allow skipping/going back multiple tracks

main/src/main/kotlin/com/github/topi314/lavaqueue/Queue.kt

@@ -24,15 +24,15 @@ class Queue(
     val history = TrackQueue()
     var userData = JsonObject(emptyMap())
 
-    fun next(): AudioTrack? {
-        val track = tracks.removeNext() ?: return null
+    fun next(count: Int = 1): AudioTrack? {
+        val track = tracks.removeNext(count) ?: return null
         player.play(track)
         return track
 
     }
 
-    fun previous(): AudioTrack? {
-        val track = history.removeLast() ?: return null
+    fun previous(count: Int = 1): AudioTrack? {
+        val track = history.removeLast(count) ?: return null
         player.play(track)
         return track
     }

main/src/main/kotlin/com/github/topi314/lavaqueue/TrackQueue.kt

@@ -70,16 +70,30 @@ class TrackQueue(
         return queue.firstOrNull()
     }
 
-    fun removeNext(): AudioTrack? {
-        return queue.removeFirstOrNull()
+    fun removeNext(count: Int = 1): AudioTrack? {
+        if (queue.isEmpty()) {
+            return null
+        }
+        return if (count >= queue.size) {
+            queue.removeFirstOrNull()
+        } else {
+            queue.subList(0, count).also { queue = queue.drop(count).toMutableList() }.last()
+        }
     }
 
     fun last(): AudioTrack? {
         return queue.lastOrNull()
     }
 
-    fun removeLast(): AudioTrack? {
-        return queue.removeLastOrNull()
+    fun removeLast(count: Int = 1): AudioTrack? {
+        if (queue.isEmpty()) {
+            return null
+        }
+        return if (count >= queue.size) {
+            queue.removeLastOrNull()
+        } else {
+            queue.subList(queue.size - count, queue.size).also { queue = queue.dropLast(count).toMutableList() }.first()
+        }
     }
 
 }

main/src/main/kotlin/com/github/topi314/lavaqueue/plugin/LavaQueueRestHandler.kt

@@ -57,14 +57,14 @@ class LavaQueueRestHandler(
     }
 
     @PostMapping("/v4/sessions/{sessionId}/players/{guildId}/queue/next")
-    fun postQueueNext(@PathVariable sessionId: String, @PathVariable guildId: Long): Track {
-        val track = lavaQueuePlugin.getQueue(socketContext(socketServer, sessionId), guildId).next() ?: throw ResponseStatusException(HttpStatus.NOT_FOUND, "No next track found")
+    fun postQueueNext(@PathVariable sessionId: String, @PathVariable guildId: Long, @RequestParam count: Int): Track {
+        val track = lavaQueuePlugin.getQueue(socketContext(socketServer, sessionId), guildId).next(count) ?: throw ResponseStatusException(HttpStatus.NOT_FOUND, "No next track found")
         return track.toTrack(playerManager, pluginInfoModifiers)
     }
 
     @PostMapping("/v4/sessions/{sessionId}/players/{guildId}/queue/previous")
-    fun postQueuePrevious(@PathVariable sessionId: String, @PathVariable guildId: Long): Track {
-        val track = lavaQueuePlugin.getQueue(socketContext(socketServer, sessionId), guildId).previous() ?: throw ResponseStatusException(HttpStatus.NOT_FOUND, "No previous track found")
+    fun postQueuePrevious(@PathVariable sessionId: String, @PathVariable guildId: Long, @RequestParam count: Int): Track {
+        val track = lavaQueuePlugin.getQueue(socketContext(socketServer, sessionId), guildId).previous(count) ?: throw ResponseStatusException(HttpStatus.NOT_FOUND, "No previous track found")
         return track.toTrack(playerManager, pluginInfoModifiers)
     }