alexa: Add media_player InputController support (#11946)

`media_player`s can support select_source so map that to an
InputController.

[1]: https://developer.amazon.com/docs/device-apis/alexa-inputcontroller.html

homeassistant/components/alexa/smart_home.py

@@ -357,6 +357,11 @@ class _AlexaPlaybackController(_AlexaInterface):
         return 'Alexa.PlaybackController'
 
 
+class _AlexaInputController(_AlexaInterface):
+    def name(self):
+        return 'Alexa.InputController'
+
+
 class _AlexaTemperatureSensor(_AlexaInterface):
     def name(self):
         return 'Alexa.TemperatureSensor'
@@ -475,6 +480,9 @@ class _MediaPlayerCapabilities(_AlexaEntity):
         if supported & playback_features:
             yield _AlexaPlaybackController(self.entity)
 
+        if supported & media_player.SUPPORT_SELECT_SOURCE:
+            yield _AlexaInputController(self.entity)
+
 
 @ENTITY_ADAPTERS.register(scene.DOMAIN)
 class _SceneCapabilities(_AlexaEntity):
@@ -1081,6 +1089,41 @@ def async_api_set_volume(hass, config, request, entity):
     return api_message(request)
 
 
+@HANDLERS.register(('Alexa.InputController', 'SelectInput'))
+@extract_entity
+@asyncio.coroutine
+def async_api_select_input(hass, config, request, entity):
+    """Process a set input request."""
+    media_input = request[API_PAYLOAD]['input']
+
+    # attempt to map the ALL UPPERCASE payload name to a source
+    source_list = entity.attributes[media_player.ATTR_INPUT_SOURCE_LIST] or []
+    for source in source_list:
+        # response will always be space separated, so format the source in the
+        # most likely way to find a match
+        formatted_source = source.lower().replace('-', ' ').replace('_', ' ')
+        if formatted_source in media_input.lower():
+            media_input = source
+            break
+    else:
+        msg = 'failed to map input {} to a media source on {}'.format(
+            media_input, entity.entity_id)
+        _LOGGER.error(msg)
+        return api_error(
+            request, error_type='INVALID_VALUE', error_message=msg)
+
+    data = {
+        ATTR_ENTITY_ID: entity.entity_id,
+        media_player.ATTR_INPUT_SOURCE: media_input,
+    }
+
+    yield from hass.services.async_call(
+        entity.domain, media_player.SERVICE_SELECT_SOURCE,
+        data, blocking=False)
+
+    return api_message(request)
+
+
 @HANDLERS.register(('Alexa.Speaker', 'AdjustVolume'))
 @extract_entity
 @asyncio.coroutine