feat(m1): kmsg watcher — reads /dev/kmsg kernel ring buffer

src-tauri/src/watcher/kmsg.rs

@@ -1,6 +1,65 @@
-use super::SystemEvent;
+use super::{EventSource, SystemEvent, now_unix};
+use tokio::fs::File;
+use tokio::io::{AsyncBufReadExt, BufReader};
 use tokio::sync::mpsc;
 
-pub async fn watch(_tx: mpsc::Sender<SystemEvent>) {
-    // implemented in Task 7
+pub async fn watch(tx: mpsc::Sender<SystemEvent>) {
+    let file = match File::open("/dev/kmsg").await {
+        Ok(f) => f,
+        Err(e) => {
+            log::warn!("kmsg watcher: cannot open /dev/kmsg: {e}");
+            return;
+        }
+    };
+
+    let mut lines = BufReader::new(file).lines();
+    while let Ok(Some(line)) = lines.next_line().await {
+        if let Some(msg) = parse_kmsg(&line) {
+            let _ = tx
+                .send(SystemEvent {
+                    source: EventSource::Kmsg,
+                    raw_line: msg,
+                    timestamp: now_unix(),
+                })
+                .await;
+        }
+    }
+}
+
+fn parse_kmsg(line: &str) -> Option<String> {
+    let msg = if let Some(pos) = line.find(';') {
+        &line[pos + 1..]
+    } else {
+        line
+    };
+    if msg.is_empty() {
+        return None;
+    }
+    Some(msg.to_string())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parses_kmsg_line_with_semicolon() {
+        let line = "6,1234,56789,-;usb 1-1: new full-speed USB device number 2";
+        assert_eq!(
+            parse_kmsg(line),
+            Some("usb 1-1: new full-speed USB device number 2".to_string())
+        );
+    }
+
+    #[test]
+    fn parses_kmsg_line_without_semicolon() {
+        let line = "plain message without header";
+        assert_eq!(parse_kmsg(line), Some("plain message without header".to_string()));
+    }
+
+    #[test]
+    fn skips_empty_message_after_semicolon() {
+        let line = "6,1234,56789,-;";
+        assert_eq!(parse_kmsg(line), None);
+    }
 }