Rework BrandedQueueEntry and UserQueueEntry implementation

playback/core/src/main/kotlin/queue/item/QueueEntry.kt

@@ -1,20 +1,36 @@
 package org.jellyfin.playback.core.queue.item
 
-// Queue Items
-sealed interface QueueEntry {
+/**
+ * The QueueEntry is a single entry in a queue. It can represent any supported media type.
+ * Implementations normally extend one of it's subclasses [BrandedQueueEntry] or [UserQueueEntry].
+ */
+interface QueueEntry {
+	/**
+	 * Whether this entry can be skipped and seeked or not. Normally set to `true`.
+	 */
 	val skippable: Boolean
-	val metadata: QueueEntryMetadata?
+
+	/**
+	 * The metadata for this item.
+	 */
+	val metadata: QueueEntryMetadata
 }
 
 /**
- * Branded queue items are used for intros, trailers, advertisements and other related videos
- * It is not possible to seek or skip these items and are normally invisible when showing a queue's contents
+ * Branded queue entries are used for intros, trailers, advertisements and other related videos. It
+ * is not possible to seek or skip these items and are normally invisible when showing a queue's
+ * contents.
  */
-abstract class BrandedQueueEntry : QueueEntry {
+open class BrandedQueueEntry : QueueEntry {
 	override val skippable = false
+	override val metadata = QueueEntryMetadata.Empty
 }
 
+/**
+ * User queue entries are used for regular media like music tracks, movies and series episodes. This
+ * is the entry type used most often.
+ */
 open class UserQueueEntry : QueueEntry {
 	override val skippable = true
-	override val metadata = QueueEntryMetadata()
+	override val metadata = QueueEntryMetadata.Empty
 }

playback/core/src/main/kotlin/queue/item/QueueEntryMetadata.kt

@@ -24,4 +24,8 @@ data class QueueEntryMetadata(
 	val trackNumber: Long? = null,
 	val writer: String? = null,
 	val year: Long? = null,
-)
+) {
+	companion object {
+		val Empty = QueueEntryMetadata()
+	}
+}

playback/jellyfin/src/main/kotlin/queue/item/BaseItemDtoUserQueueEntry.kt

@@ -1,5 +1,6 @@
 package org.jellyfin.playback.jellyfin.queue.item
 
+import org.jellyfin.playback.core.queue.item.QueueEntry
 import org.jellyfin.playback.core.queue.item.QueueEntryMetadata
 import org.jellyfin.playback.core.queue.item.UserQueueEntry
 import org.jellyfin.sdk.api.client.ApiClient
@@ -11,7 +12,8 @@ import kotlin.time.Duration.Companion.nanoseconds
 class BaseItemDtoUserQueueEntry private constructor(
 	val baseItem: BaseItemDto,
 	override val metadata: QueueEntryMetadata,
-) : UserQueueEntry() {
+	base: QueueEntry,
+) : QueueEntry by base {
 	companion object {
 		fun build(api: ApiClient, baseItem: BaseItemDto): BaseItemDtoUserQueueEntry {
 			val metadata = QueueEntryMetadata(
@@ -41,7 +43,7 @@ class BaseItemDtoUserQueueEntry private constructor(
 				}
 			)
 
-			return BaseItemDtoUserQueueEntry(baseItem, metadata)
+			return BaseItemDtoUserQueueEntry(baseItem, metadata, UserQueueEntry())
 		}
 
 		/**