text: import os
  # from threading import Thread
  from flask import Flask, render_template, session, redirect, url_for
  from flask_bootstrap import Bootstrap
  from flask_moment import Moment
  from flask_wtf import FlaskForm
  from wtforms import StringField, SubmitField
  from wtforms.validators import DataRequired
  from flask_sqlalchemy import SQLAlchemy
  from flask_migrate import Migrate
  from flask_mail import Mail, Message
  
  basedir = os.path.abspath(os.path.dirname(__file__)).replace("\\", "/")
  
  app = Flask(__name__)
  app.config['SECRET_KEY'] = 'hard to guess string'
  
  # Unix SQLite configuration:
  # app.config['SQLALCHEMY_DATABASE_URI'] =\
  #    'sqlite:////' + os.path.join(basedir, 'data.sqlite')
  
  # Windows SQLite configuration:
  app.config['SQLALCHEMY_DATABASE_URI'] =\
      'sqlite:///' + basedir + '/data.sqlite'
  
  app.config['SQLALCHEMY_COMMIT_ON_TEARDOWN'] = True
  app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
  
  # Gmail configuration:
  # must run first in cmd/terminal OR edit the configurations for the PyCharm project to include these environment
  # variables:
  # > set FLASK_APP=hello
  # > set MAIL_USERNAME=<Gmail username> (before the @gmail.com)
  # > set MAIL_PASSWORD=<Gmail password>
  # > set FLASKY_ADMIN=<Gmail username>
  # Sometimes, you'll need to setup an "App Password" for GMail: https://myaccount.google.com/apppasswords
  app.config['MAIL_SERVER'] = 'smtp.googlemail.com'
  app.config['MAIL_PORT'] = 587
  app.config['MAIL_USE_TLS'] = True
  app.config['MAIL_USERNAME'] = os.environ.get('MAIL_USERNAME')
  app.config['MAIL_PASSWORD'] = os.environ.get('MAIL_PASSWORD')
  app.config['FLASKY_MAIL_SUBJECT_PREFIX'] = '[Flasky]'
  app.config['FLASKY_MAIL_SENDER'] = 'Flasky Admin <flasky@example.com>'
  app.config['FLASKY_ADMIN'] = os.environ.get('FLASKY_ADMIN')
  
  bootstrap = Bootstrap(app)
  moment = Moment(app)
  db = SQLAlchemy(app)
  migrate = Migrate(app, db)
  mail = Mail(app)
  
  
  class Role(db.Model):
      __tablename__ = 'roles'
      id = db.Column(db.Integer, primary_key=True)
      name = db.Column(db.String(64), unique=True)
      users = db.relationship('User', backref='role', lazy='dynamic')
  
      def __repr__(self):
          return '<Role %r>' % self.name
  
  
  class User(db.Model):
      __tablename__ = 'users'
      id = db.Column(db.Integer, primary_key=True)
      username = db.Column(db.String(64), unique=True, index=True)
      role_id = db.Column(db.Integer, db.ForeignKey('roles.id'))
  
      def __repr__(self):
          return '<User %r>' % self.username
  
  
  class NameForm(FlaskForm):
      name = StringField('What is your name?', validators=[DataRequired()])
      submit = SubmitField('Submit')
  
  
  def send_async_email(appl, msg):
      with appl.app_context():
          mail.send(msg)
  
  
  def send_email(to, subject, template, **kwargs):
      msg = Message(app.config['FLASKY_MAIL_SUBJECT_PREFIX'] + ' ' + subject,
                    sender=app.config['FLASKY_MAIL_SENDER'], recipients=[to])
      msg.body = render_template(template + '.txt', **kwargs)
      msg.html = render_template(template + '.html', **kwargs)
      mail.send(msg)
      # thr = Thread(target=send_async_email, args=[app, msg])
      # thr.start()
      # return thr
  
  
  @app.errorhandler(404)
  def page_not_found(e):
      return render_template('404.html'), 404
  
  
  @app.errorhandler(500)
  def internal_server_error(e):
      return render_template('500.html'), 500
  
  
  @app.route('/', methods=['GET', 'POST'])
  def index():
      form = NameForm()
      if form.validate_on_submit():
          user = User.query.filter_by(username=form.name.data).first()
          if user is None:
              user = User(username=form.name.data)
              db.session.add(user)
              db.session.commit()
              session['known'] = False
              if app.config['FLASKY_ADMIN']:
                  send_email(app.config['FLASKY_ADMIN'], 'New User',
                             'mail/new_user', user=user)
          else:
              session['known'] = True
          session['name'] = form.name.data
          return redirect(url_for('index'))
      return render_template('index.html', form=form, name=session.get('name'),
                             known=session.get('known', False))
  