Create Currencylayer exchange rate sensor (#4062)

* Added Currencylayer exchange rate sensor

* Updated .coveragerc to include currencylayer

* Update currencylayer.py

* Added Conf_name

.coveragerc

@@ -235,6 +235,7 @@ omit =
     homeassistant/components/sensor/bom.py
     homeassistant/components/sensor/coinmarketcap.py
     homeassistant/components/sensor/cpuspeed.py
+    homeassistant/components/sensor/currencylayer.py
     homeassistant/components/sensor/darksky.py
     homeassistant/components/sensor/deutsche_bahn.py
     homeassistant/components/sensor/dht.py

homeassistant/components/sensor/currencylayer.py

@@ -0,0 +1,118 @@
+"""Support for currencylayer.com exchange rates service."""
+from datetime import timedelta
+import logging
+import requests
+import voluptuous as vol
+import homeassistant.helpers.config_validation as cv
+from homeassistant.components.sensor import PLATFORM_SCHEMA
+from homeassistant.helpers.entity import Entity
+from homeassistant.util import Throttle
+from homeassistant.const import (CONF_API_KEY, CONF_NAME, CONF_PAYLOAD)
+
+_RESOURCE = 'http://apilayer.net/api/live'
+_LOGGER = logging.getLogger(__name__)
+# Return cached results if last scan was less then this time ago.
+MIN_TIME_BETWEEN_UPDATES = timedelta(hours=2)
+CONF_BASE = 'base'
+CONF_QUOTE = 'quote'
+DEFAULT_BASE = 'USD'
+DEFAULT_NAME = 'CurrencyLayer Sensor'
+ICON = 'mdi:currency'
+
+PLATFORM_SCHEMA = PLATFORM_SCHEMA.extend({
+    vol.Required(CONF_API_KEY): cv.string,
+    vol.Required(CONF_QUOTE): vol.All(cv.ensure_list, [cv.string]),
+    vol.Optional(CONF_BASE, default=DEFAULT_BASE): cv.string,
+    vol.Optional(CONF_NAME, default=DEFAULT_NAME): cv.string,
+})
+
+
+def setup_platform(hass, config, add_devices, discovery_info=None):
+    """Setup the Currencylayer sensor."""
+    payload = config.get(CONF_PAYLOAD)
+    rest = CurrencylayerData(
+        _RESOURCE,
+        config.get(CONF_API_KEY),
+        config.get(CONF_BASE, 'USD'),
+        payload
+    )
+    response = requests.get(_RESOURCE, params={'source':
+                                               config.get(CONF_BASE, 'USD'),
+                                               'access_key':
+                                               config.get(CONF_API_KEY),
+                                               'format': 1}, timeout=10)
+    sensors = []
+    for variable in config['quote']:
+        sensors.append(CurrencylayerSensor(rest, config.get(CONF_BASE, 'USD'),
+                                           variable))
+    if "error" in response.json():
+        _LOGGER.error("Check your Currencylayer API")
+        return False
+    else:
+        add_devices(sensors)
+        rest.update()
+
+
+class CurrencylayerSensor(Entity):
+    """Implementing the Currencylayer sensor."""
+
+    def __init__(self, rest, base, quote):
+        """Initialize the sensor."""
+        self.rest = rest
+        self._quote = quote
+        self._base = base
+        self.update()
+
+    @property
+    def name(self):
+        """Return the name of the sensor."""
+        return str(self._base) + str(self._quote)
+
+    @property
+    def icon(self):
+        """Return the icon to use in the frontend, if any."""
+        return ICON
+
+    @property
+    def state(self):
+        """Return the state of the sensor."""
+        return self._state
+
+    def update(self):
+        """Update current conditions."""
+        self.rest.update()
+        value = self.rest.data
+        if value is not None:
+            self._state = round(value[str(self._base) + str(self._quote)], 4)
+
+
+# pylint: disable=too-few-public-methods
+class CurrencylayerData(object):
+    """Get data from Currencylayer.org."""
+
+    # pylint: disable=too-many-arguments
+    def __init__(self, resource, api_key, base, data):
+        """Initialize the data object."""
+        self._resource = resource
+        self._api_key = api_key
+        self._base = base
+        self.data = None
+
+    @Throttle(MIN_TIME_BETWEEN_UPDATES)
+    def update(self):
+        """Get the latest data from Currencylayer."""
+        try:
+            result = requests.get(self._resource, params={'source': self._base,
+                                                          'access_key':
+                                                          self._api_key,
+                                                          'format': 1},
+                                  timeout=10)
+            if "error" in result.json():
+                raise ValueError(result.json()["error"]["info"])
+            else:
+                self.data = result.json()['quotes']
+                _LOGGER.debug("Currencylayer data updated: %s",
+                              result.json()['timestamp'])
+        except ValueError as err:
+            _LOGGER.error("Check Currencylayer API %s", err.args)
+            self.data = None