Handlers' module can be considered an entry point to the application.
Let's assume that there exists some kind of request (GUI, HTTP, game socket, agent command or from any other source).
The process of processing the request should start from extracting a command from the request and lead to building a response, based on the result of the processing, describing a state of the game (it may be a new state, but not necessarily).
If the command is a read command, the state described should be the current state.
If the command is some kind of submit, the state is gonna be some new state of the game (returned in full details or some kind of diff of states).
request(GUI, HTTP, game socket, agent command or from any other source).readcommand, the state described should be the current state.submit, the state is gonna be some new state of the game (returned in full details or some kind of diff of states).