Stop nearby notes while app is backgrounded

app/src/main/java/com/bitchat/android/nostr/NearbyNotesController.kt

@@ -12,7 +12,7 @@ import kotlinx.coroutines.flow.asStateFlow
  *
  * Merely rendering the mesh timeline must not open a building-precision Nostr
  * subscription. A subscription is eligible only after an explicit reveal and
- * while at least one nearby-notes surface is active.
+ * while the app is foregrounded and at least one nearby-notes surface is active.
  */
 @MainThread
 class NearbyNotesController internal constructor(
@@ -25,6 +25,7 @@ class NearbyNotesController internal constructor(
     private var activeHolders = 0
     private var locationEnabled = false
     private var locationAuthorized = false
+    private var appForeground = false
     private var buildingGeohash: String? = null
     private var subscribedGeohash: String? = null
 
@@ -50,6 +51,12 @@ class NearbyNotesController internal constructor(
         reconcileSubscription()
     }
 
+    /** Closes the live subscription whenever the process leaves the foreground. */
+    fun updateAppForeground(isForeground: Boolean) {
+        appForeground = isForeground
+        reconcileSubscription()
+    }
+
     /**
      * Updates the privacy-sensitive inputs independently of view activation.
      * Permission revocation, location disable, or loss of the building cell
@@ -78,6 +85,7 @@ class NearbyNotesController internal constructor(
     private fun reconcileSubscription() {
         val target = buildingGeohash.takeIf {
             activeHolders > 0 &&
+                appForeground &&
                 _revealed.value &&
                 locationEnabled &&
                 locationAuthorized

app/src/main/java/com/bitchat/android/ui/ChatScreen.kt

@@ -29,6 +29,10 @@ import androidx.compose.ui.semantics.contentDescription
 import androidx.compose.ui.semantics.semantics
 import androidx.compose.ui.semantics.clearAndSetSemantics
 import androidx.compose.ui.zIndex
+import androidx.lifecycle.DefaultLifecycleObserver
+import androidx.lifecycle.Lifecycle
+import androidx.lifecycle.LifecycleOwner
+import androidx.lifecycle.ProcessLifecycleOwner
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import com.bitchat.android.R
 import com.bitchat.android.geohash.ChannelID
@@ -117,6 +121,30 @@ fun ChatScreen(viewModel: ChatViewModel) {
             selectedPrivatePeer == null &&
             privateChatSheetPeer == null
 
+    val processLifecycleOwner = remember { ProcessLifecycleOwner.get() }
+    DisposableEffect(processLifecycleOwner, nearbyNotesController) {
+        val lifecycle = processLifecycleOwner.lifecycle
+        val observer = object : DefaultLifecycleObserver {
+            override fun onStart(owner: LifecycleOwner) {
+                nearbyNotesController.updateAppForeground(true)
+            }
+
+            override fun onStop(owner: LifecycleOwner) {
+                nearbyNotesController.updateAppForeground(false)
+            }
+        }
+
+        lifecycle.addObserver(observer)
+        nearbyNotesController.updateAppForeground(
+            lifecycle.currentState.isAtLeast(Lifecycle.State.STARTED),
+        )
+
+        onDispose {
+            lifecycle.removeObserver(observer)
+            nearbyNotesController.updateAppForeground(false)
+        }
+    }
+
     DisposableEffect(
         isMeshTimeline,
         locationEnabled,

app/src/test/kotlin/com/bitchat/android/nostr/NearbyNotesControllerTest.kt

@@ -16,9 +16,13 @@ class NearbyNotesControllerTest {
         unsubscribe = { unsubscribeCount += 1 },
     )
 
+    private fun foregroundController() = controller().also {
+        it.updateAppForeground(true)
+    }
+
     @Test
     fun `active mesh timeline does not subscribe before explicit reveal`() {
-        val controller = controller()
+        val controller = foregroundController()
 
         controller.updateAvailability(
             locationEnabled = true,
@@ -38,7 +42,7 @@ class NearbyNotesControllerTest {
 
     @Test
     fun `reveal remains dormant until a nearby notes surface is active`() {
-        val controller = controller()
+        val controller = foregroundController()
         controller.updateAvailability(true, true, "u4pruydq")
 
         controller.reveal()
@@ -52,7 +56,7 @@ class NearbyNotesControllerTest {
 
     @Test
     fun `last deactivate unsubscribes exactly once`() {
-        val controller = controller()
+        val controller = foregroundController()
         controller.updateAvailability(true, true, "u4pruydq")
         controller.reveal()
         controller.activate()
@@ -67,9 +71,28 @@ class NearbyNotesControllerTest {
         assertEquals(1, unsubscribeCount)
     }
 
+    @Test
+    fun `backgrounding closes the subscription and foregrounding restores it`() {
+        val controller = foregroundController()
+        controller.updateAvailability(true, true, "u4pruydq")
+        controller.activate()
+        controller.reveal()
+
+        controller.updateAppForeground(false)
+
+        assertEquals(1, unsubscribeCount)
+        assertTrue(controller.revealed.value)
+
+        controller.updateAppForeground(false)
+        assertEquals(1, unsubscribeCount)
+
+        controller.updateAppForeground(true)
+        assertEquals(listOf("u4pruydq", "u4pruydq"), subscriptions)
+    }
+
     @Test
     fun `disable and permission revocation close the live subscription`() {
-        val controller = controller()
+        val controller = foregroundController()
         controller.updateAvailability(true, true, "u4pruydq")
         controller.activate()
         controller.reveal()
@@ -91,6 +114,7 @@ class NearbyNotesControllerTest {
             subscribe = { events += "subscribe:$it" },
             unsubscribe = { events += "unsubscribe" },
         )
+        controller.updateAppForeground(true)
         controller.updateAvailability(true, true, "u4pruydq")
         controller.activate()
         controller.reveal()