text: 'use strict';
  
  const moment = require('moment');
  
  class IdGenerator {
    constructor() {
      this._lastUsedTimestamp = null;
      this._counter = 0;
    }
  
    nextId() {
      const currentTimestamp = moment().valueOf();
      if (currentTimestamp === this._lastUsedTimestamp) {
        return currentTimestamp.toString(36) + '.' + (++this._counter).toString(36);
      } else {
        this._counter = 0;
        this._lastUsedTimestamp = currentTimestamp;
        return currentTimestamp.toString(36);
      }
    }
  }
  
  module.exports = IdGenerator;
  