def signup_page(request):
    if request.user.is_authenticated():
        return redirect('/')
    if request.method == 'POST':
        form = SignupForm(request.POST)
        if not (form.data['login'] and form.data['password'] and form.data['password_1'] and form.data['firstname'] and form.data['lastname']):
            return redirect('/signup?missing')
        try:
            user = User.objects.create_user(form.data['login'], password=form.data['password'], first_name=form.data['firstname'], last_name=form.data['lastname'])
            user.save()
        except IntegrityError:
            return redirect('/signup?login_used')
        if form.data['password'] != form.data['password_1']:
            return redirect('/signup?passwords_not_match')
        user = authenticate(username=form.data['login'], password=form.data['password'])
        login(request, user)
        return redirect('/')
    else:
        return render(request, 'signup_form.html', {'login_used': 'login_used' in request.GET, 'missing': 'missing' in request.GET, 'passwords_not_match': 'passwords_not_match' in request.GET})