Ensure correct extension when downloading documents

plugins/documents/app/models/document.rb

@@ -2,4 +2,19 @@ class Document < ActiveRecord::Base
   belongs_to :created_by, :class_name => 'User', :foreign_key => 'created_by_user_id'
 
   validates_presence_of :data
+
+  def filename
+    types = MIME::Types[mime]
+
+    if name.include? '.'
+      types.each do |type|
+        type.extensions.each do |extension|
+          return name if name.end_with? ".#{extension}"
+        end
+      end
+    end
+
+    "#{name}.#{types.first.preferred_extension}"
+  end
+
 end