bacstack

defmodule BACnet.Protocol.Services.GetEventInformation do
  @moduledoc """
  This module represents the BACnet Get Event Information service.

  The Get Event Information service is used to get a list of active event states from a device.
  Active event states refers to all abnormal events of event-initiating objects.

  Service Description (ASHRAE 135):
  > The GetEventInformation service is used by a client BACnet-user to obtain a summary of all "active event states". The term
  > "active event states" refers to all event-initiating objects that
  >   (a) have an Event_State property whose value is not equal to NORMAL, or
  >   (b) have an Acked_Transitions property, which has at least one of the bits (TO_OFFNORMAL, TO_FAULT, TO_NORMAL) set to FALSE.
  > This service is intended to be implemented in all devices that generate event notifications.
  """

  alias BACnet.Protocol
  alias BACnet.Protocol.ApplicationTags
  alias BACnet.Protocol.Constants

  import Protocol.Utility, only: [pattern_extract_tags: 4]
  require Constants

  @behaviour Protocol.Services.Behaviour

  # TODO: Docs
  # TODO: Add Service Procedure to docs

  @type t :: %__MODULE__{
          last_received_object_identifier: Protocol.ObjectIdentifier.t() | nil
        }

  @fields [
    :last_received_object_identifier
  ]
  @enforce_keys @fields
  defstruct @fields

  @service_name Constants.macro_assert_name(
                  :confirmed_service_choice,
                  :get_event_information
                )

  @doc """
  Get the service name atom.
  """
  @spec get_name() :: atom()
  def get_name(), do: @service_name

  @doc """
  Whether the service is of type confirmed or unconfirmed.
  """
  @spec is_confirmed() :: true
  def is_confirmed(), do: true

  @doc """
  Converts the given Confirmed Service Request into a Get Event Information Service.
  """
  @spec from_apdu(Protocol.APDU.ConfirmedServiceRequest.t()) ::
          {:ok, t()} | {:error, term()}
  def from_apdu(
        %Protocol.APDU.ConfirmedServiceRequest{
          service: @service_name
        } = request
      ) do
    with {:ok, last_received_object_identifier, _rest} <-
           pattern_extract_tags(
             request.parameters,
             {:tagged, {0, _t, _l}},
             :object_identifier,
             true
           ) do
      event = %__MODULE__{
        last_received_object_identifier: last_received_object_identifier
      }

      {:ok, event}
    else
      {:error, :missing_pattern} -> {:error, :invalid_request_parameters}
      {:error, _err} = err -> err
    end
  end

  def from_apdu(%Protocol.APDU.ConfirmedServiceRequest{} = _request) do
    {:error, :invalid_request}
  end

  @doc """
  Get the Confirmed Service request for the given Get Event Information Service.

  See the `BACnet.Protocol.Services.Protocol` function documentation for more information.
  """
  @spec to_apdu(t(), Keyword.t()) ::
          {:ok, Protocol.APDU.ConfirmedServiceRequest.t()}
          | {:error, term()}
  def to_apdu(%__MODULE__{} = service, request_data) do
    with {:ok, parameters} <-
           (case service.last_received_object_identifier do
              nil ->
                {:ok, []}

              _term ->
                with {:ok, bytes, _header} <-
                       ApplicationTags.encode_value(
                         {:object_identifier, service.last_received_object_identifier}
                       ) do
                  {:ok, [{:tagged, {0, bytes, byte_size(bytes)}}]}
                end
            end) do
      req = %Protocol.APDU.ConfirmedServiceRequest{
        segmented_response_accepted: request_data[:segmented_response_accepted] || true,
        max_segments: request_data[:max_segments] || :more_than_64,
        max_apdu:
          request_data[:max_apdu] ||
            Constants.macro_by_name(:max_apdu_length_accepted_value, :octets_1476),
        invoke_id: request_data[:invoke_id] || 0,
        sequence_number: nil,
        proposed_window_size: nil,
        service: @service_name,
        parameters: parameters
      }

      {:ok, req}
    end
  end

  defimpl Protocol.Services.Protocol do
    alias BACnet.Protocol
    alias BACnet.Protocol.Constants
    require Constants

    @spec get_name(@for.t()) :: atom()
    def get_name(%@for{} = _service), do: @for.get_name()

    @spec is_confirmed(@for.t()) :: boolean()
    def is_confirmed(%@for{} = _service), do: @for.is_confirmed()

    @spec to_apdu(@for.t(), Keyword.t()) ::
            {:ok, Protocol.APDU.ConfirmedServiceRequest.t()}
            | {:error, term()}
    def to_apdu(%@for{} = service, request_data), do: @for.to_apdu(service, request_data)
  end
end