namespace ShaderGraphPlus;

public class UndoOp
{
	public string name;
	public string undoBuffer;
	public string redoBuffer;
}

public class UndoStack
{
	private readonly List<UndoOp> _undoStack = new();
	private int _undoLevel = 0;
	private bool _redoPending = false;

	public bool CanUndo => _undoLevel != 0 && !_redoPending;
	public bool CanRedo => _undoLevel != _undoStack.Count && !_redoPending;

	public string UndoName => CanUndo ? $"Undo {_undoStack[_undoLevel - 1].name}" : null;
	public string RedoName => CanRedo ? $"Redo {_undoStack[_undoLevel].name}" : null;

	public int UndoLevel => _undoLevel;

	public IEnumerable<string> Names => _undoStack.Select( x => x.name );

	public void PushUndo( string name, string buffer )
	{
		Assert.False( _redoPending, $"Pending Redo ({UndoName})" );

		_redoPending = true;

		if ( _undoStack.Count > _undoLevel )
		{
			var count = _undoStack.Count - _undoLevel;
			_undoStack.RemoveRange( _undoStack.Count - count, count );
		}

		_undoStack.Add( new() { name = name, undoBuffer = buffer } );
		_undoLevel++;
	}

	public void PushRedo( string buffer )
	{
		Assert.True( _redoPending );

		_redoPending = false;
		_undoStack[_undoLevel - 1].redoBuffer = buffer;
	}

	public UndoOp Undo()
	{
		if ( _redoPending )
		{
			SGPLogger.Warning( "Pending Redo!" );
			return null;
		}

		if ( _undoStack.Count > 0 && _undoLevel > 0 )
		{
			_undoLevel--;

			return _undoStack[_undoLevel];
		}

		return null;
	}

	public UndoOp Redo()
	{
		if ( _redoPending )
		{
			SGPLogger.Warning( "Pending Redo!" );
			return null;
		}

		if ( _undoStack.Count > 0 && _undoLevel <= _undoStack.Count - 1 )
		{
			_undoLevel++;

			return _undoStack[_undoLevel - 1];
		}

		return null;
	}

	public UndoOp SetUndoLevel( int undoLevel )
	{
		if ( _redoPending )
		{
			SGPLogger.Warning( "Pending Redo!" );
			return null;
		}

		if ( _undoLevel == undoLevel + 1 )
			return null;

		if ( _undoStack.Count > 0 && undoLevel <= _undoStack.Count - 1 )
		{
			_undoLevel = undoLevel + 1;

			return _undoStack[_undoLevel - 1];
		}

		return null;
	}

	public void Clear()
	{
		_undoStack.Clear();
		_undoLevel = 0;
		_redoPending = false;
	}
}