Don't show next page button if there is no next page

lib/search.rb

 def search_threads(query, username, from_date, to_date, sort, offset)
   DB[<<-SQL, query, username, username, from_date, from_date, to_date, to_date, offset]
     SELECT
-      threads.*
+      threads.*,
+      count(*) OVER() AS full_count
     FROM threads
     WHERE
       to_tsvector(title) @@ plainto_tsquery(?)
     SELECT
       posts.*,
       threads.title as thread_title,
-      threads.remote_id as remote_thread_id
+      threads.remote_id as remote_thread_id,
+      count(*) OVER() AS full_count
     FROM posts
     INNER JOIN threads on posts.thread_id = threads.id
     WHERE

web/server.rb

     unless results[:errors].empty?
       erb :results, { locals: {errors: results[:errors]}, layout: :layout }
     else
+      params[:current_count] = results[:results].to_a.size
+      params[:full_count] = results[:results].empty? ? 0 : results[:results].first[:full_count]
       previous_url, next_url = build_urls(params)
 
       locals =
     def build_urls(params)
       current_page = params[:page].to_i
       previous_page = current_page > 1 ? current_page - 1 : nil
-      next_page = current_page + 1
+
+      if params[:current_count] == params[:full_count]
+        next_page = nil
+      else
+        next_page = current_page + 1
+      end
 
       url_params = { q: params[:q], type: params[:type] }
       url_params[:username] = params[:username] if params[:username]
       url_params[:from_date] = params[:from_date] if params[:from_date]
       url_params[:to_date] = params[:to_date] if params[:to_date]
 
-      [previous_page, next_page].map do |page|
+      [
         URI::Generic.build(
           path: '/search',
-          query: URI.encode_www_form(url_params.merge(page: page))
-        )
-      end
+          query: URI.encode_www_form(url_params.merge(page: previous_page))
+        ),
+        next_page.nil? ? nil : URI::Generic.build(
+          path: '/search',
+          query: URI.encode_www_form(url_params.merge(page: next_page))
+        ),
+      ]
     end
 
     def current_user

web/views/results.erb

           </a>
         <% end %>
 
-        <% unless results.empty? %>
+        <% unless results.empty? || next_url.nil? %>
           <a class="btn btn--small btn--next" href="<%= next_url %>">
             next page
           </a>