How to access classroom api after signing through Firebase using Google Sign-in - firebase

Question

I have created a unity application to sign-in using google and access google-classroom api. The sign-in is successful and the scope allows access to the courses too.
Question:
How to query the google classroom api after signing in with firebase.
endpoint : https://classroom.googleapis.com/v1/courses/105459102203
Method : GET
Parameter : CourseId which I already have
BearerToken : How to retrieve this from firebase?
When I try using auth-code and/or idToken it gives the following error:
{
"error": {
"code": 401,
"message": "Request had invalid authentication credentials. Expected OAuth 2 access token, login cookie or other valid authentication credential. See https://developers.google.com/identity/sign-in/web/devconsole-project.",
"status": "UNAUTHENTICATED"
}
}
Thanks in advance.

Answer 1

There are many ways to make a succesfully API request via firebase Auth, in particulary to Google Classroom API:
The hard way is to create a HttpInterceptor for the firebase.UserCredentials and pass it on headers of every HttpRequest, somethis like this:
headers: new HttpHeaders(
{
'Content-Type': 'application/json',
Authorization: `Bearer [${this.user$.AccessToken}]`
})
this is what I call the hard way because you have to ensure to pass and refresh tokens y every API services.
Use the javascript library "gapi" to login the client, and then use the token response as credential to login in Firebase. This aproach creates a pure OAuth2 login that serves to Firebase and further Google APIs requests, as follows:
declare var gapi;
/** Initialize Google API Client */
initClient(): void {
gapi.client.init({
apiKey: environment.firebaseConfig.apiKey,
clientId: environment.firebaseConfig.clientId,
discoveryDocs: environment.firebaseConfig.discoveryDocs,
scope: environment.firebaseConfig.scope,
});
}
/** Do a OAuth login and then pass it to a FirebaseAuth service */
async login() {
const googleAuth = gapi.auth2.getAuthInstance();
const googleUser = await googleAuth.signIn();
const token = googleUser.getAuthResponse().id_token;
const credential = firebase.auth.GoogleAuthProvider.credential(token);
await this.afAuth().signInAndRetrieveDataWithCredential(credential);
}
/** Then you're ready to make a request*/
/**
* Lists all course names and ids.
* Print the names of the first 10 courses the user has access to. If
* no courses are found an appropriate message is printed.
*/
listCourses() {
this.courses$ =
gapi.client.classroom.courses.list({pageSize=10;}).then(response => {
return from<Course[]>(response.result.courses);
});
}