Play Next Song in AVAudioPlayer

I have a tableviewcontroller that has a list of songs, and whenever a user clicks on a song, it opens another view controller and plays it. I need help whith whenever the user presses the next button or previous so that it will play the previous or next song. Here's my tableviewcontroller:



import UIKit
   
    class LibraryTableViewController: UITableViewController {
   
        var titleText = ["Heroes", "Skyline", "In The Woods"]
        var authorText = ["Kedam", "Kovan & Electro Light", "Max Pros"]
       
        @IBOutlet var songList: UITableView!
  
        override func viewDidLoad() {
            super.viewDidLoad()
        }

        // MARK: - Table view data source
   
        override func numberOfSections(in tableView: UITableView) -> Int {
            // #warning Incomplete implementation, return the number of sections
            return 1
        }
   
        override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
            // #warning Incomplete implementation, return the number of rows
            return titleText.count
        }
       
        //tableview delegate
       
        override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
            var cell : LibrarySongTableViewCell! = tableView.dequeueReusableCell(withIdentifier: "Library Cell") as! LibrarySongTableViewCell
            if(cell == nil)
            {
                cell = Bundle.main.loadNibNamed("Library Cell", owner: self, options: nil)?[0] as! LibrarySongTableViewCell;
            }
            let titleTitle = titleText[indexPath.row] as String //NOT NSString
            let authorTitle = authorText[indexPath.row] as String
            cell.titleLabel.text=titleTitle
            cell.authorLabel.text=authorTitle
            cell.imageView?.image = UIImage(named: titleTitle)
            cell.imageView?.layer.cornerRadius = 5
            return cell as LibrarySongTableViewCell
           
        }

        override func prepare(for segue: UIStoryboardSegue, sender: Any?)
        {
            if segue.identifier == "toLibraryDetail"
            {
                let detailViewController = ((segue.destination) as! LibraryDetailViewController)
                let indexPath = self.songList!.indexPathForSelectedRow!
                let topicLabelText = titleText[indexPath.row]
                let detailLabelText = authorText[indexPath.row]
                detailViewController.titleLabelText = topicLabelText
                detailViewController.authorLabelText = detailLabelText   
            }    
        }    
    }


Here is the view controller that the cell goes to to play the song:


import UIKit
        import AVFoundation
        import MediaPlayer
       
        // audioPlayer Outlet
        var libraryPlayer = AVAudioPlayer()
       
        class LibraryDetailViewController: UITableViewController, AVAudioPlayerDelegate {
       
            // Title and Author
            var titleLabelText: String!
            var authorLabelText: String!
            @IBOutlet weak var albumArt: UIImageView!
            @IBOutlet weak var titleText: UILabel!
            // Image Outlets
            @IBOutlet weak var authorText: UILabel!
            @IBOutlet weak var blurredAlbumArt: UIImageView!
            // Toolbar Outlets
            @IBOutlet weak var toolbar: UIToolbar!
            var playButton: UIBarButtonItem!
            var pauseButton: UIBarButtonItem!
            var flexibleSpace: UIBarButtonItem!
            var nextButton: UIBarButtonItem!
            var previousButton: UIBarButtonItem!
           
            override func viewDidLoad() {
                super.viewDidLoad()
                // Customize Album Art
                albumArt.image = UIImage(named: titleLabelText)
                blurredAlbumArt.image = UIImage(named: titleLabelText)
                albumArt.layer.cornerRadius = 10
                // Set label text
                titleText.text = titleLabelText
                authorText.text = authorLabelText

                // Create the audioPlayer
                do {
                   
                    libraryPlayer = try AVAudioPlayer(contentsOf: URL.init(fileURLWithPath: Bundle.main.path(forResource: titleLabelText, ofType: "mp3")!))
                    libraryPlayer.delegate = self
       
                   
                    libraryPlayer.prepareToPlay()
                   
                    var audioSession = AVAudioSession.sharedInstance()
                   
                   
                   
                    do {
                       
                        try audioSession.setCategory(AVAudioSessionCategoryPlayback)
                       
                    }
                   
                }
                   
                catch {
                   
                    print(error)               
                }
                //  Create ToolBar Buttons
                playButton = UIBarButtonItem(barButtonSystemItem: UIBarButtonSystemItem.play, target: self, action: "playButtonTapped")
                pauseButton = UIBarButtonItem(barButtonSystemItem: UIBarButtonSystemItem.pause, target: self, action: "pauseButtonTapped")
                flexibleSpace = UIBarButtonItem(barButtonSystemItem: UIBarButtonSystemItem.flexibleSpace, target: self, action: nil)
                previousButton = UIBarButtonItem(barButtonSystemItem: UIBarButtonSystemItem.rewind, target: self, action: "previousButtonTapped")
                nextButton = UIBarButtonItem(barButtonSystemItem: UIBarButtonSystemItem.fastForward, target: self, action: "nextButtonTapped")
               
                //  Customize ToolBar Buttons
                previousButton.tintColor = UIColor.lightGray
                nextButton.tintColor = UIColor.lightGray
               
                toolbar.items = [flexibleSpace, previousButton, flexibleSpace, pauseButton, flexibleSpace, nextButton, flexibleSpace]
       
               
                // Set the delegate
               
                // Play
                libraryPlayer.play()
               
       
               
                // Do any additional setup after loading the view.
            }
           
            //  Play
            func playButtonTapped() {
                toolbar.items = [flexibleSpace, previousButton, flexibleSpace, pauseButton, flexibleSpace, nextButton, flexibleSpace];
                libraryPlayer.play()
            }
           
            //  Pause
            func pauseButtonTapped() {
                toolbar.items = [flexibleSpace, previousButton, flexibleSpace, playButton, flexibleSpace, nextButton, flexibleSpace];
                libraryPlayer.pause()
            }
           
            //  Previous
            func previousButtonTapped() {
    // NEED HELP HERE
            }
           
            //  Next
            func nextButtonTapped() {
    // NEED HELP HERE
            }
       
            override func viewDidDisappear(_ animated: Bool) {
                libraryPlayer.pause()
            }
           
            override func viewDidAppear(_ animated: Bool) {
                libraryPlayer.play()
            }
       
            override func didReceiveMemoryWarning() {
                super.didReceiveMemoryWarning()
                // Dispose of any resources that can be recreated.
            }
           
       
            @IBAction func dismiss(_ sender: Any) {
                dismiss(animated: true, completion: nil)
            }
        }


Thanks so much for the help! I'm using Swift 3 and Xcode 8