"""passbook multi-factor authentication engine"""
from inspect import Signature

from django.contrib import messages
from django.contrib.auth import _clean_credentials
from django.contrib.auth.signals import user_login_failed
from django.core.exceptions import PermissionDenied
from django.forms.utils import ErrorList
from django.shortcuts import redirect, reverse
from django.utils.translation import gettext as _
from django.views.generic import FormView
from structlog import get_logger

from passbook.core.forms.authentication import PasswordFactorForm
from passbook.core.models import Nonce
from passbook.core.tasks import send_email
from passbook.factors.base import AuthenticationFactor
from passbook.factors.view import AuthenticationView
from passbook.lib.config import CONFIG
from passbook.lib.utils.reflection import path_to_class

LOGGER = get_logger()


def authenticate(request, backends, **credentials):
    """If the given credentials are valid, return a User object.

    Customized version of django's authenticate, which accepts a list of backends"""
    for backend_path in backends:
        backend = path_to_class(backend_path)()
        try:
            signature = Signature.from_callable(backend.authenticate)
            signature.bind(request, **credentials)
        except TypeError:
            LOGGER.debug("Backend doesn't accept our arguments", backend=backend)
            # This backend doesn't accept these credentials as arguments. Try the next one.
            continue
        LOGGER.debug('Attempting authentication...', backend=backend)
        try:
            user = backend.authenticate(request, **credentials)
        except PermissionDenied:
            LOGGER.debug('Backend threw PermissionDenied', backend=backend)
            # This backend says to stop in our tracks - this user should not be allowed in at all.
            break
        if user is None:
            continue
        # Annotate the user object with the path of the backend.
        user.backend = backend_path
        return user

    # The credentials supplied are invalid to all backends, fire signal
    user_login_failed.send(sender=__name__, credentials=_clean_credentials(
        credentials), request=request)

class PasswordFactor(FormView, AuthenticationFactor):
    """Authentication factor which authenticates against django's AuthBackend"""

    form_class = PasswordFactorForm
    template_name = 'login/factors/backend.html'

    def get_context_data(self, **kwargs):
        kwargs['show_password_forget_notice'] = CONFIG.y('passbook.password_reset.enabled')
        return super().get_context_data(**kwargs)

    def get(self, request, *args, **kwargs):
        if 'password-forgotten' in request.GET:
            nonce = Nonce.objects.create(user=self.pending_user)
            LOGGER.debug("DEBUG %s", str(nonce.uuid))
            # Send mail to user
            send_email.delay(self.pending_user.email, _('Forgotten password'),
                             'email/account_password_reset.html', {
                                 'url': self.request.build_absolute_uri(
                                     reverse('passbook_core:auth-password-reset',
                                             kwargs={
                                                 'nonce': nonce.uuid
                                             })
                                 )
                             })
            self.authenticator.cleanup()
            messages.success(request, _('Check your E-Mails for a password reset link.'))
            return redirect('passbook_core:auth-login')
        return super().get(request, *args, **kwargs)

    def form_valid(self, form):
        """Authenticate against django's authentication backend"""
        uid_fields = CONFIG.y('passbook.uid_fields')
        kwargs = {
            'password': form.cleaned_data.get('password'),
        }
        for uid_field in uid_fields:
            kwargs[uid_field] = getattr(self.authenticator.pending_user, uid_field)
        try:
            user = authenticate(self.request, self.authenticator.current_factor.backends, **kwargs)
            if user:
                # User instance returned from authenticate() has .backend property set
                self.authenticator.pending_user = user
                self.request.session[AuthenticationView.SESSION_USER_BACKEND] = user.backend
                return self.authenticator.user_ok()
            # No user was found -> invalid credentials
            LOGGER.debug("Invalid credentials")
            # Manually inject error into form
            # pylint: disable=protected-access
            errors = form._errors.setdefault("password", ErrorList())
            errors.append(_("Invalid password"))
            return self.form_invalid(form)
        except PermissionDenied:
            # User was found, but permission was denied (i.e. user is not active)
            LOGGER.debug("Denied access", **kwargs)
            return self.authenticator.user_invalid()