mRemoteNG/mRemoteV1/Tree/ConnectionTreeDragAndDropHandler.cs

using System.Drawing;
using System.Linq;
using System.Windows.Forms;
using BrightIdeasSoftware;
using mRemoteNG.Connection;
using mRemoteNG.Container;
using mRemoteNG.Tree.Root;


namespace mRemoteNG.Tree
{
    public class ConnectionTreeDragAndDropHandler
    {
        private readonly Color DropAllowedFeedbackColor = Color.Green;
        private readonly Color DropDeniedFeedbackColor = Color.Red;
        private string _infoMessage;
        private Color _currentFeedbackColor;
        private bool _enableFeedback;


        public void HandleEvent_ModelDropped(object sender, ModelDropEventArgs e)
        {
            if (!(e.TargetModel is ConnectionInfo dropTarget)) return;
            var dropSource = (ConnectionInfo)e.SourceModels[0];
            DropModel(dropSource, dropTarget, e.DropTargetLocation);
            e.Handled = true;
        }

        public void DropModel(ConnectionInfo dropSource,
                              ConnectionInfo dropTarget,
                              DropTargetLocation dropTargetLocation)
        {
            switch (dropTargetLocation)
            {
                case DropTargetLocation.Item:
                    DropModelOntoTarget(dropSource, dropTarget);
                    break;
                case DropTargetLocation.AboveItem:
                    DropModelAboveTarget(dropSource, dropTarget);
                    break;
                case DropTargetLocation.BelowItem:
                    DropModelBelowTarget(dropSource, dropTarget);
                    break;
            }
        }

        private void DropModelOntoTarget(ConnectionInfo dropSource, ConnectionInfo dropTarget)
        {
            if (!(dropTarget is ContainerInfo dropTargetAsContainer)) return;
            dropSource.SetParent(dropTargetAsContainer);
        }

        private void DropModelAboveTarget(ConnectionInfo dropSource, ConnectionInfo dropTarget)
        {
            if (!dropSource.Parent.Equals(dropTarget.Parent))
                dropTarget.Parent.AddChildAbove(dropSource, dropTarget);
            else
                dropTarget.Parent.SetChildAbove(dropSource, dropTarget);
        }

        private void DropModelBelowTarget(ConnectionInfo dropSource, ConnectionInfo dropTarget)
        {
            if (!dropSource.Parent.Equals(dropTarget.Parent))
                dropTarget.Parent.AddChildBelow(dropSource, dropTarget);
            else
                dropTarget.Parent.SetChildBelow(dropSource, dropTarget);
        }

        public void HandleEvent_ModelCanDrop(object sender, ModelDropEventArgs e)
        {
            _enableFeedback = true;
            _currentFeedbackColor = DropDeniedFeedbackColor;
            _infoMessage = null;
            var dropSource = e.SourceModels.Cast<ConnectionInfo>().First();
            var dropTarget = e.TargetModel as ConnectionInfo;

            e.Effect = CanModelDrop(dropSource, dropTarget, e.DropTargetLocation);
            e.InfoMessage = _infoMessage;
            e.DropSink.EnableFeedback = _enableFeedback;
            e.DropSink.FeedbackColor = _currentFeedbackColor;
            e.Handled = true;
        }

        public DragDropEffects CanModelDrop(ConnectionInfo dropSource,
                                            ConnectionInfo dropTarget,
                                            DropTargetLocation dropTargetLocation)
        {
            var dragDropEffect = DragDropEffects.None;
            if (!NodeIsDraggable(dropSource))
            {
                _infoMessage = Language.NodeNotDraggable;
                _enableFeedback = false;
            }
            else
                switch (dropTargetLocation)
                {
                    case DropTargetLocation.Item:
                        dragDropEffect = HandleCanDropOnItem(dropSource, dropTarget);
                        break;
                    case DropTargetLocation.AboveItem:
                    case DropTargetLocation.BelowItem:
                        dragDropEffect = HandleCanDropBetweenItems(dropSource, dropTarget);
                        break;
                }

            return dragDropEffect;
        }

        private DragDropEffects HandleCanDropOnItem(ConnectionInfo dropSource, ConnectionInfo dropTarget)
        {
            var dragDropEffect = DragDropEffects.None;
            if (dropTarget is ContainerInfo && !(dropTarget is RootPuttySessionsNodeInfo))
            {
                if (!IsValidDrag(dropSource, dropTarget)) return dragDropEffect;
                dragDropEffect = DragDropEffects.Move;
                _currentFeedbackColor = DropAllowedFeedbackColor;
            }
            else
            {
                _enableFeedback = false;
            }

            return dragDropEffect;
        }

        private DragDropEffects HandleCanDropBetweenItems(ConnectionInfo dropSource, ConnectionInfo dropTarget)
        {
            var dragDropEffect = DragDropEffects.None;
            if (AncestorDraggingOntoChild(dropSource, dropTarget))
                _infoMessage = Language.NodeCannotDragParentOnChild;
            else if (dropTarget is PuttySessionInfo || dropTarget is RootNodeInfo)
                _enableFeedback = false;
            else
            {
                dragDropEffect = DragDropEffects.Move;
                _currentFeedbackColor = DropAllowedFeedbackColor;
            }

            return dragDropEffect;
        }

        private bool IsValidDrag(ConnectionInfo dropSource, ConnectionInfo dropTarget)
        {
            var validDrag = false;
            if (NodeDraggingOntoSelf(dropSource, dropTarget))
                _infoMessage = Language.NodeCannotDragOnSelf;
            else if (AncestorDraggingOntoChild(dropSource, dropTarget))
                _infoMessage = Language.NodeCannotDragParentOnChild;
            else if (DraggingOntoCurrentParent(dropSource, dropTarget))
                _infoMessage = Language.NodeAlreadyInFolder;
            else
                validDrag = true;
            return validDrag;
        }

        private bool NodeIsDraggable(ConnectionInfo node)
        {
            return node != null && !(node is RootNodeInfo) && !(node is PuttySessionInfo);
        }

        private bool NodeDraggingOntoSelf(ConnectionInfo source, ConnectionInfo target)
        {
            return source.Equals(target);
        }

        private bool AncestorDraggingOntoChild(ConnectionInfo source, ConnectionInfo target)
        {
            return source is ContainerInfo sourceAsContainer &&
                   sourceAsContainer.GetRecursiveChildList().Contains(target);
        }

        private bool DraggingOntoCurrentParent(ConnectionInfo source, ConnectionInfo target)
        {
            return target is ContainerInfo targetAsContainer && targetAsContainer.Children.Contains(source);
        }
    }
}