from logging import getLogger

from django.db.models import Sum, Value, Q
from django.db.models.functions import Concat
from django.utils import timezone

from axes.attempts import (
    clean_expired_user_attempts,
    get_user_attempts,
    reset_user_attempts,
)
from axes.conf import settings
from axes.handlers.base import AxesBaseHandler, AbstractAxesHandler
from axes.helpers import (
    get_client_str,
    get_client_username,
    get_credentials,
    get_failure_limit,
    get_query_str,
)
from axes.models import AccessLog, AccessAttempt
from axes.signals import user_locked_out

log = getLogger(__name__)


class AxesDatabaseHandler(AbstractAxesHandler, AxesBaseHandler):
    """
    Signal handler implementation that records user login attempts to database and locks users out if necessary.

    .. note:: The get_user_attempts function is called several time during the authentication and lockout
              process, caching its output can be dangerous.
    """

    def reset_attempts(
        self,
        *,
        ip_address: str = None,
        username: str = None,
        ip_or_username: bool = False,
    ) -> int:
        attempts = AccessAttempt.objects.all()

        if ip_or_username:
            attempts = attempts.filter(Q(ip_address=ip_address) | Q(username=username))
        else:
            if ip_address:
                attempts = attempts.filter(ip_address=ip_address)
            if username:
                attempts = attempts.filter(username=username)

        count, _ = attempts.delete()
        log.info("AXES: Reset %d access attempts from database.", count)

        return count

    def reset_logs(self, *, age_days: int = None) -> int:
        if age_days is None:
            count, _ = AccessLog.objects.all().delete()
            log.info("AXES: Reset all %d access logs from database.", count)
        else:
            limit = timezone.now() - timezone.timedelta(days=age_days)
            count, _ = AccessLog.objects.filter(attempt_time__lte=limit).delete()
            log.info(
                "AXES: Reset %d access logs older than %d days from database.",
                count,
                age_days,
            )

        return count

    def get_failures(self, request, credentials: dict = None) -> int:
        attempts_list = get_user_attempts(request, credentials)
        attempt_count = max(
            (
                attempts.aggregate(Sum("failures_since_start"))[
                    "failures_since_start__sum"
                ]
                or 0
            )
            for attempts in attempts_list
        )
        return attempt_count

    def user_login_failed(
        self, sender, credentials: dict, request=None, **kwargs
    ):  # pylint: disable=too-many-locals
        """
        When user login fails, save AccessAttempt record in database, mark request with lockout attribute and emit lockout signal.
        """

        log.info("AXES: User login failed, running database handler for failure.")

        if request is None:
            log.error(
                "AXES: AxesDatabaseHandler.user_login_failed does not function without a request."
            )
            return

        # 1. database query: Clean up expired user attempts from the database before logging new attempts
        clean_expired_user_attempts(request.axes_attempt_time)

        username = get_client_username(request, credentials)
        client_str = get_client_str(
            username,
            request.axes_ip_address,
            request.axes_user_agent,
            request.axes_path_info,
        )

        # This replaces null byte chars that crash saving failures.
        get_data = get_query_str(request.GET).replace("\0", "0x00")
        post_data = get_query_str(request.POST).replace("\0", "0x00")

        if self.is_whitelisted(request, credentials):
            log.info("AXES: Login failed from whitelisted client %s.", client_str)
            return

        # 2. database query: Get or create access record with the new failure data
        if settings.AXES_ONLY_USER_FAILURES and username is None:
            log.warning(
                "AXES: Username is None and AXES_ONLY_USER_FAILURES is enabled, new record will NOT be created."
            )
        else:
            attempt, created = AccessAttempt.objects.get_or_create(
                username=username,
                ip_address=request.axes_ip_address,
                user_agent=request.axes_user_agent,
                defaults={
                    "get_data": get_data,
                    "post_data": post_data,
                    "http_accept": request.axes_http_accept,
                    "path_info": request.axes_path_info,
                    "failures_since_start": 1,
                    "attempt_time": request.axes_attempt_time,
                },
            )

            # Record failed attempt with all the relevant information.
            # Filtering based on username, IP address and user agent handled elsewhere,
            # and this handler just records the available information for further use.
            if created:
                log.warning(
                    "AXES: New login failure by %s. Created new record in the database.",
                    client_str,
                )

            # 3. database query if there were previous attempts in the database
            # Update failed attempt information but do not touch the username, IP address, or user agent fields,
            # because attackers can request the site with multiple different configurations
            # in order to bypass the defense mechanisms that are used by the site.
            else:
                separator = "\n---------\n"

                attempt.get_data = Concat("get_data", Value(separator + get_data))
                attempt.post_data = Concat("post_data", Value(separator + post_data))
                attempt.http_accept = request.axes_http_accept
                attempt.path_info = request.axes_path_info
                attempt.failures_since_start += 1
                attempt.attempt_time = request.axes_attempt_time
                attempt.save()

                log.warning(
                    "AXES: Repeated login failure by %s. Count = %d of %d. Updated existing record in the database.",
                    client_str,
                    attempt.failures_since_start,
                    get_failure_limit(request, credentials),
                )

        # 3. or 4. database query: Calculate the current maximum failure number from the existing attempts
        failures_since_start = self.get_failures(request, credentials)

        if (
            settings.AXES_LOCK_OUT_AT_FAILURE
            and failures_since_start >= get_failure_limit(request, credentials)
        ):
            log.warning(
                "AXES: Locking out %s after repeated login failures.", client_str
            )

            request.axes_locked_out = True
            user_locked_out.send(
                "axes",
                request=request,
                username=username,
                ip_address=request.axes_ip_address,
            )

    def user_logged_in(
        self, sender, request, user, **kwargs
    ):  # pylint: disable=unused-argument
        """
        When user logs in, update the AccessLog related to the user.
        """

        # 1. database query: Clean up expired user attempts from the database
        clean_expired_user_attempts(request.axes_attempt_time)

        username = user.get_username()
        credentials = get_credentials(username)
        client_str = get_client_str(
            username,
            request.axes_ip_address,
            request.axes_user_agent,
            request.axes_path_info,
        )

        log.info("AXES: Successful login by %s.", client_str)

        if not settings.AXES_DISABLE_ACCESS_LOG:
            # 2. database query: Insert new access logs with login time
            AccessLog.objects.create(
                username=username,
                ip_address=request.axes_ip_address,
                user_agent=request.axes_user_agent,
                http_accept=request.axes_http_accept,
                path_info=request.axes_path_info,
                attempt_time=request.axes_attempt_time,
            )

        if settings.AXES_RESET_ON_SUCCESS:
            # 3. database query: Reset failed attempts for the logging in user
            count = reset_user_attempts(request, credentials)
            log.info(
                "AXES: Deleted %d failed login attempts by %s from database.",
                count,
                client_str,
            )

    def user_logged_out(
        self, sender, request, user, **kwargs
    ):  # pylint: disable=unused-argument
        """
        When user logs out, update the AccessLog related to the user.
        """

        # 1. database query: Clean up expired user attempts from the database
        clean_expired_user_attempts(request.axes_attempt_time)

        username = user.get_username() if user else None
        client_str = get_client_str(
            username,
            request.axes_ip_address,
            request.axes_user_agent,
            request.axes_path_info,
        )

        log.info("AXES: Successful logout by %s.", client_str)

        if username and not settings.AXES_DISABLE_ACCESS_LOG:
            # 2. database query: Update existing attempt logs with logout time
            AccessLog.objects.filter(
                username=username, logout_time__isnull=True
            ).update(logout_time=request.axes_attempt_time)

    def post_save_access_attempt(self, instance, **kwargs):
        """
        Handles the ``axes.models.AccessAttempt`` object post save signal.

        When needed, all post_save actions for this backend should be located
        here.
        """

    def post_delete_access_attempt(self, instance, **kwargs):
        """
        Handles the ``axes.models.AccessAttempt`` object post delete signal.

        When needed, all post_delete actions for this backend should be located
        here.
        """
