Cleanup language support on TTS (#5255)

* Cleanup language support on TTS

* change to default_language & address comments

* Cleanup not needed code / comment from paulus

homeassistant/components/tts/demo.py

@@ -6,28 +6,50 @@ https://home-assistant.io/components/demo/
 """
 import os
 
-from homeassistant.components.tts import Provider
+import voluptuous as vol
+
+from homeassistant.components.tts import Provider, PLATFORM_SCHEMA, CONF_LANG
+
+SUPPORT_LANGUAGES = [
+    'en', 'de'
+]
+
+DEFAULT_LANG = 'en'
+
+PLATFORM_SCHEMA = PLATFORM_SCHEMA.extend({
+    vol.Optional(CONF_LANG, default=DEFAULT_LANG): vol.In(SUPPORT_LANGUAGES),
+})
 
 
 def get_engine(hass, config):
     """Setup Demo speech component."""
-    return DemoProvider()
+    return DemoProvider(config[CONF_LANG])
 
 
 class DemoProvider(Provider):
     """Demo speech api provider."""
 
-    def __init__(self):
-        """Initialize demo provider for TTS."""
-        self.language = 'en'
+    def __init__(self, lang):
+        """Initialize demo provider."""
+        self._lang = lang
 
-    def get_tts_audio(self, message, language=None):
+    @property
+    def default_language(self):
+        """Default language."""
+        return self._lang
+
+    @property
+    def supported_languages(self):
+        """List of supported languages."""
+        return SUPPORT_LANGUAGES
+
+    def get_tts_audio(self, message, language):
         """Load TTS from demo."""
         filename = os.path.join(os.path.dirname(__file__), "demo.mp3")
         try:
             with open(filename, 'rb') as voice:
                 data = voice.read()
         except OSError:
-            return
+            return (None, None)
 
         return ("mp3", data)