#!/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 ConfigParser
import logging
import optparse
import sys
import threading
import time

from core import constants
from core import enumerations
from core import load_logging_config
from core.corehandlers import CoreHandler, CoreUdpHandler
from core.coreserver import CoreServer, CoreUdpServer
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 start_udp(mainserver, server_address):
    """
    Start a thread running a UDP server on the same host,port for
        connectionless requests.

    :param CoreServer mainserver: main core tcp server to piggy back off of
    :param server_address:
    :return: CoreUdpServer
    """
    mainserver.udpserver = CoreUdpServer(server_address, CoreUdpHandler, mainserver)
    mainserver.udpthread = threading.Thread(target=mainserver.udpserver.start)
    mainserver.udpthread.daemon = True
    mainserver.udpthread.start()


def cored(cfg, use_ovs):
    """
    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:
        address = (host, port)
        server = CoreServer(address, CoreHandler, cfg)
        if use_ovs:
            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)

    # start udp server
    start_udp(server, address)

    # close handlers
    close_onexec(server.fileno())

    logging.info("tcp/udp servers 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",
    }

    usagestr = "usage: %prog [-h] [options] [args]\n\n" + \
               "CORE daemon v.%s instantiates Linux network namespace " \
               "nodes." % constants.COREDPY_VERSION
    parser = optparse.OptionParser(usage=usagestr)
    parser.add_option("-f", "--configfile", dest="configfile", type="string",
                      help="read config from specified file; default = %s" % filename)
    parser.add_option("-p", "--port", dest="port", type=int,
                      help="port number to listen on; default = %s" % defaults["port"])
    parser.add_option("-t", "--numthreads", dest="numthreads", type=int,
                      help="number of server threads; default = %s" % defaults["numthreads"])

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

    # read the config file
    if options.configfile is not None:
        filename = options.configfile
    del options.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 options.__dict__:
        val = options.__dict__[opt]
        if val is not None:
            cfg.set(section, opt, val.__str__())

    return dict(cfg.items(section)), args


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

    :return: nothing
    """
    # get a configuration merged from config file and command-line arguments
    cfg, args = get_merged_config("%s/core.conf" % constants.CORE_CONF_DIR)
    for a in args:
        logging.error("ignoring command line argument: %s", a)

    banner()

    # check if ovs flag was provided
    use_ovs = len(sys.argv) == 2 and sys.argv[1] == "ovs"

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

    sys.exit(0)


if __name__ == "__main__":
    main()