Earlier this week it only took me less than a business day to add a custom chat window to my site using Firebase. You might consider checking that out. It was

Earlier this week it only took me less than a business day to add a custom chat window to my site using Firebase. You might consider checking that out. It was a global chat, not one with friend lists and private messaging, but the API is pretty easy so I'm sure you could do what you want with a little work.