"""
Port Manager for VPN Server
Handles port allocation, testing, and management
"""

import socket
import asyncio
import logging
from typing import List, Optional, Tuple
from contextlib import closing

logger = logging.getLogger(__name__)

class PortManager:
    # Common VPN ports to try
    DEFAULT_VPN_PORTS = [
        443,    # HTTPS
        8388,   # Shadowsocks default
        8443,   # Alternative HTTPS
        1194,   # OpenVPN default
        1984,   # Outline default
        8000,   # Alternative
        8080    # Alternative HTTP
    ]

    def __init__(self):
        self.bound_ports: List[int] = []
        self.reserved_ports: List[int] = []

    async def find_available_port(self, preferred_port: int,
                                fallback_ports: List[int] = None,
                                bind_address: str = '0.0.0.0') -> Tuple[int, bool]:
        """
        Find an available port, starting with preferred_port.
        Returns: (port_number, is_preferred_port)
        """
        # Try preferred port first
        if await self._test_port(preferred_port, bind_address):
            return preferred_port, True

        # Try fallback ports
        ports_to_try = (fallback_ports or []) + self.DEFAULT_VPN_PORTS
        for port in ports_to_try:
            if port != preferred_port and await self._test_port(port, bind_address):
                return port, False

        # If no predefined ports work, scan for any available port
        port = await self._scan_for_available_port(bind_address)
        return port, False

    async def _test_port(self, port: int, bind_address: str) -> bool:
        """Test if a port is available for both TCP and UDP"""
        if port in self.bound_ports or port in self.reserved_ports:
            return False

        try:
            # Test TCP
            tcp_sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
            tcp_sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
            tcp_sock.bind((bind_address, port))
            tcp_sock.close()

            # Test UDP
            udp_sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
            udp_sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
            udp_sock.bind((bind_address, port))
            udp_sock.close()

            return True

        except OSError:
            return False

    async def _scan_for_available_port(self, bind_address: str,
                                     start_port: int = 10000,
                                     end_port: int = 65535) -> int:
        """Scan for any available port in the given range"""
        for port in range(start_port, end_port):
            if await self._test_port(port, bind_address):
                return port
        raise RuntimeError("No available ports found")

    async def reserve_port(self, port: int):
        """Reserve a port for future use"""
        if port not in self.bound_ports and port not in self.reserved_ports:
            self.reserved_ports.append(port)

    async def release_port(self, port: int):
        """Release a reserved or bound port"""
        if port in self.bound_ports:
            self.bound_ports.remove(port)
        if port in self.reserved_ports:
            self.reserved_ports.remove(port)

    async def bind_port(self, port: int, bind_address: str = '0.0.0.0') -> bool:
        """
        Attempt to bind to a port and mark it as bound if successful
        Returns True if binding was successful
        """
        if await self._test_port(port, bind_address):
            self.bound_ports.append(port)
            if port in self.reserved_ports:
                self.reserved_ports.remove(port)
            return True
        return False

    def get_bound_ports(self) -> List[int]:
        """Get list of currently bound ports"""
        return self.bound_ports.copy()

    def get_reserved_ports(self) -> List[int]:
        """Get list of currently reserved ports"""
        return self.reserved_ports.copy()