using ytLive.Services;

namespace ytLive.ViewModels;

public partial class MainViewModel
{
    /// <summary>The alert announcement strip as the preview pane shows it: a
    /// full-master-width bitmap, or null when no alert is playing (or a Flash is in
    /// its off half). Mirrors the social bar's global-overlay pattern — the strip is
    /// NOT a per-source frame, so it can't ride the alert box's
    /// <c>VideoImageSource</c>.</summary>
    private System.Windows.Media.Imaging.WriteableBitmap? _alertTickerBitmap;

    public System.Windows.Media.Imaging.WriteableBitmap? AlertTickerImageSource
    {
        get => _alertTickerBitmap;
        private set
        {
            _alertTickerBitmap = value;
            OnPropertyChanged(nameof(AlertTickerImageSource));
        }
    }

    public bool AlertTickerVisible => _alertTickerBitmap != null;

    /// <summary>Publishes one ticker frame to the preview pane. Called on the UI
    /// thread from the alert layer's own tick, so the WPF bitmap write is legal.
    /// Reuses one <see cref="System.Windows.Media.Imaging.WriteableBitmap"/> and
    /// overwrites its back buffer — a fresh bitmap every tick would churn the
    /// render cache for no reason.</summary>
    internal void PublishAlertTickerPreview(VideoFrame? frame)
    {
        if (frame == null)
        {
            if (_alertTickerBitmap != null)
            {
                AlertTickerImageSource = null;
                OnPropertyChanged(nameof(AlertTickerVisible));
            }
            return;
        }

        if (_alertTickerBitmap == null
            || _alertTickerBitmap.PixelWidth != frame.Width
            || _alertTickerBitmap.PixelHeight != frame.Height)
        {
            AlertTickerImageSource = new System.Windows.Media.Imaging.WriteableBitmap(
                frame.Width, frame.Height, 96, 96,
                System.Windows.Media.PixelFormats.Bgra32, null);
            OnPropertyChanged(nameof(AlertTickerVisible));
        }

        var target = _alertTickerBitmap!;
        target.WritePixels(
            new System.Windows.Int32Rect(0, 0, frame.Width, frame.Height),
            frame.BgraPixels, frame.Stride, 0);
        // The bitmap instance is unchanged, so the pane's Source binding still
        // points at it — nudge it so WPF re-reads the back buffer this tick.
        OnPropertyChanged(nameof(AlertTickerImageSource));
    }
}