This is a bot I built for fun the Summer after Facebook released the Messenger API. The bot lives on a Facebook page and helps people schedule appointments with the owner of the page.
To set up the bot, a user syncs a Google Calendar and a Facebook page and sets some options the bot uses to great people it interacts with.
Both the bot itself, which responds to Facebook messages, and the webapp a user uses to set it up are included in this project.
I stopped working on this long ago so it is likely some things don't work. I expect that by now there are nice libraries abstracting away much of the details in this code.