LogicSubscriber

async def start(self) -> None:
    """Create NATS subscription and start consume tasks."""
    await super().start()

    if self.calls:
        await self._create_subscription()

    self._post_start()

async def stop(self) -> None:
    """Clean up handler subscription, cancel consume task in graceful mode."""
    await super().stop()

    if self.subscription is not None:
        await self.subscription.unsubscribe()
        self.subscription = None

    if self._fetch_sub is not None:
        await self._fetch_sub.unsubscribe()
        self._fetch_sub = None

@staticmethod
def build_log_context(
    message: Optional["StreamMessage[MsgType]"],
    subject: str,
    *,
    queue: str = "",
    stream: str = "",
) -> dict[str, str]:
    """Static method to build log context out of `self.consume` scope."""
    return {
        "subject": subject,
        "queue": queue,
        "stream": stream,
        "message_id": getattr(message, "message_id", ""),
    }

def add_call(
    self,
    *,
    parser_: Optional["CustomCallable"],
    decoder_: Optional["CustomCallable"],
    dependencies_: Sequence["Dependant"],
    codec_: Optional["CodecProto"] = None,
) -> Self:
    self._call_options = _CallOptions(
        parser=parser_,
        decoder=decoder_,
        dependencies=dependencies_,
        codec=codec_,
    )
    return self

async def consume(self, msg: MsgType) -> Any:
    """Consume a message asynchronously."""
    if not self.running:
        return None

    try:
        return await self.process_message(msg)

    except StopConsume:
        # Stop handler at StopConsume exception
        await self.stop()

    except SystemExit:
        # Stop handler at `exit()` call
        await self.stop()

        if app := self._outer_config.context.get("app"):
            app.exit()

    except Exception:  # nosec B110  # ruff: ignore[try-except-pass]
        # All other exceptions were logged by CriticalLogMiddleware
        pass

async def process_message(self, msg: MsgType) -> "Response":
    """Execute all message processing stages."""
    context = self._outer_config.context
    logger_state = self._outer_config.logger

    async with AsyncExitStack() as stack:
        stack.enter_context(self.lock)

        # Enter context before middlewares
        stack.enter_context(
            context.scopes(
                (
                    ("handler_", self),
                    ("logger", logger_state.logger.logger),
                    *self._outer_config.extra_context.items(),
                ),
            ),
        )

        # reserve place for context scope under the middlewares __aexit__
        # because middlewares should be exited before context scope release
        message_scope = stack.enter_context(ExitStack())

        # enter all middlewares
        middlewares: list[BaseMiddleware] = []
        for base_m in self.__build__middlewares_stack():
            middleware = base_m(msg, context=context)
            middlewares.append(middleware)
            await stack.enter_async_context(middleware)

        cache: dict[Any, Any] = {}
        parsing_error: Exception | None = None
        for h in self.calls:
            try:
                message = await h.is_suitable(msg, cache)
            except Exception as e:
                parsing_error = e
                break

            if message is not None:
                message_scope.enter_context(
                    context.scopes(
                        (
                            ("log_context", self.get_log_context(message)),
                            ("message", message),
                        ),
                    ),
                )

                result_msg = ensure_response(
                    await h.call(
                        message=message,
                        # consumer middlewares
                        _extra_middlewares=(
                            m.consume_scope for m in middlewares[::-1]
                        ),
                    ),
                )

                if not result_msg.correlation_id:
                    result_msg.correlation_id = message.correlation_id

                for p in chain(
                    self.__get_response_publisher(message),
                    h.handler._publishers,
                ):
                    await p._publish(
                        result_msg.as_publish_command(),
                        _extra_middlewares=(
                            m.publish_scope for m in middlewares[::-1]
                        ),
                    )

                # Return data for tests
                return result_msg

        # Suitable handler was not found or
        # parsing/decoding exception occurred.
        # Reraise it to catch in tests
        if parsing_error:
            raise parsing_error

        error_msg = f"There is no suitable handler for {msg=}"
        raise SubscriberNotFound(error_msg)

    # An error was raised and processed by some middleware
    return ensure_response(None)

@abstractmethod
async def get_one(self, *, timeout: float = 5) -> Optional["StreamMessage[MsgType]"]:
    raise NotImplementedError

def get_log_context(  # ruff: ignore[no-self-use]
    self,
    message: Optional["StreamMessage[MsgType]"],
) -> dict[str, str]:
    """Generate log context."""
    return {
        "message_id": getattr(message, "message_id", ""),
    }

def schema(self) -> dict[str, "SubscriberSpec"]:
    self._build_fastdepends_model()
    return self.specification.get_schema()