What is the fine-grained topic of the following text: It all started Wednesday when TMZ reported that Taylor Swift and Calvin Harris’ relationship spiraled after Harris told Ryan Seacrest he wasn’t interested in collaborating with Swift, even though most evidence suggested she had secretly penned his hit “This Is What You Came For.” Swift’s rep eventually confirmed the superstar had written the track under the pen-name Nils Sjöberg. Only return the topic.
Taylor Swift secretly writing Calvin Harris' hit song "This Is What You Came For"