import dataclasses
import datetime
import http.client
import io
import logging
import socket
import struct
import threading
import time
from typing import Dict, Tuple

import prometheus_client

from . import Channel, Device, prometheus

logger = logging.getLogger('janet.ssdp')

_MSEARCH = """M-SEARCH * HTTP/1.1
Host: 239.255.255.250:1900
Man: "ssdp:discover"
ST: urn:schemas-sony-com:service:IRCC:1
MX: 3
User-Agent: Linux/5.8.0-40-generic UPnP/1.0 GSSDP/1.2.3

"""

_GROUP = ('239.255.255.250', 1900)


@dataclasses.dataclass
class Service:
    # Unique service name.
    usn: str
    # Service type.
    st: str
    # Location of the service.
    location: str
    # Server identifer, if any.
    server: str

    # Last time the service was seen.
    seen: datetime.datetime

    available: bool


class Discoverer:
    def __init__(self):
        self._services: Dict[Tuple[str, str], Tuple[Device, Service]] = {}
        self._lock = threading.Lock()
        self._listeners = Channel()

    def listen(self, callback):
        self._listeners.listen(callback)

    def _searcher(self, sock: socket.socket):
        while True:
            sock.sendto(_MSEARCH.replace('\n', '\r\n').encode(), _GROUP)
            time.sleep(10 * 60)

    def _reaper(self):
        while True:
            time.sleep(71)
            now = datetime.datetime.now()
            expired = []

            with self._lock:
                for key, (device, service) in self._services.items():
                    age = now - service.seen
                    if age.total_seconds() >= 20 * 60:
                        logger.warning(f'expiring {service} as its {age}s old')
                        expired.append(key)
                        service.available = False
                        self._listeners.put(device, service)

                for key in expired:
                    del self._services[key]

    def _listener(self, sock: socket.socket):
        while True:
            method, headers = self._recv(sock)

            if method == 'HTTP/1.1':
                self._response(headers)
            elif method == 'NOTIFY':
                self._notify(headers)
            elif method == 'M-SEARCH':
                pass
            else:
                logger.info(f'Dropping unhandled method {method}')
                pass

    def run(self):
        threading.Thread(target=self._reaper).start()

        sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM,
                             socket.IPPROTO_UDP)

        threading.Thread(target=self._searcher, args=(sock, )).start()
        threading.Thread(target=self._listener, args=(sock, )).start()

        mcast = socket.socket(socket.AF_INET, socket.SOCK_DGRAM,
                              socket.IPPROTO_UDP)
        mcast.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        mcast.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, 2)
        mcast.bind(('', 1900))
        group = socket.inet_aton(_GROUP[0])
        mreq = struct.pack('4sL', group, socket.INADDR_ANY)
        mcast.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, mreq)

        self._listener(mcast)

    def _response(self, headers):
        logger.debug(f'search response {headers.items()}')
        usn = headers.get('USN', None)
        nt = headers.get('ST', None)
        location = headers.get('LOCATION', None)
        server = headers.get('SERVER', '')
        self._alive(usn, nt, location, server)

    def _notify(self, headers: http.client.HTTPMessage):
        logger.debug(f'notify {headers.items()}')
        usn = headers.get('USN', '')
        if not usn:
            logger.warning('Message has no USN, dropping')
            return
        nts = headers.get('NTS', '')
        if not nts:
            logger.warning('Message has no NTS, dropping')
            return
        nt = headers.get('NT', '')

        if nts == 'ssdp:byebye':
            self._byebye(usn, nt)
        elif nts == 'ssdp:alive':
            location = headers.get('LOCATION', '')
            server = headers.get('SERVER', '')
            self._alive(usn, nt, location, server)
        else:
            logger.warning(f'Unrecognised NTS {nts}, dropping')

    def _byebye(self, usn: str, nt: str):
        with self._lock:
            key = (usn, nt)

            if key in self._services:
                device, service = self._services[key]
                logger.warning(f'byebye {service}')
                service.available = False
                self._listeners.put(device, service)

                del self._services[key]

    def _alive(self, usn: str, st: str, location: str, server: str = ''):
        if not st or not location:
            logger.warning('Message is missing ST/NT or LOCATION, dropping')
            return

        with self._lock:
            key = (usn, st)
            if key not in self._services:
                device = Device(identifiers=[f'ssdp_{usn}'],
                                name=st,
                                manufacturer=server,
                                kind='ssdp',
                                available=True)
                service = Service(usn=usn,
                                  st=st,
                                  location=location,
                                  server=server,
                                  seen=datetime.datetime.now(),
                                  available=True)
                self._services[key] = (device, service)
                logger.warning(f'discovered {service}')
            else:
                device, service = self._services[key]

            service.server = service.server or server
            service.seen = datetime.datetime.now()
            self._listeners.put(device, service)

    def _recv(self, sock) -> Tuple[str, http.client.HTTPMessage]:
        got = sock.recv(2048)
        msg = io.BytesIO(got)
        top = msg.readline().decode().rstrip().split()
        headers = http.client.parse_headers(msg)
        if len(top) != 3:
            logger.warning(f'Invalid HTTP first line {top}')
            return '', headers
        method, _, _ = top
        return method, headers


def main():
    prometheus_client.start_http_server(9876)

    ssdp = Discoverer()
    prom = prometheus.Client()
    ssdp._listeners.listen(prom.publish)

    def log(service):
        print(f'Notify {service}')

    ssdp._listeners.listen(log)
    ssdp.run()


if __name__ == '__main__':
    main()