WIP autoscaler agent

agent/nix_builder_autoscaler/providers/clock.py

@@ -0,0 +1,39 @@
+"""Injectable clock abstraction for testability."""
+
+from __future__ import annotations
+
+from datetime import UTC, datetime, timedelta
+from typing import Protocol
+
+
+class Clock(Protocol):
+    """Clock protocol — provides current UTC time."""
+
+    def now(self) -> datetime: ...
+
+
+class SystemClock:
+    """Real wall-clock implementation."""
+
+    def now(self) -> datetime:
+        """Return the current UTC time."""
+        return datetime.now(UTC)
+
+
+class FakeClock:
+    """Deterministic clock for tests."""
+
+    def __init__(self, start: datetime | None = None) -> None:
+        self._now = start or datetime(2026, 1, 1, tzinfo=UTC)
+
+    def now(self) -> datetime:
+        """Return the fixed current time."""
+        return self._now
+
+    def advance(self, seconds: float) -> None:
+        """Advance the clock by the given number of seconds."""
+        self._now += timedelta(seconds=seconds)
+
+    def set(self, dt: datetime) -> None:
+        """Set the clock to an exact time."""
+        self._now = dt