code: def confirm_email(token):
      
  
      expired, invalid, user = confirm_email_token_status(token)
  
      if not user or invalid:
          invalid = True
          do_flash(*get_message('INVALID_CONFIRMATION_TOKEN'))
  
      already_confirmed = user is not None and user.confirmed_at is not None
  
      if expired and not already_confirmed:
          send_confirmation_instructions(user)
          do_flash(*get_message('CONFIRMATION_EXPIRED', email=user.email,
                                within=_security.confirm_email_within))
      if invalid or (expired and not already_confirmed):
          return redirect(get_url(_security.confirm_error_view) or
                          url_for('send_confirmation'))
  
      if user != current_user:
          logout_user()
  
      if confirm_user(user):
          after_this_request(_commit)
          msg = 'EMAIL_CONFIRMED'
      else:
          msg = 'ALREADY_CONFIRMED'
  
      do_flash(*get_message(msg))
  
      return redirect(get_url(_security.post_confirm_view) or
                      get_url(_security.login_url))
docs: View function which handles a email confirmation request.