Google apps script for parsing the URL of the free ebook from the packtpub newsletter

code.gs

function extractPacktpubUrl() {

  try { 
    var ss = SpreadsheetApp.getActiveSheet();
  
    var label = GmailApp.getUserLabelByName("packt_free_ebook");
    var threads = label.getThreads();
    
    if (threads[0] == undefined || threads[0].getMessages()[0] == undefined) {
      Logger.log('No valid message found');
      return;
    }
    var currentThread = threads[0];
    var msg = currentThread.getMessages()[0];
    
    Logger.log('Parsing ' + msg.getSubject());
    
    var regExp = /(https.*\/packt\/free-ebook\/.*)\?/;
    var freeBookData = regExp.exec(msg.getPlainBody()); 
     
    if (!freeBookData) {
      Logger.log('No ebook data found in mail');
    } else {
    var url = [freeBookData[1]];
      ss.clear();
      ss.appendRow(url);
      Logger.log('Added URL ' + url);
    } 
  } catch (err) {
    GmailApp.sendEmail(YOUR_MAIL, 'Packtpub URL extractor error: ' + err.name, err.message + "\n\n" + err.stack);
    return;
  }
  
  const newLabel = GmailApp.createLabel(label.getName() + '_processed');
  
  currentThread.addLabel(newLabel);
  currentThread.removeLabel(label);
  currentThread.moveToArchive()
}