I want to create a PowerBI application similar to Salesforce Reports Power BI application on the AppSource market

- He expects the user to provide Salesforce credentials.
- It extracts all reports (tabular + summary) and lists on the right.
- The user selects the report, and the data corresponding to the report is retrieved from Salesforce by calling the REST API and a dataset is created for the Salesforce report.
I need to create something similar, and I cannot find the relevant documents. 1. Where can I view the source code for the above application? Is this an open source? 2. Is there any documentation on how to develop similar applications?
AppSource, .