Flip T3 to substrate-initiated actuator commands

simulator/src/commands.rs

@@ -0,0 +1,96 @@
+//! Substrate → simulator T3 receiver.
+//!
+//! The substrate is the brain: when its `automation_system` decides to
+//! actuate, it opens a QUIC bidirectional stream to one of its connected
+//! devices. The simulator side accepts those streams here, decodes the
+//! 39-byte command, applies it to local actuator state, and writes a 39-byte
+//! ack back. This closes the loop the paper's three-tier model describes.
+
+use std::sync::Arc;
+use std::sync::atomic::{AtomicBool, Ordering};
+
+use substrate::transport::{QuicMessage, SensorType};
+
+/// Convenience constructor used by `main.rs` and integration tests.
+/// `true` means the simulated engine is running normally.
+pub fn new_engine_state() -> Arc<AtomicBool> {
+    Arc::new(AtomicBool::new(true))
+}
+
+/// Loop accepting substrate-initiated bidirectional streams until the
+/// connection drops. Each stream is one (command, ack) round-trip:
+/// the simulator reads a 39-byte `QuicMessage`, mutates `engine_running` if
+/// the command targets the Relay actuator, then writes a 39-byte ack back
+/// (echoes the command with the simulator's local timestamp).
+pub async fn run_command_receiver(conn: quinn::Connection, engine_running: Arc<AtomicBool>) {
+    let remote = conn.remote_address();
+    let mut streams_seen: u64 = 0;
+
+    loop {
+        let (send, recv) = match conn.accept_bi().await {
+            Ok(s) => s,
+            Err(e) => {
+                tracing::debug!(
+                    ?remote,
+                    streams_seen,
+                    error = %e,
+                    "command receiver: accept_bi loop ended"
+                );
+                return;
+            }
+        };
+        streams_seen += 1;
+        let engine_running = engine_running.clone();
+        tokio::spawn(handle_one_command(remote, send, recv, engine_running));
+    }
+}
+
+async fn handle_one_command(
+    remote: std::net::SocketAddr,
+    mut send: quinn::SendStream,
+    mut recv: quinn::RecvStream,
+    engine_running: Arc<AtomicBool>,
+) {
+    let mut buf = [0u8; QuicMessage::WIRE_SIZE];
+    if let Err(e) = recv.read_exact(&mut buf).await {
+        tracing::trace!(?remote, error = %e, "command receiver: short read; closing stream");
+        return;
+    }
+    let cmd = match QuicMessage::decode(&buf) {
+        Ok(m) => m,
+        Err(e) => {
+            tracing::warn!(?remote, error = %e, "command receiver: decode failed");
+            let _ = send.reset(0u32.into());
+            return;
+        }
+    };
+
+    if cmd.typ() == SensorType::Relay {
+        // raw_value == 1.0 ⇒ stop the engine; 0.0 ⇒ resume.
+        let now_running = cmd.raw_value < 0.5;
+        let was_running = engine_running.swap(now_running, Ordering::SeqCst);
+        if now_running != was_running {
+            if now_running {
+                tracing::info!(device = %cmd.device_id, "Relay=0 received — engine resuming");
+            } else {
+                tracing::info!(device = %cmd.device_id, "Relay=1 received — engine stopping");
+            }
+        }
+    } else {
+        tracing::debug!(
+            ?remote,
+            sensor_type = cmd.sensor_type,
+            "command receiver: ignoring non-Relay command"
+        );
+    }
+
+    // Ack by echoing the command — the substrate's outbound drain measures
+    // latency from open_bi() to ack receipt.
+    if let Err(e) = send.write_all(&cmd.to_bytes()).await {
+        tracing::warn!(?remote, error = %e, "command receiver: ack write failed");
+        return;
+    }
+    if let Err(e) = send.finish() {
+        tracing::warn!(?remote, error = %e, "command receiver: ack finish failed");
+    }
+}