music: fix song build bottleneck

Fix redundant separator parsing obliterating loading performance.

If there are no separators configured, the parsing function would not
short-circuit and instead do a useless O(n) iteraton (including
escaping!), massively reducing performance.

Song build performance still isn't the best (blame intelligent
sorting), but it's definitely better now.

CHANGELOG.md

@@ -10,6 +10,7 @@
 - Albums implicitly linked only via "artist" tags are now placed in a special
 "appears on" section in the artist view
 - Album covers that are not 1:1 aspect ratio are no longer cropped
+- Optimized library creation phase of the music loading process
 
 #### What's Fixed
 - Prevented options such as "Add to queue" from being selected on empty artists and playlists

app/src/main/java/org/oxycblt/auxio/music/MusicRepository.kt

@@ -365,6 +365,10 @@ constructor(
             throw NoAudioPermissionException()
         }
 
+        // TODO: Parallelize this even more aggressively. I can hypothetically connect all
+        //  finalization steps (library, cache, playlists) into a single pipeline would need
+        //  to change how I indicate progress however
+
         // Start initializing the extractors. Use an indeterminate state, as there is no ETA on
         // how long a media database query will take.
         emitLoading(IndexingProgress.Indeterminate)

app/src/main/java/org/oxycblt/auxio/music/device/DeviceLibrary.kt

@@ -177,9 +177,12 @@ private class DeviceLibraryImpl(rawSongs: List<RawSong>, settings: MusicSettings
      * @return A sorted list of [SongImpl]s derived from the [RawSong] that should be suitable for
      *   grouping.
      */
-    private fun buildSongs(rawSongs: List<RawSong>, settings: MusicSettings) =
-        Sort(Sort.Mode.ByName, Sort.Direction.ASCENDING)
+    private fun buildSongs(rawSongs: List<RawSong>, settings: MusicSettings): List<Song> {
+        val songs = Sort(Sort.Mode.ByName, Sort.Direction.ASCENDING)
             .songs(rawSongs.map { SongImpl(it, settings) }.distinctBy { it.uid })
+        logD("Successfully built ${songs.size} songs")
+        return songs
+    }
 
     /**
      * Build a list of [Album]s from the given [Song]s.

app/src/main/java/org/oxycblt/auxio/music/info/Name.kt

@@ -174,6 +174,8 @@ private data class IntelligentKnownName(override val raw: String, override val s
     override val sortTokens = parseTokens(sort ?: raw)
 
     private fun parseTokens(name: String): List<SortToken> {
+        // TODO: This routine is consuming much of the song building runtime, find a way to
+        //  optimize it
         val stripped =
             name
                 // Remove excess punctuation from the string, as those u

app/src/main/java/org/oxycblt/auxio/music/metadata/TagUtil.kt

@@ -39,6 +39,8 @@ fun List<String>.parseMultiValue(settings: MusicSettings) =
         this
     }
 
+// TODO: Remove the escaping checks, it's too expensive to do this for every single tag.
+
 /**
  * Split a [String] by the given selector, automatically handling escaped characters that satisfy
  * the selector.
@@ -106,7 +108,7 @@ fun List<String>.correctWhitespace() = mapNotNull { it.correctWhitespace() }
  * @return A list of one or more [String]s that were split up by the user-defined separators.
  */
 private fun String.maybeParseBySeparators(settings: MusicSettings): List<String> {
-    // Get the separators the user desires. If null, there's nothing to do.
+    if (settings.multiValueSeparators.isEmpty()) return listOf(this)
     return splitEscaped { settings.multiValueSeparators.contains(it) }.correctWhitespace()
 }