Move the building of related posts into their own class

lib/jekyll/post.rb

@@ -1,3 +1,5 @@
+require 'jekyll/related_posts'
+
 module Jekyll
   class Post
     include Comparable
@@ -244,29 +246,7 @@ def id
     #
     # Returns an Array of related Posts.
     def related_posts(posts)
-      return [] unless posts.size > 1
-
-      if self.site.lsi
-        build_index
-
-        related = self.class.lsi.find_related(self.content, 11)
-        related - [self]
-      else
-        (posts - [self])[0..9]
-      end
-    end
-
-    def build_index
-      self.class.lsi ||= begin
-        puts "Starting the classifier..."
-        lsi = Classifier::LSI.new(:auto_rebuild => false)
-        $stdout.print("  Populating LSI... "); $stdout.flush
-        self.site.posts.each { |x| $stdout.print("."); $stdout.flush; lsi.add_item(x) }
-        $stdout.print("\n  Rebuilding LSI index... ")
-        lsi.build_index
-        puts ""
-        lsi
-      end
+      Jekyll::RelatedPosts.new(self).build
     end
 
     # Add any necessary layouts to this post.

lib/jekyll/related_posts.rb

@@ -0,0 +1,59 @@
+module Jekyll
+  class RelatedPosts
+
+    class << self
+      attr_accessor :lsi
+    end
+
+    attr_reader :post, :site
+
+    def initialize(post)
+      @post = post
+      @site = post.site
+      require 'classifier' if site.lsi
+    end
+
+    def build
+      return [] unless self.site.posts.size > 1
+
+      if self.site.lsi
+        build_index
+        lsi_related_posts
+      else
+        most_recent_posts
+      end
+    end
+
+    def build_index
+      self.class.lsi ||= begin
+        puts "Starting the classifier..."
+        lsi = Classifier::LSI.new(:auto_rebuild => false)
+        display("  Populating LSI... ")
+
+        self.site.posts.each do |x|
+          display(".")
+          lsi.add_item(x)
+        end
+
+        display("\n  Rebuilding LSI index... ")
+        lsi.build_index
+        puts ""
+        lsi
+      end
+    end
+
+    def lsi_related_posts
+      lsi.find_related(post.content, 11) - [self.post]
+    end
+
+    def most_recent_posts
+      (self.site.posts - [self.post])[0..9]
+    end
+
+    def display(output)
+      $stdout.print(output)
+      $stdout.flush
+    end
+
+  end
+end

lib/jekyll/site.rb

@@ -71,8 +71,6 @@ def reset
     #
     # Returns nothing.
     def setup
-      require 'classifier' if self.lsi
-
       # Check that the destination dir isn't the source dir or a directory
       # parent to the source dir.
       if self.source =~ /^#{self.dest}/