Implement basic upload tags change report

app/models/upload_tags_report.rb

@@ -0,0 +1,67 @@
+class UploadTagsReport < Post
+
+  def readonly?
+    true
+  end
+
+  module ApiMethods
+
+    def as_json(options = {})
+      options ||= {}
+      options[:only] ||= [:id]
+      super(options)
+    end
+
+    def to_xml(options = {}, &block)
+      options ||= {}
+      options[:only] ||= [:id, :uploader_id]
+      super(options, &block)
+    end
+
+    def method_attributes
+      [:uploader_tags, :added_tags, :removed_tags]
+    end
+
+  end
+
+  include ApiMethods
+
+  def uploader_tags_array
+    @uploader_tags ||= begin
+      added_tags = []
+      PostVersion.where(post_id: id, updater_id: uploader_id).each do |version|
+        added_tags += version.changes[:added_tags]
+      end
+      added_tags.uniq.sort
+    end
+  end
+
+  def current_tags_array
+    latest_tags = tag_array
+    latest_tags << "rating:#{rating}" if rating.present?
+    latest_tags << "parent:#{parent_id}" if parent_id.present?
+    latest_tags << "source:#{source}" if source.present?
+    latest_tags
+  end
+
+  def added_tags_array
+    current_tags_array - uploader_tags_array
+  end
+
+  def removed_tags_array
+    uploader_tags_array - current_tags_array
+  end
+
+  def uploader_tags
+    uploader_tags_array.join(' ')
+  end
+
+  def added_tags
+    added_tags_array.join(' ')
+  end
+
+  def removed_tags
+    removed_tags_array.join(' ')
+  end
+
+end