Agent Status API - Reason codes

Hi, 

I am looking into using the Agent Status API and wanted to understand a couple of things:

• The Reason an Agent is in a given status is provided in the response, but I can't seem to find a description of what each means - some are self-explanatory, but it would be good to have definitive defintions somewhere. 
  
  Can anyone answer want AGENT_LOGOUT refers to in the response code? My assumption is the Agent has logged out of Zendesk and therefore the status for the Agent changed. 
• Is there anyway via the API to see the history for an Agent what statuses they were in, for how long and why that status changed? I understand elements of this can be found in Explore, but I am attempting to understand if we can see the reason why an Agent was in a given status over time.