first pass at resolving #20

Author: Trevoke

lib/sgf.rb

@@ -1,5 +1,6 @@
 $: << File.dirname(__FILE__)
 
+require 'observer'
 require 'sgf/error'
 require 'sgf/version'
 require 'sgf/properties'

lib/sgf/node.rb

@@ -2,6 +2,7 @@ module SGF
 
   #Your basic node. It holds information about itself, its parent, and its children.
   class Node
+    include Observable
 
     attr_accessor :parent, :children, :properties, :depth
 
@@ -23,6 +24,9 @@ def add_children *nodes
       nodes.flatten!
       raise "Non-node child given!" if nodes.any? { |node| node.class != Node }
       nodes.each do |node|
+        if node.parent && node.parent.children
+          node.parent.children.delete node
+        end
         node.parent = self
         node.depth = @depth + 1
         @children << node

spec/node_spec.rb

@@ -94,4 +94,14 @@
     child.depth.should == 1
   end
 
+  it "should not be the child of many nodes" do
+    parent1 = SGF::Node.new
+    parent2 = SGF::Node.new
+    parent1.add_children @node
+    parent2.add_children @node
+    @node.parent.should eq(parent2)
+    parent2.children.should include(@node)
+    parent1.children.should_not include(@node)
+  end
+
 end