namespace BlockParty;

/// <summary>Detect a stationary playback cursor across healthy game frames. A backward step is
/// progress too (loop wrap). Deliberate pauses, track changes and missing frames reset the baseline.</summary>
internal struct AudioCursorWatch
{
	internal enum Change { None, Stalled, Recovered }
	private bool _tracking;
	private float _cursor;
	private double _movedAt;
	public bool Stalled { get; private set; }
	public double StillSeconds { get; private set; }

	public Change Update( double now, float cursor, bool active, bool reset )
	{
		if ( !active || reset || !_tracking )
		{
			_tracking = active;
			_cursor = cursor;
			_movedAt = now;
			StillSeconds = 0;
			Stalled = false;
			return Change.None;
		}

		if ( cursor != _cursor )
		{
			bool recovered = Stalled;
			_cursor = cursor;
			_movedAt = now;
			StillSeconds = 0;
			Stalled = false;
			return recovered ? Change.Recovered : Change.None;
		}

		StillSeconds = now - _movedAt;
		if ( !Stalled && StillSeconds >= 0.5 )
		{
			Stalled = true;
			return Change.Stalled;
		}
		return Change.None;
	}
}