Rewritten `serial` plugin.

`backend.serial` has been removed and the polling logic merged into the
`serial` plugin.

The `serial` plugin now supports the new entity engine as well.

platypush/backend/sensor/serial/__init__.py

@@ -1,27 +0,0 @@
-from platypush.backend.sensor import SensorBackend
-
-
-class SensorSerialBackend(SensorBackend):
-    """
-    This backend listens for new events from sensors connected through a serial
-    interface (like Arduino) acting as a wrapper for the ``serial`` plugin.
-
-    Requires:
-
-        * The :mod:`platypush.plugins.serial` plugin configured
-
-    Triggers:
-
-        * :class:`platypush.message.event.sensor.SensorDataChangeEvent` if the measurements of a sensor have changed
-        * :class:`platypush.message.event.sensor.SensorDataAboveThresholdEvent` if the measurements of a sensor have
-            gone above a configured threshold
-        * :class:`platypush.message.event.sensor.SensorDataBelowThresholdEvent` if the measurements of a sensor have
-            gone below a configured threshold
-
-    """
-
-    def __init__(self, **kwargs):
-        super().__init__(plugin='serial', **kwargs)
-
-
-# vim:sw=4:ts=4:et:

platypush/backend/sensor/serial/manifest.yaml

@@ -1,12 +0,0 @@
-manifest:
-  events:
-    platypush.message.event.sensor.SensorDataAboveThresholdEvent: if the measurements
-      of a sensor havegone above a configured threshold
-    platypush.message.event.sensor.SensorDataBelowThresholdEvent: if the measurements
-      of a sensor havegone below a configured threshold
-    platypush.message.event.sensor.SensorDataChangeEvent: if the measurements of a
-      sensor have changed
-  install:
-    pip: []
-  package: platypush.backend.sensor.serial
-  type: backend

platypush/plugins/serial/__init__.py

@@ -1,47 +1,137 @@
 import base64
+from collections import namedtuple
+from collections.abc import Collection
 import json
-import serial
+from typing import Any, List, Optional, Tuple, Union
 import threading
-import time
+from typing_extensions import override
 
-from platypush.plugins import action
+from serial import Serial
-from platypush.plugins.sensor import SensorPlugin
+
+from platypush.context import get_bus
+from platypush.entities.devices import Device
+from platypush.entities.sensors import RawSensor, NumericSensor
+from platypush.entities.managers.sensors import SensorEntityManager
+from platypush.message.event.sensor import SensorDataChangeEvent
+from platypush.plugins import RunnablePlugin, action
+from platypush.utils import get_lock, get_plugin_name_by_class
+
+_DeviceAndRate = namedtuple('_DeviceAndRate', ['device', 'baud_rate'])
 
 
-class SerialPlugin(SensorPlugin):
+class SerialPlugin(RunnablePlugin, SensorEntityManager):
     """
-    The serial plugin can read data from a serial device, as long as the serial
+    The serial plugin can read data from a serial device.
-    device returns a JSON. You can use this plugin to interact for example with
+
-    some sensors connected through an Arduino. Just make sure that the code on
+    If the device returns a JSON string, then that string will be parsed for
-    your serial device returns JSON values. If you're using an Arduino or any
+    individual values. For example:
-    ATMega compatible device, take a look at
+
-    https://github.com/bblanchon/ArduinoJson.
+        .. code-block:: json
+
+            {"temperature": 25.0, "humidity": 15.0}
+
+    If the serial device returns such a value, then ``temperature`` and
+    ``humidity`` will be parsed as separate entities with the same names as the
+    keys provided on the payload.
+
+    The JSON option is a good choice if you have an Arduino/ESP-like device
+    whose code you can control, as it allows to easily send data to Platypush
+    in a simple key-value format. The use-case would be that of an Arduino/ESP
+    device that pushes data on the wire, and this integration would then listen
+    for updates.
+
+    Alternatively, you can also use this integration in a more traditional way
+    through the :meth:`.read` and :meth:`.write` methods to read and write data
+    to the device. In such a case, you may want to disable the "smart polling"
+    by setting ``enable_polling`` to ``False`` in the configuration.
+
+    If you want an out-of-the-box solution with a Firmata-compatible firmware,
+    you may consider using the :class:`platypush.plugin.arduino.ArduinoPlugin`
+    instead.
+
+    Note that device paths on Linux may be subject to change. If you want to
+    create static naming associations for your devices (e.g. make sure that
+    your Arduino will always be symlinked to ``/dev/arduino`` instead of
+    ``/dev/ttyUSB<n>``), you may consider creating `static mappings through
+    udev
+    <https://dev.to/enbis/how-udev-rules-can-help-us-to-recognize-a-usb-to-serial-device-over-dev-tty-interface-pbk>`_.
+
+    Requires:
+
+        * **pyserial** (``pip install pyserial``)
+
+    Triggers:
+
+        * :class:`platypush.message.event.sensor.SensorDataChangeEvent`
+
     """
 
-    def __init__(self, device=None, baud_rate=9600, **kwargs):
+    _default_lock_timeout: float = 2.0
+
+    def __init__(
+        self,
+        device: Optional[str] = None,
+        baud_rate: int = 9600,
+        max_size: int = 1 << 19,
+        timeout: float = _default_lock_timeout,
+        enable_polling: bool = True,
+        **kwargs,
+    ):
         """
         :param device: Device path (e.g. ``/dev/ttyUSB0`` or ``/dev/ttyACM0``)
-        :type device: str
-
         :param baud_rate: Serial baud rate (default: 9600)
-        :type baud_rate: int
+        :param max_size: Maximum size of a JSON payload (default: 512 KB). The
+            plugin will keep reading bytes from the wire until it can form a
+            valid JSON payload, so this upper limit is required to prevent the
+            integration from listening forever and dumping garbage in memory.
+        :param timeout: This integration will ensure that only one
+            reader/writer can access the serial device at the time, in order to
+            prevent mixing up bytes in the response. This value specifies how
+            long we should wait for a pending action to terminate when we try
+            to run a new action. Default: 2 seconds.
+        :param enable_polling: If ``False``, the plugin will not poll the
+            device for updates. This can be the case if you want to
+            programmatically interface with the device via the :meth:`.read`
+            and :meth:`.write` methods instead of polling for updates in JSON
+            format.
         """
-
         super().__init__(**kwargs)
 
         self.device = device
         self.baud_rate = baud_rate
         self.serial = None
-        self.serial_lock = threading.Lock()
+        self.serial_lock = threading.RLock()
-        self.last_measurement = None
+        self.last_data: dict = {}
+        self._max_size = max_size
+        self._timeout = timeout
+        self._enable_polling = enable_polling
 
-    def _read_json(self, serial_port):
+    def _read_json(
+        self,
+        serial_port: Serial,
+        max_size: Optional[int] = None,
+    ) -> str:
+        """
+        Reads a JSON payload from the wire. It counts the number of curly
+        brackets detected, ignoring everything before the first curly bracket,
+        and it stops when the processed payload has balanced curly brackets -
+        i.e. it can be mapped to JSON.
+
+        :param serial_port: Serial connection.
+        :param max_size: Default ``max_size`` override.
+        """
         n_brackets = 0
         is_escaped_ch = False
         parse_start = False
         output = bytes()
+        max_size = max_size or self._max_size
 
         while True:
+            assert len(output) <= max_size, (
+                'Maximum allowed size exceeded while reading from the device: '
+                f'read {len(output)} bytes'
+            )
+
             ch = serial_port.read()
             if not ch:
                 break
@@ -70,15 +160,27 @@ class SerialPlugin(SensorPlugin):
 
         return output.decode().strip()
 
-    def _get_serial(self, device=None, baud_rate=None, reset=False):
+    def __get_serial(
+        self,
+        device: Optional[str] = None,
+        baud_rate: Optional[int] = None,
+        reset: bool = False,
+    ) -> Serial:
+        """
+        Return a ``Serial`` connection object to the given device.
+
+        :param device: Default device path override.
+        :param baud_rate: Default baud rate override.
+        :param reset: By default, if a connection to the device is already open
+            then the current object will be returned. If ``reset=True``, the
+            connection will be reset and a new one will be created instead.
+        """
         if not device:
-            if not self.device:
+            assert self.device, 'No device specified nor default device configured'
-                raise RuntimeError('No device specified nor default device configured')
             device = self.device
 
         if baud_rate is None:
-            if self.baud_rate is None:
+            assert self.baud_rate, 'No baud_rate specified nor default configured'
-                raise RuntimeError('No baud_rate specified nor default configured')
             baud_rate = self.baud_rate
 
         if self.serial:
@@ -87,192 +189,284 @@ class SerialPlugin(SensorPlugin):
 
             self._close_serial()
 
-        self.serial = serial.Serial(device, baud_rate)
+        self.serial = Serial(device, baud_rate)
         return self.serial
 
+    def _get_serial(
+        self,
+        device: Optional[str] = None,
+        baud_rate: Optional[int] = None,
+    ) -> Serial:
+        """
+        Return a ``Serial`` connection object to the given device.
+
+        :param device: Default device path override.
+        :param baud_rate: Default baud rate override.
+        :param reset: By default, if a connection to the device is already open
+            then the current object will be returned. If ``reset=True``, the
+            connection will be reset and a new one will be created instead.
+        """
+        try:
+            return self.__get_serial(device, baud_rate)
+        except AssertionError as e:
+            raise e
+        except Exception as e:
+            self.logger.debug(e)
+            self.wait_stop(1)
+            return self.__get_serial(device=device, baud_rate=baud_rate, reset=True)
+
     def _close_serial(self):
+        """
+        Close the serial connection if it's currently open.
+        """
         if self.serial:
             try:
                 self.serial.close()
-                self.serial = None
             except Exception as e:
-                self.logger.warning('Error while closing serial communication: {}')
+                self.logger.warning('Error while closing serial communication: %s', e)
                 self.logger.exception(e)
 
-    @action
+            self.serial = None
-    def get_measurement(self, device=None, baud_rate=None):
+
+    def _get_device_and_baud_rate(
+        self, device: Optional[str] = None, baud_rate: Optional[int] = None
+    ) -> _DeviceAndRate:
         """
-        Reads JSON data from the serial device and returns it as a message
+        Gets the device path and baud rate from the given device and baud rate
+        if set, or it falls back on the default configured ones.
 
-        :param device: Device path (default: default configured device)
+        :raise AssertionError: If neither ``device`` nor ``baud_rate`` is set
-        :type device: str
+            nor configured.
-
-        :param baud_rate: Baud rate (default: default configured baud_rate)
-        :type baud_rate: int
         """
 
         if not device:
-            if not self.device:
+            assert (
-                raise RuntimeError('No device specified nor default device configured')
+                self.device
+            ), 'No device specified and a default one is not configured'
             device = self.device
 
         if baud_rate is None:
-            if self.baud_rate is None:
+            assert (
-                raise RuntimeError('No baud_rate specified nor default configured')
+                self.baud_rate is not None
+            ), 'No baud_rate specified nor a default value is configured'
             baud_rate = self.baud_rate
 
+        return _DeviceAndRate(device, baud_rate)
+
+    @override
+    @action
+    def status(
+        self,
+        *_,
+        device: Optional[str] = None,
+        baud_rate: Optional[int] = None,
+        publish_entities: bool = True,
+        **__,
+    ) -> dict:
+        """
+        Reads JSON data from the serial device and returns it as a message
+
+        :param device: Device path (default: default configured device).
+        :param baud_rate: Baud rate (default: default configured baud_rate).
+        :param publish_entities: Whether to publish an event with the newly
+            read values (default: True).
+        """
+
+        device, baud_rate = self._get_device_and_baud_rate(device, baud_rate)
         data = None
 
-        try:
+        with get_lock(self.serial_lock, timeout=self._timeout) as serial_available:
-            serial_available = self.serial_lock.acquire(timeout=2)
             if serial_available:
-                try:
+                ser = self._get_serial(device=device, baud_rate=baud_rate)
-                    ser = self._get_serial(device=device, baud_rate=baud_rate)
-                except Exception as e:
-                    self.logger.debug(e)
-                    time.sleep(1)
-                    ser = self._get_serial(device=device, baud_rate=baud_rate, reset=True)
-
                 data = self._read_json(ser)
 
                 try:
-                    data = json.loads(data)
+                    data = dict(json.loads(data))
-                except (ValueError, TypeError):
+                except (ValueError, TypeError) as e:
-                    self.logger.warning('Invalid JSON message from {}: {}'.format(self.device, data))
+                    raise AssertionError(
+                        f'Invalid JSON message from {device}: {e}. Message: {data}'
+                    ) from e
             else:
-                data = self.last_measurement
+                data = self.last_data
-        finally:
-            try:
-                self.serial_lock.release()
-            except Exception as e:
-                self.logger.debug(e)
 
         if data:
-            self.last_measurement = data
+            self.last_data = data
+
+        if publish_entities:
+            self.publish_entities(self.last_data.items())
 
         return data
 
     @action
-    def read(self, device=None, baud_rate=None, size=None, end=None):
+    def get_measurement(
+        self, device: Optional[str] = None, baud_rate: Optional[int] = None
+    ):
+        """
+        (Deprecated) alias for :meth:`.status`.
+        """
+        return self.status(device, baud_rate)
+
+    @action
+    def read(
+        self,
+        device: Optional[str] = None,
+        baud_rate: Optional[int] = None,
+        size: Optional[int] = None,
+        end: Optional[Union[int, str]] = None,
+    ) -> str:
         """
         Reads raw data from the serial device
 
         :param device: Device to read (default: default configured device)
-        :type device: str
-
         :param baud_rate: Baud rate (default: default configured baud_rate)
-        :type baud_rate: int
-
         :param size: Number of bytes to read
-        :type size: int
+        :param end: End of message, as a character or bytecode
-
+        :return: The read message as a string if it's a valid UTF-8 string,
-        :param end: End of message byte or character
+            otherwise as a base64-encoded string.
-        :type end: int, bytes or str
         """
 
-        if not device:
+        device, baud_rate = self._get_device_and_baud_rate(device, baud_rate)
-            if not self.device:
+        assert not (
-                raise RuntimeError('No device specified nor default device configured')
+            (size is None and end is None) or (size is not None and end is not None)
-            device = self.device
+        ), 'Either size or end must be specified'
 
-        if baud_rate is None:
+        assert not (
-            if self.baud_rate is None:
+            end and isinstance(end, str) and len(end) > 1
-                raise RuntimeError('No baud_rate specified nor default configured')
+        ), 'The serial end must be a single character, not a string'
-            baud_rate = self.baud_rate
-
-        if (size is None and end is None) or (size is not None and end is not None):
-            raise RuntimeError('Either size or end must be specified')
-
-        if end and isinstance(end, str) and len(end) > 1:
-            raise RuntimeError('The serial end must be a single character, not a string')
 
         data = bytes()
 
-        try:
+        with get_lock(self.serial_lock, timeout=self._timeout) as serial_available:
-            serial_available = self.serial_lock.acquire(timeout=2)
+            assert serial_available, 'Serial read timed out'
-            if serial_available:
-                try:
-                    ser = self._get_serial(device=device, baud_rate=baud_rate)
-                except Exception as e:
-                    self.logger.debug(e)
-                    time.sleep(1)
-                    ser = self._get_serial(device=device, baud_rate=baud_rate, reset=True)
 
-                if size is not None:
+            ser = self._get_serial(device=device, baud_rate=baud_rate)
-                    for _ in range(0, size):
+            if size is not None:
-                        data += ser.read()
+                for _ in range(0, size):
-                elif end is not None:
+                    data += ser.read()
-                    if isinstance(end, str):
+            elif end is not None:
-                        end = end.encode()
+                end_byte = end.encode() if isinstance(end, str) else bytes([end])
+                ch = None
 
-                    ch = None
+                while ch != end_byte:
-                    while ch != end:
+                    ch = ser.read()
-                        ch = ser.read()
+                    if ch != end:
-
+                        data += ch
-                        if ch != end:
-                            data += ch
-            else:
-                self.logger.warning('Serial read timeout')
-        finally:
-            try:
-                self.serial_lock.release()
-            except Exception as e:
-                self.logger.debug(e)
 
         try:
-            data = data.decode()
+            data = data.decode('utf-8')
         except (ValueError, TypeError):
-            data = base64.encodebytes(data)
+            data = base64.b64encode(data).decode()
 
         return data
 
     @action
-    def write(self, data, device=None, baud_rate=None):
+    def write(
+        self,
+        data: Union[str, dict, list, bytes, bytearray],
+        device: Optional[str] = None,
+        baud_rate: Optional[int] = None,
+        binary: bool = False,
+    ):
         """
         Writes data to the serial device.
 
-        :param device: Device to write (default: default configured device)
+        :param device: Device to write (default: default configured device).
-        :type device: str
+        :param baud_rate: Baud rate (default: default configured baud_rate).
+        :param data: Data to send to the serial device. It can be any of the following:
 
-        :param baud_rate: Baud rate (default: default configured baud_rate)
+            - A UTF-8 string
-        :type baud_rate: int
+            - A base64-encoded string (if ``binary=True``)
+            - A dictionary/list that will be encoded as JSON
+            - A bytes/bytearray sequence
 
-        :param data: Data to send to the serial device
+        :param binary: If ``True``, then the message is either a
-        :type data: str, bytes or dict. If dict, it will be serialized as JSON.
+            bytes/bytearray sequence or a base64-encoded string.
         """
 
-        if not device:
+        device, baud_rate = self._get_device_and_baud_rate(device, baud_rate)
-            if not self.device:
+        if isinstance(data, (dict, list)):
-                raise RuntimeError('No device specified nor default device configured')
-            device = self.device
-
-        if baud_rate is None:
-            if self.baud_rate is None:
-                raise RuntimeError('No baud_rate specified nor default configured')
-            baud_rate = self.baud_rate
-
-        if isinstance(data, dict):
             data = json.dumps(data)
         if isinstance(data, str):
-            data = data.encode('utf-8')
+            data = base64.b64decode(data) if binary else data.encode('utf-8')
 
-        try:
+        data = bytes(data)
-            serial_available = self.serial_lock.acquire(timeout=2)
+        with get_lock(self.serial_lock, timeout=self._timeout) as serial_available:
-            if serial_available:
+            assert serial_available, 'Could not acquire the device lock'
-                try:
+            ser = self._get_serial(device=device, baud_rate=baud_rate)
-                    ser = self._get_serial(device=device, baud_rate=baud_rate)
+            self.logger.info('Writing %d bytes to %s', len(data), device)
-                except Exception as e:
+            ser.write(data)
-                    self.logger.debug(e)
-                    time.sleep(1)
-                    ser = self._get_serial(device=device, baud_rate=baud_rate, reset=True)
 
-                self.logger.info('Writing {} to {}'.format(data, self.device))
+    @override
-                ser.write(data)
+    def transform_entities(self, entities: Tuple[str, Any]) -> List[Device]:
-        finally:
+        transformed_entities = []
+
+        for k, v in entities:
+            sensor_id = f'serial:{k}'
             try:
-                self.serial_lock.release()
+                value = float(v)
+                entity_type = NumericSensor
+            except (TypeError, ValueError):
+                value = v
+                entity_type = RawSensor
+
+            transformed_entities.append(
+                entity_type(
+                    id=sensor_id,
+                    name=k,
+                    value=value,
+                )
+            )
+
+        return [
+            Device(
+                id='serial',
+                name=self.device,
+                children=transformed_entities,
+            )
+        ]
+
+    @override
+    def publish_entities(self, entities: Collection[Tuple[str, Any]], *_, **__):
+        ret = super().publish_entities(entities)
+        get_bus().post(
+            SensorDataChangeEvent(
+                data=dict(entities),
+                source=get_plugin_name_by_class(self.__class__),
+            )
+        )
+
+        return ret
+
+    @override
+    def main(self):
+        if not self._enable_polling:
+            # If the polling is disabled, we don't need to do anything here
+            self.wait_stop()
+            return
+
+        while not self.should_stop():
+            last_data = self.last_data.copy()
+            try:
+                new_data: dict = self.status(publish_entities=False).output  # type: ignore
             except Exception as e:
-                self.logger.debug(e)
+                self.logger.warning('Could not update the status: %s', e)
+                self.wait_stop(1)
+                continue
+
+            updated_entries = {
+                k: v for k, v in new_data.items() if v != last_data.get(k)
+            }
+
+            self.publish_entities(updated_entries.items())
+            self.last_data = {
+                **last_data,
+                **new_data,
+            }
+
+    @override
+    def stop(self):
+        super().stop()
+        self._close_serial()
 
 
 # vim:sw=4:ts=4:et:

platypush/plugins/serial/manifest.yaml

@@ -1,6 +1,8 @@
 manifest:
-  events: {}
+  events:
+    - platypush.message.event.sensor.SensorDataChangeEvent:
   install:
-    pip: []
+    pip:
+      - pyserial
   package: platypush.plugins.serial
   type: plugin

platypush/utils/__init__.py

@@ -5,6 +5,7 @@ import hashlib
 import importlib
 import inspect
 import logging
+from multiprocessing import Lock as PLock
 import os
 import pathlib
 import re
@@ -12,13 +13,15 @@ import signal
 import socket
 import ssl
 import urllib.request
-from typing import Optional, Tuple, Union
+from threading import Lock as TLock
+from typing import Generator, Optional, Tuple, Union
 
 from dateutil import parser, tz
 from redis import Redis
 from rsa.key import PublicKey, PrivateKey, newkeys
 
 logger = logging.getLogger('utils')
+Lock = Union[PLock, TLock]  # type: ignore
 
 
 def get_module_and_method_from_action(action):
@@ -363,7 +366,7 @@ def get_mime_type(resource: str) -> Optional[str]:
             return response.info().get_content_type()
     else:
         if hasattr(magic, 'detect_from_filename'):
-            mime = magic.detect_from_filename(resource)
+            mime = magic.detect_from_filename(resource)  # type: ignore
         elif hasattr(magic, 'from_file'):
             mime = magic.from_file(resource, mime=True)
         else:
@@ -372,7 +375,7 @@ def get_mime_type(resource: str) -> Optional[str]:
             )
 
         if mime:
-            return mime.mime_type if hasattr(mime, 'mime_type') else mime
+            return mime.mime_type if hasattr(mime, 'mime_type') else mime  # type: ignore
 
     return None
 
@@ -559,4 +562,27 @@ def to_datetime(t: Union[str, int, float, datetime.datetime]) -> datetime.dateti
     return t
 
 
+@contextlib.contextmanager
+def get_lock(
+    lock: Lock, timeout: Optional[float] = None
+) -> Generator[bool, None, None]:
+    """
+    Get a lock with an optional timeout through a context manager construct:
+
+        >>> from threading import Lock
+        >>> lock = Lock()
+        >>> with get_lock(lock, timeout=2):
+        >>>     ...
+
+    """
+    kwargs = {'timeout': timeout} if timeout else {}
+    result = lock.acquire(**kwargs)
+
+    try:
+        yield result
+    finally:
+        if result:
+            lock.release()
+
+
 # vim:sw=4:ts=4:et: