precondition stuff

app/controllers/segment_controller.rb

@@ -13,11 +13,11 @@ class SegmentController < ApplicationController
         
         segment.user_id = @user.id
 
-        a = Node.find(segment.node_a.to_i)
-        b = Node.find(segment.node_b.to_i)
+        segment.from_node = Node.find(segment.node_a.to_i)
+        segment.to_node = Node.find(segment.node_b.to_i)
         
-        unless a and a.visible and b and b.visible  
-          render :nothing => true, :status => 400
+        unless segment.precondtions_ok? # are the nodes visible?
+          render :nothing => true, :status => 412
         end
 
         if segment.save_with_history

app/controllers/way_controller.rb

@@ -10,10 +10,17 @@ class WayController < ApplicationController
 
       if way
         way.user_id = @user.id
+        unless way.precondtions_ok? # are the segments (and their nodes) visible?
+          render :nothing => true, :status => 412
+          return
+        end
+
         if way.save_with_history
           render :text => way.id
+          return
         else
           render :nothing => true, :status => 500
+          return
         end
         return
       else
@@ -33,7 +40,7 @@ class WayController < ApplicationController
 
     way = Way.find(params[:id])
     case request.method
-   
+
     when :get
       unless way.visible
         render :nothing => true, :status => 410