from functools import wraps
import logging
from django.core.cache import cache
from django.views.decorators.cache import cache_page
from django.views.decorators.vary import vary_on_headers

logger = logging.getLogger(__name__)


def invalidate_cache_patterns(*patterns):
    """
    Safely invalidates Redis cache keys matching given glob patterns.
    Falls back to cache.clear() if the cache backend does not support delete_pattern.
    """
    try:
        if hasattr(cache, 'delete_pattern'):
            total_deleted = 0
            for pattern in patterns:
                deleted = cache.delete_pattern(pattern)
                total_deleted += deleted or 0
            logger.info(f"Cache cleared for patterns {patterns} (deleted {total_deleted} keys)")
            return total_deleted
        else:
            cache.clear()
            logger.info(f"Cache cleared (fallback clear for patterns: {patterns})")
            return 1
    except Exception as e:
        logger.error(f"Cache invalidation failed for patterns {patterns}: {e}")
        return 0


def smart_cached_view(timeout=60 * 60 * 2, key_prefix=''):
    """
    Smart cache decorator for API views that:
    1. Caches responses per Accept-Language header using Django's cache_page.
    2. Bypasses cache when:
       - Cache-Control / Pragma: no-cache headers are present (e.g., Pull-to-refresh from mobile / web).
       - Query parameters: no_cache=true, refresh=true, is_bookmark=true, in_playlist=true are passed.
    """
    def decorator(view_func):
        cached_func = cache_page(timeout, key_prefix=key_prefix)(
            vary_on_headers('Accept-Language')(view_func)
        )

        @wraps(view_func)
        def _wrapped_view(request, *args, **kwargs):
            # 1. Check HTTP headers for no-cache directives
            cache_control = (request.META.get('HTTP_CACHE_CONTROL') or '').lower()
            pragma = (request.META.get('HTTP_PRAGMA') or '').lower()
            if 'no-cache' in cache_control or 'no-store' in cache_control or 'max-age=0' in cache_control or 'no-cache' in pragma:
                return view_func(request, *args, **kwargs)

            # 2. Check query params for explicit bypass
            query_params = getattr(request, 'GET', {})
            no_cache_param = (query_params.get('no_cache') or query_params.get('refresh') or '').lower()
            if no_cache_param in ('1', 'true'):
                return view_func(request, *args, **kwargs)

            # 3. Check bookmark & playlist specific bypasses
            is_bookmark = (query_params.get('is_bookmark') or query_params.get('is_bookmarked') or '').lower()
            in_playlist = (query_params.get('in_playlist') or '').lower()
            if is_bookmark in ('1', 'true') or in_playlist in ('1', 'true'):
                return view_func(request, *args, **kwargs)

            return cached_func(request, *args, **kwargs)

        return _wrapped_view

    return decorator