fix: keep dashboard logging inside curses UI

src/reactor_sim/dashboard.py

@@ -3,6 +3,8 @@
 from __future__ import annotations
 
 import curses
+import logging
+from collections import deque
 from dataclasses import dataclass
 from typing import Optional
 
@@ -35,6 +37,10 @@ class ReactorDashboard:
         self.pending_command: Optional[ReactorCommand] = None
         self.sim: Optional[ReactorSimulation] = None
         self.quit_requested = False
+        self.log_buffer: deque[str] = deque(maxlen=4)
+        self._log_handler: Optional[logging.Handler] = None
+        self._previous_handlers: list[logging.Handler] = []
+        self._logger = logging.getLogger("reactor_sim")
         self.keys = [
             DashboardKey("q", "Quit & save"),
             DashboardKey("space", "SCRAM"),
@@ -61,6 +67,7 @@ class ReactorDashboard:
         curses.init_pair(3, curses.COLOR_GREEN, -1)
         curses.init_pair(4, curses.COLOR_RED, -1)
         stdscr.nodelay(True)
+        self._install_log_capture()
         self.sim = ReactorSimulation(
             self.reactor,
             timestep=self.timestep,
@@ -79,6 +86,7 @@ class ReactorDashboard:
         finally:
             if self.save_path and self.sim and self.sim.last_state:
                 self.reactor.save_state(self.save_path, self.sim.last_state)
+            self._restore_logging()
 
     def _handle_input(self, stdscr: "curses._CursesWindow") -> None:
         while True:
@@ -265,7 +273,13 @@ class ReactorDashboard:
                 f"Failures: {', '.join(self.reactor.health_monitor.failure_log)}",
                 curses.color_pair(4) | curses.A_BOLD,
             )
-        win.addstr(4, 1, "Press 'q' to exit and persist the current snapshot.", curses.color_pair(2))
+        log_y = 3
+        for record in list(self.log_buffer):
+            if log_y >= win.getmaxyx()[0] - 1:
+                break
+            win.addstr(log_y, 1, record[: win.getmaxyx()[1] - 2], curses.color_pair(2))
+            log_y += 1
+        win.addstr(log_y, 1, "Press 'q' to exit and persist the current snapshot.", curses.color_pair(2))
 
     def _draw_section(
         self,
@@ -320,3 +334,34 @@ class ReactorDashboard:
     def _clamped_rod(self, delta: float) -> float:
         new_fraction = self.reactor.control.rod_fraction + delta
         return max(0.0, min(0.95, new_fraction))
+
+    def _install_log_capture(self) -> None:
+        if self._log_handler:
+            return
+        self._previous_handlers = list(self._logger.handlers)
+        for handler in self._previous_handlers:
+            self._logger.removeHandler(handler)
+        handler = _DashboardLogHandler(self.log_buffer)
+        handler.setFormatter(logging.Formatter("%(levelname)s | %(message)s"))
+        self._logger.addHandler(handler)
+        self._logger.propagate = False
+        self._log_handler = handler
+
+    def _restore_logging(self) -> None:
+        if not self._log_handler:
+            return
+        self._logger.removeHandler(self._log_handler)
+        for handler in self._previous_handlers:
+            self._logger.addHandler(handler)
+        self._log_handler = None
+        self._previous_handlers = []
+
+
+class _DashboardLogHandler(logging.Handler):
+    def __init__(self, buffer: deque[str]) -> None:
+        super().__init__()
+        self.buffer = buffer
+
+    def emit(self, record: logging.LogRecord) -> None:
+        msg = self.format(record)
+        self.buffer.append(msg)