feat: Initial implementation of low battery notifications for nodes (#1653)

* Add initial implementation of low battery notifications for locally-connected and favorite nodes

* Hopefully make detekt happy

* detekt pls.

* Deduplicate some of the code

* detekt'd

app/src/main/java/com/geeksville/mesh/service/MeshService.kt

@@ -213,6 +213,9 @@ class MeshService : Service(), Logging {
     private var locationFlow: Job? = null
     private var mqttMessageFlow: Job? = null
 
+    private val batteryPercentUnsupported = 0.0
+    private val batteryPercentLowThreshold = 20.0
+
     private fun getSenderName(packet: DataPacket?): String {
         val name = nodeDBbyID[packet?.from]?.user?.longName
         return name ?: getString(R.string.unknown_username)
@@ -939,7 +942,16 @@ class MeshService : Service(), Logging {
         }
         updateNodeInfo(fromNum) {
             when {
-                t.hasDeviceMetrics() -> it.deviceTelemetry = t
+                t.hasDeviceMetrics() -> {
+                    it.deviceTelemetry = t
+                    val isRemote = (fromNum != myNodeNum)
+                    if (fromNum == myNodeNum || (isRemote && it.isFavorite)) {
+                        if (t.deviceMetrics.voltage > batteryPercentUnsupported &&
+                            t.deviceMetrics.batteryLevel < batteryPercentLowThreshold) {
+                            serviceNotifications.showOrUpdateLowBatteryNotification(it, isRemote)
+                        }
+                    }
+                }
                 t.hasEnvironmentMetrics() -> it.environmentTelemetry = t
                 t.hasPowerMetrics() -> it.powerTelemetry = t
             }

app/src/main/java/com/geeksville/mesh/service/MeshServiceNotifications.kt

@@ -65,6 +65,8 @@ class MeshServiceNotifications(
             createMessageNotificationChannel()
             createAlertNotificationChannel()
             createNewNodeNotificationChannel()
+            createLowBatteryNotificationChannel()
+            createLowBatteryRemoteNotificationChannel()
         }
     }
 
@@ -173,6 +175,60 @@ class MeshServiceNotifications(
         return channelId
     }
 
+    @RequiresApi(Build.VERSION_CODES.O)
+    private fun createLowBatteryNotificationChannel(): String {
+        val channelId = "low_battery"
+        if (notificationManager.getNotificationChannel(channelId) == null) {
+            val channelName = context.getString(R.string.meshtastic_low_battery_notifications)
+            val channel = NotificationChannel(
+                channelId,
+                channelName,
+                NotificationManager.IMPORTANCE_HIGH
+            ).apply {
+                lightColor = notificationLightColor
+                lockscreenVisibility = Notification.VISIBILITY_PUBLIC
+                setShowBadge(true)
+                setSound(
+                    RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION),
+                    AudioAttributes.Builder()
+                        .setUsage(AudioAttributes.USAGE_NOTIFICATION)
+                        .setContentType(AudioAttributes.CONTENT_TYPE_SONIFICATION)
+                        .build()
+                )
+            }
+            notificationManager.createNotificationChannel(channel)
+        }
+        return channelId
+    }
+
+    // FIXME, Once we get a dedicated settings page in the app, this function should be removed and
+    //     the feature should be implemented in the regular low battery notification stuff
+    @RequiresApi(Build.VERSION_CODES.O)
+    private fun createLowBatteryRemoteNotificationChannel(): String {
+        val channelId = "low_battery_remote"
+        if (notificationManager.getNotificationChannel(channelId) == null) {
+            val channelName = context.getString(R.string.meshtastic_low_battery_temporary_remote_notifications)
+            val channel = NotificationChannel(
+                channelId,
+                channelName,
+                NotificationManager.IMPORTANCE_HIGH
+            ).apply {
+                lightColor = notificationLightColor
+                lockscreenVisibility = Notification.VISIBILITY_PUBLIC
+                setShowBadge(true)
+                setSound(
+                    RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION),
+                    AudioAttributes.Builder()
+                        .setUsage(AudioAttributes.USAGE_NOTIFICATION)
+                        .setContentType(AudioAttributes.CONTENT_TYPE_SONIFICATION)
+                        .build()
+                )
+            }
+            notificationManager.createNotificationChannel(channel)
+        }
+        return channelId
+    }
+
     private val channelId: String by lazy {
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
             createNotificationChannel()
@@ -209,6 +265,24 @@ class MeshServiceNotifications(
         }
     }
 
+    private val lowBatteryChannelId: String by lazy {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+            createLowBatteryNotificationChannel()
+        } else {
+            ""
+        }
+    }
+
+    // FIXME, Once we get a dedicated settings page in the app, this function should be removed and
+    //     the feature should be implemented in the regular low battery notification stuff
+    private val lowBatteryRemoteChannelId: String by lazy {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+            createLowBatteryRemoteNotificationChannel()
+        } else {
+            ""
+        }
+    }
+
     private fun LocalStats?.formatToString(): String = this?.allFields?.mapNotNull { (k, v) ->
         when (k.name) {
             "num_online_nodes", "num_total_nodes" -> return@mapNotNull null
@@ -258,6 +332,13 @@ class MeshServiceNotifications(
         )
     }
 
+    fun showOrUpdateLowBatteryNotification(node: NodeEntity, isRemote: Boolean) {
+        notificationManager.notify(
+            node.num, // show unique notifications
+            createLowBatteryNotification(node, isRemote)
+        )
+    }
+
     private val openAppIntent: PendingIntent by lazy {
         PendingIntent.getActivity(
             context,
@@ -409,4 +490,51 @@ class MeshServiceNotifications(
         }
         return newNodeSeenNotificationBuilder.build()
     }
+
+    lateinit var lowBatteryRemoteNotificationBuilder: NotificationCompat.Builder
+    lateinit var lowBatteryNotificationBuilder: NotificationCompat.Builder
+    private fun createLowBatteryNotification(node: NodeEntity, isRemote: Boolean): Notification {
+        val tempNotificationBuilder: NotificationCompat.Builder = if (isRemote) {
+            if (!::lowBatteryRemoteNotificationBuilder.isInitialized) {
+                lowBatteryRemoteNotificationBuilder = commonBuilder(lowBatteryChannelId)
+            }
+            lowBatteryRemoteNotificationBuilder
+        } else {
+            if (!::lowBatteryNotificationBuilder.isInitialized) {
+                lowBatteryNotificationBuilder = commonBuilder(lowBatteryRemoteChannelId)
+            }
+            lowBatteryNotificationBuilder
+        }
+        with(tempNotificationBuilder) {
+            priority = NotificationCompat.PRIORITY_DEFAULT
+            setCategory(Notification.CATEGORY_STATUS)
+            setAutoCancel(true)
+            setShowWhen(true)
+            setOnlyAlertOnce(true)
+            setWhen(System.currentTimeMillis())
+            setContentTitle(
+                context.getString(R.string.low_battery_title).format(
+                    node.shortName
+                )
+            )
+            val message = context.getString(R.string.low_battery_message).format(
+                node.longName,
+                node.deviceMetrics.batteryLevel
+            )
+            message.let {
+                setContentText(it)
+                setStyle(
+                    NotificationCompat.BigTextStyle()
+                        .bigText(it),
+                )
+            }
+        }
+        if (isRemote) {
+            lowBatteryRemoteNotificationBuilder = tempNotificationBuilder
+            return lowBatteryRemoteNotificationBuilder.build()
+        } else {
+            lowBatteryNotificationBuilder = tempNotificationBuilder
+            return lowBatteryNotificationBuilder.build()
+        }
+    }
 }

app/src/main/res/values/strings.xml

@@ -337,4 +337,8 @@
     <string name="are_you_sure">Are you sure?</string>
     <string name="router_role_confirmation_text"><![CDATA[I have read the <a href="https://meshtastic.org/docs/configuration/radio/device/#roles">Device Role Documentation</a> and the blog post about <a href="http://meshtastic.org/blog/choosing-the-right-device-role">Choosing The Right Device Role</a>.]]></string>
     <string name="i_know_what_i_m_doing">I know what I\'m doing.</string>
+    <string name="low_battery_message">Node %s has a low battery (%d%%)</string>
+    <string name="meshtastic_low_battery_notifications">Low battery notifications</string>
+    <string name="low_battery_title">Low battery: %s</string>
+    <string name="meshtastic_low_battery_temporary_remote_notifications">Low battery notifications (favorite nodes)</string>
 </resources>