fixed a bug

android/oral-trainer-sdk/src/main/java/cn/learningpad/oraltrainer/sdk/OralTrainerController.kt

@@ -11,6 +11,7 @@ import androidx.media3.common.MediaItem
 import androidx.media3.common.PlaybackException
 import androidx.media3.common.Player
 import androidx.media3.exoplayer.ExoPlayer
+import androidx.media3.exoplayer.PlayerMessage
 import androidx.media3.exoplayer.source.DefaultMediaSourceFactory
 import java.util.concurrent.CopyOnWriteArraySet
 import kotlin.math.max
@@ -30,6 +31,8 @@ class OralTrainerController internal constructor(
     private var lastSentenceIndex: Int? = null
     private var stopAtSentenceEnd = false
     private var stopAtSentenceEndIndex: Int? = null
+    private var boundaryMessage: PlayerMessage? = null
+    private var boundaryGuardToken = 0
 
     var config: PlayerConfig = initialConfig
         private set
@@ -67,13 +70,20 @@ class OralTrainerController internal constructor(
                     }
 
                     override fun onIsPlayingChanged(isPlaying: Boolean) {
+                        if (isPlaying) {
+                            refreshSentenceBoundaryGuard()
+                        } else {
+                            cancelSentenceBoundaryGuard()
+                        }
                         notifySnapshot()
                     }
 
                     override fun onMediaItemTransition(mediaItem: MediaItem?, reason: Int) {
                         lastSentenceIndex = null
+                        cancelSentenceBoundaryGuard()
                         listeners.forEach { it.onMediaChanged(currentTrainingItem()) }
                         notifySentenceIfChanged(force = true)
+                        refreshSentenceBoundaryGuard()
                         notifySnapshot()
                     }
 
@@ -83,6 +93,7 @@ class OralTrainerController internal constructor(
                         reason: Int,
                     ) {
                         notifySentenceIfChanged(force = true)
+                        refreshSentenceBoundaryGuard()
                         notifySnapshot()
                     }
 
@@ -158,6 +169,7 @@ class OralTrainerController internal constructor(
         if (index == player.currentMediaItemIndex) {
             listeners.forEach { it.onMediaChanged(updatedItem) }
             notifySentenceIfChanged(force = true)
+            refreshSentenceBoundaryGuard()
             notifySnapshot()
         }
         return true
@@ -165,11 +177,13 @@ class OralTrainerController internal constructor(
 
     fun play() {
         player.play()
+        refreshSentenceBoundaryGuard()
     }
 
     fun pause() {
         stopAtSentenceEnd = false
         stopAtSentenceEndIndex = null
+        cancelSentenceBoundaryGuard()
         player.pause()
     }
 
@@ -184,6 +198,7 @@ class OralTrainerController internal constructor(
     fun stop() {
         stopAtSentenceEnd = false
         stopAtSentenceEndIndex = null
+        cancelSentenceBoundaryGuard()
         player.stop()
     }
 
@@ -191,6 +206,7 @@ class OralTrainerController internal constructor(
         stopAtSentenceEnd = false
         stopAtSentenceEndIndex = null
         player.seekTo(max(0L, positionMs))
+        refreshSentenceBoundaryGuard()
     }
 
     fun seekRelative(deltaMs: Long) {
@@ -237,6 +253,7 @@ class OralTrainerController internal constructor(
 
     fun setContinuousPlayback(enabled: Boolean) {
         config = config.copy(continuousPlayback = enabled)
+        refreshSentenceBoundaryGuard()
     }
 
     fun playCurrentSentenceAndStop() {
@@ -245,6 +262,7 @@ class OralTrainerController internal constructor(
         stopAtSentenceEnd = true
         stopAtSentenceEndIndex = sentence.index
         player.play()
+        refreshSentenceBoundaryGuard()
     }
 
     fun currentTrainingItem(): TrainingMediaItem? {
@@ -357,6 +375,7 @@ class OralTrainerController internal constructor(
             return
         }
         released = true
+        cancelSentenceBoundaryGuard()
         mainHandler.removeCallbacks(ticker)
         listeners.clear()
         player.release()
@@ -376,8 +395,12 @@ class OralTrainerController internal constructor(
         if (!force && index == lastSentenceIndex) {
             return
         }
+        val changed = index != lastSentenceIndex
         lastSentenceIndex = index
         listeners.forEach { it.onSentenceChanged(sentence) }
+        if (changed && !config.continuousPlayback && !stopAtSentenceEnd) {
+            refreshSentenceBoundaryGuard()
+        }
     }
 
     private fun enforceSentenceBoundary() {
@@ -393,23 +416,100 @@ class OralTrainerController internal constructor(
             val index = stopAtSentenceEndIndex ?: return
             val sentence = item.sentences.getOrNull(index) ?: return
             if (position >= sentence.endMs) {
-                stopAtSentenceEnd = false
-                stopAtSentenceEndIndex = null
-                player.pause()
-                player.seekTo(sentence.startMs)
+                applySentenceEndAction(sentence)
             }
             return
         }
         if (config.continuousPlayback) {
             return
         }
-        val anchorIndex = lastSentenceIndex ?: return
+        val anchorIndex = lastSentenceIndex ?: currentSentence()?.index ?: return
         val anchor = item.sentences.getOrNull(anchorIndex) ?: return
         if (position >= anchor.endMs) {
-            player.seekTo(anchor.startMs)
+            applySentenceEndAction(anchor)
         }
     }
 
+    private fun refreshSentenceBoundaryGuard() {
+        cancelSentenceBoundaryGuard()
+        if (released || !config.sentenceMode) {
+            return
+        }
+        if (!player.isPlaying && !player.playWhenReady) {
+            return
+        }
+        val item = currentTrainingItem() ?: return
+        if (item.sentences.isEmpty()) {
+            return
+        }
+
+        val sentence = when {
+            stopAtSentenceEnd -> item.sentences.getOrNull(stopAtSentenceEndIndex ?: return)
+            config.continuousPlayback -> null
+            else -> {
+                val index = lastSentenceIndex ?: currentSentence()?.index
+                item.sentences.getOrNull(index ?: return)
+            }
+        } ?: return
+
+        val mediaItemIndex = player.currentMediaItemIndex
+        if (player.currentPosition >= sentence.endMs) {
+            applySentenceEndAction(sentence)
+            return
+        }
+
+        val token = ++boundaryGuardToken
+        boundaryMessage = player.createMessage { _, _ ->
+            if (token != boundaryGuardToken || released) {
+                return@createMessage
+            }
+            val active = currentTrainingItem() ?: return@createMessage
+            val latest = when {
+                stopAtSentenceEnd -> active.sentences.getOrNull(stopAtSentenceEndIndex ?: return@createMessage)
+                else -> active.sentences.getOrNull(sentence.index)
+            } ?: return@createMessage
+            if (player.currentMediaItemIndex != mediaItemIndex) {
+                return@createMessage
+            }
+            applySentenceEndAction(latest)
+        }
+            .setLooper(mainHandler.looper)
+            .setPosition(mediaItemIndex, sentence.endMs)
+            .setDeleteAfterDelivery(true)
+            .send()
+    }
+
+    private fun cancelSentenceBoundaryGuard() {
+        boundaryGuardToken++
+        boundaryMessage?.let { message ->
+            runCatching { message.cancel() }
+        }
+        boundaryMessage = null
+    }
+
+    private fun applySentenceEndAction(sentence: SentenceBoundary) {
+        if (stopAtSentenceEnd && stopAtSentenceEndIndex == sentence.index) {
+            stopAtSentenceEnd = false
+            stopAtSentenceEndIndex = null
+            cancelSentenceBoundaryGuard()
+            player.pause()
+            player.seekTo(sentence.startMs)
+            lastSentenceIndex = sentence.index
+            notifySentenceIfChanged(force = true)
+            notifySnapshot()
+            return
+        }
+        if (config.continuousPlayback) {
+            return
+        }
+        // Loop the current sentence without leaking into the next one.
+        player.seekTo(sentence.startMs)
+        lastSentenceIndex = sentence.index
+        notifySentenceIfChanged(force = true)
+        refreshSentenceBoundaryGuard()
+        notifySnapshot()
+    }
+
     private fun TrainingMediaItem.toMedia3Item(): MediaItem {
         val builder = MediaItem.Builder()
             .setMediaId(id)