import asyncio
import asyncio.subprocess
import socket
import dataclasses

from typing import Tuple
from typing import List
from typing import Optional

import netifaces

from ... import tools
from ... import aiotools
from ... import aioproc

from ...logging import get_logger

from .stun import Stun


# =====
@dataclasses.dataclass(frozen=True)
class _Netcfg:
    nat_type: str = dataclasses.field(default="")
    src_ip: str = dataclasses.field(default="")
    ext_ip: str = dataclasses.field(default="")
    stun_host: str = dataclasses.field(default="")
    stun_port: int = dataclasses.field(default=0)


# =====
class JanusRunner:  # pylint: disable=too-many-instance-attributes
    def __init__(  # pylint: disable=too-many-arguments
        self,
        stun_host: str,
        stun_port: int,
        stun_timeout: float,
        stun_retries: int,
        stun_retries_delay: float,

        check_interval: int,
        check_retries: int,
        check_retries_delay: float,

        cmd: List[str],
        cmd_remove: List[str],
        cmd_append: List[str],
    ) -> None:

        self.__stun = Stun(stun_host, stun_port, stun_timeout, stun_retries, stun_retries_delay)

        self.__check_interval = check_interval
        self.__check_retries = check_retries
        self.__check_retries_delay = check_retries_delay

        self.__cmd = tools.build_cmd(cmd, cmd_remove, cmd_append)

        self.__janus_task: Optional[asyncio.Task] = None
        self.__janus_proc: Optional[asyncio.subprocess.Process] = None  # pylint: disable=no-member

    def run(self) -> None:
        logger = get_logger(0)
        logger.info("Starting Janus Runner ...")
        try:
            aiotools.run(self.__run())
        except (SystemExit, KeyboardInterrupt):
            aiotools.run(self.__stop_janus())
        logger.info("Bye-bye")

    # =====

    async def __run(self) -> None:
        logger = get_logger(0)
        prev_netcfg: Optional[_Netcfg] = None
        while True:
            retry = 0
            netcfg = _Netcfg()
            for retry in range(self.__check_retries):
                netcfg = await self.__get_netcfg()
                if netcfg.ext_ip:
                    break
                await asyncio.sleep(self.__check_retries_delay)
            if retry != 0 and netcfg.ext_ip:
                logger.info("I'm fine, continue working ...")

            if netcfg != prev_netcfg:
                logger.info("Got new %s", netcfg)
                if netcfg.src_ip and netcfg.ext_ip:
                    await self.__stop_janus()
                    await self.__start_janus(netcfg)
                else:
                    logger.error("Empty src_ip or ext_ip; stopping Janus ...")
                    await self.__stop_janus()
                prev_netcfg = netcfg

            await asyncio.sleep(self.__check_interval)

    async def __get_netcfg(self) -> _Netcfg:
        src_ip = (self.__get_default_ip() or "0.0.0.0")
        (stun, (nat_type, ext_ip)) = await self.__get_stun_info(src_ip)
        return _Netcfg(nat_type, src_ip, ext_ip, stun.host, stun.port)

    def __get_default_ip(self) -> str:
        try:
            gws = netifaces.gateways()
            if "default" not in gws:
                raise RuntimeError(f"No default gateway: {gws}")

            iface = ""
            for proto in [socket.AF_INET, socket.AF_INET6]:
                if proto in gws["default"]:
                    iface = gws["default"][proto][1]
                    break
            else:
                raise RuntimeError(f"No iface for the gateway {gws['default']}")

            for addr in netifaces.ifaddresses(iface).get(proto, []):
                return addr["addr"]
        except Exception as err:
            get_logger().error("Can't get default IP: %s", tools.efmt(err))
        return ""

    async def __get_stun_info(self, src_ip: str) -> Tuple[Stun, Tuple[str, str]]:
        try:
            return (self.__stun, (await self.__stun.get_info(src_ip, 0)))
        except Exception as err:
            get_logger().error("Can't get STUN info: %s", tools.efmt(err))
            return (self.__stun, ("", ""))

    # =====

    @aiotools.atomic
    async def __start_janus(self, netcfg: _Netcfg) -> None:
        get_logger(0).info("Starting Janus ...")
        assert not self.__janus_task
        self.__janus_task = asyncio.create_task(self.__janus_task_loop(netcfg))

    @aiotools.atomic
    async def __stop_janus(self) -> None:
        if self.__janus_task:
            get_logger(0).info("Stopping Janus ...")
            self.__janus_task.cancel()
            await asyncio.gather(self.__janus_task, return_exceptions=True)
        await self.__kill_janus_proc()
        self.__janus_task = None

    # =====

    async def __janus_task_loop(self, netcfg: _Netcfg) -> None:  # pylint: disable=too-many-branches
        logger = get_logger(0)
        while True:  # pylint: disable=too-many-nested-blocks
            try:
                await self.__start_janus_proc(netcfg)
                assert self.__janus_proc is not None
                await aioproc.log_stdout_infinite(self.__janus_proc, logger)
                raise RuntimeError("Janus unexpectedly died")
            except asyncio.CancelledError:
                break
            except Exception:
                if self.__janus_proc:
                    logger.exception("Unexpected Janus error: pid=%d", self.__janus_proc.pid)
                else:
                    logger.exception("Can't start Janus")
                await self.__kill_janus_proc()
                await asyncio.sleep(1)

    async def __start_janus_proc(self, netcfg: _Netcfg) -> None:
        assert self.__janus_proc is None
        placeholders = {
            key: str(value)
            for (key, value) in dataclasses.asdict(netcfg).items()
        }
        cmd = [
            part.format(**placeholders)
            for part in self.__cmd
        ]
        self.__janus_proc = await aioproc.run_process(cmd)
        get_logger(0).info("Started Janus pid=%d: %s", self.__janus_proc.pid, cmd)

    async def __kill_janus_proc(self) -> None:
        if self.__janus_proc:
            await aioproc.kill_process(self.__janus_proc, 5, get_logger(0))
        self.__janus_proc = None