archive mails based on labels and time spent in inbox

Code.gs

function parseInterval(s) {
  var matches = new RegExp("^expire-([0-9]+)([mhdDwM])$").exec(s);
  if (!matches) {
    return null;
  }
  var count = parseInt(matches[1]);
  var unit = matches[2];
  var date = new Date();
  switch (unit) {
    case "M":
      date.setMonth(date.getMonth() - count);
      break;
    case "w":
      date.setDate(date.getDate() - 7 * count);
      break;
    case "D":  // working days
      while (count > 0) {
        date.setDate(date.getDate() - 1);
        if (date.getDay() - 1 % 7 < 6) {
          count--;
        }
      }
      break;
    case "d":
      date.setDate(date.getDate() - count);
      break;
    case "h":
      date.setHours(date.getHours() - count);
      break;
    case "m":
      date.setMinutes(date.getMinutes() - count);
      break;
    default:
      date = null;
  }
  return date;
}

function myFunction() {
  var expired = GmailApp.createLabel("expired");
  var labels = GmailApp.getUserLabels();
  for (var label of labels) {
    var name = label.getName();
    var expire_at = parseInterval(name);
    if (!expire_at) {
      //Logger.log("Ignoring label: %s", name);
      continue;
    }
    
    var threads = label.getThreads();
    //var msg = threads[0];
    for (var msg of threads) {
      if (msg.getLastMessageDate() > expire_at) {
        continue;
      }
      msg.moveToArchive();
      msg.removeLabel(label);
      msg.addLabel(expired);
      Logger.log("Archived msg: %s (%s)", msg.getFirstMessageSubject(), msg.getLastMessageDate());
    }
  }
  
}