lesavka/server/src/main.rs

//! navka-server — receive HidReport and write to /dev/hidg0
#![forbid(unsafe_code)]

use std::{pin::Pin, sync::Arc};
use tokio::{fs::OpenOptions, io::AsyncWriteExt};
use tokio_stream::{wrappers::ReceiverStream, Stream, StreamExt};
use tonic::{transport::Server, Request, Response, Status};

use navka_common::navka::{
    relay_server::{Relay, RelayServer},
    HidReport,
};

struct Handler {
    /// shared async handle to /dev/hidg0
    hid: Arc<tokio::sync::Mutex<tokio::fs::File>>,
}

#[tonic::async_trait]
impl Relay for Handler {
    type StreamStream =
        Pin<Box<dyn Stream<Item = Result<HidReport, Status>> + Send + 'static>>;

    async fn stream(
        &self,
        request: Request<tonic::Streaming<HidReport>>,
    ) -> Result<Response<Self::StreamStream>, Status> {
        let mut in_stream = request.into_inner();
        let hid = self.hid.clone();

        // echo everything back to caller & push down USB
        let (tx, rx) = tokio::sync::mpsc::channel(32);

        tokio::spawn(async move {
            while let Some(msg) = in_stream.next().await.transpose()? {
                // 1) write to /dev/hidg0
                let mut file = hid.lock().await;
                file.write_all(&msg.data).await.map_err(|e| Status::internal(e.to_string()))?;
                file.flush().await.ok();

                // 2) echo back
                tx.send(Ok(msg)).await.ok();
            }
            Ok::<_, Status>(())
        });

        Ok(Response::new(Box::pin(ReceiverStream::new(rx))))
    }
}

#[tokio::main]
async fn main() -> anyhow::Result<()> {
    let file = OpenOptions::new()
        .write(true)
        .open("/dev/hidg0")
        .await?;
    let hid = Arc::new(tokio::sync::Mutex::new(file));

    let handler = Handler { hid };

    println!("🌐 navka-server listening on 0.0.0.0:50051");
    Server::builder()
        .add_service(RelayServer::new(handler))
        .serve(([0, 0, 0, 0], 50051).into())
        .await?;
    Ok(())
}