add arest sensor

homeassistant/components/sensor/arest.py

@@ -0,0 +1,139 @@
+"""
+homeassistant.components.sensor.arest
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The arest sensor will consume an exposed aREST API of a device.
+
+Configuration:
+
+To use the arest sensor you will need to add something like the following
+to your configuration.yaml file.
+
+sensor:
+  platform: arest
+  resource: http://IP_ADDRESS
+  monitored_variables:
+    - name: temperature
+      unit: '°C'
+    - name: humidity
+      unit: '%'
+
+Variables:
+
+resource:
+*Required
+IP address of the device that is exposing an aREST API.
+
+These are the variables for the monitored_variables array:
+
+name
+*Required
+The name of the variable you wish to monitor.
+
+unit
+*Optional
+Defines the units of measurement of the sensor, if any.
+
+Details for the API : http://arest.io
+
+Format of a default JSON response by aREST:
+{
+   "variables":{
+      "temperature":21,
+      "humidity":89
+   },
+   "id":"device008",
+   "name":"Bedroom",
+   "connected":true
+}
+"""
+import logging
+from requests import get, exceptions
+
+from homeassistant.helpers.entity import Entity
+
+_LOGGER = logging.getLogger(__name__)
+
+
+def setup_platform(hass, config, add_devices, discovery_info=None):
+    """ Get the aREST sensor. """
+
+    resource = config.get('resource', None)
+
+    try:
+        response = get(resource)
+    except exceptions.MissingSchema:
+        _LOGGER.error("Missing schema in configuration. "
+                      "Add http:// to your URL.")
+        return False
+    except exceptions.ConnectionError:
+        _LOGGER.error("No route to device. "
+                      "Please check the IP address in the configuration file.")
+        return False
+
+    data = ArestData(resource)
+
+    dev = []
+    for variable in config['monitored_variables']:
+        if 'unit' not in variable:
+            variable['unit'] = ' '
+        if variable['name'] not in response.json()['variables']:
+            _LOGGER.error('Variable: "%s" does not exist', variable['name'])
+        else:
+            dev.append(ArestSensor(data,
+                                   response.json()['name'],
+                                   variable['name'],
+                                   variable['unit']))
+
+    add_devices(dev)
+
+
+class ArestSensor(Entity):
+    """ Implements an aREST sensor. """
+
+    def __init__(self, data, location, variable, unit_of_measurement):
+        self._data = data
+        self._name = '{} {}'.format(location.title(), variable.title())
+        self._variable = variable
+        self._state = 'n/a'
+        self._unit_of_measurement = unit_of_measurement
+        self.update()
+
+    @property
+    def name(self):
+        """ The name of the sensor. """
+        return self._name
+
+    @property
+    def unit_of_measurement(self):
+        """ Unit the value is expressed in. """
+        return self._unit_of_measurement
+
+    @property
+    def state(self):
+        """ Returns the state of the device. """
+        return self._state
+
+    def update(self):
+        """ Gets the latest data from aREST API and updates the states. """
+        values = self._data.update()
+        if values is not None:
+            self._state = values[self._variable]
+        else:
+            self._state = 'n/a'
+
+
+# pylint: disable=too-few-public-methods
+class ArestData(object):
+    """ Class for handling the data retrieval. """
+
+    def __init__(self, resource):
+        self.resource = resource
+
+    def update(self):
+        """ Gets the latest data from aREST API. """
+        try:
+            response = get(self.resource)
+            return response.json()['variables']
+        except exceptions.ConnectionError:
+            _LOGGER.error("No route to device. Is device offline?")
+            return None