read and reply whatsapp messages

i want an programable apk wich can reply messages from whatsapp wich is coming to me. i know many apps where you can put a text and response and when a friend ask you, the app sends the automated message. thats why i want to do the same with my own app. it need to be something simple and messages will be coded by myself in android studio. the developer only need to code the read notifications and response part leaving an space where i can program my commands.