"""
Cache configuration for thrillwiki project.

This module configures Redis-based caching with connection pooling,
session caching, and API response caching.

Why python-decouple?
- Already used in base.py for consistency
- Simpler API than django-environ
- Sufficient for our configuration needs
- Better separation of config from code

Cache Backends:
- default: General purpose caching (queries, templates, etc.)
- sessions: User session storage (separate for security)
- api: API response caching (high concurrency)
"""

from decouple import config

# =============================================================================
# Redis Configuration
# =============================================================================

REDIS_URL = config("REDIS_URL", default="redis://127.0.0.1:6379/1")

# Redis cache backend classes
DJANGO_REDIS_CACHE_BACKEND = "django_redis.cache.RedisCache"
DJANGO_REDIS_CLIENT_CLASS = "django_redis.client.DefaultClient"

# =============================================================================
# Cache Configuration
# =============================================================================
# Multiple cache backends for different purposes

CACHES = {
    # Default cache for general purpose caching
    # Used for: database queries, computed values, template fragments
    "default": {
        "BACKEND": DJANGO_REDIS_CACHE_BACKEND,
        "LOCATION": config("REDIS_URL", default="redis://127.0.0.1:6379/1"),
        "OPTIONS": {
            "CLIENT_CLASS": DJANGO_REDIS_CLIENT_CLASS,
            # Use hiredis for faster C-based parsing
            "PARSER_CLASS": "redis.connection.HiredisParser",
            # Connection pooling for better performance
            "CONNECTION_POOL_CLASS": "redis.BlockingConnectionPool",
            "CONNECTION_POOL_CLASS_KWARGS": {
                "max_connections": config(
                    "REDIS_MAX_CONNECTIONS", default=100, cast=int
                ),
                "timeout": config("REDIS_CONNECTION_TIMEOUT", default=20, cast=int),
                "socket_keepalive": True,
                "socket_keepalive_options": {
                    1: 1,   # TCP_KEEPIDLE: Start keepalive after 1s idle
                    2: 1,   # TCP_KEEPINTVL: Send probes every 1s
                    3: 3,   # TCP_KEEPCNT: Close after 3 failed probes
                },
                "retry_on_timeout": True,
                "health_check_interval": 30,
            },
            # Compress cached data to save memory
            "COMPRESSOR": "django_redis.compressors.zlib.ZlibCompressor",
            # Graceful degradation if Redis is unavailable
            "IGNORE_EXCEPTIONS": config(
                "REDIS_IGNORE_EXCEPTIONS", default=True, cast=bool
            ),
        },
        "KEY_PREFIX": config("CACHE_KEY_PREFIX", default="thrillwiki"),
        "VERSION": 1,
    },

    # Session cache - separate for security isolation
    # Uses a different Redis database (db 2)
    "sessions": {
        "BACKEND": DJANGO_REDIS_CACHE_BACKEND,
        "LOCATION": config("REDIS_SESSIONS_URL", default="redis://127.0.0.1:6379/2"),
        "OPTIONS": {
            "CLIENT_CLASS": DJANGO_REDIS_CLIENT_CLASS,
            "PARSER_CLASS": "redis.connection.HiredisParser",
            "CONNECTION_POOL_CLASS": "redis.BlockingConnectionPool",
            "CONNECTION_POOL_CLASS_KWARGS": {
                "max_connections": config(
                    "REDIS_SESSIONS_MAX_CONNECTIONS", default=50, cast=int
                ),
                "timeout": 10,
                "socket_keepalive": True,
            },
        },
        "KEY_PREFIX": "sessions",
    },

    # API cache - high concurrency for API responses
    # Uses a different Redis database (db 3)
    "api": {
        "BACKEND": DJANGO_REDIS_CACHE_BACKEND,
        "LOCATION": config("REDIS_API_URL", default="redis://127.0.0.1:6379/3"),
        "OPTIONS": {
            "CLIENT_CLASS": DJANGO_REDIS_CLIENT_CLASS,
            "PARSER_CLASS": "redis.connection.HiredisParser",
            "CONNECTION_POOL_CLASS": "redis.BlockingConnectionPool",
            "CONNECTION_POOL_CLASS_KWARGS": {
                "max_connections": config(
                    "REDIS_API_MAX_CONNECTIONS", default=100, cast=int
                ),
                "timeout": 15,
                "socket_keepalive": True,
                "retry_on_timeout": True,
            },
            # Compress API responses to save bandwidth
            "COMPRESSOR": "django_redis.compressors.zlib.ZlibCompressor",
        },
        "KEY_PREFIX": "api",
    },
}

# =============================================================================
# Session Configuration
# =============================================================================
# Use Redis for session storage for better performance and scalability

SESSION_ENGINE = "django.contrib.sessions.backends.cache"
SESSION_CACHE_ALIAS = "sessions"

# Session timeout in seconds (1 hour)
SESSION_COOKIE_AGE = config("SESSION_COOKIE_AGE", default=3600, cast=int)

# Update session on each request (sliding expiry)
SESSION_SAVE_EVERY_REQUEST = config(
    "SESSION_SAVE_EVERY_REQUEST", default=True, cast=bool
)

# Session persists until cookie expires (not browser close)
SESSION_EXPIRE_AT_BROWSER_CLOSE = config(
    "SESSION_EXPIRE_AT_BROWSER_CLOSE", default=False, cast=bool
)

# =============================================================================
# Cache Middleware Settings
# =============================================================================
# For Django's cache middleware (UpdateCacheMiddleware/FetchFromCacheMiddleware)

CACHE_MIDDLEWARE_SECONDS = config("CACHE_MIDDLEWARE_SECONDS", default=300, cast=int)
CACHE_MIDDLEWARE_KEY_PREFIX = config(
    "CACHE_MIDDLEWARE_KEY_PREFIX", default="thrillwiki"
)