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"""
Redis service for rate limiting and task queue.
"""

import os
import json
import logging
from typing import Optional, Dict, Any
from datetime import datetime, timezone
import redis
from redis.exceptions import RedisError

logger = logging.getLogger(__name__)


class RedisService:
    """Singleton Redis connection for rate limiting and task queue."""
    
    _instance = None
    _client: Optional[redis.Redis] = None
    
    def __new__(cls):
        """Ensure singleton pattern."""
        if cls._instance is None:
            cls._instance = super(RedisService, cls).__new__(cls)
        return cls._instance
    
    def __init__(self):
        """Initialize Redis connection if not already done."""
        if self._client is None:
            self._connect()
    
    def _connect(self):
        """Establish Redis connection."""
        try:
            redis_host = os.getenv("REDIS_HOST", "localhost")
            redis_port = int(os.getenv("REDIS_PORT", "6379"))
            redis_password = os.getenv("REDIS_PASSWORD")
            
            self._client = redis.Redis(
                host=redis_host,
                port=redis_port,
                password=redis_password if redis_password else None,
                decode_responses=True,
                socket_connect_timeout=5,
                socket_timeout=5
            )
            
            # Test connection
            self._client.ping()
            logger.info("Redis connection established successfully")
            
        except Exception as e:
            logger.error(f"Failed to connect to Redis: {str(e)}")
            self._client = None
    
    def is_connected(self) -> bool:
        """Check if Redis is connected."""
        return self._client is not None
    
    # ==================== RATE LIMITING ====================
    
    def check_rate_limit(
        self,
        identifier: str,
        max_requests: int = 2,
        window_seconds: int = 60
    ) -> tuple[bool, int]:
        """
        Check if request should be rate limited.
        
        Args:
            identifier: User/device/IP identifier
            max_requests: Maximum requests allowed
            window_seconds: Time window in seconds
        
        Returns:
            Tuple of (is_allowed, current_count)
        """
        if not self._client:
            # If Redis is down, allow request (fail open)
            logger.warning("Redis unavailable, bypassing rate limit")
            return True, 0
        
        try:
            key = f"ratelimit:{identifier}"
            
            # Increment counter
            count = self._client.incr(key)
            
            # Set expiry on first request
            if count == 1:
                self._client.expire(key, window_seconds)
            
            # Check if limit exceeded
            is_allowed = count <= max_requests
            
            return is_allowed, count
            
        except RedisError as e:
            logger.error(f"Rate limit check failed: {str(e)}")
            # Fail open - allow request if Redis errors
            return True, 0
    
    # ==================== IP LOGGING GATE ====================
    
    def should_log_ip(self, device_id: str, ttl_seconds: int = 300) -> bool:
        """
        Check if IP should be logged for this device (gated by TTL).
        
        Args:
            device_id: Device identifier
            ttl_seconds: Time-to-live for gate (default 5 minutes)
        
        Returns:
            True if IP should be logged, False if within TTL window
        """
        if not self._client:
            # If Redis is down, log IP
            return True
        
        try:
            key = f"iplog:{device_id}"
            
            # Try to set key with NX (only if not exists)
            result = self._client.set(key, "1", nx=True, ex=ttl_seconds)
            
            # If set succeeded, IP should be logged
            return result is not None
            
        except RedisError as e:
            logger.error(f"IP log gate check failed: {str(e)}")
            # Fail safe - log IP if Redis errors
            return True
    
    # ==================== TASK QUEUE ====================
    
    def enqueue_task(self, job_id: str, task_data: Dict[str, Any]) -> bool:
        """
        Add task to Redis queue.
        
        Args:
            job_id: Unique job identifier
            task_data: Task payload
        
        Returns:
            True if enqueued successfully
        """
        if not self._client:
            logger.error("Redis unavailable, cannot enqueue task")
            return False
        
        try:
            # Add to queue
            queue_key = "absa_tasks"
            task_payload = {
                "job_id": job_id,
                "data": task_data,
                "enqueued_at": datetime.now(timezone.utc).isoformat()
            }
            
            self._client.rpush(queue_key, json.dumps(task_payload))
            
            # Set initial status
            self.set_task_status(job_id, "PENDING")
            
            logger.info(f"Task {job_id} enqueued successfully")
            return True
            
        except RedisError as e:
            logger.error(f"Failed to enqueue task: {str(e)}")
            return False
    
    def dequeue_task(self, timeout: int = 1) -> Optional[Dict[str, Any]]:
        """
        Get next task from queue (blocking).
        
        Args:
            timeout: Block timeout in seconds
        
        Returns:
            Task payload or None
        """
        if not self._client:
            return None
        
        try:
            queue_key = "absa_tasks"
            result = self._client.blpop(queue_key, timeout=timeout)
            
            if result:
                _, task_json = result
                task = json.loads(task_json)
                logger.info(f"Dequeued task: {task['job_id']}")
                return task
            
            return None
            
        except RedisError as e:
            logger.error(f"Failed to dequeue task: {str(e)}")
            return None
    
    def set_task_status(
        self,
        job_id: str,
        status: str,
        ttl_seconds: int = 3600
    ) -> bool:
        """
        Set task status in Redis.
        
        Args:
            job_id: Job identifier
            status: Status (PENDING, RUNNING, DONE, FAILED)
            ttl_seconds: Time-to-live for status key
        
        Returns:
            True if successful
        """
        if not self._client:
            return False
        
        try:
            key = f"job:{job_id}:status"
            self._client.set(key, status, ex=ttl_seconds)
            return True
            
        except RedisError as e:
            logger.error(f"Failed to set task status: {str(e)}")
            return False
    
    def get_task_status(self, job_id: str) -> Optional[str]:
        """
        Get task status from Redis.
        
        Args:
            job_id: Job identifier
        
        Returns:
            Status string or None
        """
        if not self._client:
            return None
        
        try:
            key = f"job:{job_id}:status"
            status = self._client.get(key)
            return status
            
        except RedisError as e:
            logger.error(f"Failed to get task status: {str(e)}")
            return None
    
    def set_task_result(
        self,
        job_id: str,
        result: Dict[str, Any],
        ttl_seconds: int = 3600
    ) -> bool:
        """
        Store task result in Redis.
        
        Args:
            job_id: Job identifier
            result: Task result data
            ttl_seconds: Time-to-live for result
        
        Returns:
            True if successful
        """
        if not self._client:
            return False
        
        try:
            key = f"job:{job_id}:result"
            self._client.set(key, json.dumps(result), ex=ttl_seconds)
            return True
            
        except RedisError as e:
            logger.error(f"Failed to set task result: {str(e)}")
            return False
    
    def get_task_result(self, job_id: str) -> Optional[Dict[str, Any]]:
        """
        Get task result from Redis.
        
        Args:
            job_id: Job identifier
        
        Returns:
            Result data or None
        """
        if not self._client:
            return None
        
        try:
            key = f"job:{job_id}:result"
            result_json = self._client.get(key)
            
            if result_json:
                return json.loads(result_json)
            
            return None
            
        except RedisError as e:
            logger.error(f"Failed to get task result: {str(e)}")
            return None
    
    def close(self):
        """Close Redis connection."""
        if self._client:
            self._client.close()
            self._client = None
            logger.info("Redis connection closed")


# Singleton instance
_redis_service = None

def get_redis_service() -> RedisService:
    """Get Redis service singleton."""
    global _redis_service
    if _redis_service is None:
        _redis_service = RedisService()
    return _redis_service