content: from flask import render_template, redirect, url_for, flash, request
  from urllib.parse import urlsplit
  from flask_login import login_user, logout_user, current_user
  from flask_babel import _
  import sqlalchemy as sa
  from app import db
  from app.auth import bp
  from app.auth.forms import LoginForm, RegistrationForm, \
      ResetPasswordRequestForm, ResetPasswordForm
  from app.models import User
  from app.auth.email import send_password_reset_email
  
  
  @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 = db.session.scalar(
              sa.select(User).where(User.username == form.username.data))
          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 urlsplit(next_page).netloc != '':
              next_page = url_for('main.index')
          return redirect(next_page)
      return render_template('auth/login.html', title=_('Sign In'), form=form)
  
  
  @bp.route('/logout')
  def logout():
      logout_user()
      return redirect(url_for('main.index'))
  
  
  @bp.route('/register', methods=['GET', 'POST'])
  def register():
      if current_user.is_authenticated:
          return redirect(url_for('main.index'))
      form = RegistrationForm()
      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 are now a registered user!'))
          return redirect(url_for('auth.login'))
      return render_template('auth/register.html', title=_('Register'),
                             form=form)
  
  
  @bp.route('/reset_password_request', methods=['GET', 'POST'])
  def reset_password_request():
      if current_user.is_authenticated:
          return redirect(url_for('main.index'))
      form = ResetPasswordRequestForm()
      if form.validate_on_submit():
          user = db.session.scalar(
              sa.select(User).where(User.email == form.email.data))
          if user:
              send_password_reset_email(user)
          flash(
              _('Check your email for the instructions to reset your password'))
          return redirect(url_for('auth.login'))
      return render_template('auth/reset_password_request.html',
                             title=_('Reset Password'), form=form)
  
  
  @bp.route('/reset_password/<token>', methods=['GET', 'POST'])
  def reset_password(token):
      if current_user.is_authenticated:
          return redirect(url_for('main.index'))
      user = User.verify_reset_password_token(token)
      if not user:
          return redirect(url_for('main.index'))
      form = ResetPasswordForm()
      if form.validate_on_submit():
          user.set_password(form.password.data)
          db.session.commit()
          flash(_('Your password has been reset.'))
          return redirect(url_for('auth.login'))
      return render_template('auth/reset_password.html', form=form)
  