refactor(android): avoid accessing thermal status change for older APIs

PowerManager.OnThermalStatusChangedListener is available only
for API 29 and above. This PR makes sure that this class
is only accessed for APIs when it's available.

android/measure/src/main/java/sh/measure/android/NoopThermalStateManager.kt

@@ -0,0 +1,20 @@
+package sh.measure.android
+
+import android.os.PowerManager
+
+/**
+ * A no-op implementation of [ThermalStateManager], used for API < Q
+ * which do not have [PowerManager.OnThermalStatusChangedListener].
+ */
+internal class NoopThermalStateManager : ThermalStateManager {
+    override fun register(powerManager: PowerManager?) {
+        // No-op
+    }
+
+    override fun unregister(powerManager: PowerManager?) {
+        // No-op
+    }
+
+    override val thermalThrottlingEnabled: Boolean
+        get() = false
+}

android/measure/src/main/java/sh/measure/android/PowerStateProvider.kt

@@ -6,7 +6,6 @@ import android.content.Intent
 import android.content.IntentFilter
 import android.os.Build
 import android.os.PowerManager
-import androidx.annotation.RequiresApi
 import sh.measure.android.logger.LogLevel
 import sh.measure.android.logger.Logger
 import sh.measure.android.utils.SystemServiceProvider
@@ -15,7 +14,7 @@ internal interface PowerStateProvider {
     fun register()
     fun unregister()
     val lowPowerModeEnabled: Boolean?
-    val thermalThrottlingEnabled: Boolean?
+    val thermalThrottlingEnabled: Boolean
 }
 
 internal class PowerStateProviderImpl(
@@ -25,8 +24,16 @@ internal class PowerStateProviderImpl(
 ) : PowerStateProvider {
     override var lowPowerModeEnabled: Boolean? = null
         private set
-    override var thermalThrottlingEnabled: Boolean? = null
-        private set
+
+    override val thermalThrottlingEnabled: Boolean
+        get() = thermalStateManager.thermalThrottlingEnabled
+
+    private val thermalStateManager: ThermalStateManager =
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
+            ThermalStateManagerImpl()
+        } else {
+            NoopThermalStateManager()
+        }
 
     private val powerSaveReceiver = object : BroadcastReceiver() {
         override fun onReceive(context: Context?, intent: Intent?) {
@@ -36,25 +43,12 @@ internal class PowerStateProviderImpl(
         }
     }
 
-    private val thermalListener = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
-        PowerManager.OnThermalStatusChangedListener { status ->
-            thermalThrottlingEnabled = isThermalThrottlingEnabled(status)
-        }
-    } else {
-        null
-    }
-
     override fun register() {
         try {
             updatePowerState()
-
             val filter = IntentFilter(PowerManager.ACTION_POWER_SAVE_MODE_CHANGED)
             context.registerReceiver(powerSaveReceiver, filter)
-
-            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
-                systemServiceProvider.powerManager?.addThermalStatusListener(thermalListener!!)
-                updateThermalState()
-            }
+            thermalStateManager.register(systemServiceProvider.powerManager)
         } catch (e: Exception) {
             logger.log(LogLevel.Error, "Failed to register power state receiver", e)
         }
@@ -63,9 +57,7 @@ internal class PowerStateProviderImpl(
     override fun unregister() {
         try {
             context.unregisterReceiver(powerSaveReceiver)
-            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
-                systemServiceProvider.powerManager?.removeThermalStatusListener(thermalListener!!)
-            }
+            thermalStateManager.unregister(systemServiceProvider.powerManager)
         } catch (e: Exception) {
             logger.log(LogLevel.Error, "Failed to unregister power state receiver", e)
         }
@@ -80,33 +72,4 @@ internal class PowerStateProviderImpl(
             lowPowerModeEnabled = null
         }
     }
-
-    @RequiresApi(Build.VERSION_CODES.Q)
-    private fun updateThermalState() {
-        try {
-            val powerManager = systemServiceProvider.powerManager
-            val currentStatus = powerManager?.currentThermalStatus
-            thermalThrottlingEnabled = isThermalThrottlingEnabled(currentStatus)
-        } catch (e: Exception) {
-            logger.log(LogLevel.Error, "Failed to update thermal state", e)
-            thermalThrottlingEnabled = null
-        }
-    }
-
-    /**
-     * Thermal throttling starts considerably affecting UX from "THERMAL_STATUS_SEVERE" status
-     * onwards.
-     *
-     * @return true if thermal status is severe or worse, false otherwise.
-     */
-    private fun isThermalThrottlingEnabled(status: Int?) = when (status) {
-        PowerManager.THERMAL_STATUS_NONE -> false
-        PowerManager.THERMAL_STATUS_LIGHT -> false
-        PowerManager.THERMAL_STATUS_MODERATE -> false
-        PowerManager.THERMAL_STATUS_SEVERE -> true
-        PowerManager.THERMAL_STATUS_CRITICAL -> true
-        PowerManager.THERMAL_STATUS_EMERGENCY -> true
-        PowerManager.THERMAL_STATUS_SHUTDOWN -> true
-        else -> null
-    }
 }

android/measure/src/main/java/sh/measure/android/ThermalStateManager.kt

@@ -0,0 +1,10 @@
+package sh.measure.android
+
+import android.os.PowerManager
+
+// Base interface for thermal state management
+internal interface ThermalStateManager {
+    fun register(powerManager: PowerManager?)
+    fun unregister(powerManager: PowerManager?)
+    val thermalThrottlingEnabled: Boolean
+}

android/measure/src/main/java/sh/measure/android/ThermalStateManagerImpl.kt

@@ -0,0 +1,43 @@
+package sh.measure.android
+
+import android.os.Build
+import android.os.PowerManager
+import androidx.annotation.RequiresApi
+
+/**
+ * An implementation of [ThermalStateManager] for API > Q where
+ * [PowerManager.OnThermalStatusChangedListener] is available.
+ */
+@RequiresApi(Build.VERSION_CODES.Q)
+internal class ThermalStateManagerImpl : ThermalStateManager {
+    private var currentThermalThrottlingState: Boolean = false
+
+    private val thermalListener = PowerManager.OnThermalStatusChangedListener { status ->
+        currentThermalThrottlingState = isThermalThrottlingEnabled(status)
+    }
+
+    override fun register(powerManager: PowerManager?) {
+        powerManager?.let {
+            it.addThermalStatusListener(thermalListener)
+            currentThermalThrottlingState = isThermalThrottlingEnabled(it.currentThermalStatus)
+        }
+    }
+
+    override fun unregister(powerManager: PowerManager?) {
+        powerManager?.removeThermalStatusListener(thermalListener)
+    }
+
+    override val thermalThrottlingEnabled: Boolean
+        get() = currentThermalThrottlingState
+
+    private fun isThermalThrottlingEnabled(status: Int?) = when (status) {
+        PowerManager.THERMAL_STATUS_NONE -> false
+        PowerManager.THERMAL_STATUS_LIGHT -> false
+        PowerManager.THERMAL_STATUS_MODERATE -> false
+        PowerManager.THERMAL_STATUS_SEVERE -> true
+        PowerManager.THERMAL_STATUS_CRITICAL -> true
+        PowerManager.THERMAL_STATUS_EMERGENCY -> true
+        PowerManager.THERMAL_STATUS_SHUTDOWN -> true
+        else -> false
+    }
+}