def receive_push_messages()

in sample-code/python/main.py [0:0]

• 20 lines of code
• 12 McCabe index (conditional complexity)

def receive_push_messages():
    # Pub/Sub push subscriptions deliver messages through regular HTTP POST
    # requests, with a JSON body.
    request_body = request.get_json(silent=True)    # Returns None if not JSON

    # This app is intended only to receive Pub/Sub push messages. Reject any
    # HTTP POST request that is not a properly formed Pub/Sub push message.
    if request_body is None:
        print("ERROR: Not JSON")                # Log the issue
        return "Unsupported Media Type", 415    # Non-2XX notifies error to the sender

    if not isinstance(request_body, dict) or "message" not in request_body:
        print("ERROR: Not PubSub")  # Log the issue
        return "Bad Request", 400   # Non-2XX notifies error to the sender

    # The request_body seems to a properly formed Pub/Sub message. The message
    # itself is a field called "message".
    message = request_body["message"]

    # The data portion of the message is base64-encoded. Decode it.
    data = message.get("data", "")                  # Empty string if missing
    body = base64.b64decode(data).decode("utf-8")   # b64decode returns bytes

    # Log the decoded data to check if it was correctly received.
    print(f"DEBUG: decoded data = '{body}'")

    # The body can be any string. For the Pinball game, the body will always
    # be a JSON string, usually containing several data fields.

    # There are a number of other fields in the message that can convey
    # information, some of which are essential to understanding the Pinball
    # event.
    
    # See https://cloud.google.com/pubsub/docs for more information on
    # the structure and contents of Pub/Sub messages in general.
    
    # See the end of the codelab for specifications of the Pinball message format.

    # Determine whether you want the send a message back to the Pinball machine.
    # For most events you will not want to do this to avoid spamming the
    # machine. You will be given suggestions of events worth responding to,
    # such as a completed game with a new high score, or longest duration.

    if False:   # replace with condition that should trigger a response
        result = send_response(
            reaction_type="DisplayMessage",
            machine_id="GBL:1",
            data={"MessageKey": "LUCKY"}
        )
        print(f"Result of sending message is {result}.")

    # Acknowledge the message to prevent retries.
    return "OK", 200