Add previous page link for crawlers

app/controllers/list_controller.rb

@@ -46,7 +46,8 @@ class ListController < ApplicationController
       end
 
       list = TopicQuery.new(user, list_opts).public_send("list_#{filter}")
-      list.more_topics_url = construct_url_with(list_opts)
+      list.more_topics_url = construct_next_url_with(list_opts)
+      list.prev_topics_url = construct_prev_url_with(list_opts)
       if Discourse.anonymous_filters.include?(filter)
         @description = SiteSetting.site_description
         @rss = filter
@@ -92,8 +93,8 @@ class ListController < ApplicationController
       guardian.ensure_can_see_private_messages!(target_user.id) unless action == :topics_by
       list = generate_list_for(action.to_s, target_user, list_opts)
       url_prefix = "topics" unless action == :topics_by
-      url  = construct_url_with(list_opts, url_prefix)
+      list.more_topics_url = url_for(construct_next_url_with(list_opts, url_prefix))
-      list.more_topics_url = url_for(url)
+      list.prev_topics_url = url_for(construct_prev_url_with(list_opts, url_prefix))
       respond(list)
     end
   end
@@ -163,7 +164,8 @@ class ListController < ApplicationController
       top_options[:per_page] = SiteSetting.topics_per_period_in_top_page
       user = list_target_user
       list = TopicQuery.new(user, top_options).public_send("list_top_#{period}")
-      list.more_topics_url = construct_url_with(top_options)
+      list.more_topics_url = construct_next_url_with(top_options)
+      list.prev_topics_url = construct_prev_url_with(top_options)
       respond(list)
     end
 
@@ -202,8 +204,19 @@ class ListController < ApplicationController
   end
 
   def next_page_params(opts = nil)
+    page_params(opts).merge(page: params[:page].to_i + 1)
+  end
+
+  def prev_page_params(opts = nil)
+    page_params(opts).merge(page: params[:page].to_i > 1 ? (params[:page].to_i - 1) : 0)
+  end
+
+
+  private
+
+  def page_params(opts = nil)
     opts ||= {}
-    route_params = { format: 'json', page: params[:page].to_i + 1 }
+    route_params = {format: 'json'}
     route_params[:category]        = @category.slug if @category
     route_params[:parent_category] = @category.parent_category.slug if @category && @category.parent_category
     route_params[:sort_order]      = opts[:sort_order] if opts[:sort_order].present?
@@ -211,8 +224,6 @@ class ListController < ApplicationController
     route_params
   end
 
-  private
-
   def set_category
     slug_or_id = params.fetch(:category)
     parent_slug_or_id = params[:parent_category]
@@ -269,11 +280,16 @@ class ListController < ApplicationController
     TopicQuery.new(current_user, opts).send("list_#{action}", target_user)
   end
 
-  def construct_url_with(opts, url_prefix = nil)
+  def construct_next_url_with(opts, url_prefix = nil)
     method = url_prefix.blank? ? "#{action_name}_path" : "#{url_prefix}_#{action_name}_path"
     public_send(method, opts.merge(next_page_params(opts)))
   end
 
+  def construct_prev_url_with(opts, url_prefix = nil)
+    method = url_prefix.blank? ? "#{action_name}_path" : "#{url_prefix}_#{action_name}_path"
+    public_send(method, opts.merge(prev_page_params(opts)))
+  end
+
   def generate_top_lists(options)
     top = TopLists.new
 

app/models/topic_list.rb

@@ -4,6 +4,7 @@ class TopicList
   include ActiveModel::Serialization
 
   attr_accessor :more_topics_url,
+                :prev_topics_url,
                 :draft,
                 :draft_key,
                 :draft_sequence,

app/views/list/list.erb

@@ -4,10 +4,16 @@
 <% end %>
 </div>
 
-<% if @list.topics.length > 0 %>
+<p>
-<p><a href="<%= @list.more_topics_url.sub('.json?','?') %>" rel="next"><%= t 'next_page'%></a></p>
+  <% if params[:page].to_i > 1 %>
+    <a href="<%= @list.prev_topics_url.sub('.json?','?') %>" rel="prev" style="margin-right: 30px;"><%= t 'prev_page'%></a>
   <% end %>
 
+  <% if @list.topics.length > 0 %>
+    <a href="<%= @list.more_topics_url.sub('.json?','?') %>" rel="next"><%= t 'next_page'%></a>
+  <% end %>
+</p>
+
 <p><%= t 'powered_by_html' %></p>
 
 <% if @rss %>

config/locales/server.en.yml

@@ -76,6 +76,7 @@ en:
   invalid_characters: "contains invalid characters"
   is_invalid: "is invalid; try to be a little more descriptive"
   next_page: "next page →"
+  prev_page: "← previous page"
   page_num: "Page %{num}"
   by: "By"
   topics_in_category: "Topics in the '%{category}' category"