.

wcfs/internal/xbtree.py

@@ -192,7 +192,28 @@ def Restructure(ztree, newStructure):
 
     _bcheck(ztree)  # verify ztree before our tweaks
 
-    # XXX ...
+    # walk original and new strucutres level by level.
+    # for each level we have A1...An "old" nodes, and B1...Bm "new" nodes.
+    # XXX buckets - push till end
+    # if n == m - map A-B 1-to-1
+    # if n < m  - we have to "insert" (m-n) new nodes
+    # if n > m  - we have to "forget" (n-m) old nodes.
+    # The process of insert/forget is organized as follows:
+    # every node from B set will in the end be to a node from A set.
+    # to make this association we:
+    # - compute D(Ai,Bj) where D is wighted distance
+    # - if we need to insert, we order Bj by  δA(Bj) = min_i D(Ai,Bj)
+    #   and note Bj with max(δA(Bj)) to be associated with newly created nodes.
+    # - if we need to forget, we order Ai by  δB(Ai) = min_j D(Ai,Bj)
+    #   and note Ai with max(δB(Ai)) to be forgotten.
+    # - after As are forgotten or some Bs are associated with new, we associate
+    #   1-1 the rest of A with the rest of B since all those nodes come in key↑ order.
+    #
+    #          sum min d(a,b)     sum min d(a,b)
+    #          a∈A b∈B            b∈B a∈A
+    # D(A,B) = ──────────────  +  ──────────────
+    #               N(A)              N(B)
+    #
 
     _bcheck(ztree)  # verify ztree after our tweaks
     tstruct = StructureOf(ztree)

wcfs/internal/xbtree_test.py

@@ -328,6 +328,9 @@ def test_restructure():
         newStructure = xbtree.TopoDecode(newtopo)
         xbtree.Restructure(ztree, newStructure)
 
+        # XXX verify iteration producess the same [] of (key, v)
+        # XXX verify [k] gives the same v   (for all k)
+
     # Z0 creates new empty tree
     def Z0():
         z = Z()