private void AttemptSwap(IDragContainer <T> destination, IDragContainer <T> source)
{
// Provisionally remove item from both sides.
var removedSourceNumber = source.GetNumber();
var removedSourceItem = source.GetItem();
var removedDestinationNumber = destination.GetNumber();
var removedDestinationItem = destination.GetItem();
source.RemoveItems(removedSourceNumber);
destination.RemoveItems(removedDestinationNumber);
var sourceTakeBackNumber = CalculateTakeBack(removedSourceItem, removedSourceNumber, source, destination);
var destinationTakeBackNumber = CalculateTakeBack(removedDestinationItem, removedDestinationNumber, destination, source);
// Do take backs (if needed)
if (sourceTakeBackNumber > 0)
{
source.AddItemsByDragging(removedSourceItem, sourceTakeBackNumber);
removedSourceNumber -= sourceTakeBackNumber;
}
if (destinationTakeBackNumber > 0)
{
destination.AddItemsByDragging(removedDestinationItem, destinationTakeBackNumber);
removedDestinationNumber -= destinationTakeBackNumber;
}
// Abort if we can't do a successful swap
if (source.MaxAcceptable(removedDestinationItem) < removedDestinationNumber ||
destination.MaxAcceptable(removedSourceItem) < removedSourceNumber ||
destination.MaxAcceptable(removedSourceItem) == 0 ||
source.MaxAcceptable(removedSourceItem) == 0)
{
destination.AddItemsByDragging(removedDestinationItem, removedDestinationNumber);
source.AddItemsByDragging(removedSourceItem, removedSourceNumber);
return;
}
// Do swaps
if (removedDestinationNumber > 0)
{
source.AddItemsByDragging(removedDestinationItem, removedDestinationNumber);
}
if (removedSourceNumber > 0)
{
destination.AddItemsByDragging(removedSourceItem, removedSourceNumber);
}
}