Explicit States in EventLoop.hs

[fendor]

Explicit State

The EventLoop.hs is the core file for the Server Application. It manages multiple connections, it manages the communication, server updates, also whether the game has started, when a game is over, et cetera...

These are a lot of responsibilities, and a lot of the message handling is dependent on the current state. However, the current state of the server and the various client connections are only present through implicit conversion of the current state variables.

My proposal would be, to refactor the server variables to include a more explicit state machine. Hence, messages should have it easier to determine the current state. It should even improve performance by avoiding costly variable analysis during handling a message.

[samuelpilz]

How to implement that? There are 2 options:

• state pattern in different variations
• make illegal state impossible driven approach

[fendor]

I would aim at making illegal states impossible, as much as possible

[samuelpilz]

Then, a description of the Model is reqired in plain text. From that, a suitable data structure can be derived

[fendor]

About making illegal states impossible: It seems hard and kind of impossible to actually do that since the state is determined at runtime. However, the identified states are as follow:

• Warmup: In this phase, clients can connect to the game and send game setup messages. Ready up messages should be accumulated.
  • Possible transitions
    • Running: Triggered when the amount of logged in players is equal to the number of players that are ready.
• Running: Connection Requests are denied, ready up messages are ignored.
  • Possible transitions
    • Paused: How to trigger this transition is not decided yet.
    • Over: Someone has won the game, or everyone disconnected.
• Paused: Connections are rejected, ready up may be useful.
  • Possible transitions
    • Running: TBD
• Over: Someone has won or the game is over. Determine what of the two has happened and save it some kind of event list. After a pre determined amount of gameTicks the state transition to Warmup is triggered.
  • Possible transitions
    • Warmup: Triggered after a pre determined amount of ticks have passed.

[fendor]

First step of the refactoring has been implemented by #16