Make Artist and Entry comparable (thus sortable)

core/domain/src/main/kotlin/org/moire/ultrasonic/domain/Artist.kt

@@ -9,8 +9,22 @@ data class Artist(
     var coverArt: String? = null,
     var albumCount: Long? = null,
     var closeness: Int = 0
-) : Serializable, GenericEntry() {
+) : Serializable, GenericEntry(), Comparable<Artist> {
     companion object {
         private const val serialVersionUID = -5790532593784846982L
     }
+
+    override fun compareTo(other: Artist): Int {
+        when {
+            this.closeness == other.closeness -> {
+                return 0
+            }
+            this.closeness > other.closeness -> {
+                return -1
+            }
+            else -> {
+                return 1
+            }
+        }
+    }
 }

core/domain/src/main/kotlin/org/moire/ultrasonic/domain/MusicDirectory.kt

@@ -66,7 +66,7 @@ class MusicDirectory {
         var bookmarkPosition: Int = 0,
         var userRating: Int? = null,
         var averageRating: Float? = null
-    ) : Serializable, GenericEntry() {
+    ) : Serializable, GenericEntry(), Comparable<Entry> {
         fun setDuration(duration: Long) {
             this.duration = duration.toInt()
         }
@@ -74,5 +74,19 @@ class MusicDirectory {
         companion object {
             private const val serialVersionUID = -3339106650010798108L
         }
+
+        override fun compareTo(other: Entry): Int {
+            when {
+                this.closeness == other.closeness -> {
+                    return 0
+                }
+                this.closeness > other.closeness -> {
+                    return -1
+                }
+                else -> {
+                    return 1
+                }
+            }
+        }
     }
 }