import cangaroo/bridge
import cangaroo/errors
import cangaroo/excansock
import cangaroo/internal
import cangaroo/types.{
  type ActorMessage, type CanClient, type CanFrame, type CanSocket,
}
import gleam/erlang/atom
import gleam/erlang/process
import gleam/otp/actor
import gleam/result

fn start() -> Result(CanSocket, errors.CanError) {
  let #(status, pid) = excansock.start_link()
  case atom.to_string(status) {
    "ok" -> Ok(types.new_socket(pid))
    other_msg -> Error(errors.StartLinkError(other_msg))
  }
}

fn open(socket: CanSocket, interface: String) -> Result(Nil, errors.CanError) {
  let raw = excansock.open(types.socket_pid(socket), interface, False)
  internal.decode_result(raw)
}

pub fn start_link(interface: String) -> Result(CanClient, errors.CanError) {
  let user_frames = process.new_subject()

  let actor_result =
    {
      actor.new_with_initialiser(5000, fn(self_subject) {
        let can_tag = atom.create("can_data_frame")

        let selector =
          process.new_selector()
          |> process.select(for: self_subject)
          |> process.select_record(
            tag: can_tag,
            fields: 1,
            mapping: types.RawCanData,
          )

        use socket <- result.try(start() |> result.map_error(error_to_string))

        use _ <- result.try(
          open(socket, interface) |> result.map_error(error_to_string),
        )

        let client = types.new_client(socket, user_frames, self_subject)

        actor.initialised(client)
        |> actor.selecting(selector)
        |> actor.returning(client)
        |> Ok
      })
    }
    |> actor.on_message(handle_message)
    |> actor.start()

  case actor_result {
    Ok(started) -> Ok(started.data)
    Error(actor.InitFailed(reason)) -> Error(errors.StartLinkError(reason))
    Error(actor.InitExited(_)) -> Error(errors.StartLinkError("exited"))
    Error(actor.InitTimeout) -> Error(errors.StartLinkError("timeout"))
  }
}

fn error_to_string(err: errors.CanError) -> String {
  case err {
    errors.StartLinkError(reason) -> reason
    errors.InterfaceBoundError(interface) -> "interface_bound:" <> interface
    errors.UnknownError(reason) -> reason
    errors.InvalidMessageTypeError -> "invalid_message_type"
  }
}

fn handle_message(
  client: CanClient,
  msg: ActorMessage,
) -> actor.Next(CanClient, ActorMessage) {
  case msg {
    types.RawCanData(raw_data) -> {
      let frame = bridge.unwrap_frame(raw_data)
      let id = bridge.get_id(frame)
      let data = bridge.get_data(frame)
      let gleam_frame = types.CanFrame(id:, data:)
      process.send(types.messages(client), gleam_frame)
      actor.continue(client)
    }
    types.Shutdown -> {
      let socket = types.client_socket(client)
      let _ = excansock.close(types.socket_pid(socket))
      let _ = excansock.stop(types.socket_pid(socket))
      actor.stop()
    }
  }
}

pub fn close(client: CanClient) -> Nil {
  process.send(types.client_actor_subject(client), types.Shutdown)
  Nil
}

pub fn send(client: CanClient, frame: CanFrame) -> Result(Nil, errors.CanError) {
  let types.CanFrame(id:, data:) = frame
  let elixir_frame = bridge.new_frame(id, data)
  let socket = types.client_socket(client)
  let status = excansock.send(types.socket_pid(socket), elixir_frame)
  internal.check_status(status)
}

pub fn set_loopback(
  client: CanClient,
  value: Bool,
) -> Result(Nil, errors.CanError) {
  let socket = types.client_socket(client)
  let status = excansock.set_loopback(types.socket_pid(socket), value)
  internal.check_status(status)
}

pub fn recv_own_messages(
  client: CanClient,
  value: Bool,
) -> Result(Nil, errors.CanError) {
  let socket = types.client_socket(client)
  let status = excansock.recv_own_messages(types.socket_pid(socket), value)
  internal.check_status(status)
}

pub fn set_filters(
  client: CanClient,
  filters: List(types.CanFilter),
) -> Result(Nil, errors.CanError) {
  let socket = types.client_socket(client)
  let status = excansock.set_filters(types.socket_pid(socket), filters)
  internal.check_status(status)
}

pub fn set_error_filter(
  client: CanClient,
  filter: Int,
) -> Result(Nil, errors.CanError) {
  let socket = types.client_socket(client)
  let status = excansock.set_error_filter(types.socket_pid(socket), filter)
  internal.check_status(status)
}