Add support for undoing changes

lib/audited/audit.rb

@@ -86,6 +86,25 @@ def old_attributes
       end
     end
 
+    # Allows user to undo changes
+    def undo
+      model = self.auditable_type.constantize
+      if action == 'create'
+        # destroys a newly created record
+        model.find(auditable_id).destroy!
+      elsif action == 'destroy'
+        # creates a new record with the destroyed record attributes
+        model.create(audited_changes)
+      else
+        # changes back attributes
+        audited_object = model.find(auditable_id)
+        self.audited_changes.each do |k, v|
+          audited_object[k] = v[0]
+        end
+        audited_object.save
+      end
+    end
+
     # Allows user to be set to either a string or an ActiveRecord object
     # @private
     def user_as_string=(user)

spec/audited/audit_spec.rb

@@ -38,6 +38,28 @@ class TempModel < ::ActiveRecord::Base
       end
     end
 
+    it "should undo changes" do
+      user = Models::ActiveRecord::User.create(name: "John")
+      user.update_attribute(:name, 'Joe')
+      user.audits.last.undo
+      user.reload
+
+      expect(user.name).to eq("John")
+    end
+
+    it "should undo destroyed model" do
+      user = Models::ActiveRecord::User.create(name: "John")
+      user.destroy
+      user.audits.last.undo
+      user = Models::ActiveRecord::User.find_by(name: "John")
+      expect(user.name).to eq("John")
+    end
+
+    it "should undo created model" do
+      user = Models::ActiveRecord::User.create(name: "John")
+      expect {user.audits.last.undo}.to change(Models::ActiveRecord::User, :count).by(-1)
+    end
+
     context "when a custom audit class is not configured" do
       it "should default to #{described_class}" do
         TempModel.audited