HTTP Cache Validator

class CacheValidator:
    """
    A validator that uses HTTP caching to efficiently check for resource updates.

    This class uses persistent caching with Last-Modified validation to minimize
    bandwidth when checking if web resources have changed.
    """

    def __init__(self, cache_name: str = 'http_cache'):
        """
        Initialize the cache validator.

        Args:
            cache_name: Name of the cache database to use for storing responses
        """
        pass

    def fetch(self, url: str) -> str:
        """
        Fetch a URL, using cached version if available and not modified.

        On the first request, downloads and caches the response. On subsequent
        requests, validates if the content has changed and only downloads if modified.

        Args:
            url: The URL to fetch

        Returns:
            The response body as a string
        """
        pass

    def check_updates(self, urls: list[str]) -> dict[str, bool]:
        """
        Check multiple URLs for updates efficiently.

        Args:
            urls: List of URLs to check

        Returns:
            Dictionary mapping each URL to True if modified, False if not modified
            For URLs not yet cached, returns True (considered modified/new)
        """
        pass