"""
Redis Caching Layer
- Performance optimization
- Session caching
- API response caching
"""

import redis
import json
import os
from typing import Optional, Any
from functools import wraps
import hashlib

# Redis connection
REDIS_URL = os.environ.get('REDIS_URL', 'redis://localhost:6379/0')

try:
    redis_client = redis.from_url(REDIS_URL, decode_responses=True)
    redis_client.ping()
    REDIS_AVAILABLE = True
except Exception as e:
    print(f"⚠️ Redis not available: {e}. Using in-memory cache fallback.")
    REDIS_AVAILABLE = False
    redis_client = None

# In-memory fallback cache
_memory_cache = {}

class CacheManager:
    """Unified cache manager with Redis fallback"""
    
    def __init__(self):
        self.use_redis = REDIS_AVAILABLE
    
    def get(self, key: str) -> Optional[Any]:
        """Get value from cache"""
        try:
            if self.use_redis:
                val = redis_client.get(key)
                return json.loads(val) if val else None
            else:
                return _memory_cache.get(key)
        except Exception as e:
            print(f"Cache get error: {e}")
            return None
    
    def set(self, key: str, value: Any, ttl: int = 3600):
        """Set value in cache with TTL"""
        try:
            serialized = json.dumps(value)
            if self.use_redis:
                redis_client.setex(key, ttl, serialized)
            else:
                _memory_cache[key] = value
        except Exception as e:
            print(f"Cache set error: {e}")
    
    def delete(self, key: str):
        """Delete value from cache"""
        try:
            if self.use_redis:
                redis_client.delete(key)
            else:
                _memory_cache.pop(key, None)
        except Exception as e:
            print(f"Cache delete error: {e}")
    
    def clear(self):
        """Clear all cache"""
        try:
            if self.use_redis:
                redis_client.flushdb()
            else:
                _memory_cache.clear()
        except Exception as e:
            print(f"Cache clear error: {e}")
    
    def get_many(self, keys: list) -> dict:
        """Get multiple values"""
        result = {}
        try:
            if self.use_redis:
                vals = redis_client.mget(keys)
                for k, v in zip(keys, vals):
                    result[k] = json.loads(v) if v else None
            else:
                for k in keys:
                    result[k] = _memory_cache.get(k)
        except Exception as e:
            print(f"Cache get_many error: {e}")
        return result
    
    def set_many(self, data: dict, ttl: int = 3600):
        """Set multiple values"""
        try:
            if self.use_redis:
                pipe = redis_client.pipeline()
                for k, v in data.items():
                    pipe.setex(k, ttl, json.dumps(v))
                pipe.execute()
            else:
                _memory_cache.update(data)
        except Exception as e:
            print(f"Cache set_many error: {e}")
    
    def increment(self, key: str, amount: int = 1) -> int:
        """Increment counter"""
        try:
            if self.use_redis:
                return redis_client.incr(key, amount)
            else:
                _memory_cache[key] = _memory_cache.get(key, 0) + amount
                return _memory_cache[key]
        except Exception as e:
            print(f"Cache increment error: {e}")
            return 0
    
    def decrement(self, key: str, amount: int = 1) -> int:
        """Decrement counter"""
        try:
            if self.use_redis:
                return redis_client.decr(key, amount)
            else:
                _memory_cache[key] = _memory_cache.get(key, 0) - amount
                return _memory_cache[key]
        except Exception as e:
            print(f"Cache decrement error: {e}")
            return 0

cache = CacheManager()

def cache_key(*args, **kwargs) -> str:
    """Generate cache key from arguments"""
    key_str = json.dumps({'args': args, 'kwargs': kwargs}, sort_keys=True, default=str)
    return hashlib.md5(key_str.encode()).hexdigest()

def cached(ttl: int = 3600, key_prefix: str = ''):
    """Decorator for caching function results"""
    def decorator(func):
        @wraps(func)
        def wrapper(*args, **kwargs):
            # Generate cache key
            func_key = f"{key_prefix or func.__name__}:{cache_key(*args, **kwargs)}"
            
            # Try to get from cache
            cached_val = cache.get(func_key)
            if cached_val is not None:
                return cached_val
            
            # Call function and cache result
            result = func(*args, **kwargs)
            cache.set(func_key, result, ttl)
            return result
        
        return wrapper
    return decorator

def cache_invalidate(pattern: str = ''):
    """Invalidate cache by pattern"""
    try:
        if cache.use_redis:
            keys = redis_client.keys(pattern or '*')
            if keys:
                redis_client.delete(*keys)
        else:
            if pattern:
                to_delete = [k for k in _memory_cache.keys() if pattern in k]
                for k in to_delete:
                    del _memory_cache[k]
            else:
                _memory_cache.clear()
    except Exception as e:
        print(f"Cache invalidate error: {e}")

# Session management
class SessionManager:
    """Session management with Redis"""
    
    SESSION_PREFIX = 'session:'
    SESSION_TTL = 86400  # 24 hours
    
    @staticmethod
    def create(user_id: int, data: dict) -> str:
        """Create session"""
        import secrets
        session_id = secrets.token_urlsafe(32)
        key = f"{SessionManager.SESSION_PREFIX}{session_id}"
        cache.set(key, {'user_id': user_id, **data}, SessionManager.SESSION_TTL)
        return session_id
    
    @staticmethod
    def get(session_id: str) -> Optional[dict]:
        """Get session"""
        key = f"{SessionManager.SESSION_PREFIX}{session_id}"
        return cache.get(key)
    
    @staticmethod
    def update(session_id: str, data: dict):
        """Update session"""
        key = f"{SessionManager.SESSION_PREFIX}{session_id}"
        session = cache.get(key)
        if session:
            session.update(data)
            cache.set(key, session, SessionManager.SESSION_TTL)
    
    @staticmethod
    def delete(session_id: str):
        """Delete session"""
        key = f"{SessionManager.SESSION_PREFIX}{session_id}"
        cache.delete(key)

# Rate limiting with Redis
class RateLimiter:
    """Rate limiter using Redis"""
    
    def __init__(self, max_requests: int = 100, window_seconds: int = 60):
        self.max_requests = max_requests
        self.window_seconds = window_seconds
    
    def is_allowed(self, identifier: str) -> bool:
        """Check if request is allowed"""
        key = f"rate_limit:{identifier}"
        try:
            count = cache.increment(key)
            if count == 1:
                # Set expiry on first request
                if cache.use_redis:
                    redis_client.expire(key, self.window_seconds)
            return count <= self.max_requests
        except Exception as e:
            print(f"Rate limit error: {e}")
            return True
    
    def get_remaining(self, identifier: str) -> int:
        """Get remaining requests"""
        key = f"rate_limit:{identifier}"
        try:
            count = cache.get(key) or 0
            return max(0, self.max_requests - count)
        except Exception as e:
            print(f"Rate limit get_remaining error: {e}")
            return self.max_requests
    
    def reset(self, identifier: str):
        """Reset rate limit"""
        key = f"rate_limit:{identifier}"
        cache.delete(key)

# Query result caching
def cache_query_result(query_key: str, ttl: int = 3600):
    """Cache database query results"""
    def decorator(func):
        @wraps(func)
        def wrapper(*args, **kwargs):
            cache_k = f"query:{query_key}:{cache_key(*args, **kwargs)}"
            cached_val = cache.get(cache_k)
            if cached_val is not None:
                return cached_val
            
            result = func(*args, **kwargs)
            cache.set(cache_k, result, ttl)
            return result
        
        return wrapper
    return decorator

# Cache statistics
def get_cache_stats() -> dict:
    """Get cache statistics"""
    try:
        if cache.use_redis:
            info = redis_client.info()
            return {
                'backend': 'redis',
                'used_memory': info.get('used_memory_human', 'N/A'),
                'connected_clients': info.get('connected_clients', 0),
                'total_commands': info.get('total_commands_processed', 0)
            }
        else:
            return {
                'backend': 'memory',
                'items': len(_memory_cache),
                'memory_usage': 'N/A'
            }
    except Exception as e:
        return {'error': str(e)}

# Job-specific cache invalidation
def invalidate_job_cache(job_id: int):
    """Invalidate all cache entries related to a specific job"""
    patterns = [
        f"job:{job_id}:*",
        f"results:job_{job_id}",
        f"analysis:job_{job_id}",
        f"audit:job_{job_id}",
        f"keywords:job_{job_id}",
        f"recommendations:job_{job_id}"
    ]
    for pattern in patterns:
        cache_invalidate(pattern)

def invalidate_results_cache():
    """Invalidate all results and analysis cache"""
    patterns = [
        "results:*",
        "analysis:*",
        "audit:*",
        "query:*"
    ]
    for pattern in patterns:
        cache_invalidate(pattern)

def invalidate_url_cache(url: str):
    """Invalidate cache for a specific URL"""
    import hashlib
    url_hash = hashlib.md5(url.encode()).hexdigest()
    patterns = [
        f"url:{url_hash}:*",
        f"results:{url_hash}",
        f"analysis:{url_hash}"
    ]
    for pattern in patterns:
        cache_invalidate(pattern)