new: display current playback position and implement cross-platform position tracking

shared/src/commonMain/kotlin/fr/ajaury/gwenedeg/player/ui/PlayerScreen.kt

@@ -97,6 +97,11 @@ fun PlayerScreen(
                     style = MaterialTheme.typography.headlineMedium,
                 )
 
+                Text(
+                    text = "${uiState.positionMs} ms",
+                    style = MaterialTheme.typography.bodyMedium,
+                )
+
                 Button(
                     modifier = Modifier.size(60.dp),
                     contentPadding = PaddingValues(0.dp),
@@ -132,7 +137,7 @@ private fun PlayerScreenPlayingPreview() {
     GwenedegTheme {
         PlayerScreen(
             recordTitle = "Demat",
-            uiState = PlayerUiState(playbackState = PlaybackState.PLAYING),
+            uiState = PlayerUiState(playbackState = PlaybackState.PLAYING, positionMs = 1234),
             onMainPlayActionButtonClicked = {},
             onBackClicked = {},
         )
@@ -145,7 +150,7 @@ private fun PlayerScreenPausedPreview() {
     GwenedegTheme {
         PlayerScreen(
             recordTitle = "Demat",
-            uiState = PlayerUiState(playbackState = PlaybackState.PAUSED),
+            uiState = PlayerUiState(playbackState = PlaybackState.PAUSED, positionMs = 1234),
             onMainPlayActionButtonClicked = {},
             onBackClicked = {},
         )
@@ -158,7 +163,7 @@ private fun PlayerScreenEndedPreview() {
     GwenedegTheme {
         PlayerScreen(
             recordTitle = "Demat",
-            uiState = PlayerUiState(playbackState = PlaybackState.ENDED),
+            uiState = PlayerUiState(playbackState = PlaybackState.ENDED, positionMs = 1234),
             onMainPlayActionButtonClicked = {},
             onBackClicked = {},
         )

shared/src/commonMain/kotlin/fr/ajaury/gwenedeg/player/ui/viewmodel/PlayerUiState.kt

@@ -4,4 +4,5 @@ import fr.ajaury.gwenedeg.player.PlaybackState
 
 data class PlayerUiState(
     val playbackState: PlaybackState = PlaybackState.IDLE,
+    val positionMs: Long = 0L,
 )

shared/src/commonMain/kotlin/fr/ajaury/gwenedeg/player/ui/viewmodel/PlayerViewModel.kt

@@ -7,11 +7,17 @@ import fr.ajaury.gwenedeg.player.AudioPlayer
 import fr.ajaury.gwenedeg.player.AudioSessionManager
 import fr.ajaury.gwenedeg.player.PlaybackState
 import gwenedeg.shared.generated.resources.Res
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.WhileSubscribed
-import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.flow.combine
+import kotlinx.coroutines.flow.flatMapLatest
+import kotlinx.coroutines.flow.flow
+import kotlinx.coroutines.flow.flowOf
 import kotlinx.coroutines.flow.stateIn
+import kotlin.time.Duration.Companion.milliseconds
 import kotlin.time.Duration.Companion.seconds
 
 class PlayerViewModel(
@@ -21,13 +27,36 @@ class PlayerViewModel(
 ) : ViewModel() {
     private var filePath: String? = null
 
-    val uiState: StateFlow<PlayerUiState> = audioPlayer.playbackState
-        .map { PlayerUiState(playbackState = it) }
-        .stateIn(
-            scope = viewModelScope,
-            started = SharingStarted.WhileSubscribed(5.seconds),
-            initialValue = PlayerUiState(),
+    private val playbackState = audioPlayer.playbackState
+
+    @OptIn(ExperimentalCoroutinesApi::class)
+    private val currentPosition = playbackState
+        .flatMapLatest { state ->
+            if (state == PlaybackState.PLAYING) {
+                flow {
+                    while (true) {
+                        emit(audioPlayer.currentPosition())
+                        delay(POSITION_POLL_INTERVAL)
+                    }
+                }
+            } else {
+                flowOf(audioPlayer.currentPosition())
+            }
+        }
+
+    val uiState: StateFlow<PlayerUiState> = combine(
+        playbackState,
+        currentPosition,
+    ) { playbackState, currentPositionMs ->
+        PlayerUiState(
+            playbackState = playbackState,
+            positionMs = currentPositionMs.inWholeMilliseconds,
         )
+    }.stateIn(
+        scope = viewModelScope,
+        started = SharingStarted.WhileSubscribed(5.seconds),
+        initialValue = PlayerUiState(),
+    )
 
     init {
         audioSessionManager.activate()
@@ -60,4 +89,8 @@ class PlayerViewModel(
         audioSessionManager.deactivate()
         audioPlayer.release()
     }
+
+    companion object {
+        private val POSITION_POLL_INTERVAL = 200.milliseconds
+    }
 }