prevent double clicking of the post comment button from creating two comments

app/controllers/comments_controller.rb

@@ -26,6 +26,20 @@ class CommentsController < ApplicationController
       comment.thread_id = Keystore.incremented_value_for("thread_id")
     end
 
+    # prevent double-clicks of the post button
+    if !params[:preview].present? &&
+    (pc = Comment.find_by_story_id_and_user_id_and_parent_comment_id(story.id,
+    @user.id, comment.parent_comment_id))
+      if (Time.now - pc.created_at) < 5.minutes
+        comment.errors.add(:comment, "^You have already posted a comment " <<
+          "here recently.")
+
+        return render :partial => "commentbox", :layout => false,
+          :content_type => "text/html", :locals => { :story => story,
+          :comment => comment }
+      end
+    end
+
     if comment.valid? && !params[:preview].present? && comment.save
       comment.current_vote = { :vote => 1 }
 

app/helpers/application_helper.rb

@@ -2,11 +2,11 @@ module ApplicationHelper
   def errors_for(object, message=nil)
     html = ""
     unless object.errors.blank?
-      html << "<p><div class=\"flash-error\">\n"
+      html << "<div class=\"flash-error\">\n"
       object.errors.full_messages.each do |error|
         html << error << "<br>"
       end
-      html << "</div></p>\n"
+      html << "</div>\n"
     end
 
     raw(html)

app/views/comments/_commentbox.html.erb

@@ -1,6 +1,10 @@
 <div class="comment_form_container">
 <%= form_tag((comment.new_record? ? "/comments/post_to/#{story.short_id}" :
 "/comments/#{comment.short_id}/update"), { :id => "comment_form" }) do |f| %>
+  <% if comment && comment.errors.any? %>
+    <%= errors_for comment %>
+  <% end %>
+
   <% if comment.parent_comment_short_id.present? %>
     <%= hidden_field_tag "parent_comment_short_id",
       comment.parent_comment_short_id %>
@@ -31,14 +35,10 @@
 
   <p></p>
 <% end %>
-<% if defined?(show_comment) %>
-  <% if show_comment.valid? %>
-    <ol class="comments comments1 preview">
-      <%= render :partial => "comments/comment",
-        :locals => { :comment => show_comment, :story => story } %>
-    </ol>
-  <% else %>
-    <%= errors_for comment %>
-  <% end %>
+<% if defined?(show_comment) && show_comment.valid? %>
+  <ol class="comments comments1 preview">
+    <%= render :partial => "comments/comment",
+      :locals => { :comment => show_comment, :story => story } %>
+  </ol>
 <% end %>
 </div>