Dropped number from revision table. Also dropped timestamp. We will rely on autoincremented ID for sorting, and will for now store the time of last edit of the revision in revised_at. Later we will refactor content into a separate table (so as not to load the whole 300 kb of text and cached HTML every time we need page.revisions in code). Rake tests all pass, but watir tests indicate that some revision traversing links are still broken

app/models/revision.rb

@@ -3,24 +3,13 @@ class Revision < ActiveRecord::Base
   belongs_to :page
   composed_of :author, :mapping => [ %w(author name), %w(ip ip) ]
 
-  def created_on
-    created_at.to_date
+  def revised_on
+    revised_at
   end
 
-  def pretty_created_at
-    # Must use DateTime because Time doesn't support %e on at least some platforms
-    DateTime.new(
-      created_at.year, created_at.mon, created_at.day, created_at.hour, created_at.min
-    ).strftime "%B %e, %Y %H:%M" 
-  end
-
-  # todo: drop next_revision, previuous_revision and number from here - unused code
-  def next_revision
-    Revision.find_by_number_and_page_id(number+1, page_id)
-  end
-
-  def previous_revision
-    @previous_revions ||= number > 0 ? Revision.find_by_number_and_page_id(number-1, page_id) : nil
+  # TODO this method belongs in the view helpers (only views use it)
+  def pretty_created_on
+    revised_on.to_date.strftime "%B %e, %Y %H:%M:%S" 
   end
 
   # Returns an array of all the WikiIncludes present in the content of this revision.
@@ -30,7 +19,7 @@ class Revision < ActiveRecord::Base
       @wiki_includes_cache = chunks.map { |c| ( c.escaped? ? nil : c.page_name ) }.compact.uniq
     end
     @wiki_includes_cache
-  end  
+  end
 
   # Returns an array of all the WikiReferences present in the content of this revision.
   def wiki_references
@@ -72,8 +61,14 @@ class Revision < ActiveRecord::Base
     @display_cache
   end
 
+  # TODO this probably doesn't belong in revision (because it has to call back the page)
   def display_diff
-    previous_revision ? HTMLDiff.diff(previous_revision.display_content, display_content) : display_content
+    previous_revision = page.previous_revision(self)
+    if previous_revision 
+      HTMLDiff.diff(previous_revision.display_content, display_content) 
+    else 
+      display_content
+    end
   end
 
   def clear_display_cache
@@ -112,18 +107,8 @@ class Revision < ActiveRecord::Base
   end
 
   protected
-  before_create :set_revision_number, :set_timestamp
+
   after_create :force_rendering
   after_save :clear_display_cache
-  
-  # TODO Refactor this away. Revisions collection should not rely on the revision number for 
-  # sorting etc - revisions must be easy to delete (this helps fighting wiki spam)
-  def set_revision_number
-    self.number = self.class.count(['page_id = ?', page_id]) + 1
-  end
-  
-  def set_timestamp
-    self.timestamp = (Time.now.to_f * 1000).to_i.to_s
-  end
 
 end