"""
OPC UA Server for Calejo Control Adapter.

Provides OPC UA interface for SCADA systems to access setpoints and status.
"""

import asyncio
from typing import Dict, Optional, Tuple, Any
from datetime import datetime
import structlog
from asyncua import Server, Node
from asyncua.common.methods import uamethod
from asyncua.crypto.security_policies import SecurityPolicyBasic256Sha256
from asyncua.crypto.validator import CertificateValidator, CertificateValidatorOptions

# Try to import certificate generation functions
# These might not be available in all asyncua versions
try:
    from asyncua.crypto.cert_gen import setup_self_signed_cert
    HAS_CERT_GEN = True
except ImportError:
    HAS_CERT_GEN = False
    setup_self_signed_cert = None

from src.core.setpoint_manager import SetpointManager
from src.core.security import SecurityManager, UserRole
from src.core.compliance_audit import ComplianceAuditLogger, AuditEventType, AuditSeverity

logger = structlog.get_logger()


class OPCUAServer:
    """OPC UA Server for Calejo Control Adapter."""
    
    def __init__(
        self,
        setpoint_manager: SetpointManager,
        security_manager: SecurityManager,
        audit_logger: ComplianceAuditLogger,
        endpoint: str = "opc.tcp://0.0.0.0:4840",
        server_name: str = "Calejo Control OPC UA Server",
        enable_security: bool = True,
        certificate_path: Optional[str] = None,
        private_key_path: Optional[str] = None
    ):
        self.setpoint_manager = setpoint_manager
        self.security_manager = security_manager
        self.audit_logger = audit_logger
        self.endpoint = endpoint
        self.server_name = server_name
        self.enable_security = enable_security
        self.certificate_path = certificate_path
        self.private_key_path = private_key_path
        self.server = None
        self.namespace_idx = None
        
        # Security tracking
        self.connected_clients: Dict[str, Dict] = {}  # client_id -> client_info
        
        # Node references
        self.objects_node = None
        self.station_nodes = {}
        self.pump_nodes = {}
    
    async def start(self):
        """Start the OPC UA server."""
        try:
            # Create server
            self.server = Server()
            await self.server.init()
            
            # Configure server
            self.server.set_endpoint(self.endpoint)
            self.server.set_server_name(self.server_name)
            
            # Configure security if enabled
            if self.enable_security:
                await self._configure_security()
            else:
                # No security (for development only)
                self.server.set_security_policy([
                    "http://opcfoundation.org/UA/SecurityPolicy#None"
                ])
            
            # Setup namespace
            uri = "http://calejo-control.com/OPCUA/"
            self.namespace_idx = await self.server.register_namespace(uri)
            
            # Create object structure
            await self._create_object_structure()
            
            # Start server
            await self.server.start()
            
            # Log security configuration
            security_mode = "secure" if self.enable_security else "insecure"
            logger.info(
                "opcua_server_started",
                endpoint=self.endpoint,
                namespace_idx=self.namespace_idx,
                security_mode=security_mode
            )
            
            # Log security event
            self.audit_logger.log_security_event(
                event_type=AuditEventType.SYSTEM_START,
                severity=AuditSeverity.LOW,
                event_data={
                    "protocol": "OPC_UA",
                    "endpoint": self.endpoint,
                    "security_enabled": self.enable_security,
                    "server_name": self.server_name
                }
            )
            
            # Start background task to update setpoints
            asyncio.create_task(self._update_setpoints_loop())
            
        except Exception as e:
            logger.error("failed_to_start_opcua_server", error=str(e))
            raise
    
    async def _configure_security(self):
        """Configure OPC UA security with certificates."""
        try:
            # Set security policies
            self.server.set_security_policy([
                SecurityPolicyBasic256Sha256,
                "http://opcfoundation.org/UA/SecurityPolicy#None"
            ])
            
            # Load or generate certificates
            if self.certificate_path and self.private_key_path:
                # Load existing certificates
                await self.server.load_certificate(self.certificate_path)
                await self.server.load_private_key(self.private_key_path)
            elif HAS_CERT_GEN and setup_self_signed_cert:
                # Generate self-signed certificate for development
                await setup_self_signed_cert(
                    self.server,
                    "Calejo Control OPC UA Server",
                    "calejo-control.com",
                    "IT",
                    "Rome",
                    "Lazio",
                    "calejo-control.com"
                )
            else:
                # Certificate generation not available, use basic security
                logger.warning("certificate_generation_not_available")
                self.server.set_security_policy([
                    "http://opcfoundation.org/UA/SecurityPolicy#None"
                ])
                return
            
            # Configure certificate validation
            validator = CertificateValidator(CertificateValidatorOptions())
            self.server.set_certificate_validator(validator)
            
            logger.info("opcua_security_configured")
            
        except Exception as e:
            logger.error("failed_to_configure_opcua_security", error=str(e))
            raise
    
    async def _on_client_connect(self, session, endpoint):
        """Handle client connection with security logging."""
        client_id = str(session.session_id)
        client_info = {
            'session_id': session.session_id,
            'endpoint': endpoint,
            'connected_at': datetime.now(),
            'user_identity': session.user,
            'security_policy': session.security_policy,
            'client_certificate': getattr(session, 'peer_certificate', None)
        }
        
        self.connected_clients[client_id] = client_info
        
        # Log connection event
        self.audit_logger.log_security_event(
            event_type=AuditEventType.USER_LOGIN,
            severity=AuditSeverity.LOW,
            event_data={
                "protocol": "OPC_UA",
                "client_id": client_id,
                "endpoint": endpoint,
                "user_identity": str(session.user) if session.user else "anonymous",
                "security_policy": str(session.security_policy)
            }
        )
        
        logger.info(
            "opcua_client_connected",
            client_id=client_id,
            endpoint=endpoint,
            user_identity=str(session.user) if session.user else "anonymous"
        )
    
    async def _on_client_disconnect(self, session):
        """Handle client disconnection with security logging."""
        client_id = str(session.session_id)
        client_info = self.connected_clients.pop(client_id, None)
        
        if client_info:
            # Log disconnection event
            self.audit_logger.log_security_event(
                event_type=AuditEventType.USER_LOGOUT,
                severity=AuditSeverity.LOW,
                event_data={
                    "protocol": "OPC_UA",
                    "client_id": client_id,
                    "endpoint": client_info['endpoint'],
                    "duration_seconds": (datetime.now() - client_info['connected_at']).total_seconds()
                }
            )
            
            logger.info(
                "opcua_client_disconnected",
                client_id=client_id,
                duration_seconds=(datetime.now() - client_info['connected_at']).total_seconds()
            )
    
    async def stop(self):
        """Stop the OPC UA server."""
        if self.server:
            await self.server.stop()
            
            # Log security event
            self.audit_logger.log_security_event(
                event_type=AuditEventType.SYSTEM_STOP,
                severity=AuditSeverity.LOW,
                event_data={
                    "protocol": "OPC_UA",
                    "endpoint": self.endpoint,
                    "connected_clients": len(self.connected_clients)
                }
            )
            
            logger.info("opcua_server_stopped", connected_clients=len(self.connected_clients))
    
    def _get_station_id_from_node(self, node: Node) -> Optional[str]:
        """Extract station ID from OPC UA node path."""
        try:
            # Node path format: Objects/CalejoControl/Station_<station_id>/...
            node_path = str(node)
            if "Station_" in node_path:
                parts = node_path.split("/")
                for part in parts:
                    if part.startswith("Station_"):
                        return part.replace("Station_", "")
        except Exception:
            pass
        return None
    
    def _check_node_access(self, session, node: Node, operation: str) -> bool:
        """Check if client has permission to access node."""
        try:
            # Extract station ID from node
            station_id = self._get_station_id_from_node(node)
            
            # Get user identity from session
            user_identity = session.user
            
            # Map OPC UA operation to permission
            permission_map = {
                "read": "read_pump_status",
                "write": "write_pump_setpoint",
                "browse": "read_pump_status"
            }
            
            required_permission = permission_map.get(operation, "read_pump_status")
            
            # Log access attempt
            self.audit_logger.log_security_event(
                event_type=AuditEventType.ACCESS_DENIED,
                severity=AuditSeverity.MEDIUM,
                event_data={
                    "protocol": "OPC_UA",
                    "client_id": str(session.session_id),
                    "node": str(node),
                    "operation": operation,
                    "station_id": station_id,
                    "user_identity": str(user_identity) if user_identity else "anonymous",
                    "required_permission": required_permission
                }
            )
            
            # For now, allow all access (will be enhanced with proper user mapping)
            # In production, this would validate against user permissions
            return True
            
        except Exception as e:
            logger.error("failed_to_check_node_access", error=str(e))
            return False
    
    async def _create_object_structure(self):
        """Create the OPC UA object structure."""
        # Get objects node
        self.objects_node = self.server.get_objects_node()
        
        # Create Calejo Control folder
        calejo_folder = await self.objects_node.add_folder(
            self.namespace_idx,
            "CalejoControl"
        )
        
        # Create stations and pumps structure
        stations = self.setpoint_manager.discovery.get_stations()
        
        for station_id, station in stations.items():
            
            # Create station folder
            station_folder = await calejo_folder.add_folder(
                self.namespace_idx,
                f"Station_{station_id}"
            )
            
            # Add station info variables
            station_name_var = await station_folder.add_variable(
                self.namespace_idx,
                "StationName",
                station.get('station_name', station_id)
            )
            await station_name_var.set_writable(False)
            
            # Create pumps for this station
            pumps = self.setpoint_manager.discovery.get_pumps(station_id)
            
            for pump in pumps:
                pump_id = pump['pump_id']
                
                # Create pump object
                pump_obj = await station_folder.add_object(
                    self.namespace_idx,
                    f"Pump_{pump_id}"
                )
                
                # Add pump variables
                pump_name_var = await pump_obj.add_variable(
                    self.namespace_idx,
                    "PumpName",
                    pump.get('pump_name', pump_id)
                )
                await pump_name_var.set_writable(False)
                
                control_type_var = await pump_obj.add_variable(
                    self.namespace_idx,
                    "ControlType",
                    pump.get('control_type', 'UNKNOWN')
                )
                await control_type_var.set_writable(False)
                
                # Add setpoint variable (writable for SCADA override)
                setpoint_var = await pump_obj.add_variable(
                    self.namespace_idx,
                    "Setpoint_Hz",
                    0.0
                )
                await setpoint_var.set_writable(True)
                
                # Add safety status variable
                safety_status_var = await pump_obj.add_variable(
                    self.namespace_idx,
                    "SafetyStatus",
                    "normal"
                )
                await safety_status_var.set_writable(False)
                
                # Add timestamp variable
                timestamp_var = await pump_obj.add_variable(
                    self.namespace_idx,
                    "LastUpdate",
                    datetime.now().isoformat()
                )
                await timestamp_var.set_writable(False)
                
                # Store node references
                self.pump_nodes[(station_id, pump_id)] = {
                    'object': pump_obj,
                    'setpoint': setpoint_var,
                    'safety_status': safety_status_var,
                    'timestamp': timestamp_var
                }
            
            self.station_nodes[station_id] = station_folder
        
        # Add server status variables
        server_status_folder = await calejo_folder.add_folder(
            self.namespace_idx,
            "ServerStatus"
        )
        
        server_status_var = await server_status_folder.add_variable(
            self.namespace_idx,
            "Status",
            "running"
        )
        await server_status_var.set_writable(False)
        
        uptime_var = await server_status_folder.add_variable(
            self.namespace_idx,
            "Uptime",
            0
        )
        await uptime_var.set_writable(False)
        
        total_pumps_var = await server_status_folder.add_variable(
            self.namespace_idx,
            "TotalPumps",
            len(self.pump_nodes)
        )
        await total_pumps_var.set_writable(False)
        
        # Add security status variables
        security_status_folder = await calejo_folder.add_folder(
            self.namespace_idx,
            "SecurityStatus"
        )
        
        security_enabled_var = await security_status_folder.add_variable(
            self.namespace_idx,
            "SecurityEnabled",
            self.enable_security
        )
        await security_enabled_var.set_writable(False)
        
        connected_clients_var = await security_status_folder.add_variable(
            self.namespace_idx,
            "ConnectedClients",
            len(self.connected_clients)
        )
        await connected_clients_var.set_writable(False)
        
        last_security_event_var = await security_status_folder.add_variable(
            self.namespace_idx,
            "LastSecurityEvent",
            "server_started"
        )
        await last_security_event_var.set_writable(False)
    
    async def _update_setpoints_loop(self):
        """Background task to update setpoints periodically."""
        while True:
            try:
                await self._update_setpoints()
                await asyncio.sleep(5)  # Update every 5 seconds
            except Exception as e:
                logger.error("failed_to_update_setpoints", error=str(e))
                await asyncio.sleep(10)  # Wait longer on error
    
    async def _update_setpoints(self):
        """Update all setpoint values in OPC UA server."""
        for (station_id, pump_id), nodes in self.pump_nodes.items():
            try:
                # Get current setpoint
                setpoint = self.setpoint_manager.get_current_setpoint(station_id, pump_id)
                
                if setpoint is not None:
                    # Update setpoint variable
                    await nodes['setpoint'].write_value(float(setpoint))
                    
                    # Update safety status
                    safety_status = "normal"
                    if self.setpoint_manager.emergency_stop_manager.is_emergency_stop_active(station_id, pump_id):
                        safety_status = "emergency_stop"
                    elif self.setpoint_manager.watchdog.is_failsafe_active(station_id, pump_id):
                        safety_status = "failsafe"
                    
                    await nodes['safety_status'].write_value(safety_status)
                    
                    # Update timestamp
                    await nodes['timestamp'].write_value(datetime.now().isoformat())
                    
            except Exception as e:
                logger.error(
                    "failed_to_update_pump_setpoint",
                    station_id=station_id,
                    pump_id=pump_id,
                    error=str(e)
                )
    
    def get_security_status(self) -> Dict[str, Any]:
        """Get current security status of OPC UA server."""
        return {
            "security_enabled": self.enable_security,
            "connected_clients": len(self.connected_clients),
            "certificate_configured": bool(self.certificate_path and self.private_key_path),
            "client_details": [
                {
                    "client_id": client_id,
                    "connected_at": info['connected_at'].isoformat(),
                    "endpoint": info['endpoint'],
                    "user_identity": str(info['user_identity']) if info['user_identity'] else "anonymous",
                    "security_policy": str(info['security_policy'])
                }
                for client_id, info in self.connected_clients.items()
            ]
        }