import socket
import struct
import asyncio
from config import settings


def check_multicast_reachable(mcast_addr: str = "239.0.0.1", port: int = 9999, timeout: float = 2.0) -> bool:
    try:
        sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
        sock.settimeout(timeout)
        ttl = struct.pack("b", 1)
        sock.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, ttl)

        mreq = struct.pack("4sL", socket.inet_aton(mcast_addr), socket.INADDR_ANY)
        sock.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, mreq)

        sock.sendto(b"ping", (mcast_addr, port))
        try:
            data, addr = sock.recvfrom(1024)
            sock.close()
            return True
        except socket.timeout:
            sock.close()
            return True
    except Exception:
        return False


class MulticastDetector:
    def __init__(self):
        self._multicast_available: bool | None = None

    def is_available(self) -> bool:
        if self._multicast_available is not None:
            return self._multicast_available

        if not settings.multicast_enabled:
            self._multicast_available = False
            return False

        self._multicast_available = check_multicast_reachable()
        return self._multicast_available

    def get_stream_url(self, stream_key: str, node: dict, quality: dict | None = None):
        use_multicast = self.is_available()
        host = node["host"]

        if use_multicast:
            hash_val = abs(hash(stream_key)) % 255
            mcast_addr = f"{settings.multicast_address_base.rsplit('.', 1)[0]}.{hash_val + 1}"
            mcast_port = settings.multicast_port_base + (abs(hash(stream_key)) % 1000)
            return {
                "type": "multicast",
                "url": f"udp://@{mcast_addr}:{mcast_port}",
                "unicast_fallback": f"http://{host}:{node['hls_port']}/{stream_key}/index.m3u8",
            }

        return {
            "type": "hls",
            "url": f"http://{host}:{node['hls_port']}/{stream_key}/index.m3u8",
        }


multicast_detector = MulticastDetector()