refactor: put shared ui screen code into ui.viewkit

1 files changed, 39 insertions, 3 deletions

diff --git a/app/backends/__init__.py b/app/backends/__init__.py
index f6a1d9b..2b7fbe6 100644
--- a/app/backends/__init__.py
+++ b/app/backends/__init__.py
@@ -25,10 +25,17 @@ registry.
 """
 
 import shlex
+import time
 from dataclasses import dataclass, field
 from pathlib import Path
 from typing import Callable, Dict, List, Optional
 
+# How long detect_all() results stay fresh (see detect_all). Long enough to
+# cover a burst of menu renders, short enough that state changed by an
+# outside actor (a remote server appearing) surfaces promptly.
+DETECT_TTL_SECONDS = 2.0
+_detect_cache = None
+
 
 @dataclass
 class ServerSpec:
@@ -200,10 +207,39 @@ def get(key: str) -> Optional[BackendInfo]:
     return _BY_KEY.get(key)
 
 
-def detect_all() -> List[BackendStatus]:
-    """Detect every registered backend's status, in registry order."""
+def detect_all(*, refresh: bool = False) -> List[BackendStatus]:
+    """Detect every registered backend's status, in registry order.
+
+    Detection is not free — each backend probes the filesystem and, for
+    remote servers, the network — so results are cached for a short
+    window (DETECT_TTL_SECONDS). Menu renders that happen in quick
+    succession (popping back and forth between hub screens) reuse the
+    cached statuses; anything past the TTL re-probes. REFRESH forces an
+    immediate re-detection: callers use it right after an action that can
+    change status (setup, uninstall, server start/stop) so the next render
+    never shows stale state.
+    """
     _build_registry()
-    return [info.detect() for info in REGISTRY]
+    global _detect_cache
+    now = time.monotonic()
+    if not refresh and _detect_cache is not None:
+        at, statuses = _detect_cache
+        if now - at < DETECT_TTL_SECONDS:
+            return list(statuses)
+    statuses = [info.detect() for info in REGISTRY]
+    _detect_cache = (now, statuses)
+    return list(statuses)
+
+
+def invalidate_detect_cache() -> None:
+    """Drop the cached statuses so the next detect_all() re-probes.
+
+    Called by the hub after any action that can change a backend's on-disk
+    or running state (setup wizards, uninstallers, server toggles,
+    conversion runs with autostart, settings writes).
+    """
+    global _detect_cache
+    _detect_cache = None
 
 
 def detect(key: str) -> Optional[BackendStatus]: