Include last modified headers and conditional get support in posts co…

…ntroller.

app/controllers/posts_controller.rb

@@ -2,6 +2,7 @@ class PostsController < ApplicationController
   def index
     @tag = params[:tag]
     @posts = Post.find_recent(:tag => @tag, :include => :tags)
+    fresh_when last_modified: posts_last_updated(@posts), public: true
 
     respond_to do |format|
       format.html
@@ -11,6 +12,16 @@ def index
 
   def show
     @post = Post.find_by_permalink(*([:year, :month, :day, :slug].collect {|x| params[x] } << {:include => [:comments, :tags]}))
+    fresh_when last_modified: @post.last_changed_at.utc, public: true
     @comment = Comment.new
   end
+
+  private
+
+  def posts_last_updated(posts)
+    (
+      [Comment.where(post_id: posts.map(&:id)).maximum(:updated_at)] +
+      posts.map(&:updated_at)
+    ).max
+  end
 end

app/models/post.rb

@@ -37,6 +37,10 @@ def published?
     published_at?
   end
 
+  def last_changed_at
+    [comments.maximum(:updated_at), updated_at].compact.max
+  end
+
   attr_accessor :published_at_natural
   def published_at_natural
     @published_at_natural ||= published_at.send_with_default(:strftime, 'now', "%Y-%m-%d %H:%M")