"""Live service monitor — like `avahi-browse` without -t.

Prints events as they happen:
    +  service appeared
    =  service appeared and was resolved (address:port)
    -  service disappeared

With no --type it browses the DNS-SD meta-service
(`_services._dns-sd._udp.local.`) to discover types dynamically and attaches a
browser to each — the equivalent of `avahi-browse -a`.
"""
import time

from zeroconf import Zeroconf, ServiceBrowser, ServiceListener


class _EventListener(ServiceListener):
    def __init__(self, resolve: bool = True) -> None:
        self.resolve = resolve

    def add_service(self, zc: Zeroconf, type_: str, name: str) -> None:  # noqa: N802
        line = f"+ {type_:<30} {name}"
        if self.resolve:
            info = zc.get_service_info(type_, name, timeout=1500)
            if info:
                addrs = ", ".join(info.parsed_addresses() or []) or "-"
                line = f"= {type_:<30} {name}  {addrs}:{info.port}"
        print(line, flush=True)

    def update_service(self, zc: Zeroconf, type_: str, name: str) -> None:  # noqa: N802
        return

    def remove_service(self, zc: Zeroconf, type_: str, name: str) -> None:  # noqa: N802
        print(f"- {type_:<30} {name}", flush=True)


class _TypeSpawner(ServiceListener):
    """On discovering a new service TYPE, attach a browser for it."""

    def __init__(self, zc: Zeroconf, svc_listener: ServiceListener) -> None:
        self.zc = zc
        self.svc_listener = svc_listener
        self.browsers: dict[str, ServiceBrowser] = {}

    def add_service(self, zc: Zeroconf, type_: str, name: str) -> None:  # noqa: N802
        # For the meta-service, `name` is the discovered type (e.g. _http._tcp.local.)
        if name not in self.browsers:
            self.browsers[name] = ServiceBrowser(zc, name, self.svc_listener)

    def update_service(self, *a) -> None:  # noqa: N802
        return

    def remove_service(self, *a) -> None:  # noqa: N802
        return


def watch(service_type: str | None = None, resolve: bool = True) -> None:
    zc = Zeroconf()
    svc = _EventListener(resolve=resolve)
    try:
        if service_type:
            ServiceBrowser(zc, service_type, svc)
        else:
            ServiceBrowser(zc, "_services._dns-sd._udp.local.",
                           _TypeSpawner(zc, svc))
        print("[mdns] watching — Ctrl+C to stop", flush=True)
        while True:
            time.sleep(1)
    except KeyboardInterrupt:
        pass
    finally:
        zc.close()