Google Sign In + Firebase

GoogleSignInActivityContract.kt

package se.caspeco.mobileorder.ui.login

import android.content.Context
import android.content.Intent
import androidx.activity.result.contract.ActivityResultContract
import com.github.ajalt.timberkt.Timber
import com.google.android.gms.auth.api.signin.GoogleSignIn
import com.google.android.gms.auth.api.signin.GoogleSignInAccount
import com.google.android.gms.auth.api.signin.GoogleSignInOptions
import com.google.android.gms.common.api.ApiException
import com.google.android.gms.tasks.Task

class GoogleSignInActivityContract : ActivityResultContract<
    GoogleSignInOptions, 
    GoogleSignInActivityContract.Result
>() {

    override fun createIntent(context: Context, input: GoogleSignInOptions?): Intent {
        val client = GoogleSignIn.getClient(context, input ?: error("No GoogleSignInOptions Provided"))
        return client.signInIntent
    }

    override fun parseResult(resultCode: Int, intent: Intent?): Result {
        return handleSignInResult(GoogleSignIn.getSignedInAccountFromIntent(intent))
    }

    private fun handleSignInResult(completedTask: Task<GoogleSignInAccount>): Result {
        return try {
            Result.Success(completedTask.result)
        } catch (e: Exception) {
            // The ApiException status code indicates the detailed failure reason.
            // Please refer to the GoogleSignInStatusCodes class reference for more information.
            (e as? ApiException)?.let { Timber.w { "signInResult:failed code=" + it.statusCode } }
            Result.Failure(e)
        }
    }

    sealed class Result {
        data class Success(val googleSignInAccount: GoogleSignInAccount) : Result()
        data class Failure(val exception: Exception) : Result()
    }
}

LoginActivity.kt

class LoginActivity ...

    // Before onCreate
    private val googleSignInRequest = registerForActivityResult(
        GoogleSignInActivityContract(),
        ::onGoogleSignInResult
    )
    
    private val googleSignInOptions: GoogleSignInOptions
        get() = GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
            .requestIdToken(getString(R.string.GooglePlayServiceKey_WebClient))
            .requestEmail()
            .requestProfile()
            .build()
    
    private fun onGoogleSignInResult(result: GoogleSignInActivityContract.Result) = when (result) {
        is GoogleAuthSuccess -> handleGoogleLogin(result.googleSignInAccount)
        is GoogleAuthFailure -> Timber.e(result.exception)
    }
    
    // Trigger function
    fun startGoogleSignIn() = googleSignInRequest.launch(googleSignInOptions)
    
    private fun handleGoogleLogin(googleSignInAccount: GoogleSignInAccount) {
        launchIO { // coroutine shorthand
            val googleCredentials = GoogleAuthProvider.getCredential(googleSignInAccount.idToken, null)
            val signInTask = FirebaseAuth.getInstance().signInWithCredential(googleCredentials)
            when (signInTask.await()) {
                is AuthResult -> { // <- Successfully signed in to firebase with Google Credentials
                    val googleName = googleSignInAccount.displayName ?: "Mr. Smith"
                    val googleEmail = googleSignInAccount.email ?: error("No email available")
                    // Handle account information ...
                }
                else -> {
                    Timber.e { "Failed" }
                    postEvent(LoginModels.LoginEvent.LoginFailed)
                }
            }
        }
    }