"""Client VPN Profile management service for user/technician VPN connections."""

from datetime import datetime
from typing import Optional
from sqlalchemy.orm import Session

from ..models.client_vpn_profile import ClientVPNProfile, ClientVPNProfileStatus
from ..models.vpn_server import VPNServer
from ..models.user import User
from ..models.gateway import Gateway
from ..models.access import UserGatewayAccess
from ..models.certificate_authority import CertificateAuthority
from .certificate_service import CertificateService
from ..config import get_settings
import ipaddress

settings = get_settings()


class ClientVPNProfileService:
    """Service for managing VPN profiles for users/technicians."""

    def __init__(self, db: Session):
        self.db = db
        self.cert_service = CertificateService(db)

    def get_or_create_profile(self, user: User) -> Optional[ClientVPNProfile]:
        """Get existing profile for user or create a new one."""
        # Check if user already has a profile
        if user.client_vpn_profile and user.client_vpn_profile.is_ready:
            return user.client_vpn_profile

        # Find active VPN server (prefer primary, then any active)
        server = self.db.query(VPNServer).filter(
            VPNServer.is_active == True,
            VPNServer.is_primary == True
        ).first()

        if not server:
            server = self.db.query(VPNServer).filter(
                VPNServer.is_active == True
            ).first()

        if not server:
            return None

        if not server.certificate_authority or not server.certificate_authority.is_ready:
            return None

        # Create new profile
        return self.create_profile(user, server.id)

    def create_profile(
        self,
        user: User,
        vpn_server_id: int
    ) -> ClientVPNProfile:
        """Create a new VPN profile for a user."""

        # Get VPN server
        server = self.db.query(VPNServer).filter(
            VPNServer.id == vpn_server_id
        ).first()

        if not server:
            raise ValueError(f"VPN Server with id {vpn_server_id} not found")

        if not server.certificate_authority.is_ready:
            raise ValueError("CA is not ready (DH parameters may still be generating)")

        # Generate unique common name
        cert_cn = f"client-{user.username}-{user.id}"

        # Check if profile already exists
        existing = self.db.query(ClientVPNProfile).filter(
            ClientVPNProfile.user_id == user.id
        ).first()

        if existing:
            # Delete old profile and create new
            self.db.delete(existing)
            self.db.commit()

        # Create profile
        profile = ClientVPNProfile(
            user_id=user.id,
            vpn_server_id=vpn_server_id,
            ca_id=server.ca_id,
            cert_cn=cert_cn,
            status=ClientVPNProfileStatus.PENDING
        )

        self.db.add(profile)
        self.db.commit()
        self.db.refresh(profile)

        # Generate client certificate
        self._generate_client_cert(profile)

        return profile

    def _generate_client_cert(self, profile: ClientVPNProfile):
        """Generate client certificate for profile."""
        ca = profile.certificate_authority

        cert_data = self.cert_service.generate_client_certificate(
            ca=ca,
            common_name=profile.cert_cn
        )

        profile.client_cert = cert_data["cert"]
        profile.client_key = cert_data["key"]
        profile.valid_from = cert_data["valid_from"]
        profile.valid_until = cert_data["valid_until"]
        profile.status = ClientVPNProfileStatus.ACTIVE

        self.db.commit()

    def generate_client_config(self, profile: ClientVPNProfile, split_tunnel: bool = True) -> str:
        """Generate OpenVPN client configuration (.ovpn) for a profile.

        Args:
            profile: The client VPN profile
            split_tunnel: If True, only VPN traffic goes through tunnel (default).
                         If False, all traffic goes through VPN (no internet).
        """

        if not profile.is_ready:
            raise ValueError("Profile is not ready")

        server = profile.vpn_server
        ca = profile.certificate_authority

        config_lines = [
            "# OpenVPN Client Configuration",
            f"# User: {profile.user.username}",
            f"# Server: {server.name}",
            f"# Generated: {datetime.utcnow().isoformat()}",
            f"# Split Tunneling: {'Enabled' if split_tunnel else 'Disabled'}",
            "",
            "client",
            "dev tun",
            f"proto {server.protocol.value}",
            f"remote {server.hostname} {server.port}",
            "",
            "resolv-retry infinite",
            "nobind",
            "persist-key",
            "persist-tun",
            "",
            "remote-cert-tls server",
            f"cipher {server.cipher.value}",
            f"auth {server.auth.value}",
            "",
            "verb 3",
            "",
        ]

        # Split Tunneling Configuration
        if split_tunnel:
            config_lines.extend([
                "# Split Tunneling - Only VPN traffic through tunnel",
                "# Ignore any redirect-gateway push from server",
                "pull-filter ignore \"redirect-gateway\"",
                "",
            ])

            # Add route for VPN network
            vpn_network = server.vpn_network
            vpn_netmask = server.vpn_netmask
            config_lines.append(f"# Route for VPN network")
            config_lines.append(f"route {vpn_network} {vpn_netmask}")
            config_lines.append("")

            # Add routes for gateway subnets the user has access to
            routes_added = self._get_gateway_routes(profile.user)
            if routes_added:
                config_lines.append("# Routes for accessible gateway networks")
                for route in routes_added:
                    config_lines.append(f"route {route['network']} {route['netmask']}  # {route['name']}")
                config_lines.append("")

        # Add CA certificate
        config_lines.extend([
            "<ca>",
            ca.ca_cert.strip(),
            "</ca>",
            "",
        ])

        # Add client certificate
        config_lines.extend([
            "<cert>",
            profile.client_cert.strip(),
            "</cert>",
            "",
        ])

        # Add client key
        config_lines.extend([
            "<key>",
            profile.client_key.strip(),
            "</key>",
            "",
        ])

        # Add TLS-Auth key if enabled
        if server.tls_auth_enabled and server.ta_key:
            config_lines.extend([
                "key-direction 1",
                "<tls-auth>",
                server.ta_key.strip(),
                "</tls-auth>",
            ])

        return "\n".join(config_lines)

    def _get_gateway_routes(self, user: User) -> list[dict]:
        """Get routes for all gateway subnets the user has access to."""
        routes = []
        seen_networks = set()

        # Get gateways the user has access to
        if user.is_admin:
            # Admins have access to all gateways in their tenant
            gateways = self.db.query(Gateway).filter(
                Gateway.tenant_id == user.tenant_id
            ).all()
        else:
            # Regular users - check access table
            access_entries = self.db.query(UserGatewayAccess).filter(
                UserGatewayAccess.user_id == user.id
            ).all()
            gateway_ids = [a.gateway_id for a in access_entries]
            gateways = self.db.query(Gateway).filter(
                Gateway.id.in_(gateway_ids)
            ).all() if gateway_ids else []

        for gateway in gateways:
            # Add route for gateway's VPN subnet if defined
            if gateway.vpn_subnet and gateway.vpn_subnet not in seen_networks:
                try:
                    network = ipaddress.ip_network(gateway.vpn_subnet, strict=False)
                    routes.append({
                        "network": str(network.network_address),
                        "netmask": str(network.netmask),
                        "name": gateway.name
                    })
                    seen_networks.add(gateway.vpn_subnet)
                except ValueError:
                    pass  # Invalid subnet, skip

        return routes

    def get_vpn_config_for_user(self, user: User) -> Optional[str]:
        """Get or create VPN config for a user."""
        profile = self.get_or_create_profile(user)
        if not profile:
            return None

        return self.generate_client_config(profile)

    def revoke_profile(self, profile: ClientVPNProfile, reason: str = "unspecified"):
        """Revoke a user's VPN profile certificate."""
        if profile.client_cert:
            self.cert_service.revoke_certificate(
                ca=profile.certificate_authority,
                cert_pem=profile.client_cert,
                reason=reason
            )

        profile.status = ClientVPNProfileStatus.REVOKED
        profile.is_active = False
        self.db.commit()

    def renew_profile(self, profile: ClientVPNProfile):
        """Renew the certificate for a profile."""
        # Revoke old certificate
        if profile.client_cert:
            self.cert_service.revoke_certificate(
                ca=profile.certificate_authority,
                cert_pem=profile.client_cert,
                reason="superseded"
            )

        # Generate new certificate
        self._generate_client_cert(profile)
        self.db.commit()