fix(pty): respond to DSR cursor position queries for inline TUI compatibility

crates/pilotty-cli/src/daemon/pty.rs

@@ -8,6 +8,83 @@ use portable_pty::{native_pty_system, Child, CommandBuilder, MasterPty, PtySize}
 use tokio::sync::mpsc;
 use tracing::{debug, error, warn};
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+enum DsrParseState {
+    Ground,
+    Esc,
+    Csi,
+    Csi6,
+}
+
+/// Tracks terminal cursor position and detects DSR cursor-position requests.
+struct CursorTracker {
+    parser: vt100::Parser,
+    dsr_state: DsrParseState,
+}
+
+impl CursorTracker {
+    fn new(size: TermSize) -> Self {
+        Self {
+            parser: vt100::Parser::new(size.rows, size.cols, 0),
+            dsr_state: DsrParseState::Ground,
+        }
+    }
+
+    fn resize(&mut self, size: TermSize) {
+        self.parser.screen_mut().set_size(size.rows, size.cols);
+    }
+
+    fn process_output(&mut self, bytes: &[u8]) -> Vec<(u16, u16)> {
+        let mut positions = Vec::new();
+        let mut segment_start = 0;
+
+        for (idx, &b) in bytes.iter().enumerate() {
+            if self.advance_dsr_state(b) {
+                self.parser.process(&bytes[segment_start..=idx]);
+                positions.push(self.cursor_position_one_indexed());
+                segment_start = idx + 1;
+            }
+        }
+
+        if segment_start < bytes.len() {
+            self.parser.process(&bytes[segment_start..]);
+        }
+
+        positions
+    }
+
+    fn cursor_position_one_indexed(&self) -> (u16, u16) {
+        let (row, col) = self.parser.screen().cursor_position();
+        (row.saturating_add(1), col.saturating_add(1))
+    }
+
+    fn advance_dsr_state(&mut self, b: u8) -> bool {
+        let mut detected = false;
+
+        self.dsr_state = match (self.dsr_state, b) {
+            (DsrParseState::Ground, 0x1b) => DsrParseState::Esc,
+            (DsrParseState::Ground, _) => DsrParseState::Ground,
+
+            (DsrParseState::Esc, b'[') => DsrParseState::Csi,
+            (DsrParseState::Esc, 0x1b) => DsrParseState::Esc,
+            (DsrParseState::Esc, _) => DsrParseState::Ground,
+
+            (DsrParseState::Csi, b'6') => DsrParseState::Csi6,
+            (DsrParseState::Csi, 0x1b) => DsrParseState::Esc,
+            (DsrParseState::Csi, _) => DsrParseState::Ground,
+
+            (DsrParseState::Csi6, b'n') => {
+                detected = true;
+                DsrParseState::Ground
+            }
+            (DsrParseState::Csi6, 0x1b) => DsrParseState::Esc,
+            (DsrParseState::Csi6, _) => DsrParseState::Ground,
+        };
+
+        detected
+    }
+}
+
 /// Terminal size in columns and rows.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub struct TermSize {
@@ -130,6 +207,8 @@ pub struct AsyncPtyHandle {
     reader_thread: Option<std::thread::JoinHandle<()>>,
     /// Handle to the writer thread for cleanup.
     writer_thread: Option<std::thread::JoinHandle<()>>,
+    /// Tracks cursor position from PTY output for DSR responses.
+    cursor_tracker: Arc<std::sync::Mutex<CursorTracker>>,
 }
 
 impl AsyncPtyHandle {
@@ -148,10 +227,20 @@ impl AsyncPtyHandle {
         let (write_tx, write_rx) = mpsc::channel::<Vec<u8>>(64);
         let (read_tx, read_rx) = mpsc::channel::<Vec<u8>>(64);
 
+        let cursor_tracker = Arc::new(std::sync::Mutex::new(CursorTracker::new(initial_size)));
+
         // Spawn reader thread
         let reader_shutdown = shutdown.clone();
+        let reader_write_tx = write_tx.clone();
+        let reader_tracker = cursor_tracker.clone();
         let reader_thread = std::thread::spawn(move || {
-            Self::reader_loop(reader, read_tx, reader_shutdown);
+            Self::reader_loop(
+                reader,
+                read_tx,
+                reader_write_tx,
+                reader_tracker,
+                reader_shutdown,
+            );
         });
 
         // Spawn writer thread
@@ -168,6 +257,7 @@ impl AsyncPtyHandle {
             size: std::sync::Mutex::new(initial_size),
             reader_thread: Some(reader_thread),
             writer_thread: Some(writer_thread),
+            cursor_tracker,
         })
     }
 
@@ -185,6 +275,11 @@ impl AsyncPtyHandle {
             .size
             .lock()
             .map_err(|_| anyhow::anyhow!("Size mutex poisoned"))? = size;
+
+        self.cursor_tracker
+            .lock()
+            .map_err(|_| anyhow::anyhow!("Cursor tracker mutex poisoned"))?
+            .resize(size);
         Ok(())
     }
     /// Send bytes to the PTY stdin.
@@ -245,6 +340,8 @@ impl AsyncPtyHandle {
     fn reader_loop(
         mut reader: Box<dyn Read + Send>,
         read_tx: mpsc::Sender<Vec<u8>>,
+        write_tx: mpsc::Sender<Vec<u8>>,
+        cursor_tracker: Arc<std::sync::Mutex<CursorTracker>>,
         shutdown: Arc<std::sync::atomic::AtomicBool>,
     ) {
         let mut buf = vec![0u8; READ_BUFFER_SIZE];
@@ -261,6 +358,32 @@ impl AsyncPtyHandle {
                     break;
                 }
                 Ok(n) => {
+                    let dsr_positions = match cursor_tracker.lock() {
+                        Ok(mut tracker) => tracker.process_output(&buf[..n]),
+                        Err(_) => {
+                            warn!("Cursor tracker mutex poisoned; skipping DSR detection");
+                            Vec::new()
+                        }
+                    };
+
+                    if !dsr_positions.is_empty() {
+                        for (row, col) in dsr_positions {
+                            let response = format!("\x1b[{};{}R", row, col).into_bytes();
+                            match write_tx.try_send(response) {
+                                Ok(()) => {}
+                                Err(mpsc::error::TrySendError::Full(_)) => {
+                                    warn!(
+                                        "PTY write channel full; dropping synthetic DSR response"
+                                    );
+                                }
+                                Err(mpsc::error::TrySendError::Closed(_)) => {
+                                    debug!("PTY write channel closed while sending DSR response");
+                                    break;
+                                }
+                            }
+                        }
+                    }
+
                     // Use blocking send since we're in a thread
                     if read_tx.blocking_send(buf[..n].to_vec()).is_err() {
                         debug!("PTY read channel closed");
@@ -347,9 +470,50 @@ impl Drop for AsyncPtyHandle {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use regex::Regex;
     use std::io::Read;
     use std::time::Duration;
 
+    #[test]
+    fn test_cursor_tracker_collects_cursor_positions_for_dsr_queries() {
+        let mut tracker = CursorTracker::new(TermSize { cols: 80, rows: 24 });
+
+        assert_eq!(tracker.process_output(b"hello"), Vec::<(u16, u16)>::new());
+        assert_eq!(tracker.process_output(b"\x1b[6n"), vec![(1, 6)]);
+        assert_eq!(
+            tracker.process_output(b"x\x1b[6n\x1b[6n"),
+            vec![(1, 7), (1, 7)]
+        );
+    }
+
+    #[test]
+    fn test_cursor_tracker_detects_dsr_across_chunk_boundary() {
+        let mut tracker = CursorTracker::new(TermSize { cols: 80, rows: 24 });
+
+        assert_eq!(tracker.process_output(b"\x1b["), Vec::<(u16, u16)>::new());
+        assert_eq!(tracker.process_output(b"6"), Vec::<(u16, u16)>::new());
+        assert_eq!(tracker.process_output(b"n"), vec![(1, 1)]);
+    }
+
+    #[test]
+    fn test_cursor_tracker_captures_position_at_dsr_boundary_with_trailing_output() {
+        let mut tracker = CursorTracker::new(TermSize { cols: 80, rows: 24 });
+
+        let positions = tracker.process_output(b"abc\x1b[6nxyz");
+
+        assert_eq!(positions, vec![(1, 4)]);
+        assert_eq!(tracker.cursor_position_one_indexed(), (1, 7));
+    }
+
+    #[test]
+    fn test_cursor_tracker_reports_one_indexed_position() {
+        let mut tracker = CursorTracker::new(TermSize { cols: 80, rows: 24 });
+        tracker.process_output(b"abc");
+
+        // Cursor is after 3 chars on first row => 1-indexed (1, 4)
+        assert_eq!(tracker.cursor_position_one_indexed(), (1, 4));
+    }
+
     #[test]
     fn test_spawn_echo_and_read_output() {
         let session = PtySession::spawn(
@@ -509,6 +673,52 @@ mod tests {
             .expect("resize to smaller should succeed");
     }
 
+    #[tokio::test]
+    async fn test_async_pty_responds_to_dsr_cursor_query() {
+        let session = PtySession::spawn(
+            &[
+                "bash".to_string(),
+                "-lc".to_string(),
+                "printf 'abc\\033[6nxyz'; IFS=';' read -r -d R row col; printf 'ok:%s;%s\\n' \"$row\" \"$col\""
+                    .to_string(),
+            ],
+            TermSize::default(),
+            None,
+        )
+        .expect("Failed to spawn bash DSR test");
+
+        let handle = AsyncPtyHandle::new(session).expect("Failed to create async handle");
+
+        let result = tokio::time::timeout(Duration::from_secs(2), async {
+            let mut collected = Vec::new();
+            while let Some(chunk) = handle.read().await {
+                collected.extend_from_slice(&chunk);
+                if String::from_utf8_lossy(&collected).contains("ok:") {
+                    break;
+                }
+            }
+            collected
+        })
+        .await;
+
+        let bytes = result.expect("Timed out waiting for DSR response");
+        let output = String::from_utf8_lossy(&bytes);
+        let captures = Regex::new(r"ok:\x1b\[(\d+);(\d+)")
+            .expect("valid regex")
+            .captures(&output)
+            .expect("Expected shell to receive DSR response with cursor coordinates");
+        let row: u16 = captures[1].parse().expect("row should parse");
+        let col: u16 = captures[2].parse().expect("col should parse");
+
+        assert_eq!(
+            (row, col),
+            (1, 4),
+            "Unexpected DSR response in output: {output:?}"
+        );
+
+        handle.shutdown().await;
+    }
+
     #[test]
     fn test_spawn_with_cwd() {
         // Spawn pwd in /tmp and verify it outputs a path containing "tmp"