android: Update track subtitles based on context

android/app/src/main/java/stream/kleeamp/mobile/library/AlbumPane.kt

@@ -126,6 +126,7 @@ fun LibraryAlbumPane(
                     items(shown, key = { it.id }) { s ->
                         PlaylistMemberRow(
                             s = s,
+                            subtitle = s.artist,
                             current = current,
                             playing = playing,
                             queue = shown,

android/app/src/main/java/stream/kleeamp/mobile/library/ArtistPane.kt

@@ -123,6 +123,7 @@ fun LibraryArtistPane(
                     items(shown, key = { it.id }) { s ->
                         PlaylistMemberRow(
                             s = s,
+                            subtitle = s.albumArtistAlbum,
                             current = current,
                             playing = playing,
                             queue = shown,

android/app/src/main/java/stream/kleeamp/mobile/library/SongCover.kt

@@ -365,6 +365,7 @@ internal fun PlaylistMemberRow(
     queue: List<Station>,
     onPlay: (Station, List<Station>) -> Unit,
     onOpenMenu: (Station) -> Unit,
+    subtitle: String = s.artistAlbum,
 ) {
     val p = LocalPalette.current
     ListRow(
@@ -385,7 +386,7 @@ internal fun PlaylistMemberRow(
     ) {
         Mono(s.name, KleeampType.rowPrimary, if (current?.url == s.url) p.accent else p.ink, maxLines = 1)
         Mono(
-            s.artistAlbum.ifBlank {
+            subtitle.ifBlank {
                 when {
                     s.source == StationSource.Local -> durationLabel(s.durationMs)
                     s.source == StationSource.Podcast -> "podcast"

android/app/src/main/java/stream/kleeamp/mobile/model/Station.kt

@@ -50,6 +50,12 @@ data class Station(
             .filter { it.isNotBlank() }
             .joinToString(" · ")
 
+    /** `album artist · album`, falling back to track artist when album artist is blank. */
+    val albumArtistAlbum: String
+        get() = listOf(albumArtist.ifBlank { artist }, album)
+            .filter { it.isNotBlank() }
+            .joinToString(" · ")
+
     /**
      * A finite thing with an end, as opposed to a live stream. Decides whether
      * the queue is handed to the player as a real playlist it can advance

android/app/src/test/java/stream/kleeamp/mobile/model/StationTest.kt

@@ -1,5 +1,6 @@
 package stream.kleeamp.mobile.model
 
+import org.junit.Assert.assertEquals
 import org.junit.Assert.assertFalse
 import org.junit.Assert.assertTrue
 import org.junit.Test
@@ -12,6 +13,34 @@ class StationTest {
         source = source,
     )
 
+    @Test fun albumArtistAlbumPrefersAlbumArtist() {
+        val song = station(StationSource.Local, "l1").copy(
+            artist = "Daft Punk / Gabrielle",
+            albumArtist = "Daft Punk",
+            album = "Alive 2007",
+        )
+        assertEquals("Daft Punk · Alive 2007", song.albumArtistAlbum)
+        assertEquals("Daft Punk / Gabrielle · Alive 2007", song.artistAlbum)
+    }
+
+    @Test fun albumArtistAlbumFallsBackToTrackArtist() {
+        val song = station(StationSource.Local, "l1").copy(
+            artist = "Track Artist",
+            album = "Album",
+        )
+        assertEquals("Track Artist · Album", song.albumArtistAlbum)
+        assertEquals("Track Artist · Album", song.copy(albumArtist = "   ").albumArtistAlbum)
+    }
+
+    @Test fun albumArtistAlbumOmitsBlankFieldsAndSeparators() {
+        val song = station(StationSource.Local, "l1")
+        assertEquals("", song.albumArtistAlbum)
+        assertEquals("Album Artist", song.copy(albumArtist = "Album Artist").albumArtistAlbum)
+        assertEquals("Track Artist", song.copy(artist = "Track Artist").albumArtistAlbum)
+        assertEquals("Album", song.copy(album = "Album").albumArtistAlbum)
+        assertEquals("", song.copy(artist = " ", albumArtist = " ", album = " ").albumArtistAlbum)
+    }
+
     @Test fun channelTrackIdIsATrack() {
         val track = station(StationSource.Cliamp, "cliamp:edm:42")
         assertTrue(track.isChannelTrack)