address review: signal now playing with an event flow, not an int

app/src/main/kotlin/com/subtracks/MainActivity.kt

@@ -9,13 +9,14 @@ import androidx.activity.ComponentActivity
 import androidx.activity.compose.setContent
 import androidx.activity.enableEdgeToEdge
 import androidx.activity.result.contract.ActivityResultContracts
-import androidx.compose.runtime.mutableIntStateOf
 import androidx.core.content.ContextCompat
+import com.subtracks.ui.NowPlayingLauncher
 import com.subtracks.ui.SubtracksRoot
 import com.subtracks.ui.theme.SubtracksTheme
+import org.koin.core.context.GlobalContext
 
 class MainActivity : ComponentActivity() {
-    private val nowPlayingRequest = mutableIntStateOf(0)
+    private val nowPlayingLauncher: NowPlayingLauncher by lazy { GlobalContext.get().get() }
 
     private val requestNotifications =
         registerForActivityResult(ActivityResultContracts.RequestPermission()) { }
@@ -25,11 +26,11 @@ class MainActivity : ComponentActivity() {
         requestNotificationPermission()
         enableEdgeToEdge()
         if (shouldRecordNowPlayingLaunch(intent?.action, restoringState = savedInstanceState != null)) {
-            nowPlayingRequest.intValue++
+            nowPlayingLauncher.request()
         }
         setContent {
             SubtracksTheme {
-                SubtracksRoot(nowPlayingRequest = nowPlayingRequest.intValue)
+                SubtracksRoot()
             }
         }
     }
@@ -37,7 +38,7 @@ class MainActivity : ComponentActivity() {
     override fun onNewIntent(intent: Intent) {
         super.onNewIntent(intent)
         setIntent(intent)
-        if (intent.action == ACTION_OPEN_NOW_PLAYING) nowPlayingRequest.intValue++
+        if (intent.action == ACTION_OPEN_NOW_PLAYING) nowPlayingLauncher.request()
     }
 
     private fun requestNotificationPermission() {

app/src/main/kotlin/com/subtracks/di/AppModule.kt

@@ -28,6 +28,7 @@ import com.subtracks.playback.MediaSessionConnection
 import com.subtracks.playback.PlaybackController
 import com.subtracks.playback.PlayerConnection
 import com.subtracks.playback.Scrobbler
+import com.subtracks.ui.NowPlayingLauncher
 import com.subtracks.ui.RootViewModel
 import com.subtracks.ui.downloads.DownloadsViewModel
 import com.subtracks.ui.home.HomeListViewModel
@@ -108,6 +109,7 @@ fun appModule(
             it.attach(playback.state, playback.positionMs)
         }
     }
+    single { NowPlayingLauncher() }
     viewModel { RootViewModel(get()) }
     viewModel { LibraryViewModel(get(), get(), get(), get(), get(), get()) }
     viewModel { HomeViewModel(get(), get(), get(), get()) }

app/src/main/kotlin/com/subtracks/ui/AppRoot.kt

@@ -181,10 +181,7 @@ internal fun focusPops(
 }
 
 @Composable
-fun SubtracksRoot(
+fun SubtracksRoot(root: RootViewModel = koinViewModel()) {
-    root: RootViewModel = koinViewModel(),
-    nowPlayingRequest: Int = 0,
-) {
     when (val hasSource = root.hasSource.collectAsStateWithLifecycle().value) {
         null -> {
             LoadingState()
@@ -198,14 +195,14 @@ fun SubtracksRoot(
             val playbackController = koinInject<PlaybackController>()
             LaunchedEffect(Unit) { playbackController.connect() }
             val playbackReady by playbackController.ready.collectAsStateWithLifecycle()
-            if (playbackReady) MainNavigation(nowPlayingRequest) else LoadingState()
+            if (playbackReady) MainNavigation() else LoadingState()
         }
     }
 }
 
 @OptIn(ExperimentalLayoutApi::class)
 @Composable
-private fun MainNavigation(nowPlayingRequest: Int) {
+private fun MainNavigation() {
     val navController = rememberNavController()
     val currentRoute =
         navController
@@ -215,13 +212,13 @@ private fun MainNavigation(nowPlayingRequest: Int) {
             ?.route
     val tabBarVisible = currentRoute == Routes.LIBRARY
     val playbackController = koinInject<PlaybackController>()
+    val nowPlayingLauncher = koinInject<NowPlayingLauncher>()
     val libraryRepository = koinInject<LibraryRepository>()
     val downloadRepository = koinInject<DownloadRepository>()
     val playback by playbackController.state.collectAsStateWithLifecycle()
     val downloads by downloadRepository.states().collectAsStateWithLifecycle()
     var showingQueue by rememberSaveable { mutableStateOf(false) }
     var nowPlayingOpen by rememberSaveable { mutableStateOf(false) }
-    var handledNowPlayingRequest by remember { mutableStateOf(0) }
     var nowPlayingProgress by remember { mutableFloatStateOf(0f) }
     var miniPlayerTopPx by remember { mutableFloatStateOf(0f) }
     var nowPlayingFadeOut by remember { mutableStateOf(false) }
@@ -306,9 +303,9 @@ private fun MainNavigation(nowPlayingRequest: Int) {
             nowPlayingProgress = 0f
         }
     }
-    LaunchedEffect(nowPlayingRequest, playerVisible) {
+    LaunchedEffect(playerVisible) {
-        if (playerVisible && nowPlayingRequest > handledNowPlayingRequest) {
+        if (!playerVisible) return@LaunchedEffect
-            handledNowPlayingRequest = nowPlayingRequest
+        nowPlayingLauncher.openNowPlaying.collect {
             if (navController.currentDestination?.route in DETAIL_ROUTES) {
                 navController.popBackStack(Routes.LIBRARY, inclusive = false)
             }

app/src/main/kotlin/com/subtracks/ui/NowPlayingLauncher.kt

@@ -0,0 +1,15 @@
+package com.subtracks.ui
+
+import kotlinx.coroutines.channels.Channel
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.receiveAsFlow
+
+class NowPlayingLauncher {
+    private val requests = Channel<Unit>(Channel.CONFLATED)
+
+    val openNowPlaying: Flow<Unit> = requests.receiveAsFlow()
+
+    fun request() {
+        requests.trySend(Unit)
+    }
+}

app/src/test/kotlin/com/subtracks/ui/NowPlayingLauncherTest.kt

@@ -0,0 +1,27 @@
+package com.subtracks.ui
+
+import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.test.runTest
+import kotlinx.coroutines.withTimeoutOrNull
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNull
+import org.junit.Test
+
+class NowPlayingLauncherTest {
+    @Test
+    fun aRequestMadeBeforeCollectionIsDelivered() =
+        runTest {
+            val launcher = NowPlayingLauncher()
+            launcher.request()
+            assertEquals(Unit, launcher.openNowPlaying.first())
+        }
+
+    @Test
+    fun repeatedRequestsCollapseToTheLatest() =
+        runTest {
+            val launcher = NowPlayingLauncher()
+            repeat(3) { launcher.request() }
+            assertEquals(Unit, launcher.openNowPlaying.first())
+            assertNull(withTimeoutOrNull(100) { launcher.openNowPlaying.first() })
+        }
+}