gui-cs.Terminal.Gui/Terminal.Gui/Views/SpinnerView/SpinnerView.cs

//------------------------------------------------------------------------------
// Windows Terminal supports Unicode and Emoji characters, but by default
// conhost shells (e.g., PowerShell and cmd.exe) do not. See
// <https://spectreconsole.net/best-practices>.
//------------------------------------------------------------------------------

namespace Terminal.Gui;

/// <summary>A <see cref="View"/> which displays (by default) a spinning line character.</summary>
/// <remarks>
///     By default animation only occurs when you call <see cref="SpinnerView.AdvanceAnimation()"/>. Use
///     <see cref="AutoSpin"/> to make the automate calls to <see cref="SpinnerView.AdvanceAnimation()"/>.
/// </remarks>
public class SpinnerView : View
{
    private const int DEFAULT_DELAY = 130;
    private static readonly SpinnerStyle DEFAULT_STYLE = new SpinnerStyle.Line ();

    private bool _bounce = DEFAULT_STYLE.SpinBounce;
    private bool _bounceReverse;
    private int _currentIdx;
    private int _delay = DEFAULT_STYLE.SpinDelay;
    private DateTime _lastRender = DateTime.MinValue;
    private string [] _sequence = DEFAULT_STYLE.Sequence;
    private SpinnerStyle _style = DEFAULT_STYLE;
    private object _timeout;

    /// <summary>Creates a new instance of the <see cref="SpinnerView"/> class.</summary>
    public SpinnerView ()
    {
        Width = Dim.Auto (minimumContentDim: 1);
        Height = Dim.Auto (minimumContentDim: 1);
        _delay = DEFAULT_DELAY;
        _bounce = false;
        SpinReverse = false;
        SetStyle (DEFAULT_STYLE);

        AdvanceAnimation ();
    }

    /// <summary>
    ///     Gets or sets whether spinning should occur automatically or be manually triggered (e.g. from a background
    ///     task).
    /// </summary>
    public bool AutoSpin
    {
        get => _timeout != null;
        set
        {
            if (value)
            {
                AddAutoSpinTimeout ();
            }
            else
            {
                RemoveAutoSpinTimeout ();
            }
        }
    }

    /// <summary>
    ///     Gets whether the current spinner style contains emoji or other special characters. Does not check Custom
    ///     sequences.
    /// </summary>
    public bool HasSpecialCharacters => _style.HasSpecialCharacters;

    /// <summary>Gets whether the current spinner style contains only ASCII characters.  Also checks Custom sequences.</summary>
    public bool IsAsciiOnly => GetIsAsciiOnly ();

    /// <summary>Gets or sets the animation frames used to animate the spinner.</summary>
    public string [] Sequence
    {
        get => _sequence;
        set => SetSequence (value);
    }

    /// <summary>
    ///     Gets or sets whether spinner should go back and forth through the frames rather than going to the end and
    ///     starting again at the beginning.
    /// </summary>
    public bool SpinBounce
    {
        get => _bounce;
        set => SetBounce (value);
    }

    /// <summary>Gets or sets the number of milliseconds to wait between characters in the animation.</summary>
    /// <remarks>
    ///     This is the maximum speed the spinner will rotate at.  You still need to call
    ///     <see cref="SpinnerView.AdvanceAnimation()"/> or <see cref="SpinnerView.AutoSpin"/> to advance/start animation.
    /// </remarks>
    public int SpinDelay
    {
        get => _delay;
        set => SetDelay (value);
    }

    /// <summary>
    ///     Gets or sets whether spinner should go through the frames in reverse order. If SpinBounce is true, this sets
    ///     the starting order.
    /// </summary>
    public bool SpinReverse { get; set; }

    /// <summary>Gets or sets the Style used to animate the spinner.</summary>
    public SpinnerStyle Style
    {
        get => _style;
        set => SetStyle (value);
    }

    /// <summary>
    ///     Advances the animation frame and notifies main loop that repainting needs to happen. Repeated calls are
    ///     ignored based on <see cref="SpinDelay"/>.
    /// </summary>
    /// <remarks>Ensure this method is called on the main UI thread e.g. via <see cref="Application.Invoke"/></remarks>
    public void AdvanceAnimation ()
    {
        if (DateTime.Now - _lastRender > TimeSpan.FromMilliseconds (SpinDelay))
        {
            if (Sequence is { } && Sequence.Length > 1)
            {
                var d = 1;

                if ((_bounceReverse && !SpinReverse) || (!_bounceReverse && SpinReverse))
                {
                    d = -1;
                }

                _currentIdx += d;

                if (_currentIdx >= Sequence.Length)
                {
                    if (SpinBounce)
                    {
                        if (SpinReverse)
                        {
                            _bounceReverse = false;
                        }
                        else
                        {
                            _bounceReverse = true;
                        }

                        _currentIdx = Sequence.Length - 1;
                    }
                    else
                    {
                        _currentIdx = 0;
                    }
                }

                if (_currentIdx < 0)
                {
                    if (SpinBounce)
                    {
                        if (SpinReverse)
                        {
                            _bounceReverse = true;
                        }
                        else
                        {
                            _bounceReverse = false;
                        }

                        _currentIdx = 1;
                    }
                    else
                    {
                        _currentIdx = Sequence.Length - 1;
                    }
                }

                Text = "" + Sequence [_currentIdx]; //.EnumerateRunes;
            }

            _lastRender = DateTime.Now;
        }

        SetNeedsDisplay ();
    }

    /// <inheritdoc/>
    protected override void Dispose (bool disposing)
    {
        RemoveAutoSpinTimeout ();

        base.Dispose (disposing);
    }

    private void AddAutoSpinTimeout ()
    {
        if (_timeout is { })
        {
            return;
        }

        _timeout = Application.AddTimeout (
                                           TimeSpan.FromMilliseconds (SpinDelay),
                                           () =>
                                           {
                                               Application.Invoke (AdvanceAnimation);

                                               return true;
                                           }
                                          );
    }

    private bool GetIsAsciiOnly ()
    {
        if (HasSpecialCharacters)
        {
            return false;
        }

        if (_sequence is { } && _sequence.Length > 0)
        {
            foreach (string frame in _sequence)
            {
                foreach (char c in frame)
                {
                    if (!char.IsAscii (c))
                    {
                        return false;
                    }
                }
            }

            return true;
        }

        return true;
    }

    private int GetSpinnerWidth ()
    {
        var max = 0;

        if (_sequence is { } && _sequence.Length > 0)
        {
            foreach (string frame in _sequence)
            {
                if (frame.Length > max)
                {
                    max = frame.Length;
                }
            }
        }

        return max;
    }

    private void RemoveAutoSpinTimeout ()
    {
        if (_timeout is { })
        {
            Application.RemoveTimeout (_timeout);
            _timeout = null;
        }
    }

    private void SetBounce (bool bounce) { _bounce = bounce; }

    private void SetDelay (int delay)
    {
        if (delay > -1)
        {
            _delay = delay;
        }
    }

    private void SetSequence (string [] frames)
    {
        if (frames is { } && frames.Length > 0)
        {
            _style = new SpinnerStyle.Custom ();
            _sequence = frames;
            Width = GetSpinnerWidth ();
        }
    }

    private void SetStyle (SpinnerStyle style)
    {
        if (style is { })
        {
            _style = style;
            _sequence = style.Sequence;
            _delay = style.SpinDelay;
            _bounce = style.SpinBounce;
            Width = GetSpinnerWidth ();
        }
    }
}