"""
Redis integration with async client and connection pooling.
Provides shared Redis instance for all applications.
"""

from typing import Optional, Any
import json
from redis import asyncio as aioredis
from redis.asyncio import Redis, ConnectionPool
from core.config import settings


# Create Redis connection pool
redis_pool: Optional[ConnectionPool] = None
redis_client: Optional[Redis] = None


async def init_redis() -> Redis:
    """
    Initialize Redis client with connection pool.
    
    This should be called at application startup.
    
    Returns:
        Redis: Async Redis client
    """
    global redis_pool, redis_client
    
    redis_pool = ConnectionPool.from_url(
        settings.redis_url,
        max_connections=settings.redis_max_connections,
        decode_responses=settings.redis_decode_responses,
    )
    
    redis_client = Redis(connection_pool=redis_pool)
    
    return redis_client


async def get_redis() -> Redis:
    """
    Dependency that provides Redis client.
    
    Usage in FastAPI:
        @app.get("/cache")
        async def get_cache(redis: Redis = Depends(get_redis)):
            ...
    
    Returns:
        Redis: Async Redis client
    
    Raises:
        RuntimeError: If Redis client is not initialized
    """
    if redis_client is None:
        raise RuntimeError("Redis client not initialized. Call init_redis() at startup.")
    return redis_client


async def check_redis_connection() -> bool:
    """
    Check if Redis connection is healthy.
    
    Returns:
        bool: True if connection is healthy, False otherwise
    """
    try:
        if redis_client is None:
            return False
        redis_client.ping()
        return True
    except Exception:
        return False


async def close_redis_connection() -> None:
    """
    Close Redis connection pool.
    
    This should be called at application shutdown.
    """
    global redis_pool, redis_client
    
    if redis_client:
        await redis_client.aclose()
        redis_client = None
    
    if redis_pool:
        await redis_pool.disconnect()
        redis_pool = None


class RedisCache:
    """
    Redis cache utility with common operations.
    
    Provides helper methods for caching with TTL and JSON serialization.
    """
    
    def __init__(self, redis: Redis, prefix: str = ""):
        """
        Initialize cache with Redis client and optional key prefix.
        
        Args:
            redis: Redis client instance
            prefix: Optional key prefix for namespace isolation
        """
        self.redis = redis
        self.prefix = prefix
    
    def _make_key(self, key: str) -> str:
        """Generate prefixed key."""
        return f"{self.prefix}:{key}" if self.prefix else key
    
    async def get(self, key: str) -> Optional[str]:
        """
        Get value by key.
        
        Args:
            key: Cache key
        
        Returns:
            Optional[str]: Cached value or None if not found
        """
        return await self.redis.get(self._make_key(key))
    
    async def set(
        self,
        key: str,
        value: str,
        ttl: Optional[int] = None
    ) -> bool:
        """
        Set value with optional TTL.
        
        Args:
            key: Cache key
            value: Value to cache
            ttl: Time to live in seconds (optional)
        
        Returns:
            bool: True if successful
        """
        return await self.redis.set(
            self._make_key(key),
            value,
            ex=ttl
        )
    
    async def get_json(self, key: str) -> Optional[Any]:
        """
        Get JSON value by key.
        
        Args:
            key: Cache key
        
        Returns:
            Optional[Any]: Deserialized JSON value or None
        """
        value = await self.get(key)
        if value is None:
            return None
        try:
            return json.loads(value)
        except json.JSONDecodeError:
            return None
    
    async def set_json(
        self,
        key: str,
        value: Any,
        ttl: Optional[int] = None
    ) -> bool:
        """
        Set JSON value with optional TTL.
        
        Args:
            key: Cache key
            value: Value to serialize and cache
            ttl: Time to live in seconds (optional)
        
        Returns:
            bool: True if successful
        """
        json_value = json.dumps(value)
        return await self.set(key, json_value, ttl)
    
    async def delete(self, key: str) -> int:
        """
        Delete key.
        
        Args:
            key: Cache key
        
        Returns:
            int: Number of keys deleted
        """
        return await self.redis.delete(self._make_key(key))
    
    async def exists(self, key: str) -> bool:
        """
        Check if key exists.
        
        Args:
            key: Cache key
        
        Returns:
            bool: True if key exists
        """
        return await self.redis.exists(self._make_key(key)) > 0
    
    async def expire(self, key: str, ttl: int) -> bool:
        """
        Set TTL for existing key.
        
        Args:
            key: Cache key
            ttl: Time to live in seconds
        
        Returns:
            bool: True if successful
        """
        return await self.redis.expire(self._make_key(key), ttl)
    
    async def increment(self, key: str, amount: int = 1) -> int:
        """
        Increment numeric value.
        
        Args:
            key: Cache key
            amount: Increment amount (default 1)
        
        Returns:
            int: New value after increment
        """
        return await self.redis.incrby(self._make_key(key), amount)
    
    async def decrement(self, key: str, amount: int = 1) -> int:
        """
        Decrement numeric value.
        
        Args:
            key: Cache key
            amount: Decrement amount (default 1)
        
        Returns:
            int: New value after decrement
        """
        return await self.redis.decrby(self._make_key(key), amount)