nebkor-maelstrom/src/lib.rs

230 lines
7.0 KiB
Rust

use std::{
collections::HashMap,
io::{BufRead, Write},
sync::{
atomic::{AtomicU64, Ordering},
mpsc::{channel, Receiver, Sender},
Arc, Mutex, OnceLock,
},
thread::{self},
};
pub use serde_json::Value;
pub mod protocol;
pub use protocol::{Body, ErrorCode, Message, Payload};
pub mod kv;
pub type NodeyNodeFace = Arc<Mutex<dyn Node>>;
pub type OnInit = Box<dyn Fn(&Runner)>;
pub type RpcPromise = Receiver<Message>;
pub type RpcResult = std::result::Result<Option<Value>, ErrorCode>;
pub trait Node {
fn handle(&mut self, runner: &Runner, msg: Message);
}
pub struct Runner {
node: NodeyNodeFace,
node_id: OnceLock<String>,
nodes: OnceLock<Vec<String>>,
backdoor: OnceLock<Sender<Message>>,
promises: Arc<Mutex<HashMap<u64, Sender<Message>>>>,
outbound_tx: OnceLock<Sender<Message>>,
msg_id: AtomicU64,
}
impl Runner {
pub fn new<N: Node + 'static>(node: N) -> Self {
let node = Arc::new(Mutex::new(node));
Runner {
node,
nodes: OnceLock::new(),
node_id: OnceLock::new(),
backdoor: OnceLock::new(),
outbound_tx: OnceLock::new(),
promises: Default::default(),
msg_id: AtomicU64::new(1),
}
}
/// Start processing messages from stdin and sending them to your node. The `on_init` argument
/// is an optional callback that will be called with `&self` after the `init` message from
/// Maelstrom has been processed.
///
/// # Examples
///
/// ```no_run
/// use nebkor_maelstrom::{Body, Message, Node, Runner};
/// struct Foo;
/// impl Node for Foo {fn handle(&mut self, _runner: &Runner, _msg: Message) { /* empty impl */ }}
///
/// let runner = Runner::new(Foo);
///
/// let on_init = |rnr: &Runner| {
/// eprintln!("received the `init` message!");
/// let msg = Message { body: Body::from_type("yo_yo_yo"), ..Default::default() };
/// // send `msg` to the node to be processed by its `handle()` method
/// rnr.get_backdoor().send(msg).unwrap();
/// };
/// let on_init = Box::new(on_init);
///
/// runner.run(Some(on_init));
/// ```
pub fn run(&self, on_init: Option<OnInit>) {
let (outbound_tx, outbound_rx) = channel();
let _ = self.outbound_tx.get_or_init(|| outbound_tx);
// decouple processing output from handling messages
thread::spawn(move || {
let mut stdout = std::io::stdout().lock();
while let Ok(msg) = outbound_rx.recv() {
let msg = serde_json::to_string(&msg).unwrap();
writeln!(&mut stdout, "{msg}").unwrap();
}
});
self.process_input(on_init);
}
/// Get a Sender that will send Messages to the node as input. Useful for triggering periodic
/// behavior from a separate thread, or for sending a Message to the node from `on_init`. See
/// the `broadcast` example for a use of it.
pub fn get_backdoor(&self) -> Sender<Message> {
self.backdoor.get().unwrap().clone()
}
pub fn node_id(&self) -> &str {
self.node_id.get().unwrap()
}
pub fn next_msg_id(&self) -> u64 {
self.msg_id.fetch_add(1, Ordering::SeqCst)
}
/// A list of all nodes in the network, including this one.
pub fn nodes(&self) -> &[String] {
self.nodes.get().unwrap()
}
/// Construct a new `Message` from `body` and send it to `req.src`.
pub fn reply(&self, req: &Message, body: Body) {
let mut body = body;
let dest = req.src.as_str();
let in_reply_to = req.body.msg_id;
body.in_reply_to = in_reply_to;
self.send(dest, body);
}
/// Construct a new `Message` from `body` and send it to `dest`.
pub fn send(&self, dest: &str, body: Body) {
let msg = self.mk_msg(dest, body);
self.outbound_tx.get().unwrap().send(msg).unwrap();
}
/// Returns a Receiver<Message> that will receive the reply from the request.
pub fn rpc(&self, dest: &str, body: Body) -> RpcPromise {
let msg = self.mk_msg(dest, body);
let (tx, rx) = channel();
{
let msg_id = msg.body.msg_id;
let mut g = self.promises.lock().unwrap();
g.insert(msg_id, tx);
}
self.outbound_tx.get().unwrap().send(msg).unwrap();
rx
}
// internal methods
fn init(&self, msg: &Message) {
let node_id = msg
.body
.payload
.get("node_id")
.unwrap()
.as_str()
.unwrap()
.to_owned();
let nodes = msg
.body
.payload
.get("node_ids")
.unwrap()
.as_array()
.unwrap()
.iter()
.map(|s| s.as_str().unwrap().to_string())
.collect();
let _ = self.node_id.get_or_init(|| node_id);
let _ = self.nodes.get_or_init(|| nodes);
}
fn process_input(&self, on_init: Option<OnInit>) {
// for sending Messages to the node's inputs
let (encoded_input_tx, encoded_input_rx) = channel();
let _ = self.backdoor.get_or_init(|| encoded_input_tx.clone());
// decouple stdin from processing
let proms = self.promises.clone();
thread::spawn(move || {
let stdin = std::io::stdin().lock();
for line in stdin.lines().map_while(std::result::Result::ok) {
let msg: Message = serde_json::from_str(&line).unwrap();
let irt = msg.body.in_reply_to;
if let Some(promise) = proms.lock().unwrap().remove(&irt) {
// this is the result of an RPC call
promise.send(msg).unwrap();
} else {
// just let the node's `handle()` method handle it
encoded_input_tx.send(msg).unwrap();
}
}
});
// first Message is always `init`:
let msg = encoded_input_rx.recv().unwrap();
{
self.init(&msg);
let body = Body::from_type("init_ok");
self.reply(&msg, body);
if let Some(on_init) = on_init {
on_init(self);
}
}
// every other message is for the node's handle() method
let mut node = self.node.lock().unwrap();
for msg in encoded_input_rx {
node.handle(self, msg);
}
}
fn mk_msg(&self, dest: &str, body: Body) -> Message {
let mut body = body;
if body.msg_id == 0 {
body.msg_id = self.next_msg_id();
}
Message::from_dest(dest)
.with_body(body)
.with_src(self.node_id())
}
}
pub fn check_err(msg: &Message) -> RpcResult {
if msg.body.typ.as_str() == "error" {
let error = msg.body.code.unwrap();
return Err(error);
}
Ok(None)
}
pub fn mk_payload(payload: &[(&str, Value)]) -> Payload {
payload
.iter()
.map(|p| (p.0.to_string(), p.1.clone()))
.collect()
}