fix(reaction): Stamp connect times from the ACL broadcast

The connection timestamp cache was only maintained while the connected-devices
flow had a subscriber. If the process died while a device stayed connected and
that device then disconnected and reconnected with nothing running, the
restarted collection found the old entry still keyed by a currently-connected
address, kept it through the prune, and reported the original connect time —
so the popup age check rejected an arbitrarily old connection.

The ACL broadcasts arrive at a manifest-registered receiver that wakes the
process regardless of any flow subscription, so the stamp is taken there
instead: connect stamps (keeping an existing one, which is the earlier and
therefore truer time), disconnect drops the entry. The flow keeps its own
stamp-on-first-sight and prune as a backstop for the force-stopped state and
missed broadcasts.

ACL_DISCONNECTED was already in the receiver's expected actions but was never
registered in the manifest. It does not start the monitor: a disconnect is not
a reason to start monitoring, and the start triggers here are deliberately
conservative.

app/src/main/AndroidManifest.xml

@@ -86,6 +86,7 @@
             android:label="Service trigger">
             <intent-filter>
                 <action android:name="android.bluetooth.device.action.ACL_CONNECTED" />
+                <action android:name="android.bluetooth.device.action.ACL_DISCONNECTED" />
             </intent-filter>
         </receiver>
 

app/src/main/java/eu/darken/capod/common/bluetooth/BluetoothManager2.kt

@@ -237,6 +237,26 @@ class BluetoothManager2 @Inject constructor(
     private val seenDevicesLock = Mutex()
     private val seenDevicesCache = mutableMapOf<String, Instant>()
 
+    /**
+     * Stamps the connect time from the ACL broadcast, which reaches a manifest-registered receiver
+     * whether or not [connectedDevices] is being collected. An existing stamp wins: the earlier one
+     * is the real connect time.
+     */
+    fun markDeviceConnected(address: BluetoothAddress) {
+        appScope.launch {
+            seenDevicesLock.withLock {
+                if (seenDevicesCache.containsKey(address)) return@withLock
+                seenDevicesCache[address] = timeSource.now()
+            }
+        }
+    }
+
+    fun markDeviceDisconnected(address: BluetoothAddress) {
+        appScope.launch {
+            seenDevicesLock.withLock { seenDevicesCache.remove(address) }
+        }
+    }
+
     val connectedDevices: Flow<List<BluetoothDevice2>> = isBluetoothEnabled
         .flatMapLatest { enabled ->
             if (enabled) monitorProfile(BluetoothProfile.HEADSET)

app/src/main/java/eu/darken/capod/monitor/core/receiver/BluetoothEventReceiver.kt

@@ -7,6 +7,7 @@ import android.content.BroadcastReceiver
 import android.content.Context
 import android.content.Intent
 import dagger.hilt.android.AndroidEntryPoint
+import eu.darken.capod.common.bluetooth.BluetoothManager2
 import eu.darken.capod.common.bluetooth.hasFeature
 import eu.darken.capod.common.debug.logging.Logging.Priority.WARN
 import eu.darken.capod.common.debug.logging.log
@@ -19,6 +20,7 @@ import javax.inject.Inject
 class BluetoothEventReceiver : BroadcastReceiver() {
 
     @Inject lateinit var monitorControl: MonitorControl
+    @Inject lateinit var bluetoothManager: BluetoothManager2
 
     override fun onReceive(context: Context, intent: Intent) {
         log(TAG) { "onReceive($context, $intent)" }
@@ -48,6 +50,15 @@ class BluetoothEventReceiver : BroadcastReceiver() {
             log { "Device has the following we features we support $supportedFeatures" }
         }
 
+        when (intent.action) {
+            BluetoothDevice.ACTION_ACL_CONNECTED -> bluetoothManager.markDeviceConnected(bluetoothDevice.address)
+            BluetoothDevice.ACTION_ACL_DISCONNECTED -> {
+                bluetoothManager.markDeviceDisconnected(bluetoothDevice.address)
+                // A disconnect is not a reason to start monitoring.
+                return
+            }
+        }
+
         log(TAG) { "Starting monitor" }
         monitorControl.startMonitor(forceStart = false)
     }

app/src/test/java/eu/darken/capod/common/bluetooth/BluetoothManager2Test.kt

@@ -7,9 +7,12 @@ import android.content.Context
 import io.kotest.matchers.shouldBe
 import io.mockk.every
 import io.mockk.mockk
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.cancel
 import kotlinx.coroutines.flow.first
-import kotlinx.coroutines.test.TestScope
+import kotlinx.coroutines.test.UnconfinedTestDispatcher
 import kotlinx.coroutines.test.runTest
+import org.junit.jupiter.api.AfterEach
 import org.junit.jupiter.api.Test
 import testhelpers.BaseTest
 import testhelpers.TestTimeSource
@@ -34,8 +37,16 @@ class BluetoothManager2Test : BaseTest() {
     }
     private val timeSource = TestTimeSource()
 
-    private fun TestScope.create() = BluetoothManager2(
-        appScope = backgroundScope,
+    // Unconfined, so the appScope.launch bodies of the mark* methods complete in place.
+    private val appScope = CoroutineScope(UnconfinedTestDispatcher())
+
+    @AfterEach
+    fun teardown() {
+        appScope.cancel()
+    }
+
+    private fun create() = BluetoothManager2(
+        appScope = appScope,
         dispatcherProvider = TestDispatcherProvider(),
         context = mockk<Context>(),
         manager = btManager,
@@ -61,6 +72,47 @@ class BluetoothManager2Test : BaseTest() {
         manager.bonded(ADDRESS_A).seenFirstAt shouldBe timeSource.now()
     }
 
+    /**
+     * The ACL broadcast arrives whether or not anything is collecting the connected-devices flow,
+     * so the stamp it leaves has to survive until the device disconnects.
+     */
+    @Test
+    fun `an ACL connect stamp survives the passage of time`() = runTest {
+        val manager = create()
+        val connectedAt = timeSource.now()
+
+        manager.markDeviceConnected(ADDRESS_A)
+
+        timeSource.advanceBy(Duration.ofSeconds(60))
+
+        manager.bonded(ADDRESS_A).seenFirstAt shouldBe connectedAt
+    }
+
+    @Test
+    fun `a repeated ACL connect keeps the first stamp`() = runTest {
+        val manager = create()
+        val connectedAt = timeSource.now()
+
+        manager.markDeviceConnected(ADDRESS_A)
+
+        timeSource.advanceBy(Duration.ofSeconds(60))
+        manager.markDeviceConnected(ADDRESS_A)
+
+        manager.bonded(ADDRESS_A).seenFirstAt shouldBe connectedAt
+    }
+
+    @Test
+    fun `an ACL disconnect drops the stamp`() = runTest {
+        val manager = create()
+
+        manager.markDeviceConnected(ADDRESS_A)
+
+        timeSource.advanceBy(Duration.ofSeconds(60))
+        manager.markDeviceDisconnected(ADDRESS_A)
+
+        manager.bonded(ADDRESS_A).seenFirstAt shouldBe timeSource.now()
+    }
+
     companion object {
         private const val ADDRESS_A = "AA:BB:CC:DD:EE:F1"
         private const val ADDRESS_B = "AA:BB:CC:DD:EE:F2"