"""authentik access helper classes"""
from typing import Any, Optional

from django.contrib import messages
from django.contrib.auth.mixins import AccessMixin
from django.contrib.auth.views import redirect_to_login
from django.http import HttpRequest, HttpResponse
from django.utils.translation import gettext as _
from django.views.generic.base import View
from structlog.stdlib import get_logger

from authentik.core.models import Application, Provider, User
from authentik.flows.views.executor import SESSION_KEY_APPLICATION_PRE, SESSION_KEY_POST
from authentik.lib.sentry import SentryIgnoredException
from authentik.policies.denied import AccessDeniedResponse
from authentik.policies.engine import PolicyEngine
from authentik.policies.types import PolicyRequest, PolicyResult

LOGGER = get_logger()


class RequestValidationError(SentryIgnoredException):
    """Error raised in pre_permission_check, when a request is invalid."""

    response: Optional[HttpResponse]

    def __init__(self, response: Optional[HttpResponse] = None):
        super().__init__()
        if response:
            self.response = response


class BaseMixin:
    """Base Mixin class, used to annotate View Member variables"""

    request: HttpRequest


class PolicyAccessView(AccessMixin, View):
    """Mixin class for usage in Authorization views.
    Provider functions to check application access, etc"""

    provider: Provider
    application: Application

    def pre_permission_check(self):
        """Optionally hook in before permission check to check if a request is valid.
        Can raise `RequestValidationError` to return a response."""

    def resolve_provider_application(self):
        """Resolve self.provider and self.application. *.DoesNotExist Exceptions cause a normal
        AccessDenied view to be shown. An Http404 exception
        is not caught, and will return directly"""
        raise NotImplementedError

    def dispatch(self, request: HttpRequest, *args: Any, **kwargs: Any) -> HttpResponse:
        try:
            self.pre_permission_check()
        except RequestValidationError as exc:
            if exc.response:
                return exc.response
            return self.handle_no_permission()
        try:
            self.resolve_provider_application()
        except (Application.DoesNotExist, Provider.DoesNotExist) as exc:
            LOGGER.warning("failed to resolve application", exc=exc)
            return self.handle_no_permission_authenticated(
                PolicyResult(False, _("Failed to resolve application"))
            )
        # Check if user is unauthenticated, so we pass the application
        # for the identification stage
        if not request.user.is_authenticated:
            return self.handle_no_permission()
        # Check permissions
        result = self.user_has_access()
        if not result.passing:
            return self.handle_no_permission_authenticated(result)
        return super().dispatch(request, *args, **kwargs)

    def handle_no_permission(self) -> HttpResponse:
        """User has no access and is not authenticated, so we remember the application
        they try to access and redirect to the login URL. The application is saved to show
        a hint on the Identification Stage what the user should login for."""
        if self.application:
            self.request.session[SESSION_KEY_APPLICATION_PRE] = self.application
        # Because this view might get hit with a POST request, we need to preserve that data
        # since later views might need it (mostly SAML)
        if self.request.method.lower() == "post":
            self.request.session[SESSION_KEY_POST] = self.request.POST
        return redirect_to_login(
            self.request.get_full_path(),
            self.get_login_url(),
            self.get_redirect_field_name(),
        )

    def handle_no_permission_authenticated(
        self, result: Optional[PolicyResult] = None
    ) -> HttpResponse:
        """Function called when user has no permissions but is authenticated"""
        response = AccessDeniedResponse(self.request)
        if result:
            response.policy_result = result
        return response

    def modify_policy_request(self, request: PolicyRequest) -> PolicyRequest:
        """optionally modify the policy request"""
        return request

    def user_has_access(self, user: Optional[User] = None) -> PolicyResult:
        """Check if user has access to application."""
        user = user or self.request.user
        policy_engine = PolicyEngine(self.application, user or self.request.user, self.request)
        policy_engine.use_cache = False
        policy_engine.request = self.modify_policy_request(policy_engine.request)
        policy_engine.build()
        result = policy_engine.result
        LOGGER.debug(
            "PolicyAccessView user_has_access",
            user=user.username,
            app=self.application.slug,
            result=result,
        )
        if not result.passing:
            for message in result.messages:
                messages.error(self.request, _(message))
        return result
