[Closes #6] Implement node modification

src/zipper.erl

@@ -1,17 +1,28 @@
 -module(zipper).
 
 -export([
+         %% Creation
          new/4,
          %% Traverse
          up/1,
          down/1,
          left/1,
+         leftmost/1,
          right/1,
+         rightmost/1,
          next/1,
          is_end/1,
          prev/1,
          root/1,
          traverse/2,
+         %% Editing
+         insert_left/2,
+         insert_right/2,
+         replace/2,
+         edit/3,
+         insert_child/2,
+         append_child/2,
+         remove/1,
          %% Info
          node/1,
          children/1,
@@ -30,7 +41,7 @@ new(IsBranch, Children, MakeNode, Root) ->
     #{spec => #{is_branch => IsBranch,
                 children => Children,
                 make_node => MakeNode
-                },
+               },
       node => Root,
       info => #{lefts => [],
                 rights => [],
@@ -42,8 +53,19 @@ new(IsBranch, Children, MakeNode, Root) ->
 -spec up(zipper()) -> zipper() | undefined.
 up(#{info := #{parent_node := undefined}}) ->
     undefined;
+up(Zipper = #{spec := #{make_node := MakeNode},
+              node := Node,
+              info := #{lefts := Lefts,
+                        rights := Rights,
+                        parent_node := ParentNode,
+                        parent_info := ParentInfo,
+                        is_modified := true}}) ->
+    Children = lists:reverse(Lefts) ++ [Node | Rights],
+    NewParentNode = MakeNode(ParentNode, Children),
+    Zipper#{node => NewParentNode,
+            info => ParentInfo};
 up(Zipper = #{info := #{parent_node := Parent,
-                         parent_info := ParentInfo}}) ->
+                        parent_info := ParentInfo}}) ->
     Zipper#{node => Parent,
             info => ParentInfo}.
 
@@ -58,8 +80,7 @@ down(Zipper = #{node := Node,
                     info => #{lefts => [],
                               rights => Rights,
                               parent_node => Node,
-                              parent_info => Info
-                             }
+                              parent_info => Info}
                    };
         false ->
             undefined
@@ -76,6 +97,18 @@ left(Zipper = #{info := Info = #{lefts := [NewNode | Lefts],
             node => NewNode
            }.
 
+-spec leftmost(zipper()) -> zipper().
+leftmost(Zipper = #{info := #{lefts := []}}) ->
+    Zipper;
+leftmost(Zipper = #{info := Info = #{lefts := Lefts,
+                                     rights := Rights},
+                    node := Node}) ->
+    Fun = fun(Item, Acc) -> [Item | Acc] end,
+    [NewNode | NewRights] = lists:foldl(Fun,  [Node | Rights], Lefts),
+    Zipper#{info => Info#{lefts => [],
+                          rights => NewRights},
+            node => NewNode}.
+
 -spec right(zipper()) -> zipper().
 right(#{info := #{rights := []}}) ->
     undefined;
@@ -84,8 +117,17 @@ right(Zipper = #{info := Info = #{rights := [NewNode | Rights],
                  node := Node}) ->
     Zipper#{info => Info#{rights := Rights,
                           lefts := [Node | Lefts]},
-            node := NewNode
-           }.
+            node := NewNode}.
+
+-spec rightmost(zipper()) -> zipper().
+rightmost(Zipper = #{info := Info = #{rights := Rights,
+                                      lefts := Lefts},
+                     node := Node}) ->
+    Fun = fun(Item, Acc) -> [Item | Acc] end,
+    [NewNode | NewLefts] = lists:foldl(Fun,  [Node | Lefts], Rights),
+    Zipper#{info => Info#{lefts => NewLefts,
+                          rights => []},
+            node => NewNode}.
 
 -spec next(zipper()) -> zipper().
 next(Zipper = #{info := 'end'}) ->
@@ -128,15 +170,6 @@ prev_recur(Zipper) ->
             prev_recur(RightMost)
     end.
 
-rightmost(Zipper = #{info := Info = #{rights := Rights,
-                                      lefts := Lefts},
-                     node := Node}) ->
-    Fun = fun(Item, Acc) -> [Item | Acc] end,
-    [NewNode | NewLefts] = lists:foldl(Fun,  [Node | Lefts], Rights),
-    Zipper#{info => Info#{lefts => NewLefts,
-                          rights => []},
-            node => NewNode}.
-
 -spec root(zipper()) -> zipper().
 root(Zipper) ->
     case up(Zipper) of
@@ -150,6 +183,73 @@ traverse([], Zipper) ->
 traverse([Op | Rest], Zipper) ->
     traverse(Rest, zipper:Op(Zipper)).
 
+-spec insert_left(term(), zipper()) -> zipper().
+insert_left(_, #{info := #{parent_node := undefined}}) ->
+    throw(insert_at_top);
+insert_left(Node, Zipper = #{info := Info = #{lefts := Lefts}}) ->
+    NewInfo = Info#{lefts => [Node | Lefts],
+                    is_modified => true},
+    Zipper#{info => NewInfo}.
+
+-spec insert_right(term(), zipper()) -> zipper().
+insert_right(_, #{info := #{parent_node := undefined}}) ->
+    throw(insert_at_top);
+insert_right(Node, Zipper = #{info := Info = #{rights := Rights}}) ->
+    NewInfo = Info#{rights => [Node | Rights],
+                    is_modified => true},
+    Zipper#{info => NewInfo}.
+
+-spec replace(term(), zipper()) -> zipper().
+replace(Node, Zipper = #{info := Info}) ->
+    Zipper#{node => Node,
+            info => Info#{is_modified => true}}.
+
+-spec edit(fun(), list(), zipper()) -> zipper().
+edit(Fun, Args, Zipper = #{node := Node, info := Info}) ->
+    NewNode = erlang:apply(Fun, [Node | Args]),
+    Zipper#{node => NewNode,
+            info => Info#{is_modified => true}}.
+
+-spec insert_child(term(), zipper()) -> zipper().
+insert_child(Child, Zipper = #{spec := #{make_node := MakeNode}}) ->
+    Node = zipper:node(Zipper),
+    Children  = zipper:children(Zipper),
+    NewNode = MakeNode(Node, [Child | Children]),
+    replace(NewNode, Zipper).
+
+-spec append_child(term(), zipper()) -> zipper().
+append_child(Child, Zipper = #{spec := #{make_node := MakeNode}}) ->
+    Node = zipper:node(Zipper),
+    Children  = zipper:children(Zipper),
+    NewNode = MakeNode(Node, Children ++ [Child]),
+    replace(NewNode, Zipper).
+
+-spec remove(zipper()) -> zipper().
+remove(#{info := #{parent_node := undefined}}) ->
+    throw(remove_at_top);
+remove(#{spec := Spec = #{make_node := MakeNode},
+         info := #{lefts := [],
+                   rights := Rights,
+                   parent_node := ParentNode,
+                   parent_info := ParentInfo}}) ->
+    NewParentNode = MakeNode(ParentNode, Rights),
+    #{spec => Spec,
+      node => NewParentNode,
+      info => ParentInfo#{is_modified => true}};
+remove(#{spec := Spec,
+         info := Info  = #{lefts := [Node | Lefts]}}) ->
+    NewZipper = #{spec => Spec,
+                  node => Node,
+                  info => Info#{lefts => Lefts,
+                                is_modified => true}},
+    prev_removed(NewZipper).
+
+prev_removed(Zipper) ->
+    case down(Zipper) of
+        undefined -> Zipper;
+        Child -> prev_removed(rightmost(Child))
+    end.
+
 -spec node(zipper()) -> zipper().
 node(#{node := Node}) ->
     Node.

src/zipper_default.erl

@@ -2,12 +2,14 @@
 
 -export([list/1, bin_tree/1, map_tree/2]).
 
+-spec list(list()) -> zipper:zipper().
 list(Root) ->
     IsBranchFun = fun is_list/1,
     ChildrenFun = fun(List) -> List end,
     MakeNodeFun = fun(_Node, Children) -> Children end,
     zipper:new(IsBranchFun, ChildrenFun, MakeNodeFun, Root).
 
+-spec bin_tree({term(), term(), term()}) -> zipper:zipper().
 bin_tree(Root) ->
     IsBranchFun = fun(Node) ->
                           is_tuple(Node)
@@ -17,6 +19,7 @@ bin_tree(Root) ->
     MakeNodeFun = fun(Node, [Left, Right]) -> {Node, Left, Right} end,
     zipper:new(IsBranchFun, ChildrenFun, MakeNodeFun, Root).
 
+-spec map_tree(map(), term()) -> zipper:zipper().
 map_tree(Root, ChildrenKey) ->
     IsBranchFun = fun (M) ->
                           is_map(M)