track searches that return no results

app/views/posts/index.html.erb

@@ -59,4 +59,5 @@
   <% if @post_set.has_wiki? %>
     <meta name="description" content="<%= @post_set.wiki_page.presenter.blurb %>"></meta>
   <% end %>
+  <%= missed_post_search_count_js %>
 <% end %>

app/views/posts/partials/common/_search.html.erb

@@ -13,6 +13,7 @@
     <% if params[:random] %>
       <%= hidden_field_tag :random, params[:random] %>
     <% end %>
+    <%= hidden_field_tag "ms", "1" %>
     <%= submit_tag "Go", :name => nil %>
   <% end %>
 </section>

app/views/posts/partials/index/_missed_search_count.html.erb

@@ -0,0 +1,12 @@
+<script type="text/javascript">
+  $(function() {
+    var tags = $("#tags").val();
+    if (Danbooru.get_url_parameter("ms") === "1" && tags && tags.length > 0 && $(".post-preview").size() < 10) {
+      $.post("<%= Danbooru.config.report_server %>/missed_searches", {
+        session_id: "<%= session_id %>",
+        tags: $("#tags").val(),
+        sig: "<%= sig %>"
+      });
+    }
+  });
+</script>