TokenProvider.scala

import java.io.FileInputStream
import java.security.interfaces.RSAPrivateKey
import java.util.Date

import com.auth0.jwt.JWT
import com.auth0.jwt.algorithms.Algorithm
import com.google.api.client.googleapis.auth.oauth2.GoogleCredential

class GCBTokenProvider(privateKey: RSAPrivateKey, privateKeyId: String, serviceName: String, api: String, user: String) {
  def getToken: String = {
    val now = System.currentTimeMillis();
    val algorithm = Algorithm.RSA256(null,privateKey)
    val signedJwt = JWT.create()
      .withKeyId(privateKeyId)
      .withIssuer(user)
      .withSubject(user)
      .withAudience(s"https://$serviceName/$api")
      .withIssuedAt(new Date(now))
      .withExpiresAt(new Date(now + 3600 * 1000L))
      .sign(algorithm)
    signedJwt
  }
}

object GCBTokenProvider extends App {
  val serviceName = "resultstore.googleapis.com"
  val apiName = "google.devtools.resultstore.v2.ResultStoreFileDownload"
  val credentials = GoogleCredential
    .fromStream(new FileInputStream("/Users/ors/Downloads/labeldex-service-account.json"))

  val email: String =  ???//

  val privateKey: RSAPrivateKey = credentials.getServiceAccountPrivateKey.asInstanceOf[RSAPrivateKey]
  val privateKeyId: String = credentials.getServiceAccountPrivateKeyId

  val provider = new GCBTokenProvider(privateKey,privateKeyId,serviceName,apiName,email)

  println (provider.getToken)
}