wrongmove/services/listing_cache.py

"""Redis-based caching for listing GeoJSON query results."""
import hashlib
import json
import logging
import os
from typing import Generator
from urllib.parse import urlparse, urlunparse

import redis

from models.listing import QueryParameters

logger = logging.getLogger(__name__)

CACHE_PREFIX = "listings:geojson:"
CACHE_TTL_SECONDS = 30 * 60  # 30 minutes
CACHE_DB = 2


def _get_redis_client() -> redis.Redis:
    """Get Redis client using Celery broker URL but overriding to db=2."""
    broker_url = os.getenv("CELERY_BROKER_URL", "redis://localhost:6379/0")
    parsed = urlparse(broker_url)
    cache_url = urlunparse(parsed._replace(path=f"/{CACHE_DB}"))
    return redis.from_url(cache_url, decode_responses=True)


def make_cache_key(query_params: QueryParameters) -> str:
    """Generate a cache key from query parameters."""
    params_json = query_params.model_dump_json()
    hash_suffix = hashlib.sha256(params_json.encode()).hexdigest()[:16]
    return f"{CACHE_PREFIX}{hash_suffix}"


def get_cached_count(query_params: QueryParameters) -> int | None:
    """Return the number of cached features for a query, or None if not cached."""
    try:
        client = _get_redis_client()
        key = make_cache_key(query_params)
        if not client.exists(key):
            return None
        return client.llen(key)
    except redis.RedisError as e:
        logger.warning(f"Redis cache read error: {e}")
        return None


def get_cached_features(
    query_params: QueryParameters, batch_size: int = 50
) -> Generator[list[dict], None, None]:
    """Yield batches of cached GeoJSON features."""
    try:
        client = _get_redis_client()
        key = make_cache_key(query_params)
        total = client.llen(key)

        for start in range(0, total, batch_size):
            end = start + batch_size - 1
            items = client.lrange(key, start, end)
            batch = [json.loads(item) for item in items]
            if batch:
                yield batch
    except redis.RedisError as e:
        logger.warning(f"Redis cache read error during streaming: {e}")


def cache_features_batch(query_params: QueryParameters, features: list[dict]) -> None:
    """Append a batch of features to the cache list."""
    if not features:
        return
    try:
        client = _get_redis_client()
        key = make_cache_key(query_params)
        pipeline = client.pipeline()
        for feature in features:
            pipeline.rpush(key, json.dumps(feature))
        # Set/refresh TTL
        pipeline.expire(key, CACHE_TTL_SECONDS)
        pipeline.execute()
    except redis.RedisError as e:
        logger.warning(f"Redis cache write error: {e}")


def invalidate_cache() -> None:
    """Delete all listing GeoJSON cache entries."""
    try:
        client = _get_redis_client()
        cursor = 0
        deleted = 0
        while True:
            cursor, keys = client.scan(cursor, match=f"{CACHE_PREFIX}*", count=100)
            if keys:
                pipeline = client.pipeline()
                for key in keys:
                    pipeline.delete(key)
                pipeline.execute()
                deleted += len(keys)
            if cursor == 0:
                break
        if deleted:
            logger.info(f"Invalidated {deleted} listing cache entries")
    except redis.RedisError as e:
        logger.warning(f"Redis cache invalidation error: {e}")