Add closest template helper

homeassistant/helpers/location.py

@@ -0,0 +1,27 @@
+"""Location helpers for Home Assistant."""
+
+from homeassistant.const import ATTR_LATITUDE, ATTR_LONGITUDE
+from homeassistant.core import State
+from homeassistant.util import location as loc_util
+
+
+def has_location(state):
+    """Test if state contains a valid location."""
+    return (isinstance(state, State) and
+            isinstance(state.attributes.get(ATTR_LATITUDE), float) and
+            isinstance(state.attributes.get(ATTR_LONGITUDE), float))
+
+
+def closest(latitude, longitude, states):
+    """Return closest state to point."""
+    with_location = [state for state in states if has_location(state)]
+
+    if not with_location:
+        return None
+
+    return min(
+        with_location,
+        key=lambda state: loc_util.distance(
+            latitude, longitude, state.attributes.get(ATTR_LATITUDE),
+            state.attributes.get(ATTR_LONGITUDE))
+    )