"""passbook policy task"""
from multiprocessing import Process
from multiprocessing.connection import Connection
from typing import Optional

from django.core.cache import cache
from sentry_sdk.hub import Hub
from sentry_sdk.tracing import Span
from structlog import get_logger

from passbook.policies.exceptions import PolicyException
from passbook.policies.models import Policy, PolicyBinding
from passbook.policies.types import PolicyRequest, PolicyResult

LOGGER = get_logger()


def cache_key(binding: PolicyBinding, request: PolicyRequest) -> str:
    """Generate Cache key for policy"""
    prefix = f"policy_{binding.policy_binding_uuid.hex}_{binding.policy.pk.hex}"
    if request.http_request:
        prefix += f"_{request.http_request.session.session_key}"
    if request.user:
        prefix += f"#{request.user.pk}"
    return prefix


class PolicyProcess(Process):
    """Evaluate a single policy within a seprate process"""

    connection: Connection
    binding: PolicyBinding
    request: PolicyRequest

    def __init__(
        self,
        binding: PolicyBinding,
        request: PolicyRequest,
        connection: Optional[Connection],
    ):
        super().__init__()
        self.binding = binding
        self.request = request
        if not isinstance(self.request, PolicyRequest):
            raise ValueError(f"{self.request} is not a Policy Request.")
        if connection:
            self.connection = connection

    def execute(self) -> PolicyResult:
        """Run actual policy, returns result"""
        with Hub.current.start_span(op="policy.process.execute",) as span:
            span: Span
            span.set_data("policy", self.binding.policy)
            span.set_data("request", self.request)
            LOGGER.debug(
                "P_ENG(proc): Running policy",
                policy=self.binding.policy,
                user=self.request.user,
                process="PolicyProcess",
            )
            try:
                policy_result = self.binding.policy.passes(self.request)
            except PolicyException as exc:
                LOGGER.debug("P_ENG(proc): error", exc=exc)
                policy_result = PolicyResult(False, str(exc))
            policy_result.source_policy = self.binding.policy
            # Invert result if policy.negate is set
            if self.binding.negate:
                policy_result.passing = not policy_result.passing
            LOGGER.debug(
                "P_ENG(proc): Finished",
                policy=self.binding.policy,
                result=policy_result,
                process="PolicyProcess",
                passing=policy_result.passing,
                user=self.request.user,
            )
            key = cache_key(self.binding, self.request)
            cache.set(key, policy_result)
            LOGGER.debug("P_ENG(proc): Cached policy evaluation", key=key)
            return policy_result

    def run(self):
        """Task wrapper to run policy checking"""
        self.connection.send(self.execute())