I recently developed a reporting feature to a system. The report had to be portable, both human and machine readable, and the human-part had to look nice to management people.

I considered generating 2 separate reports, in JSON for machines and in PDF for humans. The PDF part turned out to be difficult.

In the end I settled with XML. Its machine readable by nature and with XSLT it becomes human readable in the browser. The programming language provided XML encoder in the standard library which made the task very easy.

I still find XSLT a pain to deal with though!