Add prospective data types for more complex item attachments

src/Dodge/Item/Grammar.hs

@@ -19,8 +19,23 @@ import Dodge.DoubleTree
 type ComposedItemStructure 
     = (Item,ComposedItem,[(ComposeLinkType,ComposedItem)], [(ComposeLinkType,ComposedItem)])
 
+type PartiallyComposedItem = (Item,ItemStructuralFunction,LinkTest)
+
 type CIL = (ComposedItem,[(ComposeLinkType,ComposedItem)], [(ComposeLinkType,ComposedItem)])
 
+data LinkTest = LinkTest 
+    { _tryLeftLink :: PartiallyComposedItem -> Maybe LinkUpdate
+    , _tryRightLink :: PartiallyComposedItem -> Maybe LinkUpdate
+    }
+
+-- may want to upgrade the children's possible links as well, but this is not obvious
+data LinkUpdate = LinkUpdate
+    { _luLinkType :: ComposeLinkType
+    , _luNewLinkTest :: LinkTest
+    , _luParentUpdate :: (Item,PartiallyComposedItem) -> (Item,PartiallyComposedItem)
+    , _luChildUpdate :: (Item,PartiallyComposedItem) -> (Item,PartiallyComposedItem)
+    }
+
 cisToItem :: ComposedItemStructure -> Item
 cisToItem (x,_,_,_) = x