Java send facebook pre-populated message after Chat API deprecation?

I'm trying to write small app that would send custom message to the list of facebook users with user only specifying the message inside program and pressing send, no more user interaction needed. I'm good making everything except sending messages itself. I thought it won't be hard with Facebook API, but recently they removed/are removing pre-population of message with text. I naively thought i can maybe just send http request with a cookie, but found out that everything in that cookie is encrypted/hashed and now I'm a bit lost.