Simple bookings using Google Calendar API

Hello, I have existing android app, and i need to add a booking calendar feature, where all app users can book appointments with each other using Google Calendar API. Each user of the app already has existing user_id right now. This project is to create a custom android java class+XML that does the following: 1. If an app user don't have calendar on google calendar, create one for them such that they can access any other app users calendar by having the other users user_id without asking permission. 2. When user X displays users Y calendar on Android screen to make a booking, it must show all existing bookings on calendar Y from all users, plus any existing booking from user X own calendar. 3. When user X makes a booking or deletes a booking on any users calendar, user X own calendar must be updated to reflect the same. 4. Remind the user with an alert when any booking on his own calendar is getting near.