feat(m1): inotify app log watcher — tails log files for known apps

src-tauri/Cargo.toml

@@ -31,3 +31,6 @@ tauri-plugin-log = "2"
 tauri-plugin-notification = "2"
 tauri-plugin-shell = "2"
 tauri-plugin-fs = "2"
+
+[dev-dependencies]
+tempfile = "3"

src-tauri/src/watcher/inotify.rs

@@ -1,7 +1,121 @@
-use super::SystemEvent;
+use super::{now_unix, EventSource, SystemEvent};
+use notify::{recommended_watcher, RecursiveMode, Watcher};
 use std::collections::HashMap;
+use std::io::{Read, Seek};
 use tokio::sync::mpsc;
 
-pub async fn watch(_log_paths: HashMap<String, String>, _tx: mpsc::Sender<SystemEvent>) {
+pub async fn watch(log_paths: HashMap<String, String>, tx: mpsc::Sender<SystemEvent>) {
-    // implemented in Task 8
+    if log_paths.is_empty() {
+        return;
+    }
+
+    let expanded: HashMap<String, String> = log_paths
+        .iter()
+        .map(|(k, v)| (k.clone(), expand_tilde(v)))
+        .collect();
+
+    tokio::task::spawn_blocking(move || {
+        let (notify_tx, notify_rx) = std::sync::mpsc::channel();
+        let mut watcher = match recommended_watcher(notify_tx) {
+            Ok(w) => w,
+            Err(e) => {
+                log::error!("inotify watcher init failed: {e}");
+                return;
+            }
+        };
+
+        // positions: path -> (app_name, byte_offset)
+        let mut positions: HashMap<String, (String, u64)> = HashMap::new();
+
+        for (app_name, path) in &expanded {
+            let pb = std::path::Path::new(path);
+            if pb.exists() {
+                let len = std::fs::metadata(pb).map(|m| m.len()).unwrap_or(0);
+                positions.insert(path.clone(), (app_name.clone(), len));
+                watcher.watch(pb, RecursiveMode::NonRecursive).ok();
+            }
+        }
+
+        for result in notify_rx {
+            if let Ok(event) = result {
+                for path in event.paths {
+                    let path_str = path.to_string_lossy().to_string();
+                    if let Some((app_name, pos)) = positions.get_mut(&path_str) {
+                        let (lines, new_pos) = read_new_lines(&path_str, *pos);
+                        *pos = new_pos;
+                        for line in lines {
+                            tx.blocking_send(SystemEvent {
+                                source: EventSource::AppLog {
+                                    app: app_name.clone(),
+                                },
+                                raw_line: line,
+                                timestamp: now_unix(),
+                            })
+                            .ok();
+                        }
+                    }
+                }
+            }
+        }
+    });
+}
+
+pub fn expand_tilde(path: &str) -> String {
+    if let Some(rest) = path.strip_prefix("~/") {
+        let home = std::env::var("HOME").unwrap_or_else(|_| "/home/user".into());
+        format!("{home}/{rest}")
+    } else {
+        path.to_string()
+    }
+}
+
+pub fn read_new_lines(path: &str, from_byte: u64) -> (Vec<String>, u64) {
+    let mut file = match std::fs::File::open(path) {
+        Ok(f) => f,
+        Err(_) => return (vec![], from_byte),
+    };
+    if file.seek(std::io::SeekFrom::Start(from_byte)).is_err() {
+        return (vec![], from_byte);
+    }
+    let mut content = String::new();
+    let _ = file.read_to_string(&mut content);
+    let new_pos = from_byte + content.len() as u64;
+    let lines: Vec<String> = content
+        .lines()
+        .filter(|l| !l.is_empty())
+        .map(|l| l.to_string())
+        .collect();
+    (lines, new_pos)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn expand_tilde_home() {
+        let home = std::env::var("HOME").unwrap_or("/home/user".into());
+        let expanded = expand_tilde("~/.config/retroarch/retroarch.log");
+        assert!(expanded.starts_with(&home));
+        assert!(expanded.ends_with(".config/retroarch/retroarch.log"));
+    }
+
+    #[test]
+    fn expand_tilde_no_tilde() {
+        let path = "/absolute/path/to/file.log";
+        assert_eq!(expand_tilde(path), path);
+    }
+
+    #[tokio::test]
+    async fn reads_new_lines_from_file() {
+        use std::io::Write;
+        let dir = tempfile::tempdir().unwrap();
+        let path = dir.path().join("test.log");
+        let mut f = std::fs::File::create(&path).unwrap();
+        write!(f, "line one\n").unwrap();
+
+        let (lines, pos) = read_new_lines(path.to_str().unwrap(), 0);
+        assert_eq!(lines, vec!["line one".to_string()]);
+        assert!(pos > 0);
+    }
 }