Remove self and decendants from the parent feed selector, closing #89.

The self link is the only one that is really problematic, but intuitively we don't want users to hang the tree from the tree without doing some thinking beforehand.

app/helpers/feeds_helper.rb

@@ -1,11 +1,15 @@
 module FeedsHelper
 
   # Generate a depth first ordered tree.
-  def dfs_tree(roots = Feed.roots)
+  def dfs_tree(roots = Feed.roots, break_at = nil)
     nodes = []
     roots.each do |node|
-      nodes += [node]
-      nodes += node.descendants unless node.descendants.empty?
+      nodes += [node] unless (node == break_at)      
+      nodes += node.descendants unless (node.descendants.empty? || node == break_at)
+    end
+    if !break_at.nil?
+      rejectable = break_at.descendants
+      nodes = nodes.reject{|n| rejectable.include?(n) || n == break_at}
     end
     nodes
   end

app/views/feeds/_form.html.erb

@@ -25,13 +25,13 @@
 			</div>
 		</div>
 		<%
-                  feeds = dfs_tree(Feed.roots).collect{|c| [raw("&nbsp;&nbsp;")* c.depth + c.name, c.id ]}
-                  unless feeds.empty?
+                  parent_feeds = dfs_tree(Feed.roots, @feed)
+                  unless parent_feeds.empty?
                 %>
 		<div class="clearfix">
 			<%= f.label t(:parent) %>
 	  	<div class="input">
-				<%= f.select :parent_id, dfs_tree(Feed.roots).collect{|c| [raw("&nbsp;&nbsp;")* c.depth + c.name, c.id ]}, {:include_blank => true }, :class => "span6" %>
+				<%= f.select :parent_id, parent_feeds.collect{|c| [raw("&nbsp;&nbsp;")* c.depth + c.name, c.id ]}, {:include_blank => true }, :class => "span6" %>
 			</div>
 		</div>
 		<% end %>

test/unit/helpers/feeds_helper_test.rb

@@ -1,4 +1,29 @@
 require 'test_helper'
 
 class FeedsHelperTest < ActionView::TestCase
+
+  test 'default dfs tree' do
+    tree = dfs_tree()
+    assert_equal tree.length, Feed.all.length
+
+    i = tree.index(feeds(:announcements))
+    j = tree.index(feeds(:boring_announcements))
+    assert_equal tree[j+1], feeds(:sleepy_announcements)
+
+    if j-i == 1
+      offset = j+2
+    else
+      offset = i+1
+    end
+    assert_equal tree[offset], feeds(:important_announcements)   
+  end
+
+  test 'excluding dfs tree' do
+    feed = feeds(:boring_announcements)
+    tree = dfs_tree(Feed.roots, feed)
+    assert_equal tree.length, Feed.all.length-2
+
+    assert !tree.include?(feeds(:boring_announcements))
+    assert !tree.include?(feeds(:sleepy_announcements))
+  end
 end