# A synchronous and simple Maelstrom crate

`nebkor-maelstreom` is a lean and simple synchronous library for writing
[Maelstrom](https://github.com/jepsen-io/maelstrom/tree/0186f398f96564a0453dda97c07daeac67c3d8d7)-compatible
distributed actors. It has three dependencies:

 - serde
 - serde_json
 - serde_repr
 
For a simple example, see the [gg-echo](https://git.kittencollective.com/nebkor/chatty-catties/src/branch/main/gg-echo/src/main.rs) program:

``` rust
use nebkor_maelstrom::{Body, Message, Node, Runner};

struct Echo;

impl Node for Echo {
    fn handle(&mut self, runner: &Runner, msg: Message) {
        let typ = &msg.body.typ;
        if typ.as_str() == "echo" {
            let body = Body::from_type("echo_ok").with_payload(msg.body.payload.clone());
            runner.reply(&msg, body);
        }
    }
}

fn main() {
    let node = Echo;

    let runner = Runner::new(node);

    runner.run(None);
}
```

## How to use

Create a struct and implement `nebkor_maelstrom::Node` for it, which involves a single method,
`handle(&mut self, &Runner, Message)`. This method is passed a `Runner` which contains methods like
`send`, `reply`, and `rpc`.

In your main function, instantiate that struct and pass that into `Runner::new()` to get a
Runner. The `run()` method takes an optional closure that will be run when the `init` Message is
received; see the
[broadcast](https://git.kittencollective.com/nebkor/chatty-catties/src/commit/af6d2c0b2720669f91a758c8c5755a146a914be4/gg-broadcast/src/main.rs#L10-L30)
program for an example of that, where it spawns a thread to send periodic messages to the node.

## Design considerations

I wanted the client code to be as simple as possible, with the least amount of boilerplate. Using
`&mut self` as the receiver for the `handle()` method lets you easily mutate state in your node if
you need to, without the ceremony of `Rc<Mutex<>>` and the like. Eschewing `async` results in an
order of magnitude fewer dependencies, and the entire workspace (crate and clients) can be compiled
in a couple seconds.

## Acknowledgments

I straight-up stole the design of the IO/network system from
[Maelbreaker](https://github.com/rafibayer/maelbreaker/), which allowed me to get a working RPC
call. Thanks!