"""DNS update helper and thread for heartbeat daemon."""
from __future__ import annotations
import threading
import subprocess
from subprocess import Popen, PIPE, STDOUT
from typing import Optional


def create_nsupdate_payload(hostname: str, newip: str, dyndomain: str, dnsttl: str = "5") -> str:
    D = {"domain": dyndomain, "fqdn": f"{hostname}.dy.{dyndomain}", "dnsttl": dnsttl, "newip": newip, "ts": __import__("time").strftime("%Y-%m-%d.%H:%M:%S", __import__("time").gmtime())}
    if ":" in newip:
        nsup = (
            """update delete %(fqdn)s AAAA
update add %(fqdn)s %(dnsttl)s AAAA %(newip)s
update delete %(fqdn)s TXT
update add %(fqdn)s %(dnsttl)s TXT "Created: %(ts)s"
send
answer

""" % D
        )
    else:
        nsup = (
            """update delete %(fqdn)s A
update add %(fqdn)s %(dnsttl)s A %(newip)s
update delete %(fqdn)s TXT
update add %(fqdn)s %(dnsttl)s TXT "Created: %(ts)s"
send
answer

""" % D
        )
    return nsup


def nsupdate(hostname: str, newip: str, dyndomain: str, nsupdate_bin: str = "/usr/local/bin/nsupdate", rndc_key: str = "/etc/dhcpc/rndc-key") -> Optional[str]:
    """Perform DNS update via nsupdate command.

    Returns None on success, else returns combined stdout/stderr as a string.
    """
    nsup = create_nsupdate_payload(hostname, newip, dyndomain)
    cmd = [nsupdate_bin, "-k", rndc_key, "-v"]
    try:
        p = Popen(cmd, shell=False, bufsize=0, stdin=PIPE, stdout=PIPE, stderr=STDOUT)
    except OSError as e:
        return f"nsupdate: execution failed: {e}"
    except Exception as e:
        return f"nsupdate: some error occured: {e}"

    (output, err) = p.communicate(nsup.encode())
    out = output.decode() if output else ""
    if out.find("status: NOERROR") >= 0:
        return None
    return out


def dnsupdatethread(hbdclass, cfg: dict, log: Optional[callable] = None, email: Optional[callable] = None):
    """Thread target: process dns update queue from hbdclass.Host.dnsQ.

    hbdclass: module with Host class that exposes dnsQ queue
    cfg: configuration mapping with 'dyndomains' and 'nsupdate_bin'
    log: callable(host, message)
    email: callable(subject, message)
    """
    while True:
        name, addr = hbdclass.Host.dnsQ.get()
        m = f"changed address to {addr}"
        for dyndomain in cfg.get("dyndomains", []):
            err = nsupdate(name, addr, dyndomain, nsupdate_bin=cfg.get("nsupdate_bin", "/usr/local/bin/nsupdate"))
            if err:
                m += f", DNS update failed: {err}"
                if email:
                    try:
                        email("error: nsupdate failed", f"{name}.dy.{dyndomain}: {m}")
                    except Exception:
                        pass
            else:
                m += ", DNS updated."
        hbdclass.Host.dnsQ.task_done()
        if log:
            try:
                log(name, m)
            except Exception:
                pass


def start_dns_thread(hbdclass, cfg: dict, log: Optional[callable] = None, email: Optional[callable] = None) -> threading.Thread:
    t = threading.Thread(target=dnsupdatethread, args=(hbdclass, cfg, log, email))
    t.daemon = True
    t.start()
    return t