Merge sonar-socket-experiment back into sonar

[davidyu]

1. remove all message sending from God and delegate to various systems that need to do it
   • all input should be handled outside of God (98f0121, 6bbcb2a).
   • all network updates should be handled outside of God (77d9b32f3cb2875a5658b9f969f39810e2e80654).
2. allow all systems access EntityBuilder and the Client Socket without lambda-passing (b9ef756, 77d9b32f3cb2875a5658b9f969f39810e2e80654).

[davidyu]

Thought dump

To do 2. (ONLY w.r.t making Client socket accessible), I can make the player entity contain the ClientCmp (which has the socket), and then all relevant systems will have access. But this seems hacky. Alternatively, all interested systems could do a query for entities with the ClientCmp (there is only one), and refer to it there. This is more roundabount (and it is perhaps not so efficient if we have to iterate over all entities every time we process), but its intent is more clear and less confusing than giving the ClientCmp to the player.

What we really need is for the ClientSys (which for now, manages reading from the socket, but in the future, should also manage writing to the socket) to subscribe to and receive events from other systems. It should also notify other systems when it reads from the socket and finds relevant data for them.

Message passing must be implemented, though, and it makes the game more complex than I'd like it to be.

This can be implemented in a more distributed manner by implementing a NetworkSystem interface (with read/write methods and an identifier). Each System reads and writes updates that it cares about, and the socket is implemented in a higher level system (parallel to World rather than under it). The master socket system will read from the socket and multiplex incoming data to the correct systems. The downside is that this unnecessarily ties systems to network logic. Recall that the ideal implementation is one where the dev just adds a SyncCmp to any entity he wants synchronized, and the SyncSys will take care of everything (also realize this is very non-distributed).

To make EntityBuilder accessible to all systems, just make it into a system, and everyone else can grab it via World.getSystem( EntityAssemblySys )

[davidyu]

It is possible to make everything nice and pretty with a SyncSys, designed as follows:

• Update once per second (or whatever interval specified by God; can be passed as param)
• Let this Sys care about entities with either SyncCmp OR ClientCmp
• Maintain a temporary buffer
  • When iterating over SyncCmp entities, iterate over all sync-able components. We can mark sync-ability with inheritance, existence of a method (SyncSerialize/Deserialize), or macros. Write all relevant data into temporary buffer.
  • When iterating over ClientCmp, dump everything in the temporary buffer into the socket. A further optimization can be made to ignore stale data (clear this buffer after the iteration loop; we'd have to make sure to update the ClientCmp last).

Cons:

• Potentially slow because of double-buffer weirdness. We force flush the temp buffer, though, and the socket is also flushed, so it should be fine, theoretically. There might be problems if we slowly read from buffer and dump what we read into the socket. But if we can get a string/bytearray out of the temp buffer and just push that into the socket, we'll be fine.

[davidyu]

Done in a89a35dfd6effbd9acb4a6b15589642e1b56cd88