#!/usr/bin/env python
"""
core-daemon: the CORE daemon is a server process that receives CORE API
messages and instantiates emulated nodes and networks within the kernel. Various
message handlers are defined and some support for sending messages.
"""

import argparse
import ConfigParser
import logging
import sys
import threading
import time

from core import load_logging_config
from core import constants
from core import enumerations
from core.corehandlers import CoreHandler
from core.coreserver import CoreServer
from core.grpc.server import CoreGrpcServer
from core.misc.utils import close_onexec

load_logging_config()


def banner():
    """
    Output the program banner printed to the terminal or log file.

    :return: nothing
    """
    logging.info("CORE daemon v.%s started %s", constants.COREDPY_VERSION, time.ctime())


def cored(cfg):
    """
    Start the CoreServer object and enter the server loop.

    :param dict cfg: core configuration
    :param bool use_ovs: flag to determine if ovs nodes should be used
    :return: nothing
    """
    host = cfg["listenaddr"]
    port = int(cfg["port"])
    if host == "" or host is None:
        host = "localhost"

    try:
        server = CoreServer((host, port), CoreHandler, cfg)
        if cfg["ovs"] == "True":
            from core.netns.openvswitch import OVS_NODES
            server.coreemu.update_nodes(OVS_NODES)
    except:
        logging.exception("error starting main server on:  %s:%s", host, port)
        sys.exit(1)

    # initialize grpc api
    if cfg["grpc"] == "True":
        grpc_server = CoreGrpcServer(server.coreemu)
        grpc_thread = threading.Thread(target=grpc_server.listen)
        grpc_thread.daemon = True
        grpc_thread.start()

    close_onexec(server.fileno())
    logging.info("server started, listening on: %s:%s", host, port)
    server.serve_forever()


def get_merged_config(filename):
    """
    Return a configuration after merging config file and command-line arguments.

    :param str filename: file name to merge configuration settings with
    :return: merged configuration
    :rtype: dict
    """
    # these are the defaults used in the config file
    defaults = {
        "port": "%d" % enumerations.CORE_API_PORT,
        "listenaddr": "localhost",
        "xmlfilever": "1.0",
        "numthreads": "1",
    }

    parser = argparse.ArgumentParser(
        description="CORE daemon v.%s instantiates Linux network namespace nodes." % constants.COREDPY_VERSION)
    parser.add_argument("-f", "--configfile", dest="configfile",
                        help="read config from specified file; default = %s" % filename)
    parser.add_argument("-p", "--port", dest="port", type=int,
                        help="port number to listen on; default = %s" % defaults["port"])
    parser.add_argument("-n", "--numthreads", dest="numthreads", type=int,
                        help="number of server threads; default = %s" % defaults["numthreads"])
    parser.add_argument("--ovs", action="store_true", help="enable experimental ovs mode, default is false")
    parser.add_argument("--grpc", action="store_true", help="enable grpc api, default is false")

    # parse command line options
    args = parser.parse_args()

    # read the config file
    if args.configfile is not None:
        filename = args.configfile
    del args.configfile
    cfg = ConfigParser.SafeConfigParser(defaults)
    cfg.read(filename)

    section = "core-daemon"
    if not cfg.has_section(section):
        cfg.add_section(section)

    # merge command line with config file
    for opt in args.__dict__:
        val = args.__dict__[opt]
        if val is not None:
            cfg.set(section, opt, str(val))

    return dict(cfg.items(section))


def main():
    """
    Main program startup.

    :return: nothing
    """
    # get a configuration merged from config file and command-line arguments
    cfg = get_merged_config("%s/core.conf" % constants.CORE_CONF_DIR)
    banner()

    try:
        cored(cfg)
    except KeyboardInterrupt:
        logging.info("keyboard interrupt, stopping core daemon")


if __name__ == "__main__":
    main()