//Assume this project is cloned and referenced as library with the namespace CloudStorageApi

var creds = 'your-creds-file-id'; //JSON File with GCP Credentials for accessing the bucket
var name  = 'sample-cloud-storage-project'; //Namespace for cGoa (see File->Project Properties after running once for the scopes)
var recipient = '[email protected]';

var flagFileName = '___flag_copied_files.flag'; //only copy files if the flag is present

function configure() {
   CloudStorageApi.ConfigureScript(creds, name);
}

function copyTask(bucket,folder, subject) { 
  configure();
  
  //Check if there are new files
  var exists = CloudStorageApi.getService().fileExists(bucket,flagFileName);
 
  if (exists) {
    CloudStorageApi.copyFromBucket(bucket,folder,false, flagFileName);
    CloudStorageApi.getService().deleteFileByName(bucket,flagFileName);
    
    //If there is a subject, send an email report
    if (subject != 'undefined') {
      MailApp.sendEmail(recipient, subject, "Cloud Storage API:\n\nFiles copied."); 
    }
  }    
}

//Sample usage
function copyFromBucketA() {
  copyTask('bucket-name', 'destination-folder-id','BucketA FileCopy');
}