feat(linux): change power management sensor to power state sensor

- rename power management to power state
- use a single sensor for different states

internal/agent/device_linux.go

@@ -36,6 +36,6 @@ func sensorWorkers() []func(context.Context, device.SensorTracker) {
 		linux.UsersUpdater,
 		linux.Versions,
 		linux.TempUpdater,
-		linux.PowerMgmtUpdater)
+		linux.PowerStateUpdater)
 	return workers
 }

internal/linux/powerStateSensor.go

@@ -0,0 +1,91 @@
+// Copyright (c) 2023 Joshua Rich <[email protected]>
+//
+// This software is released under the MIT License.
+// https://opensource.org/licenses/MIT
+
+package linux
+
+import (
+	"context"
+
+	"github.com/godbus/dbus/v5"
+	"github.com/joshuar/go-hass-agent/internal/device"
+	"github.com/rs/zerolog/log"
+)
+
+type powerStateSensor struct {
+	linuxSensor
+}
+
+func (s *powerStateSensor) Icon() string {
+	switch s.value.(string) {
+	case "Suspended":
+		return "mdi:power-sleep"
+	case "Powered Off":
+		return "mdi:power-off"
+	}
+	return "mdi:power-on"
+}
+
+func PowerStateUpdater(ctx context.Context, tracker device.SensorTracker) {
+	sensorCh := make(chan interface{})
+	go func() {
+		defer close(sensorCh)
+		<-ctx.Done()
+	}()
+	go func() {
+		for sensor := range sensorCh {
+			if err := tracker.UpdateSensors(ctx, sensor); err != nil {
+				log.Error().Err(err).Msg("Could not update power state sensor.")
+			}
+		}
+	}()
+
+	sensorCh <- newPowerState("Powered On")
+
+	err := NewBusRequest(ctx, SystemBus).
+		Path("/org/freedesktop/login1").
+		Match([]dbus.MatchOption{
+			dbus.WithMatchInterface("org.freedesktop.login1.Manager"),
+		}).
+		Event("org.freedesktop.DBus.Properties.PropertiesChanged").
+		Handler(func(s *dbus.Signal) {
+			switch s.Name {
+			case "org.freedesktop.login1.Manager.PrepareForSleep":
+				if assertTruthiness(s.Body[0]) {
+					sensorCh <- newPowerState("Suspended")
+				} else {
+					sensorCh <- newPowerState("Powered On")
+				}
+			case "org.freedesktop.login1.Manager.PrepareForShutdown":
+				if assertTruthiness(s.Body[0]) {
+					sensorCh <- newPowerState("Powered Off")
+				} else {
+					sensorCh <- newPowerState("Powered On")
+				}
+			}
+		}).
+		AddWatch(ctx)
+	if err != nil {
+		log.Warn().Err(err).
+			Msg("Failed to create user D-Bus watch. Will not track powered off state.")
+	}
+}
+
+func newPowerState(state string) *powerStateSensor {
+	return &powerStateSensor{
+		linuxSensor: linuxSensor{
+			sensorType: powerState,
+			value:      state,
+			source:     srcDbus,
+			diagnostic: true,
+		},
+	}
+}
+
+func assertTruthiness(v interface{}) bool {
+	if isTrue, ok := v.(bool); ok && isTrue {
+		return true
+	}
+	return false
+}

internal/linux/sensorType.go

@@ -55,8 +55,7 @@ const (
 	version                                 // Distribution Version
 	users                                   // Current Users
 	deviceTemp                              // Temperature
-	isSuspended                             // Suspended
-	isShutdown                              // Powered Off
+	powerState                              // Power State
 )
 
 // sensorType represents the unique type of sensor data being reported. Every