Fix inconsistent playback end behavior issues (#1616)

## Description
The exact behavior of what happens when playback ends based on the
user's settings would change between versions. This PR defines the
behaviors better and includes unit tests to verify future changes won't
break it again.

### Related issues
Fixes #1548
Related to https://github.com/damontecres/Wholphin/pull/1257

### Testing
Emulator & unit tests

## Screenshots
N/A

## AI or LLM usage
None

app/src/main/java/com/github/damontecres/wholphin/ui/playback/PlaybackViewModel.kt

@@ -1034,14 +1034,26 @@ class PlaybackViewModel
                         }
 
                         is PlaylistItem.Media -> {
-                            if (currentItem is PlaylistItem.Intro) {
-                                Timber.v("Current item is intro, so playing next up immediately")
-                                playNextUp()
-                            } else if (preferences.appPreferences.playbackPreferences.showNextUpWhen != ShowNextUpWhen.NEXT_UP_NEVER) {
-                                Timber.v("Setting next up to ${nextItem.id}")
-                                _state.update { it.copy(nextUp = nextItem.item) }
-                            } else {
-                                controllerViewState.showControls()
+                            val prefs = preferences.appPreferences.playbackPreferences
+                            when {
+                                currentItem is PlaylistItem.Intro -> {
+                                    Timber.v("Current item is intro, so playing next up immediately")
+                                    playNextUp()
+                                }
+
+                                prefs.showNextUpWhen == ShowNextUpWhen.NEXT_UP_NEVER && !prefs.autoPlayNext -> {
+                                    Timber.v("Never show or auto play next up, returning")
+                                    navigationManager.goBack()
+                                }
+
+                                prefs.showNextUpWhen != ShowNextUpWhen.NEXT_UP_NEVER -> {
+                                    Timber.v("Setting next up to ${nextItem.id}")
+                                    _state.update { it.copy(nextUp = nextItem.item) }
+                                }
+
+                                else -> {
+                                    controllerViewState.showControls()
+                                }
                             }
                         }
 

app/src/test/java/com/github/damontecres/wholphin/ui/playback/PlaybackViewModelTests.kt

@@ -10,6 +10,7 @@ import com.github.damontecres.wholphin.data.model.BaseItem
 import com.github.damontecres.wholphin.data.model.JellyfinServer
 import com.github.damontecres.wholphin.data.model.JellyfinUser
 import com.github.damontecres.wholphin.data.model.Playlist
+import com.github.damontecres.wholphin.data.model.PlaylistItem
 import com.github.damontecres.wholphin.preferences.AppPreferences
 import com.github.damontecres.wholphin.preferences.PlaybackPreferences
 import com.github.damontecres.wholphin.preferences.ShowNextUpWhen
@@ -456,11 +457,12 @@ class PlaybackViewModelTests {
         }
 
     @Test
-    fun `Show next up never`() =
+    fun `Show next up never with automatic play`() =
         runTest(testDispatcher) {
             setupForPlaylist()
             setupPreferences {
                 showNextUpWhen = ShowNextUpWhen.NEXT_UP_NEVER
+                autoPlayNext = true
             }
 
             val viewModel = createViewModel(Destination.PlaybackList(playlist.id))
@@ -476,7 +478,108 @@ class PlaybackViewModelTests {
 
             viewModel.state.value.also { state ->
                 Assert.assertNull(state.nextUp)
+                Assert.assertTrue(state.hasNext)
             }
+            verify(exactly = 0) { mockNavigationManager.goBack() }
+        }
+
+    @Test
+    fun `Show next up never without automatic play`() =
+        runTest(testDispatcher) {
+            setupForPlaylist()
+            setupPreferences {
+                showNextUpWhen = ShowNextUpWhen.NEXT_UP_NEVER
+                autoPlayNext = false
+            }
+
+            val viewModel = createViewModel(Destination.PlaybackList(playlist.id))
+
+            viewModel.state.value.also { state ->
+                Assert.assertEquals(playlistItems.items, state.playlist.items)
+                Assert.assertEquals(0, state.playlistIndex)
+                Assert.assertNull(state.nextUp)
+            }
+
+            viewModel.onPlaybackStateChanged(Player.STATE_ENDED)
+            testScheduler.advanceUntilIdle()
+
+            viewModel.state.value.also { state ->
+                Assert.assertNull(state.nextUp)
+                Assert.assertTrue(state.hasNext)
+            }
+            verify(exactly = 1) { mockNavigationManager.goBack() }
+        }
+
+    @Test
+    fun `Playback ends with no next up`() =
+        runTest(testDispatcher) {
+            setupForPlaylist()
+            setupPreferences {
+                showNextUpWhen = ShowNextUpWhen.END_OF_PLAYBACK
+                autoPlayNext = false
+            }
+
+            val viewModel = createViewModel(Destination.PlaybackList(playlist.id))
+
+            viewModel.state.value.also { state ->
+                Assert.assertEquals(playlistItems.items, state.playlist.items)
+                Assert.assertEquals(0, state.playlistIndex)
+                Assert.assertNull(state.nextUp)
+            }
+            viewModel.playNextUp()
+            viewModel.playNextUp()
+            testScheduler.advanceUntilIdle()
+
+            viewModel.onPlaybackStateChanged(Player.STATE_ENDED)
+            testScheduler.advanceUntilIdle()
+
+            viewModel.state.value.also { state ->
+                Assert.assertNull(state.nextUp)
+                Assert.assertFalse(state.hasNext)
+            }
+            verify(exactly = 1) { mockNavigationManager.goBack() }
+        }
+
+    @Test
+    fun `Intro playback ends always play next`() =
+        runTest(testDispatcher) {
+            setupPreferences {
+                cinemaMode = true
+                showNextUpWhen = ShowNextUpWhen.NEXT_UP_NEVER
+                autoPlayNext = false
+            }
+            setupForPlaylist()
+            coEvery { mockUserLibraryApi.getItem(movie.id) } returns successResponse(movie)
+            coEvery { mockUserLibraryApi.getIntros(movie.id, any()) } returns
+                successQueryResult(listOf(intro))
+
+            val viewModel = createViewModel(Destination.PlaybackList(playlist.id))
+
+            viewModel.state.value.also { state ->
+                Assert.assertEquals(
+                    listOf(PlaylistItem.Intro(BaseItem(intro))) + playlistItems.items,
+                    state.playlist.items,
+                )
+                Assert.assertEquals(0, state.playlistIndex)
+                Assert.assertNull(state.nextUp)
+            }
+
+            viewModel.onPlaybackStateChanged(Player.STATE_ENDED)
+            testScheduler.advanceUntilIdle()
+
+            viewModel.state.value.also { state ->
+                Assert.assertEquals(1, state.playlistIndex)
+                Assert.assertNull(state.nextUp)
+            }
+            verify(exactly = 0) { mockNavigationManager.goBack() }
+
+            val mediaItems = mutableListOf<MediaItem>()
+            verify(exactly = 2) {
+                mockPlayer.setMediaItem(withArg { mediaItems.add(it) }, any<Long>())
+            }
+            Assert.assertEquals(2, mediaItems.size)
+            Assert.assertEquals(intro.id.toString(), mediaItems[0].mediaId)
+            Assert.assertEquals(movie.id.toString(), mediaItems[1].mediaId)
         }
 
     @Test