_message, #{session_id}, #{inspect(message)})")

    # If this message is an Inform, it can be ignored, because the response to that
    # has already been queue in the plug_element by init.
    # If this message is empty, it means that the session is about to end, unless
    # we have something more to send.

    # Anything else means that the front element in the script_element must be responsible for
    # this thing arriving, and the script is currently awaiting this reply, so we must :reply
    # now.
    {plug, script, unmatched, sspid} =
      case length(Map.keys(message)) do
        0 ->
          # Empty message here. This means examine the script_element to see if there are
          # any new scripted message to push into the plug queue. If nothing can be found,
          # push "" into the plug_element - ending the session. The Plug should kill it...
          Logger.debug(
            "Empty message discovered: sspid: #{inspect(state.sspid)}, script_element: #{inspect(state.script_element)}"
          )

          case state.script_element do
            nil ->
              # nothing in the script thing, we can end the session... if the session script process has exited.
              Logger.debug("No script_element")

              case state.sspid do
                nil ->
                  # no session script
                  Logger.debug("No script pid")
                  # we can stop...
                  {{204, ""}, nil, [], state.sspid}

                sspid ->
                  # Session script is going, but no element?? Maybee this is before it could queue
                  # or maybee its in some long operation
                  if Process.alive?(sspid) do
                    Logger.debug("Script system IS alive ....")
                    # If we have an :unscripted waiting, reply now
                    {:noreply, nil, state.unmatched_incomming_list, sspid}
                  else
                    Logger.debug(
                      "Script system is not actually alive, it only seems so. Missed an :exit?"
                    )

                    {{204, ""}, nil, [], nil}
                  end
              end

            %{command: :unscripted, from: script_from, state: :unhandled} ->
              Logger.debug("Replying to :unscripted command")
              GenServer.reply(script_from, state.unmatched_incomming_list)
              {:noreply, nil, [], state.sspid}

            %{command: command, from: script_from, state: :unhandled} ->
              # And unhandled message from script?
              Logger.debug("There is a script element")
              # Transform the command to a plug_element thing, and mark it :sent
              case gen_request(command.method, command.args, "script", state.cwmp_version) do
                {:ok, {id, req}} ->
                  {{200, req}, %{command: command, from: script_from, state: :sent, id: id},
                   state.unmatched_incomming_list, state.sspid}

                {:error, msg} ->
                  Logger.debug("gen_request error: #{msg}")
                  # must send reply to SS with error, even though this should never happen,
                  # then we must continue to wait in the plug
                  GenServer.reply(script_from, {:error, msg})
                  {:noreply, nil, state.unmatched_incomming_list, state.sspid}
              end

            _ ->
              Logger.debug(
                "Cant identify script_element, clearing and discontinuing session: #{inspect(state.script_element)}"
              )

              {{204, ""}, nil, [], nil}
          end

        3 ->
          Logger.debug(
            "CWMP message discovered: script_element: #{inspect(state.script_element)}"
          )

          # This could be a response that has to go to script land. In fact if the script_element
          # is empty this is weird and should be ignored and logged.

          # Could be that message is an Inform, in which case we just generate an InformResponse and dont stack anything in the plug element.
          case has_inform?(message.entries) do
            true ->
              Logger.debug("Session server saw inform, generating response")

              id =
                if !is_nil(message.header) && Map.has_key?(message.header, :id) do
                  message.header.id
                else
                  0
                end

              {{200,
                CWMP.Protocol.Generator.generate!(
                  %CWMP.Protocol.Messages.Header{id: id},
                  %CWMP.Protocol.Messages.InformResponse{max_envelopes: 1},
                  message.cwmp_version
                )}, state.script_element, [], state.sspid}

            false ->
              case state.script_element do
                nil ->
                  Logger.debug("Incomming non-inform message with no script element...")
                  # what? - ignore that......or queue it somewhere in state if someone wants it")
                  # Stuff the message into the junk list - the list of unsolicited messages.
                  # We should still respond...
                  {reply, msg} = construct_reply(message)

                  if state.sspid != nil and Process.alive?(state.sspid) do
                    Logger.debug("Script pid found to be alive")
                    {reply, nil, msg, state.sspid}
                  else
                    Logger.debug("Script pid found to be dead")
                    {reply, nil, msg, nil}
                  end

                %{command: :unscripted, from: _from, state: :unhandled} ->
                  Logger.debug(
                    "We have a script wanting the unmatched list - we should still reply to this though"
                  )

                  {reply, msg} = construct_reply(message)
                  {reply, state.script_element, msg, state.sspid}

                # This only matches script elements that have acutally been sent to the CPE
                # If we have a script element waiting for the session to enter into a state
                # where we can send it, we will no come here on any autonomous
                # CPE message lige TransferComplete...
                %{command: _command, from: from, state: :sent, id: generated_header_id} ->
                  # Check if the incomming message matches the one generated
                  # by the script system - this can be done by ID comparison

                  # Compare ID of incomming to ID of scripted message
                  if message.header.id == generated_header_id do
                    Logger.debug("Incomming message is meant for script")
                    GenServer.reply(from, message)

                    # We have nothing to reply with here, so we must stuff this in OutstandingPlug and
                    # wait for someting from the Script, either next message or :EXIT
                    # we have to answer :noreply here, and
                    {:noreply, nil, [], state.sspid}
                  else
                    Logger.debug(
                      "Incomming message is unmatched to script - we should reply somehow?"
                    )

                    # If this is a Response to a CPE request, then we have to end the session at once with
                    # a Fault.
                    # If on the other hand this is an arbitrary request from a CPE, stack it in the unmatched
                    # list and :reply with an appropriate response from here.

                    # Generate a response for every message in the envelope.
                    # TODO: Generate response for every message in entries and wrap
                    # it in one envelope. This can be done by using CMWP.Protocol.Generate.generate(req)
                    # directly, or expanding cwmp_ex to include the capacity to take a list of
                    # entries.
                    {reply, msg} = construct_reply(message)
                    {reply, state.script_element, msg, state.sspid}
                  end

                # In this case, then the incomming request can not be a response, and must
                # be stored into the junk list
                %{command: _command, from: _from, state: :unhandled} ->
                  {reply, msg} = construct_reply(message)

                  if state.sspid != nil and Process.alive?(state.sspid) do
                    Logger.debug("Script pid found to be alive")
                    {reply, state.script_element, msg, state.sspid}
                  else
                    Logger.debug("Script pid found to be dead")
                    {reply, nil, msg, nil}
                  end
              end
          end

        _ ->
          Logger.debug("Unknown message discovered - ignored")
          {state.plug_element, state.script_element, state.sspid}
      end

    Logger.debug(
      "process_message returning with #{inspect(plug)}, #{inspect(script)}, #{inspect(unmatched)} #{inspect(sspid)}"
    )

    case plug do
      :noreply ->
        {:noreply,
         %{
           state
           | plug_element: %{message: message, from: from, state: :waiting},
             unmatched_incomming_list: state.unmatched_incomming_list ++ unmatched,
             sspid: sspid
         }}

      _ ->
        {:reply, plug,
         %{
           state
           | script_element: script,
             unmatched_incomming_list: state.unmatched_incomming_list ++ unmatched,
             sspid: sspid
         }}
    end
  end

  # def handle_call(request,from,state) do
  #   super(request,from,state)
  # end

  def has_inform?([]), do: false
  def has_inform?([%CWMP.Protocol.Messages.Inform{} | _]), do: true
  def has_inform?([_ | es]), do: has_inform?(es)

  @doc """
  this is spawn_linked and should `apply` the call to the module
  """
  def session_prestart(gspid, script_module, device_id, message, sessionid, fun) do
    # Set the metadata for the scripting process
    Logger.metadata(sessionid: sessionid, serial: device_id.serial_number)

    case fun do
      nil ->
        case script_module do
          nil -> Logger.error("Impossible to start a session with no script module or function")
          spec_mod -> apply(spec_mod, :session_start, [gspid, device_id, message])
        end

      f when is_function(f) ->
        apply(fun, [gspid, device_id, message])

      _ ->
        Logger.error("Can not figure out how to call the session_start function")
    end
  end

  # PRIVATE METHODS

  defp via_tuple(session_id) do
    {:via, :gproc, {:n, :l, {:session_id, session_id}}}
  end

  defp construct_reply(message) do
    entry = hd(message.entries)

    id =
      cond do
        Map.has_key?(message, :header) && message.header != nil ->
          message.header.id

        true ->
          0
      end

    case message_type(entry) do
      {:cpe, _messagetype} ->
        # ...Response and that type
        # just respond with {} since responses should
        # be always "handled" here..
        {{204, ""}, [message]}

      {:acs, CWMP.Protocol.Messages.GetRPCMethods} ->
        {{200,
          CWMP.Protocol.Generator.generate!(
            %CWMP.Protocol.Messages.Header{id: id},
            %CWMP.Protocol.Messages.GetRPCMethodsResponse{
              methods: [
                "GetRPCMethods",
                "Inform",
                "TransferComplete",
                "AutonomousTransferComplete",
                "Kicked",
                "RequestDownload",
                "DUStateChangeComplete",
                "AutonomousDUStateChangeComplete"
              ]
            },
            message.cwmp_version
          )}, [message]}

      {:acs, CWMP.Protocol.Messages.TransferComplete} ->
        {{200,
          CWMP.Protocol.Generator.generate!(
            %CWMP.Protocol.Messages.Header{id: id},
            %CWMP.Protocol.Messages.TransferCompleteResponse{},
            message.cwmp_version
          )}, [message]}

      {:acs, CWMP.Protocol.Messages.AutonomousTransferComplete} ->
        {{200,
          CWMP.Protocol.Generator.generate!(
            %CWMP.Protocol.Messages.Header{id: id},
            %CWMP.Protocol.Messages.AutonomousTransferCompleteResponse{},
            message.cwmp_version
          )}, [message]}

      {:acs, CWMP.Protocol.Messages.Kicked} ->
        {{200,
          CWMP.Protocol.Generator.generate!(
            %CWMP.Protocol.Messages.Header{id: id},
            %CWMP.Protocol.Messages.KickedResponse{next_url: entry.next},
            message.cwmp_version
          )}, [message]}

      {:acs, CWMP.Protocol.Messages.RequestDownload} ->
        {{200,
          CWMP.Protocol.Generator.generate!(
            %CWMP.Protocol.Messages.Header{id: id},
            %CWMP.Protocol.Messages.RequestDownloadResponse{},
            message.cwmp_version
          )}, [message]}

      {:acs, CWMP.Protocol.Messages.DUStateChangeComplete} ->
        {{200,
          CWMP.Protocol.Generator.generate!(
            %CWMP.Protocol.Messages.Header{id: id},
            %CWMP.Protocol.Messages.DUStateChangeCompleteResponse{},
            message.cwmp_version
          )}, [message]}

      {:acs, CWMP.Protocol.Messages.AutonomousDUStateChangeComplete} ->
        {{200,
          CWMP.Protocol.Generator.generate!(
            %CWMP.Protocol.Messages.Header{id: id},
            %CWMP.Protocol.Messages.AutonomousDUStateChangeCompleteResponse{},
            message.cwmp_version
          )}, [message]}

      _ ->
        # unknown message type, what to do? - Fault back?
        {{204, ""}, [message]}
    end
  end

  defp message_type(entry) do
    case entry do
      %CWMP.Protocol.Messages.GetRPCMethods{} -> {:acs, entry.__struct__}
      %CWMP.Protocol.Messages.Inform{} -> {:acs, entry.__struct__}
      %CWMP.Protocol.Messages.TransferComplete{} -> {:acs, entry.__struct__}
      %CWMP.Protocol.Messages.AutonomousTransferComplete{} -> {:acs, entry.__struct__}
      %CWMP.Protocol.Messages.Kicked{} -> {:acs, entry.__struct__}
      %CWMP.Protocol.Messages.RequestDownload{} -> {:acs, entry.__struct__}
      %CWMP.Protocol.Messages.DUStateChangeComplete{} -> {:acs, entry.__struct__}
      %CWMP.Protocol.Messages.AutonomousDUStateChangeComplete{} -> {:acs, entry.__struct__}
      %CWMP.Protocol.Messages.SetParameterValuesResponse{} -> {:cpe, entry.__struct__}
      %CWMP.Protocol.Messages.GetParameterValuesResponse{} -> {:cpe, entry.__struct__}
      %CWMP.Protocol.Messages.GetParameterNamesResponse{} -> {:cpe, entry.__struct__}
      %CWMP.Protocol.Messages.SetParameterAttributesResponse{} -> {:cpe, entry.__struct__}
      %CWMP.Protocol.Messages.GetParameterAttributesResponse{} -> {:cpe, entry.__struct__}
      %CWMP.Protocol.Messages.AddObjectResponse{} -> {:cpe, entry.__struct__}
      %CWMP.Protocol.Messages.DeleteObjectResponse{} -> {:cpe, entry.__struct__}
      %CWMP.Protocol.Messages.DownloadResponse{} -> {:cpe, entry.__struct__}
      %CWMP.Protocol.Messages.RebootResponse{} -> {:cpe, entry.__struct__}
      %CWMP.Protocol.Messages.GetQueuedTransfersResponse{} -> {:cpe, entry.__struct__}
      %CWMP.Protocol.Messages.ScheduleInformResponse{} -> {:cpe, entry.__struct__}
      %CWMP.Protocol.Messages.SetVouchersResponse{} -> {:cpe, entry.__struct__}
      %CWMP.Protocol.Messages.GetOptionsResponse{} -> {:cpe, entry.__struct__}
      %CWMP.Protocol.Messages.UploadResponse{} -> {:cpe, entry.__struct__}
      %CWMP.Protocol.Messages.FactoryResetResponse{} -> {:cpe, entry.__struct__}
      %CWMP.Protocol.Messages.GetAllQueuedTransfersResponse{} -> {:cpe, entry.__struct__}
      %CWMP.Protocol.Messages.ScheduleDownloadResponse{} -> {:cpe, entry.__struct__}
      %CWMP.Protocol.Messages.CancelTransferResponse{} -> {:cpe, entry.__struct__}
      %CWMP.Protocol.Messages.ChangeDUStateResponse{} -> {:cpe, entry.__struct__}
      %CWMP.Protocol.Messages.Fault{} -> {:cpe, entry.__struct__}
      _ -> {:unknown, entry.__struct__}
    end
  end

  # interpret queue data, transform to appropriate CWMP.Protocol.Messages. struct and
  # ask CWMP.Protocol to generate
  defp gen_request(method, args, _source, cwmp_version) do
    Logger.debug("gen_request: #{method}")

    case validateArgs(method, args) do
      true ->
        id = generateID()
        header = %CWMP.Protocol.Messages.Header{id: id}

        message =
          case method do
            "GetRPCMethods" ->
              CWMP.Protocol.Generator.generate!(
                header,
                %CWMP.Protocol.Messages.GetRPCMethods{},
                cwmp_version
              )

            "SetParameterValues" ->
              params =
                for a <- args,
                    do: %CWMP.Protocol.Messages.ParameterValueStruct{
                      name: a.name,
                      type: a.type,
                      value: a.value
                    }

              CWMP.Protocol.Generator.generate!(
                header,
                %CWMP.Protocol.Messages.SetParameterValues{parameters: params},
                cwmp_version
              )

            "GetParameterValues" ->
              params =
                for a <- args,
                    do: %CWMP.Protocol.Messages.GetParameterValuesStruct{name: a, type: "string"}

              CWMP.Protocol.Generator.generate!(
                header,
                %CWMP.Protocol.Messages.GetParameterValues{parameters: params},
                cwmp_version
              )

            "GetParameterNames" ->
              params = %CWMP.Protocol.Messages.GetParameterNames{
                parameter_path: args.parameter_path,
                next_level: args.next_level
              }

              CWMP.Protocol.Generator.generate!(header, params, cwmp_version)

            "SetParameterAttributes" ->
              params =
                for a <- args,
                    do: %CWMP.Protocol.Messages.SetParameterAttributesStruct{
                      name: a.name,
                      notification_change: a.notification_change,
                      notification: a.notification,
                      accesslist_change: a.accesslist_change,
                      accesslist: a.accesslist
                    }

              CWMP.Protocol.Generator.generate!(
                header,
                %CWMP.Protocol.Messages.SetParameterAttributes{parameters: params},
                cwmp_version
              )

            "GetParameterAttributes" ->
              CWMP.Protocol.Generator.generate!(
                header,
                %CWMP.Protocol.Messages.GetParameterAttributes{parameters: args},
                cwmp_version
              )

            "AddObject" ->
              CWMP.Protocol.Generator.generate!(
                header,
                struct(CWMP.Protocol.Messages.AddObject, args),
                cwmp_version
              )

            "DeleteObject" ->
              CWMP.Protocol.Generator.generate!(
                header,
                struct(CWMP.Protocol.Messages.DeleteObject, args),
                cwmp_version
              )

            "Reboot" ->
              CWMP.Protocol.Generator.generate!(
                header,
                %CWMP.Protocol.Messages.Reboot{},
                cwmp_version
              )

            "Download" ->
              CWMP.Protocol.Generator.generate!(
                header,
                struct(CWMP.Protocol.Messages.Download, args),
                cwmp_version
              )

            "GetQueuedTransfers" ->
              CWMP.Protocol.Generator.generate!(
                header,
                %CWMP.Protocol.Messages.GetQueuedTransfers{},
                cwmp_version
              )

            "ScheduleInform" ->
              CWMP.Protocol.Generator.generate!(
                header,
                struct(CWMP.Protocol.Messages.ScheduleInform, args),
                cwmp_version
              )

            "SetVouchers" ->
              voucherlist =
                for xmlsig <- args, do: struct(CWMP.Protocol.Messages.XMLSignatureStruct, xmlsig)

              CWMP.Protocol.Generator.generate!(
                header,
                %CWMP.Protocol.Messages.SetVouchers{voucherlist: voucherlist},
                cwmp_version
              )

            "GetOptions" ->
              CWMP.Protocol.Generator.generate!(
                header,
                %CWMP.Protocol.Messages.GetOptions{option_name: args},
                cwmp_version
              )

            "Upload" ->
              CWMP.Protocol.Generator.generate!(
                header,
                struct(CWMP.Protocol.Messages.Upload, args),
                cwmp_version
              )

            "FactoryReset" ->
              CWMP.Protocol.Generator.generate!(
                header,
                %CWMP.Protocol.Messages.FactoryReset{},
                cwmp_version
              )

            "GetAllQueuedTransfers" ->
              CWMP.Protocol.Generator.generate!(
                header,
                %CWMP.Protocol.Messages.GetAllQueuedTransfers{},
                cwmp_version
              )

            "ScheduleDownload" ->
              CWMP.Protocol.Generator.generate!(
                header,
                struct(CWMP.Protocol.Messages.ScheduleDownload, args),
                cwmp_version
              )

            "CancelTransfer" ->
              CWMP.Protocol.Generator.generate!(
                header,
                %CWMP.Protocol.Messages.CancelTransfer{commandkey: args},
                cwmp_version
              )

            "ChangeDUState" ->
              CWMP.Protocol.Generator.generate!(
                header,
                struct(CWMP.Protocol.Messages.ChangeDUState, args),
                cwmp_version
              )

            _ ->
              {:error, "Cant match request method: #{method}"}
          end

        {:ok, {id, message}}

      false ->
        {:error, "arguments for request #{method} do not validate"}
    end
  end

  defp validateArgs(method, args) do
    case method do
      "GetRPCMethods" ->
        # No args for this one
        true

      "SetParameterValues" ->
        # args must be list of maps with name,type and value keys
        case args do
          l when is_list(l) and length(l) > 0 ->
            Enum.all?(args, fn a ->
              Map.has_key?(a, :name) && Map.has_key?(a, :type) && Map.has_key?(a, :value)
            end)

          _ ->
            false
        end

      "GetParameterValues" ->
        # args must be map with name and type key in all elements
        case args do
          l when is_list(l) and length(l) > 0 ->
            Enum.all?(args, fn a -> String.valid?(a) end)

          _ ->
            false
        end

      "GetParameterNames" ->
        # args must be map with path and next_level keys
        is_map(args) and Map.has_key?(args, :parameter_path) and Map.has_key?(args, :next_level)

      "SetParameterAttributes" ->
        # args must be map with path and next_level keys
        case args do
          l when is_list(l) and length(l) > 0 ->
            Enum.all?(args, fn a ->
              Map.has_key?(a, :name) and Map.has_key?(a, :notification_change) and
                Map.has_key?(a, :notification) and Map.has_key?(a, :accesslist_change) and
                Map.has_key?(a, :accesslist) and is_list(a.accesslist)
            end)

          _ ->
            false
        end

      "GetParameterAttributes" ->
        # args must be list of string, at least 1 element in list
        is_list(args) and length(args) > 0 and String.valid?(hd(args))

      "AddObject" ->
        # args must be map with at least key "object_name" and value must end in .
        if is_map(args) and Map.has_key?(args, :object_name) do
          String.last(args.object_name) == "."
        else
          false
        end

      "DeleteObject" ->
        # args must be map with at least key "object_name" and value must end in .
        if is_map(args) and Map.has_key?(args, :object_name) do
          String.last(args.object_name) == "."
        else
          false
        end

      "Reboot" ->
        # takes no params, always true
        true

      "Download" ->
        is_map(args) and Map.has_key?(args, :url) and Map.has_key?(args, :filesize) and
          Map.has_key?(args, :filetype)

      "GetQueuedTransfers" ->
        # takes no params, always true
        true

      "ScheduleInform" ->
        # args is a map with "commandkey" and "delay_seconds"
        if is_map(args) and Map.has_key?(args, :commandkey) and Map.has_key?(args, :delay_seconds) do
          if is_integer(args.delay_seconds) do
            true
          else
            Integer.parse(args.delay_seconds) != :error
          end
        else
          false
        end

      "SetVouchers" ->
        # args is a list of maps with keys
        #  signature_value:
        #  key_info
        #    key_value
        #      dsa_p
        #      dsa_q
        #      dsa_g
        #      dsa_y
        #    x509_data
        #      issuer_serial
        #        issuer_name
        #        serial_number
        #     subject_name
        #     certificates []
        #  options, list of maps with
        #    v_serial_num
        #    deviceid
        #      manufacturer
        #      oui
        #      product_class
        #      serial_number
        #    option_ident
        #    option_desc
        #    start_date (Timex.DateTime)
        #    duration
        #    duration_units
        #    mode
        #    sha1_digest
        if is_list(args) do
          Enum.all?(args, fn a ->
            if Map.has_key?(a, :signature_value) and Map.has_key?(a, :key_info) and
                 Map.has_key?(a, :options) do
              Logger.debug("step1")

              if is_list(a.options) and length(a.options) > 0 and
                   Map.has_key?(a.key_info, :key_value) and Map.has_key?(a.key_info, :x509_data) do
                Logger.debug("step2")

                if Map.has_key?(a.key_info.key_value, :dsa_p) and
                     Map.has_key?(a.key_info.key_value, :dsa_q) and
                     Map.has_key?(a.key_info.key_value, :dsa_g) and
                     Map.has_key?(a.key_info.key_value, :dsa_y) do
                  Logger.debug("step3")

                  if Map.has_key?(a.key_info.x509_data, :issuer_serial) and
                       Map.has_key?(a.key_info.x509_data, :subject_name) and
                       Map.has_key?(a.key_info.x509_data, :certificates) and
                       is_list(a.key_info.x509_data.certificates) and
                       Map.has_key?(a.key_info.x509_data.issuer_serial, :issuer_name) and
                       Map.has_key?(a.key_info.x509_data.issuer_serial, :serial_number) do
                    Logger.debug("step4")
                    # check all the options
                    matching =
                      Enum.all?(a.options, fn o ->
                        Map.has_key?(o, :v_serial_num) and Map.has_key?(o, :deviceid) and
                          Map.has_key?(o, :option_ident) and Map.has_key?(o, :option_desc) and
                          Map.has_key?(o, :start_date) and Map.has_key?(o, :duration) and
                          Map.has_key?(o, :duration_units) and Map.has_key?(o, :mode) and
                          Map.has_key?(o, :sha1_digest) and
                          Map.has_key?(o.deviceid, :manufacturer) and
                          Map.has_key?(o.deviceid, :oui) and
                          Map.has_key?(o.deviceid, :product_class) and
                          Map.has_key?(o.deviceid, :serial_number)
                      end)

                    matching
                  else
                    false
                  end
                else
                  false
                end
              else
                false
              end
            else
              false
            end
          end)
        else
          false
        end

      "GetOptions" ->
        # args is just a string with the option name
        String.valid?(args)

      "Upload" ->
        # args must at least contain commandkey, url and filetype
        is_map(args) and Map.has_key?(args, :commandkey) and Map.has_key?(args, :url) and
          Map.has_key?(args, :filetype)

      "FactoryReset" ->
        # takes no params, always true
        true

      "GetAllQueuedTransfers" ->
        # takes no params, always true
        true

      "ScheduleDownload" ->
        if is_map(args) and Map.has_key?(args, :url) and Map.has_key?(args, :filesize) and
             Map.has_key?(args, :filetype) and Map.has_key?(args, :timewindowlist) and
             is_list(args.timewindowlist) and length(args.timewindowlist) > 0 do
          # Check that all elements of the timelist list conform
          Enum.all?(args.timewindowlist, fn tw ->
            is_map(tw) and Map.has_key?(tw, :window_start) and Map.has_key?(tw, :window_end) and
              Map.has_key?(tw, :window_mode) and Map.has_key?(tw, :max_retries)
          end)
        else
          false
        end

      "CancelTransfer" ->
        # args is just a string with the option name
        String.valid?(args)

      "ChangeDUState" ->
        if is_map(args) and Map.has_key?(args, :commandkey) and Map.has_key?(args, :operations) and
             is_list(args.operations) and length(args.operations) > 0 do
          # Check that all elements of the operations list conform
          Enum.all?(args.operations, fn o ->
            if is_map(o) do
              case o do
                %CWMP.Protocol.Messages.InstallOpStruct{} ->
                  Map.has_key?(o, :url) and Map.has_key?(o, :uuid) and Map.has_key?(o, :username) and
                    Map.has_key?(o, :password) and Map.has_key?(o, :execution_env_ref)

                %CWMP.Protocol.Messages.UpdateOpStruct{} ->
                  Map.has_key?(o, :url) and Map.has_key?(o, :uuid) and Map.has_key?(o, :username) and
                    Map.has_key?(o, :password) and Map.has_key?(o, :version)

                %CWMP.Protocol.Messages.UninstallOpStruct{} ->
                  Map.has_key?(o, :url) and Map.has_key?(o, :uuid) and
                    Map.has_key?(o, :execution_env_ref)
              end
            else
              false
            end
          end)
        else
          false
        end

      _ ->
        false
    end
  end

  defp generateID do
    Base.encode16(:erlang.md5(:crypto.strong_rand_bytes(32)), case: :lower)
  end
end