#!/usr/bin/env python
import argparse
import enum
import select
import socket
import subprocess
import time
from argparse import ArgumentDefaultsHelpFormatter
from functools import cmp_to_key
from queue import Queue
from threading import Thread
from typing import Dict, Tuple

from core import utils
from core.api.grpc.client import CoreGrpcClient
from core.api.grpc.core_pb2 import NodeType

SDT_HOST = "127.0.0.1"
SDT_PORT = 50000
ROUTE_LAYER = "CORE Route"
DEAD_TIME = 3
ROUTE_TIME = 3
PACKET_CHOICES = ["udp", "tcp", "icmp"]


class RouteEnum(enum.Enum):
    ADD = 0
    DEL = 1


class SdtClient:
    def __init__(self, address: Tuple[str, int]) -> None:
        self.sock = socket.create_connection(address)
        self.links = []
        self.send(f'layer "{ROUTE_LAYER}"')

    def close(self) -> None:
        self.sock.close()

    def send(self, cmd: str) -> None:
        sdt_cmd = f"{cmd}\n".encode()
        self.sock.sendall(sdt_cmd)

    def add_link(self, node1, node2) -> None:
        route_id = f"{node1}-{node2}-r"
        link_id = f"{node1},{node2},{route_id}"
        cmd = f'link {link_id} linkLayer "{ROUTE_LAYER}" line yellow,2'
        self.send(cmd)
        self.links.append(link_id)

    def delete_links(self) -> None:
        for link_id in self.links:
            cmd = f"delete link,{link_id}"
            self.send(cmd)
        self.links.clear()


class RouterMonitor:
    def __init__(self, src_id: str, src: str, dst: str, pkt: str,
                 sdt_host: str, sdt_port: int) -> None:
        self.queue = Queue()
        self.core = CoreGrpcClient()
        self.src_id = src_id
        self.src = src
        self.dst = dst
        self.pkt = pkt
        self.seen = {}
        self.running = False
        self.route_time = None
        self.listeners = []
        self.sdt = SdtClient((sdt_host, sdt_port))
        self.nodes = self.get_nodes()

    def get_nodes(self) -> Dict[str, str]:
        nodes = {}
        with self.core.context_connect():
            response = self.core.get_sessions()
            sessions = response.sessions
            session = None
            if sessions:
                session = sessions[0]
            if not session:
                raise Exception("no current core sessions")
            print("session: ", session.dir)
            response = self.core.get_session(session.id)
            for node in response.session.nodes:
                if node.type != NodeType.DEFAULT:
                    continue
                nodes[node.id] = node.channel
        return nodes

    def start(self) -> None:
        self.running = True
        for node_id, node in self.nodes.items():
            print("listening on node: ", node)
            thread = Thread(target=self.listen, args=(node_id, node), daemon=True)
            thread.start()
            self.listeners.append(thread)
        self.manage()

    def manage(self) -> None:
        self.route_time = time.monotonic()
        while self.running:
            route_enum, node, seen = self.queue.get()
            if route_enum == RouteEnum.ADD:
                self.seen[node] = seen
            elif node in self.seen:
                del self.seen[node]

            if (time.monotonic() - self.route_time) >= ROUTE_TIME:
                self.manage_routes()
                self.route_time = time.monotonic()

    def route_sort(self, x: Tuple[str, int], y: Tuple[str, int]) -> int:
        x_node = x[0]
        y_node = y[0]
        if x_node == self.src_id:
            return 1
        if y_node == self.src_id:
            return -1
        x_ttl, y_ttl = x[1], y[1]
        return x_ttl - y_ttl

    def manage_routes(self) -> None:
        self.sdt.delete_links()
        if not self.seen:
            return
        values = sorted(self.seen.items(),
                        key=cmp_to_key(self.route_sort),
                        reverse=True)
        print("current route:")
        for index, node_data in enumerate(values):
            next_index = index + 1
            if next_index == len(values):
                break
            next_node_id = values[next_index][0]
            node_id, ttl = node_data
            print(f"{node_id} -> {next_node_id}")
            self.sdt.add_link(node_id, next_node_id)

    def stop(self) -> None:
        self.running = False
        self.sdt.delete_links()
        self.sdt.close()
        for thread in self.listeners:
            thread.join()
        self.listeners.clear()

    def listen(self, node_id, node) -> None:
        cmd = (
            f"tcpdump -lnv src host {self.src} and dst host {self.dst} and {self.pkt}"
        )
        node_cmd = f"vcmd -c {node} -- {cmd}"
        p = subprocess.Popen(node_cmd, shell=True, stdout=subprocess.PIPE,
                             stderr=subprocess.DEVNULL)
        current = time.monotonic()
        try:
            while not p.poll() and self.running:
                ready, _, _ = select.select([p.stdout], [], [], 1)
                if ready:
                    line = p.stdout.readline().strip().decode()
                    if line:
                        line = line.split("ttl", 1)[1]
                        ttl = int(line.split(",", 1)[0])
                        p.stdout.readline()
                        self.queue.put((RouteEnum.ADD, node_id, ttl))
                        current = time.monotonic()
                else:
                    if (time.monotonic() - current) >= DEAD_TIME:
                        self.queue.put((RouteEnum.DEL, node_id, None))
        except Exception as e:
            print(f"listener error: {e}")


def main() -> None:
    if not utils.which("tcpdump", required=False):
        print("core-route-monitor requires tcpdump to be installed")
        return

    parser = argparse.ArgumentParser(
        description="core route monitor",
        formatter_class=ArgumentDefaultsHelpFormatter,
    )
    parser.add_argument("--id", required=True,
                        help="source node id for determining path")
    parser.add_argument("--src", default="10.0.0.20",
                        help="source address for route monitoring")
    parser.add_argument("--dst", default="10.0.2.20",
                        help="destination address for route monitoring")
    parser.add_argument("--pkt", default="icmp", choices=PACKET_CHOICES,
                        help="packet type")
    parser.add_argument("--sdt-host", default=SDT_HOST, help="sdt host address")
    parser.add_argument("--sdt-port", type=int, default=SDT_PORT, help="sdt port")
    args = parser.parse_args()

    monitor = RouterMonitor(
        args.id,
        args.src,
        args.dst,
        args.pkt,
        args.sdt_host,
        args.sdt_port,
    )
    try:
        monitor.start()
    except KeyboardInterrupt:
        monitor.stop()
        print("ending route monitor")


if __name__ == "__main__":
    main()