private void MergeSlots(ISlot fromSlot, ISlot toSlot)
{
if (toSlot.SpaceLeft(toSlot.StoredItem) == 0)
{
return;
}
int toSlotSpaceLeft = toSlot.SpaceLeft(toSlot.StoredItem);
int canMergeNum = (toSlotSpaceLeft >= fromSlot.SlotCount) ? fromSlot.SlotCount : toSlotSpaceLeft;
fromSlot.RemoveStackPortion(canMergeNum);
toSlot.AddStackPortion(toSlot.StoredItem, canMergeNum);
}