backend/caching/factory.py

"""Cache factory for initialising caching infrastructure.

This module provides factory functions and singleton instances for
cache management across the application.
"""

import logging
from typing import Optional

from backend.caching.redis_cache import (
    FinancialDataCacheManager,
    HybridCache,
)
from backend.config import settings

logger = logging.getLogger(__name__)


class CacheFactory:
    """Factory for creating and managing cache instances.

    Provides singleton pattern for cache instances to ensure
    consistent cache usage across the application.
    """

    _cache_instance: Optional[HybridCache] = None
    _manager_instance: Optional[FinancialDataCacheManager] = None

    @classmethod
    def get_cache(cls, force_new: bool = False) -> HybridCache:
        """Get or create HybridCache instance.

        Args:
            force_new: Force creation of new instance.

        Returns:
            HybridCache instance.
        """
        if cls._cache_instance is None or force_new:
            cls._cache_instance = cls.create_cache()

        return cls._cache_instance

    @classmethod
    def get_manager(cls, force_new: bool = False) -> FinancialDataCacheManager:
        """Get or create FinancialDataCacheManager instance.

        Args:
            force_new: Force creation of new instance.

        Returns:
            FinancialDataCacheManager instance.
        """
        if cls._manager_instance is None or force_new:
            cache = cls.get_cache()
            cls._manager_instance = FinancialDataCacheManager(cache)

        return cls._manager_instance

    @classmethod
    def create_cache(cls) -> HybridCache:
        """Create a new HybridCache instance from settings.

        Returns:
            Configured HybridCache instance.
        """
        if not settings.cache_enabled:
            logger.info("Caching is disabled in settings")
            return HybridCache(
                redis_url=None,
                redis_token=None,
                enable_fallback=True,
            )

        cache = HybridCache(
            redis_url=settings.upstash_redis_url,
            redis_token=settings.upstash_redis_token,
            enable_fallback=settings.cache_fallback_enabled,
            fallback_size=settings.cache_fallback_max_size,
        )

        logger.info(
            f"Cache initialised with backend: {cache.stats.backend.value}"
        )
        return cache

    @classmethod
    def reset(cls) -> None:
        """Reset singleton instances.

        Useful for testing or when configuration changes.
        """
        cls._cache_instance = None
        cls._manager_instance = None
        logger.info("Cache factory reset")


def get_cache() -> HybridCache:
    """Get global cache instance.

    Convenience function for accessing the singleton cache.

    Returns:
        HybridCache instance.

    Example:
        >>> from backend.caching.factory import get_cache
        >>> cache = get_cache()
        >>> cache.set("key", "value", ttl=300)
        >>> value = cache.get("key")
    """
    return CacheFactory.get_cache()


def get_cache_manager() -> FinancialDataCacheManager:
    """Get global cache manager instance.

    Convenience function for accessing the singleton cache manager.

    Returns:
        FinancialDataCacheManager instance.

    Example:
        >>> from backend.caching.factory import get_cache_manager
        >>> manager = get_cache_manager()
        >>> manager.cache_market_data("AAPL", {"price": 150.00})
        >>> data = manager.get_market_data("AAPL")
    """
    return CacheFactory.get_manager()


# Global instances (initialised on first import)
cache = get_cache()
cache_manager = get_cache_manager()