From 193f04842ebb8e842932e5fb77449278f202d183 Mon Sep 17 00:00:00 2001
From: Arpit Jalan <arpit@techapj.com>
Date: Sat, 26 Sep 2015 22:53:25 +0530
Subject: [PATCH] FIX: permalinks should work for Discourse categories

---
 app/controllers/list_controller.rb | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/app/controllers/list_controller.rb b/app/controllers/list_controller.rb
index d894ee1f37c..bea88a69e62 100644
--- a/app/controllers/list_controller.rb
+++ b/app/controllers/list_controller.rb
@@ -228,11 +228,11 @@ class ListController < ApplicationController
     parent_category_id = nil
     if parent_slug_or_id.present?
       parent_category_id = Category.query_parent_category(parent_slug_or_id)
-      raise Discourse::NotFound if parent_category_id.blank?
+      redirect_or_not_found and return if parent_category_id.blank?
     end
 
     @category = Category.query_category(slug_or_id, parent_category_id)
-    raise Discourse::NotFound if !@category
+    redirect_or_not_found and return if !@category
 
     @description_meta = @category.description_text
     guardian.ensure_can_see!(@category)
@@ -308,4 +308,23 @@ class ListController < ApplicationController
     periods
   end
 
+  def redirect_or_not_found
+    url = request.fullpath
+    permalink = Permalink.find_by_url(url)
+
+    if permalink.present?
+      # permalink present, redirect to that URL
+      if permalink.external_url
+        redirect_to permalink.external_url, status: :moved_permanently
+      elsif permalink.target_url
+        redirect_to "#{Discourse::base_uri}#{permalink.target_url}", status: :moved_permanently
+      else
+        raise Discourse::NotFound
+      end
+    else
+      # redirect to 404
+      raise Discourse::NotFound
+    end
+  end
+
 end