#434

backend/app/controllers/concerns/counts_listing.rb

@@ -6,7 +6,8 @@ module CountsListing
     resource = is_a?(CountsPostsController) ? 'posts' : 'tags'
     query = CountsQuery.new(version_scope, resource, request.query_parameters.except('locale')
         .merge('locale' => locale.code))
-    result = { count: query.count, page: query.page, limit: query.limit }
+    result = { count: query.count, page: query.page, limit: query.limit,
+               at: request.query_parameters['at'].presence || Time.current.utc.iso8601(6) }
     if query.mode == 'summary'
       result.merge!(query.summary)
     else

backend/app/controllers/counts_exports_controller.rb

@@ -0,0 +1,20 @@
+class CountsExportsController < ApplicationController
+  wrap_parameters false
+
+  def index
+    locale = resolve_locale!
+    exporter = CountsExporter.new(request.request_parameters.merge(request.query_parameters),
+                                  language_code: locale.language_code)
+    response.headers['Content-Type'] = exporter.format == 'json' ?
+        'application/json; charset=utf-8' : 'text/csv; charset=utf-8'
+    response.headers['Content-Disposition'] =
+        "attachment; filename=\"counts-#{ exporter.resource }.#{ exporter.format }\""
+    response.headers['Cache-Control'] = 'private, no-store'
+    response.headers['X-Accel-Buffering'] = 'no'
+    # Rack::ETag otherwise materialises the response to calculate a digest.
+    response.headers['Last-Modified'] = Time.current.httpdate
+    self.response_body = exporter.body
+  rescue ArgumentError, TypeError, JSON::ParserError
+    head :bad_request
+  end
+end

backend/app/controllers/post_versions_controller.rb

@@ -38,13 +38,7 @@ class PostVersionsController < ApplicationController
   private
 
   def version_scope
-    PostVersion.joins(<<~SQL.squish)
-          LEFT JOIN
-            post_versions prev
-            ON
-              prev.post_id = post_versions.post_id
-              AND prev.version_no = post_versions.version_no - 1
-        SQL
+    PostVersion.with_previous_version
         .select('post_versions.*',
                 'prev.title AS prev_title',
                 'prev.url AS prev_url',