"""Redis client singleton.

Provides a lazily-initialised Redis connection that is reused across
the application.  The connection URL is read from ``settings.REDIS_URL``.

Usage::

    from app.infrastructure.redis_client import get_redis

    r = get_redis()
    r.set("key", "value", ex=300)
"""

import logging

import redis

from app.config import settings

logger = logging.getLogger(__name__)

_redis_client: redis.Redis | None = None


def get_redis() -> redis.Redis:
    """Return a shared Redis client, creating it on first call."""
    global _redis_client
    if _redis_client is None:
        _redis_client = redis.from_url(
            settings.REDIS_URL,
            decode_responses=True,
        )
        logger.info("Redis client connected to %s", settings.REDIS_URL)
    return _redis_client