Offload connectivity monitor to a background thread

Change-Id: I9a2ef7766ae6abc6d8a7c86a4b49ef3c795e446c

core/data/src/main/kotlin/com/google/samples/apps/nowinandroid/core/data/util/ConnectivityManagerNetworkMonitor.kt

@@ -26,17 +26,25 @@ import android.net.NetworkRequest.Builder
 import android.os.Build.VERSION
 import android.os.Build.VERSION_CODES
 import androidx.core.content.getSystemService
+import androidx.tracing.Trace
+import androidx.tracing.trace
+import com.google.samples.apps.nowinandroid.core.network.Dispatcher
+import com.google.samples.apps.nowinandroid.core.network.NiaDispatchers.IO
 import dagger.hilt.android.qualifiers.ApplicationContext
+import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.channels.awaitClose
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.callbackFlow
 import kotlinx.coroutines.flow.conflate
+import kotlinx.coroutines.flow.flowOn
 import javax.inject.Inject
 
 internal class ConnectivityManagerNetworkMonitor @Inject constructor(
     @ApplicationContext private val context: Context,
+    @Dispatcher(IO) private val ioDispatcher: CoroutineDispatcher,
 ) : NetworkMonitor {
     override val isOnline: Flow<Boolean> = callbackFlow {
+        trace("NetworkMonitor.callbackFlow") {
             val connectivityManager = context.getSystemService<ConnectivityManager>()
             if (connectivityManager == null) {
                 channel.trySend(false)
@@ -63,20 +71,26 @@ internal class ConnectivityManagerNetworkMonitor @Inject constructor(
                 }
             }
 
+            trace("NetworkMonitor.registerNetworkCallback") {
                 val request = Builder()
                     .addCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET)
                     .build()
                 connectivityManager.registerNetworkCallback(request, callback)
+            }
 
             /**
              * Sends the latest connectivity status to the underlying channel.
              */
             channel.trySend(connectivityManager.isCurrentlyConnected())
 
+            Trace.endSection()
+
             awaitClose {
                 connectivityManager.unregisterNetworkCallback(callback)
             }
         }
+    }
+        .flowOn(ioDispatcher)
         .conflate()
 
     @Suppress("DEPRECATION")