multitenetsaas/backend/core/caching/django_integration.py

"""
Django integration for caching strategies.
Provides middleware, decorators, and template tags for easy caching.
"""

import json
import logging
from typing import Any, Dict, List, Optional, Union
from django.core.cache import cache
from django.http import HttpRequest, HttpResponse
from django.conf import settings
from django.contrib.auth import get_user_model
from django.contrib.auth.middleware import AuthenticationMiddleware
from django.utils.deprecation import MiddlewareMixin
from django.template import Library
from django.template.loader import render_to_string
from django.db import connection
from rest_framework.response import Response
from rest_framework.decorators import api_view

from .cache_manager import CacheManager, MalaysianDataCache, QueryCache
from .strategies import (
    WriteThroughCache, WriteBehindCache, ReadThroughCache,
    RefreshAheadCache, CacheAsidePattern, MultiLevelCache,
    MalaysianCacheStrategies, cache_view_response, cache_query_results
)
from .config import CacheConfig

logger = logging.getLogger(__name__)
User = get_user_model()
register = Library()


class TenantCacheMiddleware(MiddlewareMixin):
    """Middleware for tenant-aware caching."""

    def __init__(self, get_response):
        self.get_response = get_response
        self.cache_manager = CacheManager()
        self.malaysian_cache = MalaysianDataCache(self.cache_manager)

    def process_request(self, request: HttpRequest) -> Optional[HttpResponse]:
        """Process request with tenant-aware caching."""
        # Add cache manager to request
        request.cache_manager = self.cache_manager
        request.malaysian_cache = self.malaysian_cache

        # Cache tenant-specific data
        if hasattr(request, 'tenant') and request.tenant:
            tenant_key = f"tenant_data_{request.tenant.id}"
            request.tenant_cache = self.cache_manager.get(tenant_key, {})
        else:
            request.tenant_cache = {}

        return None

    def process_response(self, request: HttpRequest, response: HttpResponse) -> HttpResponse:
        """Process response with caching."""
        # Add cache headers
        response['X-Cache-Tenant'] = getattr(request, 'tenant', {}).get('schema_name', 'public')
        response['X-Cache-Status'] = 'MISS'  # Will be updated by cache middleware

        return response


class CacheMiddleware(MiddlewareMixin):
    """Advanced caching middleware."""

    def __init__(self, get_response):
        self.get_response = get_response
        self.cache_manager = CacheManager()
        self.cache_aside = CacheAsidePattern(self.cache_manager)

        # Define cacheable paths and conditions
        self.cacheable_paths = getattr(settings, 'CACHEABLE_PATHS', [
            '/api/products/',
            '/api/categories/',
            '/api/static-data/',
        ])

        self.non_cacheable_paths = getattr(settings, 'NON_CACHEABLE_PATHS', [
            '/api/auth/',
            '/api/admin/',
            '/api/cart/',
            '/api/orders/',
        ])

    def process_request(self, request: HttpRequest) -> Optional[HttpResponse]:
        """Process request with caching."""
        if self._should_bypass_cache(request):
            return None

        cache_key = self._generate_cache_key(request)
        cached_response = self.cache_manager.get(cache_key)

        if cached_response:
            response = HttpResponse(cached_response['content'])
            response['X-Cache-Status'] = 'HIT'
            response['Content-Type'] = cached_response.get('content_type', 'application/json')
            return response

        return None

    def process_response(self, request: HttpRequest, response: HttpResponse) -> HttpResponse:
        """Process response with caching."""
        if self._should_bypass_cache(request) or getattr(response, '_cache_exempt', False):
            response['X-Cache-Status'] = 'BYPASS'
            return response

        if self._should_cache_response(request, response):
            cache_key = self._generate_cache_key(request)
            cache_data = {
                'content': response.content,
                'content_type': response.get('Content-Type', 'application/json'),
                'status_code': response.status_code,
            }

            timeout = self._get_cache_timeout(request)
            self.cache_manager.set(cache_key, cache_data, timeout)
            response['X-Cache-Status'] = 'MISS'

        return response

    def _should_bypass_cache(self, request: HttpRequest) -> bool:
        """Check if request should bypass cache."""
        # Never cache authenticated user requests by default
        if request.user.is_authenticated:
            if getattr(settings, 'CACHE_AUTHENTICATED_REQUESTS', False):
                return False
            return True

        # Check method
        if request.method not in ['GET', 'HEAD']:
            return True

        # Check paths
        for path in self.non_cacheable_paths:
            if request.path.startswith(path):
                return True

        return False

    def _should_cache_response(self, request: HttpRequest, response: HttpResponse) -> bool:
        """Check if response should be cached."""
        if response.status_code != 200:
            return False

        # Check cacheable paths
        for path in self.cacheable_paths:
            if request.path.startswith(path):
                return True

        return False

    def _generate_cache_key(self, request: HttpRequest) -> str:
        """Generate cache key for request."""
        key_parts = [
            request.path,
            request.method,
        ]

        if request.GET:
            key_parts.append(str(sorted(request.GET.items())))

        # Add user info if authenticated
        if request.user.is_authenticated:
            key_parts.append(f"user_{request.user.id}")

        # Add tenant info
        if hasattr(request, 'tenant'):
            key_parts.append(f"tenant_{request.tenant.id}")

        key = "|".join(key_parts)
        return f"view_cache_{hash(key)}"

    def _get_cache_timeout(self, request: HttpRequest) -> int:
        """Get cache timeout for request."""
        # Different timeouts for different paths
        if request.path.startswith('/api/static-data/'):
            return 3600  # 1 hour for static data
        elif request.path.startswith('/api/products/'):
            return 1800  # 30 minutes for products
        else:
            return 300  # 5 minutes default


class DatabaseCacheMiddleware(MiddlewareMixin):
    """Middleware for database query caching."""

    def __init__(self, get_response):
        self.get_response = get_response
        self.cache_manager = CacheManager()
        self.query_cache = QueryCache(self.cache_manager)
        self.queries_executed = []
        self.cache_hits = 0

    def process_request(self, request: HttpRequest) -> Optional[HttpResponse]:
        """Initialize query tracking."""
        self.queries_executed = []
        self.cache_hits = 0

        # Add query cache to request
        request.query_cache = self.query_cache

        return None

    def process_response(self, request: HttpRequest, response: HttpResponse) -> HttpResponse:
        """Add query cache statistics to response."""
        response['X-Cache-Queries'] = str(len(self.queries_executed))
        response['X-Cache-Query-Hits'] = str(self.cache_hits)

        return response


class MalaysianCacheMiddleware(MiddlewareMixin):
    """Middleware for Malaysian-specific caching."""

    def __init__(self, get_response):
        self.get_response = get_response
        self.cache_manager = CacheManager()
        self.malaysian_cache = MalaysianDataCache(self.cache_manager)
        self.malaysian_strategies = MalaysianCacheStrategies(self.cache_manager)

    def process_request(self, request: HttpRequest) -> Optional[HttpResponse]:
        """Add Malaysian cache to request."""
        request.malaysian_cache = self.malaysian_cache
        request.malaysian_strategies = self.malaysian_strategies

        return None


# Template Tags
@register.simple_tag
def get_cached_postcode(postcode: str) -> str:
    """Get cached postcode data in template."""
    cache_manager = CacheManager()
    malaysian_cache = MalaysianDataCache(cache_manager)

    data = malaysian_cache.get_cached_postcode_data(postcode)
    if data:
        return f"{data.get('city', 'Unknown')}, {data.get('state', 'Unknown')}"
    return "Unknown location"


@register.simple_tag
def get_cached_sst_rate(state: str, category: str = "standard") -> str:
    """Get cached SST rate in template."""
    cache_manager = CacheManager()
    malaysian_cache = MalaysianDataCache(cache_manager)

    rate = malaysian_cache.get_cached_sst_rate(state, category)
    if rate is not None:
        return f"{rate * 100:.0f}%"
    return "Rate not available"


@register.simple_tag
def get_user_cache_info(user) -> str:
    """Get user cache information."""
    if not user or not user.is_authenticated:
        return "Anonymous"

    cache_manager = CacheManager()
    key = f"user_profile_{user.id}"
    cached_data = cache_manager.get(key)

    if cached_data:
        return f"Cached user data available for {user.username}"
    return f"No cached data for {user.username}"


# API Views
@api_view(['GET'])
def cache_stats(request):
    """Get cache statistics."""
    if not request.user.is_staff:
        return Response({"error": "Unauthorized"}, status=403)

    cache_manager = CacheManager()
    stats = cache_manager.get_cache_stats()

    return Response(stats)


@api_view(['POST'])
def clear_cache(request):
    """Clear cache."""
    if not request.user.is_staff:
        return Response({"error": "Unauthorized"}, status=403)

    cache_manager = CacheManager()

    # Clear specific cache keys
    cache_type = request.data.get('type', 'all')

    if cache_type == 'tenant':
        tenant_id = request.data.get('tenant_id')
        success = cache_manager.clear_tenant_cache(tenant_id)
    elif cache_type == 'malaysian':
        # Clear Malaysian data cache
        success = cache_manager.clear_tenant_cache()
    else:
        # Clear all cache
        success = cache_manager.clear_tenant_cache()

    if success:
        return Response({"message": f"Cache cleared successfully"})
    else:
        return Response({"error": "Failed to clear cache"}, status=500)


@api_view(['GET'])
def warm_cache(request):
    """Warm cache with frequently accessed data."""
    if not request.user.is_staff:
        return Response({"error": "Unauthorized"}, status=403)

    from .cache_manager import cache_warmer

    # Warm Malaysian data
    warmed = cache_warmer.warm_malaysian_data()

    # Warm user data if specified
    user_ids = request.GET.getlist('user_ids')
    if user_ids:
        user_ids = [int(uid) for uid in user_ids]
        warmed_users = cache_warmer.warm_user_data(user_ids)
        warmed['users'] = warmed_users

    return Response({
        "message": "Cache warming completed",
        "warmed_items": warmed
    })


# Django Settings Integration
def get_cache_config() -> Dict[str, Any]:
    """Get cache configuration for Django settings."""
    return {
        'CACHES': {
            'default': {
                'BACKEND': 'django_redis.cache.RedisCache',
                'LOCATION': getattr(settings, 'REDIS_URL', 'redis://127.0.0.1:6379/1'),
                'OPTIONS': {
                    'CLIENT_CLASS': 'django_redis.client.DefaultClient',
                },
                'KEY_PREFIX': 'malaysian_sme_',
            },
            'locmem': {
                'BACKEND': 'django.core.cache.backends.locmem.LocMemCache',
                'LOCATION': 'unique-snowflake',
            },
        },
        'CACHE_MIDDLEWARE_ALIAS': 'default',
        'CACHE_MIDDLEWARE_SECONDS': 300,
        'CACHE_MIDDLEWARE_KEY_PREFIX': 'malaysian_sme_',
    }


# Signal Handlers
def invalidate_user_cache(sender, instance, **kwargs):
    """Invalidate cache when user is updated."""
    cache_manager = CacheManager()
    cache_key = f"user_profile_{instance.id}"
    cache_manager.delete(cache_key)

    # Clear tenant cache if user is tenant owner
    if hasattr(instance, 'owned_tenants'):
        for tenant in instance.owned_tenants.all():
            cache_manager.clear_tenant_cache(tenant.id)


def invalidate_model_cache(sender, instance, **kwargs):
    """Invalidate cache when model is updated."""
    cache_manager = CacheManager()
    query_cache = QueryCache(cache_manager)

    model_name = instance.__class__.__name__.lower()
    query_cache.invalidate_model_cache(model_name)


# Django Admin Integration
class CacheAdminMixin:
    """Mixin for Django admin cache management."""

    def save_model(self, request, obj, form, change):
        """Override save to invalidate cache."""
        super().save_model(request, obj, form, change)

        # Invalidate cache
        cache_manager = CacheManager()
        model_name = obj.__class__.__name__.lower()
        query_cache = QueryCache(cache_manager)
        query_cache.invalidate_model_cache(model_name)

    def delete_model(self, request, obj):
        """Override delete to invalidate cache."""
        cache_manager = CacheManager()
        model_name = obj.__class__.__name__.lower()
        query_cache = QueryCache(cache_manager)
        query_cache.invalidate_model_cache(model_name)

        super().delete_model(request, obj)