Feature(Go): Web terminal relay with PTY mode and graceful close (Phase 6)

server/go/web/ws.go

@@ -46,11 +46,12 @@ type wsClient struct {
 	once   sync.Once
 
 	// Mutated under wsHub.mu (or only by the read loop owning this client).
-	nonce    string // outstanding challenge — cleared after a successful login
-	token    string // set once authenticated
-	role     string // mirrors session role after login
-	addr     string // client address for logs
-	watching string // device ID this browser is currently streaming, "" when on the list
+	nonce        string // outstanding challenge — cleared after a successful login
+	token        string // set once authenticated
+	role         string // mirrors session role after login
+	addr         string // client address for logs
+	watching     string // device ID this browser is currently streaming, "" when on the list
+	termWatching string // device ID for an open web terminal session, "" otherwise
 }
 
 // queue writes a JSON text frame onto the send buffer. Drops silently if the
@@ -176,6 +177,61 @@ func (h *wsHub) OnScreenFrame(deviceID string, packet []byte, _ bool) {
 	}
 }
 
+// OnTerminalReady notifies the requesting browser that its term_open
+// handshake completed. mode is "pty" or "legacy" — xterm.js disables the
+// resize callback in legacy mode (no PTY behind the cmd pipe).
+func (h *wsHub) OnTerminalReady(deviceID string, isPTY bool) {
+	mode := "legacy"
+	if isPTY {
+		mode = "pty"
+	}
+	msg := mustJSON(map[string]any{
+		"cmd":  "term_ready",
+		"id":   deviceID,
+		"mode": mode,
+	})
+	h.mu.RLock()
+	defer h.mu.RUnlock()
+	for c := range h.clients {
+		if c.termWatching == deviceID && c.token != "" {
+			c.queue(msg)
+		}
+	}
+}
+
+// OnTerminalData ships one chunk of raw shell output (already wrapped in
+// the "TRM1" magic header) over the binary WS frame. Single-viewer is
+// enforced upstream so at most one client matches per device.
+func (h *wsHub) OnTerminalData(deviceID string, packet []byte) {
+	h.mu.RLock()
+	defer h.mu.RUnlock()
+	for c := range h.clients {
+		if c.termWatching == deviceID && c.token != "" {
+			c.queueBinary(packet)
+		}
+	}
+}
+
+// OnTerminalClosed fires when the device's shell exits or the sub-conn
+// drops. The browser closes its xterm panel. We also clear termWatching
+// so a subsequent term_open from the same browser isn't rejected as
+// "already open" by stale state.
+func (h *wsHub) OnTerminalClosed(deviceID string, reason string) {
+	msg := mustJSON(map[string]any{
+		"cmd":    "term_closed",
+		"ok":     true,
+		"reason": reason,
+	})
+	h.mu.Lock()
+	defer h.mu.Unlock()
+	for c := range h.clients {
+		if c.termWatching == deviceID && c.token != "" {
+			c.termWatching = ""
+			c.queue(msg)
+		}
+	}
+}
+
 // OnDeviceUpdate forwards heartbeat-derived liveness data so the device-list
 // rows can refresh RTT and active-window labels without re-fetching.
 func (h *wsHub) OnDeviceUpdate(id string, rtt int, activeWindow string) {
@@ -221,6 +277,13 @@ func (h *wsHub) unregister(c *wsClient) {
 	if c.watching != "" && h.countWatchers(c.watching) == 0 {
 		h.devices.CloseScreen(c.watching)
 	}
+	// Terminal sessions are single-viewer by design, so any open session
+	// belongs to this client. Tear it down so the next viewer doesn't
+	// hit ErrTerminalBusy from an abandoned session.
+	if c.termWatching != "" {
+		h.devices.CloseTerminalSession(c.termWatching)
+		c.termWatching = ""
+	}
 	// Do NOT revoke the token: tokens are session-scoped, not WS-scoped.
 	// Frontend may close+reopen the WS at any time (visibilitychange handler,
 	// brief network blip, reload) and must be able to resume with the same