Internal use web pages (2 pages) by JavaScript, OAuth and API integration

A Japanese giant publisher wants to build an internal-use webpage "Dashboard" which visualizes the data of a mobile app which the company owns.

The dashboard consists of just 2 pages. 1st page is for authentication(OAuth) and 2nd page is a static web page by using d3.js.

The data is stored on Looker as its data analytics environment and Looker has API to return the numbers of the data.
FYI: Looker API reference ----------

In dashboard, we want to have Tree-like UI.
Example: ----------

Thank you,