harmonia/Harmonia.UI/ViewModels/PlaybackBarViewModel.cs

using Avalonia.Controls;
using Avalonia.Media.Imaging;
using Avalonia.Threading;
using Harmonia.Core.Caching;
using Harmonia.Core.Imaging;
using Harmonia.Core.Models;
using Harmonia.Core.Player;
using Harmonia.Core.Playlists;
using Harmonia.Core.Scanner;
using System;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

namespace Harmonia.UI.ViewModels;

public partial class PlaybackBarViewModel : ViewModelBase
{
    private readonly IAudioPlayer _audioPlayer;
    private readonly IAudioImageCache _audioImageCache;
    private readonly DispatcherTimer _timer;

    private CancellationTokenSource? _audioImageCancellationTokenSource;

    private Song? _song;
    public Song? Song
    {
        get
        {
            return _song;
        }
        private set
        {
            _song = value;
            OnPropertyChanged();

            CurrentPosition = 0; // What if player is being loaded and returning to save state?
            Position = 0;
            MaxPosition = value?.Length.TotalSeconds ?? 0;
        }
    }

    private Bitmap? _songImageSource;
    public Bitmap? SongImageSource
    {
        get
        {
            return _songImageSource;
        }
        private set
        {
            _songImageSource = value;
            OnPropertyChanged();
        }
    }

    private double _currentPosition;
    public double CurrentPosition
    {
        get
        {
            return _currentPosition;
        }
        set
        {
            _currentPosition = value;
            OnPropertyChanged();

            if (_isPositionChangeInProgress)
                _audioPlayer.Position = value;
        }
    }

    private double _position;
    public double Position
    {
        get
        {
            return _position;
        }
        private set
        {
            _position = value;
            OnPropertyChanged();
        }
    }

    private double _maxPosition;
    public double MaxPosition
    {
        get
        {
            return _maxPosition;
        }
        set
        {
            _maxPosition = value;
            OnPropertyChanged();
        }
    }

    private bool _isPositionChangeInProgress;
    public bool IsPositionChangeInProgress
    {
        get { return _isPositionChangeInProgress; }
        set
        {
            _isPositionChangeInProgress = value;
            OnPropertyChanged();
        }
    }

    public bool IsRandom
    {
        get
        {
            return _audioPlayer.IsRandom;
        }
        private set
        {
            _audioPlayer.IsRandom = value;
            OnPropertyChanged();
        }
    }

    public string Greeting => "Welcome to Harmonia!";

    public PlaybackBarViewModel(IAudioPlayer audioPlayer, IAudioImageCache audioImageCache, IPlaylistRepository playlistRepository, IAudioFileScanner audioFileScanner)
    {
        _audioPlayer = audioPlayer;
        _audioPlayer.PlayingSongChanged += OnAudioPlayerPlayingSongChanged;

        _audioImageCache = audioImageCache;

        _timer = new(TimeSpan.FromMilliseconds(100), DispatcherPriority.Default, TickTock);
    }

    private void OnAudioPlayerPlayingSongChanged(object? sender, EventArgs e)
    {
        Song = _audioPlayer.PlayingSong?.Song;
        Task.Run(UpdateImage);
    }

    private async Task UpdateImage()
    {
        // TODO: Show default picture
        if (Song == null)
            return;

        if (_audioImageCancellationTokenSource != null)
            await _audioImageCancellationTokenSource.CancelAsync();

        _audioImageCancellationTokenSource = new();
        CancellationToken cancellationToken = _audioImageCancellationTokenSource.Token;

        SongPictureInfo? songPictureInfo = await _audioImageCache.GetAsync(Song, cancellationToken);

        if (songPictureInfo == null)
            return;

        await Dispatcher.UIThread.InvokeAsync(() => SetSongImageSource(songPictureInfo));
    }

    private void SetSongImageSource(SongPictureInfo songPictureInfo)
    {
        SongImageSource = new(songPictureInfo.Stream);
    }

    private void TickTock(object? sender, object e)
    {
        Position = _audioPlayer.Position;

        if (IsPositionChangeInProgress)
            return;

        CurrentPosition = _audioPlayer.Position;
    }

    public void Play()
    {
        _audioPlayer.Play();
    }

    public void Pause()
    {
        _audioPlayer.Pause();
    }

    public void Stop()
    {
        _audioPlayer.Stop();
        CurrentPosition = 0;
        Position = 0;
    }

    public void Previous()
    {
        _audioPlayer.PreviousAsync();
    }

    public void Next()
    {
        _audioPlayer.NextAsync();
    }
}