"""
Connection management for WebSocket communications.

This module manages WebSocket connections, tracks connection status,
and provides utilities for connection lifecycle management.
"""

import logging
from datetime import datetime, timedelta
from typing import Dict, Any, Optional, List, Set
from threading import Lock
import json

import redis


logger = logging.getLogger(__name__)


class ConnectionManagerError(Exception):
    """Base exception for connection manager errors."""
    pass


class ConnectionManager:
    """Manages WebSocket connections and their lifecycle."""
    
    def __init__(self, redis_client: redis.Redis, connection_timeout: int = 300):
        """
        Initialize the connection manager.
        
        Args:
            redis_client: Redis client for connection persistence
            connection_timeout: Connection timeout in seconds (default: 5 minutes)
        """
        self.redis_client = redis_client
        self.connection_timeout = connection_timeout
        self.connections_prefix = "ws_connection:"
        self.session_connections_prefix = "session_connections:"
        self.user_connections_prefix = "user_connections:"
        
        # In-memory cache for active connections (faster access)
        self._active_connections: Dict[str, Dict[str, Any]] = {}
        self._connections_lock = Lock()
    
    def add_connection(self, client_id: str, connection_info: Dict[str, Any]) -> None:
        """
        Add a new WebSocket connection.
        
        Args:
            client_id: Unique client identifier (socket ID)
            connection_info: Connection information dictionary
            
        Raises:
            ConnectionManagerError: If connection cannot be added
        """
        try:
            with self._connections_lock:
                # Add to in-memory cache
                self._active_connections[client_id] = connection_info.copy()
                
                # Persist to Redis
                connection_key = f"{self.connections_prefix}{client_id}"
                self.redis_client.setex(
                    connection_key,
                    self.connection_timeout,
                    json.dumps(connection_info)
                )
                
                # Add to session connections set
                session_id = connection_info['session_id']
                session_connections_key = f"{self.session_connections_prefix}{session_id}"
                self.redis_client.sadd(session_connections_key, client_id)
                self.redis_client.expire(session_connections_key, self.connection_timeout)
                
                # Add to user connections set
                user_id = connection_info['user_id']
                user_connections_key = f"{self.user_connections_prefix}{user_id}"
                self.redis_client.sadd(user_connections_key, client_id)
                self.redis_client.expire(user_connections_key, self.connection_timeout)
                
                logger.info(f"Added connection {client_id} for session {session_id}")
                
        except redis.RedisError as e:
            logger.error(f"Redis error adding connection {client_id}: {e}")
            # Keep in memory even if Redis fails
        except Exception as e:
            logger.error(f"Error adding connection {client_id}: {e}")
            raise ConnectionManagerError(f"Failed to add connection: {e}")
    
    def remove_connection(self, client_id: str) -> Optional[Dict[str, Any]]:
        """
        Remove a WebSocket connection.
        
        Args:
            client_id: Client identifier to remove
            
        Returns:
            Optional[Dict[str, Any]]: Connection info if found, None otherwise
        """
        try:
            with self._connections_lock:
                # Get connection info before removal
                connection_info = self._active_connections.get(client_id)
                
                if not connection_info:
                    # Try to get from Redis
                    connection_info = self._get_connection_from_redis(client_id)
                
                if connection_info:
                    # Remove from in-memory cache
                    self._active_connections.pop(client_id, None)
                    
                    # Remove from Redis
                    connection_key = f"{self.connections_prefix}{client_id}"
                    self.redis_client.delete(connection_key)
                    
                    # Remove from session connections set
                    session_id = connection_info['session_id']
                    session_connections_key = f"{self.session_connections_prefix}{session_id}"
                    self.redis_client.srem(session_connections_key, client_id)
                    
                    # Remove from user connections set
                    user_id = connection_info['user_id']
                    user_connections_key = f"{self.user_connections_prefix}{user_id}"
                    self.redis_client.srem(user_connections_key, client_id)
                    
                    logger.info(f"Removed connection {client_id}")
                    
                return connection_info
                
        except redis.RedisError as e:
            logger.error(f"Redis error removing connection {client_id}: {e}")
            # Still remove from memory
            with self._connections_lock:
                return self._active_connections.pop(client_id, None)
        except Exception as e:
            logger.error(f"Error removing connection {client_id}: {e}")
            return None
    
    def get_connection(self, client_id: str) -> Optional[Dict[str, Any]]:
        """
        Get connection information.
        
        Args:
            client_id: Client identifier
            
        Returns:
            Optional[Dict[str, Any]]: Connection info if found, None otherwise
        """
        try:
            with self._connections_lock:
                # Check in-memory cache first
                connection_info = self._active_connections.get(client_id)
                
                if connection_info:
                    return connection_info.copy()
                
                # Check Redis
                connection_info = self._get_connection_from_redis(client_id)
                
                if connection_info:
                    # Cache in memory
                    self._active_connections[client_id] = connection_info.copy()
                    return connection_info
                
                return None
                
        except Exception as e:
            logger.error(f"Error getting connection {client_id}: {e}")
            return None
    
    def update_connection(self, client_id: str, connection_info: Dict[str, Any]) -> bool:
        """
        Update connection information.
        
        Args:
            client_id: Client identifier
            connection_info: Updated connection information
            
        Returns:
            bool: True if updated successfully, False otherwise
        """
        try:
            with self._connections_lock:
                # Update in-memory cache
                if client_id in self._active_connections:
                    self._active_connections[client_id] = connection_info.copy()
                    
                    # Update in Redis
                    connection_key = f"{self.connections_prefix}{client_id}"
                    self.redis_client.setex(
                        connection_key,
                        self.connection_timeout,
                        json.dumps(connection_info)
                    )
                    
                    logger.debug(f"Updated connection {client_id}")
                    return True
                
                return False
                
        except redis.RedisError as e:
            logger.error(f"Redis error updating connection {client_id}: {e}")
            # Update in memory only
            with self._connections_lock:
                if client_id in self._active_connections:
                    self._active_connections[client_id] = connection_info.copy()
                    return True
                return False
        except Exception as e:
            logger.error(f"Error updating connection {client_id}: {e}")
            return False
    
    def update_connection_activity(self, client_id: str) -> bool:
        """
        Update connection activity timestamp.
        
        Args:
            client_id: Client identifier
            
        Returns:
            bool: True if updated successfully, False otherwise
        """
        try:
            connection_info = self.get_connection(client_id)
            if connection_info:
                connection_info['last_activity'] = datetime.utcnow().isoformat()
                return self.update_connection(client_id, connection_info)
            
            return False
            
        except Exception as e:
            logger.error(f"Error updating connection activity {client_id}: {e}")
            return False
    
    def get_session_connections(self, session_id: str) -> List[str]:
        """
        Get all connection IDs for a session.
        
        Args:
            session_id: Session identifier
            
        Returns:
            List[str]: List of client IDs connected to the session
        """
        try:
            session_connections_key = f"{self.session_connections_prefix}{session_id}"
            client_ids = self.redis_client.smembers(session_connections_key)
            
            # Convert bytes to strings and filter active connections
            active_client_ids = []
            for client_id_bytes in client_ids:
                client_id = client_id_bytes.decode('utf-8')
                if self.get_connection(client_id):
                    active_client_ids.append(client_id)
                else:
                    # Clean up stale reference
                    self.redis_client.srem(session_connections_key, client_id)
            
            return active_client_ids
            
        except redis.RedisError as e:
            logger.error(f"Redis error getting session connections: {e}")
            return []
        except Exception as e:
            logger.error(f"Error getting session connections: {e}")
            return []
    
    def get_user_connections(self, user_id: str) -> List[str]:
        """
        Get all connection IDs for a user.
        
        Args:
            user_id: User identifier
            
        Returns:
            List[str]: List of client IDs connected for the user
        """
        try:
            user_connections_key = f"{self.user_connections_prefix}{user_id}"
            client_ids = self.redis_client.smembers(user_connections_key)
            
            # Convert bytes to strings and filter active connections
            active_client_ids = []
            for client_id_bytes in client_ids:
                client_id = client_id_bytes.decode('utf-8')
                if self.get_connection(client_id):
                    active_client_ids.append(client_id)
                else:
                    # Clean up stale reference
                    self.redis_client.srem(user_connections_key, client_id)
            
            return active_client_ids
            
        except redis.RedisError as e:
            logger.error(f"Redis error getting user connections: {e}")
            return []
        except Exception as e:
            logger.error(f"Error getting user connections: {e}")
            return []
    
    def get_all_connections(self) -> Dict[str, Dict[str, Any]]:
        """
        Get all active connections.
        
        Returns:
            Dict[str, Dict[str, Any]]: Dictionary of client_id -> connection_info
        """
        try:
            with self._connections_lock:
                return self._active_connections.copy()
        except Exception as e:
            logger.error(f"Error getting all connections: {e}")
            return {}
    
    def cleanup_expired_connections(self) -> int:
        """
        Clean up expired connections.
        
        Returns:
            int: Number of connections cleaned up
        """
        try:
            cleaned_count = 0
            cutoff_time = datetime.utcnow() - timedelta(seconds=self.connection_timeout)
            
            with self._connections_lock:
                expired_client_ids = []
                
                for client_id, connection_info in self._active_connections.items():
                    try:
                        connected_at = datetime.fromisoformat(connection_info['connected_at'])
                        last_activity = connection_info.get('last_activity')
                        
                        if last_activity:
                            last_activity_time = datetime.fromisoformat(last_activity)
                            if last_activity_time < cutoff_time:
                                expired_client_ids.append(client_id)
                        elif connected_at < cutoff_time:
                            expired_client_ids.append(client_id)
                            
                    except (ValueError, KeyError):
                        # Invalid timestamp, mark for cleanup
                        expired_client_ids.append(client_id)
                
                # Remove expired connections
                for client_id in expired_client_ids:
                    self.remove_connection(client_id)
                    cleaned_count += 1
            
            if cleaned_count > 0:
                logger.info(f"Cleaned up {cleaned_count} expired connections")
            
            return cleaned_count
            
        except Exception as e:
            logger.error(f"Error cleaning up expired connections: {e}")
            return 0
    
    def get_connection_stats(self) -> Dict[str, Any]:
        """
        Get connection statistics.
        
        Returns:
            Dict[str, Any]: Connection statistics
        """
        try:
            with self._connections_lock:
                total_connections = len(self._active_connections)
                
                # Count connections by session and user
                sessions = set()
                users = set()
                languages = {}
                
                for connection_info in self._active_connections.values():
                    sessions.add(connection_info['session_id'])
                    users.add(connection_info['user_id'])
                    
                    language = connection_info.get('language', 'unknown')
                    languages[language] = languages.get(language, 0) + 1
                
                return {
                    'total_connections': total_connections,
                    'unique_sessions': len(sessions),
                    'unique_users': len(users),
                    'languages': languages,
                    'timestamp': datetime.utcnow().isoformat()
                }
                
        except Exception as e:
            logger.error(f"Error getting connection stats: {e}")
            return {
                'total_connections': 0,
                'unique_sessions': 0,
                'unique_users': 0,
                'languages': {},
                'timestamp': datetime.utcnow().isoformat()
            }
    
    def _get_connection_from_redis(self, client_id: str) -> Optional[Dict[str, Any]]:
        """Get connection info from Redis."""
        try:
            connection_key = f"{self.connections_prefix}{client_id}"
            connection_data = self.redis_client.get(connection_key)
            
            if connection_data:
                return json.loads(connection_data)
            
            return None
            
        except (redis.RedisError, json.JSONDecodeError) as e:
            logger.warning(f"Error getting connection from Redis: {e}")
            return None


def create_connection_manager(redis_client: redis.Redis, 
                            connection_timeout: int = 300) -> ConnectionManager:
    """
    Factory function to create a ConnectionManager instance.
    
    Args:
        redis_client: Redis client instance
        connection_timeout: Connection timeout in seconds
        
    Returns:
        ConnectionManager: Configured connection manager
    """
    return ConnectionManager(redis_client, connection_timeout)