ack.txt

Scenario:  Client send a Direct Message to Client2:
    1. Client creates Message
    2. Client adds hash to Message as .msg_hash
    3. Client adds has to ack_checker dictionary as False (not yet ACKed)
    4. Client sends DM to Client2
    5. Client2 receives Message
    6. Client2 creates ACK message where data = incoming message.msg_hash
    7. Client2 sends ACK as DM to Client1
    8. Client1 executes self.handle_ack with ACK message
    9. Client1 check whether has from ACK message.data is in ack_tracker
    10. Client1 updates ack_tracker entry to True if exists
    11. Client1 MAY wait to confirm receipt before timeout/retry

    --> Offline message
    12. If timeout/retry exceeded, we send an offline copy of the message
    13. Client changes message event_id to OFFLINE_MESSAGE and sends to SERVER
    14. SERVER check for valid recipient and that target is indeed offline (error message send it not)
    15. SERVER adds message to recipient's offline_message list
    16. SERVER sends ACK and message to Client1

    --> Re-register
    17. Client2 re-registers 
    18. SERVER updates Client2 registration as needed
    19. SERVER notifies Client2 that offline messages exists
    20. SERVER sends each message to Client2
    21. Client2 sends ACKs to SERVER for each message
    22. SERVER removes messages from offline queue