修复切换剧集后会播放旧的缓存的问题

app/shared/src/commonMain/kotlin/ui/subject/episode/EpisodeViewModel.kt

@@ -20,6 +20,7 @@ import kotlinx.coroutines.flow.debounce
 import kotlinx.coroutines.flow.distinctUntilChanged
 import kotlinx.coroutines.flow.drop
 import kotlinx.coroutines.flow.emitAll
+import kotlinx.coroutines.flow.emptyFlow
 import kotlinx.coroutines.flow.filterNotNull
 import kotlinx.coroutines.flow.first
 import kotlinx.coroutines.flow.flatMapLatest
@@ -31,8 +32,11 @@ import me.him188.ani.app.data.danmaku.DanmakuManager
 import me.him188.ani.app.data.media.MediaSourceManager
 import me.him188.ani.app.data.media.createFetchFetchSessionFlow
 import me.him188.ani.app.data.media.fetch.FilteredMediaSourceResults
+import me.him188.ani.app.data.media.fetch.MediaFetchSession
 import me.him188.ani.app.data.media.fetch.create
 import me.him188.ani.app.data.media.resolver.VideoSourceResolver
+import me.him188.ani.app.data.media.selector.MediaSelector
+import me.him188.ani.app.data.media.selector.MediaSelectorAutoSelect
 import me.him188.ani.app.data.media.selector.MediaSelectorFactory
 import me.him188.ani.app.data.media.selector.autoSelect
 import me.him188.ani.app.data.media.selector.eventHandling
@@ -181,26 +185,73 @@ private class EpisodeViewModelImpl(
  // Media Selection
 
  // 会在更换 ep 时更换
- private val mediaFetchSession = episodeInfo.filterNotNull().flatMapLatest {
+ private val mediaFetchSession = episodeInfo.flatMapLatest { episodeInfo ->
  mediaSourceManager.createFetchFetchSessionFlow(
- subjectInfo.map { subjectInfo ->
- MediaFetchRequest.create(subjectInfo, it)
+ if (episodeInfo == null) {
+ emptyFlow()
+ } else {
+ subjectInfo.map { subjectInfo ->
+ MediaFetchRequest.create(subjectInfo, episodeInfo)
+ }
  },
  )
  }.shareInBackground(started = SharingStarted.Lazily)
 
+
+ /**
+ * 更换 EP 是否已经完成了.
+ *
+ * 之所以需要这个状态, 是因为当切换 EP 时, [mediaFetchSession] 会变更,
+ * 随后 [MediaFetchSession.cumulativeResults] 会传递给 [mediaSelector],
+ * 但是 [MediaSelector.mediaList] 是 share 在后台的, 也就是说它可能会在任意时间之后才会发现 [mediaFetchSession] 有更新.
+ *
+ * 这就导致当切换 EP 后, [MediaSelector.mediaList] 会有一段时间仍然是旧的值.
+ *
+ * 问题在于, [mediaFetchSession] 的变更会触发 [MediaSelectorAutoSelect.selectCached].
+ * 自动选择可能比 [MediaSelector.mediaList] 更新更早, 所以自动选择就会用久的 `mediaList` 选择缓存, 导致将会播放旧的视频.
+ *
+ *
+ * 因此我们增加 [switchEpisodeCompleted], 在操作 EP 时, 先将其设置为 `false`, 然后再修改 [episodeId],
+ * 并在 [mediaSelector] 更新时设置为 true.
+ *
+ * 这样也并不是一定安全的, 有可能在我们修改 [episodeId] 后, 正好旧的查询触发了 [MediaSelector.mediaList] 更新,
+ * 就导致 [switchEpisodeCompleted] 被设置为 `true`, [MediaSelectorAutoSelect.selectCached] 仍然会参考旧的 `mediaList` 选择缓存.
+ *
+ * 但是这种情况发生的概率比较小, 仅限于后台还有一个查询正在进行的时候用户切换了 EP, 并且旧的 EP 要至少有一个缓存, 而且恰好在一个比较短的时间内旧的查询完成了.
+ *
+ *
+ * 一个更恰当的解决方法可能是把 [mediaSelector] 变成 flow. 当切换 EP 时直接把 [mediaSelector] 重新创建, 就不可能访问到旧的状态了.
+ * 但是这会导致所有依赖 [mediaSelector] 的客户都更换为 flow 方式, 这很可能会导致更多问题. 因为我们先使用这个临时解决方案.
+ */
+ private val switchEpisodeCompleted = MutableStateFlow(false)
+
+ private suspend inline fun awaitSwitchEpisodeCompleted() {
+ switchEpisodeCompleted.first { it }
+ }
+
  private val mediaSelector = MediaSelectorFactory.withKoin(getKoin())
  .create(
  subjectId,
  mediaFetchSession.flatMapLatest { it.cumulativeResults },
  )
  .apply {
  autoSelect.run {
- launchInBackground { mediaFetchSession.collectLatest { awaitCompletedAndSelectDefault(it) } }
- launchInBackground { mediaFetchSession.collectLatest { selectCached(it) } }
+ launchInBackground {
+ mediaFetchSession.collectLatest {
+ awaitSwitchEpisodeCompleted()
+ awaitCompletedAndSelectDefault(it)
+ }
+ }
+ launchInBackground {
+ mediaFetchSession.collectLatest {
+ awaitSwitchEpisodeCompleted()
+ selectCached(it)
+ }
+ }
 
  launchInBackground {
  mediaFetchSession.collectLatest {
+ awaitSwitchEpisodeCompleted()
  if (settingsRepository.mediaSelectorSettings.flow.first().autoEnableLastSelected) {
  autoEnableLastSelected(it)
  }
@@ -214,6 +265,11 @@ private class EpisodeViewModelImpl(
  }
  }
  }
+ launchInBackground {
+ mediaList.collect {
+ switchEpisodeCompleted.value = true
+ }
+ }
  }
 
  override val mediaSelectorPresentation: MediaSelectorPresentation =
@@ -273,6 +329,8 @@ private class EpisodeViewModelImpl(
  onSelect = {
  mediaSelector.unselect() // 否则不会自动选择
  playerState.stop()
+
+ switchEpisodeCompleted.value = false // 要在修改 episodeId 之前才安全, 但会有极小的概率在 fetchSession 更新前有 mediaList 更新
  episodeId.value = it.episodeId // ep 要在取消选择 media 之后才能变, 否则会导致使用旧的 media
  },
  currentEpisodeId = episodeId,

app/shared/src/commonMain/kotlin/ui/subject/episode/video/PlayerLauncher.kt

@@ -3,8 +3,8 @@ package me.him188.ani.app.ui.subject.episode.video
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.SharedFlow
 import kotlinx.coroutines.flow.SharingStarted
-import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.filterNotNull
+import kotlinx.coroutines.flow.first
 import kotlinx.coroutines.flow.transformLatest
 import me.him188.ani.app.data.media.resolver.EpisodeMetadata
 import me.him188.ani.app.data.media.resolver.ResolutionFailures
@@ -60,22 +60,20 @@ class PlayerLauncher(
  * - The sources are available but user has not yet selected one.
  */
  private val videoSource: SharedFlow<VideoSource<*>?> = mediaSelector.selected
- .combine(episodeInfo.filterNotNull()) { media, episodeInfo ->
- media to episodeInfo
- }
- .transformLatest { (media, episodeInfo) ->
+ .transformLatest { media ->
  emit(null)
  if (media == null) return@transformLatest
 
  try {
+ val info = episodeInfo.filterNotNull().first()
  videoLoadingState.value = VideoLoadingState.ResolvingSource
  emit(
  videoSourceResolver.resolve(
  media,
  EpisodeMetadata(
- title = episodeInfo.displayName,
- ep = episodeInfo.ep,
- sort = episodeInfo.sort,
+ title = info.displayName,
+ ep = info.ep,
+ sort = info.sort,
  ),
  ),
  )