text: # extensions
  from flask import render_template, flash, redirect, url_for, request
  from werkzeug.urls import url_parse
  from flask_login import current_user, login_user, logout_user, login_required
  # local modules
  from app import db  
  from app.auth import bp
  from app.auth.forms import LoginForm, SignUpForm
  from app.models import User
  
  
  @bp.route('/login', methods=['GET', 'POST'])
  def login():
      if current_user.is_authenticated:
          return redirect(url_for('main.index'))
      form = LoginForm()
      if form.validate_on_submit(): 
          user = User.query.filter_by(username=form.username.data).first()
          if user is None or not user.check_password(form.password.data):
              flash('Invalid username or password')
              return redirect(url_for('auth.login'))
          login_user(user, remember=form.remember_me.data)
          next_page = request.args.get('next')
          if not next_page or url_parse(next_page).netloc != '':
              return redirect(url_for('main.index'))
          return redirect(next_page)
      login_html = render_template('auth/login.html', title='Log In', form=form)
      return login_html
  
  @bp.route('/logout')
  def logout():
      logout_user()
      return redirect(url_for('main.index'))
  
  @bp.route('/signup', methods=['GET', 'POST'])
  def signup():
      if current_user.is_authenticated:
          return redirect(url_for('main.index'))
      form = SignUpForm()
      if form.validate_on_submit():
          user = User(username=form.username.data, email=form.email.data)
          user.set_password(form.password.data)
          db.session.add(user)
          db.session.commit()
          flash("Congratulations, you're now signed up!")
          return redirect(url_for('auth.login')) # upon signing up, send to login page (why not send directly to index?)
      return render_template('auth/signup.html', title='Sign Up', form=form)
  