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ccu_emulator/refresh.py

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+from __future__ import annotations
+
+import time
+from dataclasses import dataclass, field
+
+
+@dataclass
+class PeriodicRefresh:
+    """Small scheduler for optional CCU state-refresh frames."""
+
+    frames: list[bytes] = field(default_factory=list)
+    interval: float = 0.0
+    _next_due: float | None = None
+    _index: int = 0
+
+    @property
+    def enabled(self) -> bool:
+        return bool(self.frames) and self.interval > 0
+
+    def start(self, now: float | None = None) -> None:
+        if not self.enabled:
+            self._next_due = None
+            return
+        self._next_due = (time.monotonic() if now is None else now) + self.interval
+
+    def due_frames(self, now: float | None = None) -> list[bytes]:
+        if not self.enabled:
+            return []
+        current = time.monotonic() if now is None else now
+        if self._next_due is None:
+            self._next_due = current + self.interval
+            return []
+        if current < self._next_due:
+            return []
+
+        frame = self.frames[self._index % len(self.frames)]
+        self._index += 1
+
+        while self._next_due <= current:
+            self._next_due += self.interval
+        return [frame]