Add internal metrics sensor for relay on time

src/lib/sensors/__init__.py

@@ -9,6 +9,7 @@
 from lib.sensors.PMSA003I import PMSA003I
 from lib.sensors.sensor_module import SensorModule
 from lib.sensors.file_logging import FileLogger
+from lib.sensors.internal_metrics import InternalMetrics
 from lib.sensors.alarm import Alarm
 from lib.displays.display import Display
 from lib.networking import WirelessNetwork
@@ -32,6 +33,8 @@ def __init__(self, i2c: I2C, display: Display, wifi: WirelessNetwork, space_stat
         self.file_logger = FileLogger(init_files=True)
         self.load_modules(self.SENSOR_MODULES)
         self._configure_modules()
+        self.internal_metrics = InternalMetrics(self.space_state)
+        self.configured_modules['InternalMetrics'] = self.internal_metrics
         self.alarm = Alarm(self.display, self.space_state)
         if CO2_ALARM_THRESHOLD_PPM > 0 and 'SCD30' in self.configured_modules:
             self.alarm.enable()

src/lib/sensors/internal_metrics.py

@@ -0,0 +1,39 @@
+from lib.relay_history import RTCUnreliableError
+from lib.sensors.sensor_module import SensorModule
+from lib.space_state import SpaceState
+from lib.ulogging import uLogger
+
+class InternalMetrics(SensorModule):
+    """
+    Reports internal SMIBHID metrics as sensor readings, rather than
+    readings from an external, physically attached, I2C sensor.
+    """
+
+    def __init__(self, space_state: SpaceState) -> None:
+        super().__init__([{"name": "relay_on_time", "unit": "s"}])
+        self.log = uLogger("InternalMetrics")
+        self.space_state = space_state
+
+    def _get_relay_on_time(self) -> float | None:
+        """
+        Return cumulative relay active seconds from relay history, or None
+        if relay history is not available or not enabled.
+        """
+        relay_history = getattr(self.space_state, "relay_history", None)
+        if relay_history is None:
+            self.log.info("Relay history not available - no relay on time to report")
+            return None
+
+        try:
+            return relay_history.get_total_active_seconds(bool(self.space_state._last_relay_state))
+        except RTCUnreliableError:
+            self.log.info("System clock not yet reliable - no relay on time to report")
+            return None
+
+    def get_reading(self) -> dict[str, float | None]:
+        """
+        Get internal metrics reading in SMIBHID format.
+        """
+        return {
+            "relay_on_time": self._get_relay_on_time()
+        }