Vyapar Billing Data Retrieval Tool

I need a robust, secure solution that can log in to an authorised Vyapar account, pull every piece of billing-related information, and let me export it in the formats I actually use day-to-day. The core... (Budget: ₹1500 - ₹12500 INR, Jobs: Android, API, C# Programming, Desktop App, JSON, Mobile App Development, Software Architecture)