So, I've been pretty deep in WASM architecture, and the WASI APIs. I've pretty much gotten to the point where we can launch an emissary and interact with it. So, now, it's time to actually build out the 3DOM APIs for interacting with the emissary and the message passing loops. Initially I'm going to start building a Rust Module for this. I do want to do this with other languages as it becomes practical. I'd love to be able to do C# and Python, but I don't think they're quite there yet. I've used mono-wasm to generate c# wasm, and pyodide for Python, but so far they're not particularly oriented to WASI yet and are more intended to run on a website (and interact with a DOM).
I think it will mostly go like this: one exposed setup method from the API layer, which will receive a protobuf buffer. This will be using 'proto 3' and will be decoded and processed. This gives us a backward and forward compatible startup. The startup will register callbacks on the rust side for the message pump to process. Then the emissary's 'main' basically returns. A channel is created via grpc to the browser and eventually to the entity/avatar server. Protobuf packets are passed in via these callback mechanisms. The emissary runs and then returns and possibly returns one or more protobuf packets. For now, I don't intend the emissary to have a thread to run when it is not processing a callback. Initially I'd rather an emissary not be able to do things like mining bitcoin or other such undesirable activity. The service managing the emissary will probably have a call timeout and will disable it if it doesn't respond in a timely fashion.
This facility kind of makes it hard to directly do gRPC, but at least we can do gRPC-like behavior passing protobufs around. I can cheat and have a grpc wrapper call which contains a command type and the protobuf as a raw vector. The server calls are tricker, as the interior emissary-to-server gRPC calls are theoretically private (and ad-hoc)--so their formats can't be known by this middleware layer which is operating the emissary for the browser. There are some up-and-coming grpc proxies out there. Or I will have to do my own, which is just calling methods on the emissary and returning an answer (no actual network involved). With my WASI layer, I could actually permit the emissary to open a socket, but I don't trust this yet.
So, now I actually have to work out exactly what the browser-emissary interaction (which I've been calling the 3DOM api) actually is and how it works. I've got some prototypes of this that I worked out last summer, but now I have to start building my .proto files to implement it.
Initially there will be no world, and no entity server to work this out. I'll have the concept of a "system entity", which can simply run inside the loading area (which will eventually will become a mini-world which is served from inside the browser). Also, eventually we'll have an avatar server, but initially the avatar is mostly just a vr camera FPS rig, with no smarts. I'll be doing some checkins soon of some of this structure.
The emissary will have an initial built-in parasitic overhead to have to have a copy of the loading module and the protobuf module. Eventually I'm sure I'll be able to dynamically link such things so they can be shared between emissaries. There's an effort for a package manager for webassembly (like npm) called wapm. Perhaps there can be a package manifest and emissaries can be dynamically loaded. I am ultimately intending for there to be hundreds, if not tens of thousands of emissaries to exist (in the distant future). So optimization, sharing, hot-deploy, and versioning will have to be seamless.
