Add demo to showcase using the GPIO trigger with assistant library. (g…

…oogle#112)

* Add demo to showcase using the GPIO trigger with assistant library.

* Remove settrace and fix a formatting issue (pep8).

src/assistant_library_demo.py

@@ -43,8 +43,7 @@ def process_event(event):
     if event.type == EventType.ON_START_FINISHED:
         status_ui.status('ready')
         if sys.stdout.isatty():
-            print('Say "OK, Google" or press the VoiceHat button then speak,'
-                  'or press Ctrl+C to quit...')
+            print('Say "OK, Google" then speak, or press Ctrl+C to quit...')
 
     elif event.type == EventType.ON_CONVERSATION_TURN_STARTED:
         status_ui.status('listening')

src/assistant_library_with_button_demo.py

@@ -0,0 +1,108 @@
+#!/usr/bin/env python3
+# Copyright 2017 Google Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Run a recognizer using the Google Assistant Library with button support.
+
+The Google Assistant Library has direct access to the audio API, so this Python
+code doesn't need to record audio. Hot word detection "OK, Google" is supported.
+
+The Google Assistant Library can be installed with:
+    env/bin/pip install google-assistant-library==0.0.2
+
+It is available for Raspberry Pi 2/3 only; Pi Zero is not supported.
+"""
+
+import logging
+import sys
+import threading
+
+import aiy.assistant.auth_helpers
+import aiy.voicehat
+from google.assistant.library import Assistant
+from google.assistant.library.event import EventType
+
+logging.basicConfig(
+    level=logging.INFO,
+    format="[%(asctime)s] %(levelname)s:%(name)s:%(message)s"
+)
+
+
+class MyAssistant(object):
+    """An assistant that runs in the background.
+
+    The Google Assistant Library event loop blocks the running thread entirely.
+    To support the button trigger, we need to run the event loop in a separate
+    thread. Otherwise, the on_button_pressed() method will never get a chance to
+    be invoked.
+    """
+    def __init__(self):
+        self._task = threading.Thread(target=self._run_task)
+        self._can_start_conversation = False
+        self._assistant = None
+
+    def start(self):
+        """Starts the assistant.
+
+        Starts the assistant event loop and begin processing events.
+        """
+        self._task.start()
+
+    def _run_task(self):
+        credentials = aiy.assistant.auth_helpers.get_assistant_credentials()
+        with Assistant(credentials) as assistant:
+            self._assistant = assistant
+            for event in assistant.start():
+                self._process_event(event)
+
+    def _process_event(self, event):
+        status_ui = aiy.voicehat.get_status_ui()
+        if event.type == EventType.ON_START_FINISHED:
+            status_ui.status('ready')
+            self._can_start_conversation = True
+            # Start the voicehat button trigger.
+            aiy.voicehat.get_button().on_press(self._on_button_pressed)
+            if sys.stdout.isatty():
+                print('Say "OK, Google" or press the button, then speak. '
+                      'Press Ctrl+C to quit...')
+
+        elif event.type == EventType.ON_CONVERSATION_TURN_STARTED:
+            self._can_start_conversation = False
+            status_ui.status('listening')
+
+        elif event.type == EventType.ON_END_OF_UTTERANCE:
+            status_ui.status('thinking')
+
+        elif event.type == EventType.ON_CONVERSATION_TURN_FINISHED:
+            status_ui.status('ready')
+            self._can_start_conversation = True
+
+        elif event.type == EventType.ON_ASSISTANT_ERROR and event.args and event.args['is_fatal']:
+            sys.exit(1)
+
+    def _on_button_pressed(self):
+        # Check if we can start a conversation. 'self._can_start_conversation'
+        # is False when either:
+        # 1. The assistant library is not yet ready; OR
+        # 2. The assistant library is already in a conversation.
+        if self._can_start_conversation:
+            self._assistant.start_conversation()
+
+
+def main():
+    MyAssistant().start()
+
+
+if __name__ == '__main__':
+    main()