API for Android Emulator

I have a task for the future - to create some online-based solution with Apps on Android Emulators and make smtg with App online using REST API. For instance, I have VM with Android SDK and WhatsAPP on them. I need click button on site to

1) login in WhatsAPP 2) send message 3) logout App in Android Emulator

I know how to install and make interesting scripts if I have Android Studio on my PC and only one App. But how to do "remote managing" App inside Emulator ? May be you could advise some solutions I could use with REST API to manage emulator with app inside?

Thanks!