"""Utilities for reading the pre-seeded Cerbos policy metadata from Redis."""

import logging

from ddtrace.trace import tracer

from pdp.connectors.cerbos_policy_parser import PolicyMetadataDatabase
from pdp.connectors.redis_client import NullSerializer, RedisConnector
from pdp.constants.constants import CACHE_ENTRY_CERBOS_POLICY_METADATA

logger = logging.getLogger(__name__)


class CerbosPolicyDBLookupError(Exception):
    pass


class CerbosPolicyDBParseError(Exception):
    pass


@tracer.wrap()
async def get_cerbos_policy_metadata(
    redis_connector: RedisConnector,
) -> PolicyMetadataDatabase:
    """Read the pre-seeded policy metadata database from Redis.

    Raises CerbosPolicyDBLookupError if the key is missing — a missing key
    indicates a misconfigured deployment and should surface as a 500.
    Raises CerbosPolicyDBParseError if the cached value cannot be deserialized.
    """
    raw: str | None = await redis_connector.get(
        key=CACHE_ENTRY_CERBOS_POLICY_METADATA, serializer=NullSerializer()
    )
    if raw is None:
        msg = (
            f"Cache entry '{CACHE_ENTRY_CERBOS_POLICY_METADATA}' not found. "
            "Run 'make seed_policy_metadata_cache' (or the Jenkins stage) "
            "to populate it."
        )
        logger.error(msg)
        raise CerbosPolicyDBLookupError(msg)
    try:
        return PolicyMetadataDatabase.from_json(raw)
    except Exception as exc:
        msg = (
            f"Failed to parse cache entry '{CACHE_ENTRY_CERBOS_POLICY_METADATA}': {exc}"
        )
        logger.error(msg)
        raise CerbosPolicyDBParseError(msg) from exc