refactor: improve TTY detection using /proc/self/stat and device number parsing

Co-authored-by: aider (openai/andrew.openrouter.qwen.qwen3-coder) <aider@aider.chat>

src/meta_plugin/system.rs

@@ -373,43 +373,34 @@ impl TtyMetaPlugin {
 }
 
 impl MetaPlugin for TtyMetaPlugin {
-    fn is_supported(&self) -> bool {
-        // Check if the 'tty' command is available
-        std::process::Command::new("sh")
-            .arg("-c")
-            .arg("command -v tty")
-            .output()
-            .map(|output| output.status.success())
-            .unwrap_or(false)
-    }
-
     fn create(&self) -> Result<Box<dyn Write>> {
         Ok(Box::new(io::sink()))
     }
 
     fn finalize(&mut self) -> io::Result<String> {
-        // Try to get the TTY from the TTY environment variable first
-        if let Ok(tty) = env::var("TTY") {
-            if !tty.is_empty() {
-                return Ok(tty);
-            }
-        }
-        
-        // Use the tty command to get the current terminal
-        match std::process::Command::new("tty").output() {
-            Ok(output) => {
-                if output.status.success() {
-                    let tty_path = String::from_utf8_lossy(&output.stdout);
-                    let trimmed = tty_path.trim();
-                    if trimmed.is_empty() || trimmed == "not a tty" {
-                        Ok("not a tty".to_string())
-                    } else {
-                        Ok(trimmed.to_string())
+        // Try to get TTY from /proc/self/stat
+        match std::fs::read_to_string("/proc/self/stat") {
+            Ok(stat_content) => {
+                // The 7th field (index 6) in /proc/self/stat contains the controlling terminal (TTY)
+                let fields: Vec<&str> = stat_content.split_whitespace().collect();
+                if fields.len() > 6 {
+                    if let Ok(tty_nr) = fields[6].parse::<u32>() {
+                        if tty_nr != 0 {
+                            // Convert tty_nr to device path
+                            match self.tty_name(tty_nr) {
+                                Some(tty_name) => return Ok(tty_name),
+                                None => return Ok("unknown tty".to_string()),
+                            }
+                        }
                     }
-                } else {
-                    Ok("not a tty".to_string())
                 }
             }
+            Err(_) => {}
+        }
+        
+        // Fallback: try to get TTY from /dev/tty
+        match std::fs::read_link("/dev/tty") {
+            Ok(path) => Ok(format!("/dev/{}", path.to_string_lossy())),
             Err(_) => Ok("not a tty".to_string()),
         }
     }
@@ -421,8 +412,37 @@ impl MetaPlugin for TtyMetaPlugin {
     fn meta_name(&mut self) -> String {
         self.meta_name.clone()
     }
-    
-    fn program_info(&self) -> Option<(&str, Vec<&str>)> {
-        Some(("tty", vec![]))
+}
+
+impl TtyMetaPlugin {
+    // Convert tty device number to device name
+    fn tty_name(&self, tty_nr: u32) -> Option<String> {
+        let major = (tty_nr >> 8) as u16;
+        let minor = (tty_nr & 0xff) as u16;
+        
+        // Handle common TTY device types
+        match major {
+            4 => {
+                // TTY devices
+                if minor < 64 {
+                    Some(format!("/dev/tty{}", minor))
+                } else {
+                    None
+                }
+            },
+            136..=143 => {
+                // PTS devices
+                Some(format!("/dev/pts/{}", minor))
+            },
+            3 => {
+                // TTY devices
+                if minor < 64 {
+                    Some(format!("/dev/tty{}", minor))
+                } else {
+                    None
+                }
+            },
+            _ => None,
+        }
     }
 }