//! navka-server – bridge HID reports between client (gRPC) and /dev/hidg0
#![forbid(unsafe_code)]

use anyhow::Result;
use navka_common::navka::{
    hid_report::*, relay_server::Relay, HidReport, RelayServer,
};
use std::{path::Path, sync::Arc};
use tokio::{
    fs::OpenOptions,
    io::AsyncWriteExt,
    signal,
    sync::{mpsc, Mutex},
};
use tonic::{transport::Server, Request, Response, Status};

/// Implementation of the gRPC service generated by tonic-build.
#[derive(Debug)]
pub struct RelaySvc {
    /// Shared handle to /dev/hidg0 (protected by a mutex because several
    /// gRPC streams may write concurrently).
    hidg: Arc<Mutex<tokio::fs::File>>,
}

#[tonic::async_trait]
impl Relay for RelaySvc {
    type StreamStream = tokio_stream::wrappers::ReceiverStream<Result<HidReport, Status>>;

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

        // Channel we’ll use if one day we need to send something back.
        let (tx, rx) = mpsc::channel(32);

        let hidg = self.hidg.clone();
        tokio::spawn(async move {
            while let Some(report) = inbound.message().await.transpose()? {
                // Write raw 8-byte packet to the gadget device
                hidg.lock().await.write_all(&report.data).await?;
            }
            Ok::<(), anyhow::Error>(())
        });

        Ok(Response::new(tokio_stream::wrappers::ReceiverStream::new(rx)))
    }
}

#[tokio::main]
async fn main() -> Result<()> {
    // Open /dev/hidg0 once and share it.
    let hid_dev = if Path::new("/dev/hidg0").exists() {
        OpenOptions::new().write(true).open("/dev/hidg0").await?
    } else {
        anyhow::bail!("/dev/hidg0 not found – is navka-gadget running?");
    };

    let svc = RelayServer::new(RelaySvc {
        hidg: Arc::new(Mutex::new(hid_dev)),
    });

    println!("🛰️  navka-server listening on 0.0.0.0:50051");
    Server::builder()
        .add_service(svc)
        .serve_with_shutdown("0.0.0.0:50051".parse()?, async {
            signal::ctrl_c().await.ok();
        })
        .await?;

    Ok(())
}