android(fix): crash loop on reconnect with heart rate alert enabled

android/app/src/main/kotlin/me/kavishdevar/librepods/database/apple/AppleDao.kt

@@ -3,6 +3,7 @@ package me.kavishdevar.librepods.database.apple
 import android.util.Log
 import androidx.room3.Dao
 import androidx.room3.Query
+import androidx.room3.Transaction
 import androidx.room3.Upsert
 import me.kavishdevar.librepods.bluetooth.MacAddress
 import me.kavishdevar.librepods.data.apple.AppleCache
@@ -23,18 +24,23 @@ interface AppleDao {
     @Upsert
     suspend fun upsert(device: AppleEntity)
 
+    // read-modify-write: without a transaction, concurrent saves (cache is saved on every state change)
+    // overwrite each other with stale columns, which is how metadata ended up empty in the db
+    @Transaction
     suspend fun updateSettings(macAddress: MacAddress, settings: AppleSettings) {
         Log.d(TAG, "Updating settings for $macAddress: $settings")
         val device = get(macAddress)?: AppleEntity(macAddress = macAddress, settings = settings, metadata = AppleMetadata(), cache = AppleCache())
         upsert(device.copy(settings = settings))
     }
 
+    @Transaction
     suspend fun updateMetadata(macAddress: MacAddress, metadata: AppleMetadata) {
         Log.d(TAG, "Updating metadata for $macAddress: $metadata")
         val device = get(macAddress)?: AppleEntity(macAddress = macAddress, settings = AppleSettings(), metadata = metadata, cache = AppleCache())
         upsert(device.copy(metadata = metadata))
     }
 
+    @Transaction
     suspend fun saveCache(macAddress: MacAddress, cache: AppleCache) {
         Log.d(TAG, "Saving cache for $macAddress: $cache")
         val device = get(macAddress)?: AppleEntity(macAddress = macAddress, settings = AppleSettings(), metadata = AppleMetadata(), cache = cache)

android/app/src/main/kotlin/me/kavishdevar/librepods/devices/AppleDevice.kt

@@ -261,9 +261,16 @@ class AppleDevice(
         }
     }
 
+    // null until the AirPods send their information packet (or it is restored from the db)
+    private fun firmwareMajorVersion(): Int? = metadata.value.version3.firstOrNull()?.digitToIntOrNull()
+
     fun startHeadTracking() {
+        val firmwareMajor = firmwareMajorVersion() ?: run {
+            Log.w(TAG, "firmware version unknown, not starting head tracking")
+            return
+        }
         aacp.setSensorServiceReportInterval(
-            sensorServiceType = if (metadata.value.version3.first().digitToInt() >= 8) SensorServiceType.DEVMOTION6 else SensorServiceType.ACTIVITY,
+            sensorServiceType = if (firmwareMajor >= 8) SensorServiceType.DEVMOTION6 else SensorServiceType.ACTIVITY,
             interval = _settings.value.headTrackingInterval
         )
         _state.update {
@@ -274,10 +281,13 @@ class AppleDevice(
     }
 
     fun stopHeadTracking() {
-        aacp.setSensorServiceReportInterval(
-            sensorServiceType = if (metadata.value.version3.first().digitToInt() >= 8) SensorServiceType.DEVMOTION6 else SensorServiceType.ACTIVITY,
-            interval = Duration.ZERO
-        )
+        val firmwareMajor = firmwareMajorVersion()
+        if (firmwareMajor != null) {
+            aacp.setSensorServiceReportInterval(
+                sensorServiceType = if (firmwareMajor >= 8) SensorServiceType.DEVMOTION6 else SensorServiceType.ACTIVITY,
+                interval = Duration.ZERO
+            )
+        }
         _state.update {
             it.copy(
                 headTrackingState = BuddyState.INACTIVE,
@@ -338,8 +348,12 @@ class AppleDevice(
 
     // AACPManager sets hrmActive true when a valid reading is received
     fun startHr(): Boolean {
+        val firmwareMajor = firmwareMajorVersion() ?: run {
+            Log.w(TAG, "firmware version unknown, not starting heart rate monitoring")
+            return false
+        }
         val success = aacp.setSensorServiceReportInterval(
-            sensorServiceType = if (metadata.value.version3.first().digitToInt() >= 9) SensorServiceType.HEARTRATE_COMMAND else SensorServiceType.HEARTRATE,
+            sensorServiceType = if (firmwareMajor >= 9) SensorServiceType.HEARTRATE_COMMAND else SensorServiceType.HEARTRATE,
             interval = 1.seconds
         )
         if (success) {
@@ -352,8 +366,12 @@ class AppleDevice(
         return success
     }
     fun stopHr(): Boolean {
+        val firmwareMajor = firmwareMajorVersion() ?: run {
+            Log.w(TAG, "firmware version unknown, can't stop heart rate monitoring")
+            return false
+        }
         val success = aacp.setSensorServiceReportInterval(
-            sensorServiceType = if (metadata.value.version3.first().digitToInt() >= 9) SensorServiceType.HEARTRATE_COMMAND else SensorServiceType.HEARTRATE,
+            sensorServiceType = if (firmwareMajor >= 9) SensorServiceType.HEARTRATE_COMMAND else SensorServiceType.HEARTRATE,
             interval = Duration.ZERO
         )
         if (state.value.hrmState != BuddyState.INACTIVE && success) _state.update {

android/app/src/main/kotlin/me/kavishdevar/librepods/services/LibrePodsService.kt

@@ -54,6 +54,7 @@ import me.kavishdevar.librepods.bluetooth.MacAddress
 import me.kavishdevar.librepods.bluetooth.aacp.types.ControlCommandIdentifier
 import me.kavishdevar.librepods.bluetooth.aacp.types.MagicKeyType
 import me.kavishdevar.librepods.bluetooth.verifyRPA
+import me.kavishdevar.librepods.data.apple.BuddyState
 import me.kavishdevar.librepods.data.heartrate.HeartRateSample
 import me.kavishdevar.librepods.data.recording.Recording
 import me.kavishdevar.librepods.database.app.AppSettingsEntity
@@ -876,6 +877,13 @@ class LibrePodsService: Service() {
 
                 appleRepository.saveMetadata(device.macAddress, metadata)
 
+                // startHr() needs the firmware version; on connect it may not have been known yet
+                if (previousMetadata.version3.isEmpty() && metadata.version3.isNotEmpty() &&
+                    device.settings.value.hrmAlertEnabled && device.state.value.hrmState == BuddyState.INACTIVE
+                ) {
+                    device.startHr()
+                }
+
                 setAppleBluetoothMetadata(device)
 
                 val notificationManager = getSystemService(NotificationManager::class.java)