Host Message SLA

Airbnb tracks how quickly hosts answer guests. You receive messages from many conversation threads as rows [thread_id, sender, timestamp], sorted by timestamp (non-decreasing; rows with equal timestamps are processed in the given order). sender is either "guest" or "host".

Each thread is either idle or waiting for a host reply, starting idle:

• A guest message makes an idle thread start waiting, with the clock started at that message's timestamp. A guest message on a thread that is already waiting does not restart the clock.
• A host message on a waiting thread ends the wait. If host_timestamp - wait_start > deadline, that wait counts as one violation. A host message on an idle thread does nothing.
• After all messages are processed, any thread still waiting counts one more violation if now - wait_start > deadline; if not, it is still within its SLA and does not count.

Return [thread_id, violation_count] for every thread that appears in messages (including threads with 0 violations), sorted by thread_id in ascending string order.