import sys
import time
import traceback

from awsiot.greengrasscoreipc.clientv2 import GreengrassCoreIPCClientV2
from awsiot.greengrasscoreipc.model import (
    SubscriptionResponseMessage,
    UnauthorizedError
)

def main():
    topic = "test/topic"

    try:
        ipc_client = GreengrassCoreIPCClientV2()
        # Subscription operations return a tuple with the response and the operation.
        _, operation = ipc_client.subscribe_to_topic(topic=topic, on_stream_event=on_stream_event,
                                                     on_stream_error=on_stream_error, on_stream_closed=on_stream_closed)
        print('Successfully subscribed to topic: ' + topic)

        # Keep the main thread alive, or the process will exit.
        try:
            while True:
                time.sleep(10)
        except KeyboardInterrupt:
            print('Subscribe interrupted.')

        # To stop subscribing, close the stream.
        operation.close()
    except UnauthorizedError:
        print('Unauthorized error while subscribing to topic: ' +
              topic, file=sys.stderr)
        traceback.print_exc()
        exit(1)
    except Exception:
        print('Exception occurred', file=sys.stderr)
        traceback.print_exc()
        exit(1)

def on_stream_event(event: SubscriptionResponseMessage) -> None:
    try:
        message = str(event.binary_message.message, 'utf-8')
        topic = event.binary_message.context.topic
        print('Received new message on topic %s: %s' % (topic, message))
    except AttributeError as e:
        print(f'Error accessing message attributes: {e}', file=sys.stderr)
    except UnicodeDecodeError as e:
        print(f'Error decoding message: {e}', file=sys.stderr)
    except Exception as e:
        print(f'Unexpected error in on_stream_event: {e}', file=sys.stderr)
        traceback.print_exc()

def on_stream_error(error: Exception) -> bool:
    print('Received a stream error.', file=sys.stderr)
    traceback.print_exc()
    return False  # Return True to close stream, False to keep stream open.

def on_stream_closed() -> None:
    print('Subscribe to topic stream closed.')

if __name__ == '__main__':
    main()