Prompt Title: Google OAuth with Kotlin.

To get a user's profile information from Google after obtaining an access token, you can use the Google OAuth 2.0 client library for Java. Here's an example code snippet that demonstrates how to retrieve the user's profile information:

kotlinCopy code
import com.google.api.client.auth.oauth2.Credential
import com.google.api.client.googleapis.auth.oauth2.GoogleCredential
import com.google.api.client.googleapis.auth.oauth2.GoogleOAuthConstants
import com.google.api.client.googleapis.auth.oauth2.GoogleTokenResponse
import com.google.api.client.googleapis.auth.oauth2.GoogleAuthorizationCodeFlow
import com.google.api.client.googleapis.auth.oauth2.GoogleAuthorizationCodeRequestUrl
import com.google.api.client.http.javanet.NetHttpTransport
import com.google.api.client.json.JsonFactory
import com.google.api.client.json.jackson2.JacksonFactory
import com.google.api.services.oauth2.Oauth2
import com.google.api.services.oauth2.model.Userinfo

// Define the JSON factory and HTTP transport for the Google API client library
private val JSON_FACTORY: JsonFactory = JacksonFactory.getDefaultInstance()
private val HTTP_TRANSPORT = NetHttpTransport()

// Set up the OAuth 2.0 client credentials
private const val CLIENT_ID = "<your-client-id>"
private const val CLIENT_SECRET = "<your-client-secret>"
private const val REDIRECT_URI = "<your-redirect-uri>"

// Define the scope of access to the user's profile information
private val SCOPE = listOf("https://www.googleapis.com/auth/userinfo.email", "https://www.googleapis.com/auth/userinfo.profile")

// Define the Google authorization flow
private val FLOW = GoogleAuthorizationCodeFlow.Builder(HTTP_TRANSPORT, JSON_FACTORY, CLIENT_ID, CLIENT_SECRET, SCOPE).build()

fun getUserProfile(accessToken: String): Userinfo? {
    // Create a Google credential object from the access token
    val credential = GoogleCredential().setAccessToken(accessToken)

    // Create an OAuth2 object for accessing the user's profile information
    val oauth2 = Oauth2.Builder(HTTP_TRANSPORT, JSON_FACTORY, credential).setApplicationName(GoogleOAuthConstants.APPLICATION_NAME).build()

    // Retrieve the user's profile information using the OAuth2 object
    val userinfo = oauth2.userinfo().get().execute()

    return userinfo
}

In this example, the getUserProfile function takes an access token as input and uses it to create a Google credential object. It then creates an OAuth2 object for accessing the user's profile information and retrieves the user's profile information using the userinfo().get() method. The function returns the Userinfo object containing the user's profile information. Note that you will need to have the appropriate scopes set up in your Google OAuth 2.0 configuration to access the user's profile information.