#!/usr/bin/env python
#
# CORE
# Copyright (c)2010-2013 the Boeing Company.
# See the LICENSE file included in this distribution.
#
# authors: Tom Goff <thomas.goff@boeing.com>
#          Jeff Ahrenholz <jeffrey.m.ahrenholz@boeing.com>
#

"""
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 atexit
import importlib
import optparse
import os
import signal
import socket
import sys
import threading
import time

from core import constants
from core import corehandlers
from core import coreserver
from core import enumerations
from core import logger
from core import services
from core.api import coreapi
from core.corehandlers import CoreDatagramRequestHandler
from core.enumerations import MessageFlags
from core.enumerations import RegisterTlvs
from core.misc import nodemaps
from core.misc import nodeutils
from core.misc.utils import closeonexec
from core.misc.utils import daemonize

DEFAULT_MAXFD = 1024


def startudp(core_server, server_address):
    """
    Start a thread running a UDP server on the same host,port for connectionless requests.

    :param core.coreserver.CoreServer core_server: core server instance
    :param tuple[str, int] server_address: server address
    :return: created core udp server
    :rtype: core.coreserver.CoreUdpServer
    """
    core_server.udpserver = coreserver.CoreUdpServer(server_address, CoreDatagramRequestHandler, core_server)
    core_server.udpthread = threading.Thread(target=core_server.udpserver.start)
    core_server.udpthread.daemon = True
    core_server.udpthread.start()
    return core_server.udpserver


def startaux(core_server, aux_address, aux_handler):
    """
    Start a thread running an auxiliary TCP server on the given address.
    This server will communicate with client requests using a handler
    using the aux_handler class. The aux_handler can provide an alternative
    API to CORE.

    :param core.coreserver.CoreServer core_server: core server instance
    :param tuple[str, int] aux_address: auxiliary server address
    :param str aux_handler: auxiliary handler string to import
    :return: auxiliary server
    """
    handlermodname, dot, handlerclassname = aux_handler.rpartition(".")
    handlermod = importlib.import_module(handlermodname)
    handlerclass = getattr(handlermod, handlerclassname)
    core_server.auxserver = coreserver.CoreAuxServer(aux_address, handlerclass, core_server)
    core_server.auxthread = threading.Thread(target=core_server.auxserver.start)
    core_server.auxthread.daemon = True
    core_server.auxthread.start()
    return core_server.auxserver


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

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


def cored(cfg=None):
    """
    Start the CoreServer object and enter the server loop.

    :param dict cfg: core configuration
    :return: nothing
    """
    host = cfg["listenaddr"]
    port = int(cfg["port"])
    if host == "" or host is None:
        host = "localhost"
    try:
        server = coreserver.CoreServer((host, port), corehandlers.CoreRequestHandler, cfg)
    except:
        logger.exception("error starting main server on:  %s:%s", host, port)
        sys.exit(1)

    closeonexec(server.fileno())
    logger.info("main server started, listening on: %s:%s\n" % (host, port))

    udpserver = startudp(server, (host, port))
    closeonexec(udpserver.fileno())

    auxreqhandler = cfg["aux_request_handler"]
    if auxreqhandler:
        handler, auxport = auxreqhandler.rsplit(":")
        auxserver = startaux(server, (host, int(auxport)), handler)
        closeonexec(auxserver.fileno())

    server.serve_forever()


# TODO: should sessions and the main core daemon both catch at exist to shutdown independently?
def cleanup():
    """
    Runs server shutdown and cleanup when catching an exit signal.

    :return: nothing
    """
    while coreserver.CoreServer.servers:
        server = coreserver.CoreServer.servers.pop()
        server.shutdown()


atexit.register(cleanup)


def sighandler(signum, stackframe):
    """
    Signal handler when different signals are sent.

    :param int signum: singal number sent
    :param stackframe: stack frame sent
    :return: nothing
    """
    logger.error("terminated by signal: %s", signum)
    sys.exit(signum)


signal.signal(signal.SIGHUP, sighandler)
signal.signal(signal.SIGINT, sighandler)
signal.signal(signal.SIGTERM, sighandler)
signal.signal(signal.SIGUSR1, sighandler)
signal.signal(signal.SIGUSR2, sighandler)


def logrotate(stdout, stderr, stdoutmode=0644, stderrmode=0644):
    """
    Log rotation method.

    :param stdout: stdout
    :param stderr: stderr
    :param int stdoutmode: stdout mode
    :param int stderrmode: stderr mode
    :return:
    """

    def reopen(fileno, filename, mode):
        err = 0
        fd = -1
        try:
            fd = os.open(filename,
                         os.O_WRONLY | os.O_CREAT | os.O_APPEND, mode)
            os.dup2(fd, fileno)
        except OSError as e:
            err = e.errno
        finally:
            if fd >= 0:
                os.close(fd)
            return err

    if stdout:
        err = reopen(1, stdout, stdoutmode)
    if stderr:
        if stderr == stdout and not err:
            try:
                os.dup2(1, 2)
            except OSError as e:
                pass
        else:
            reopen(2, stderr, stderrmode)


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",
                "pidfile": "%s/run/core-daemon.pid" % constants.CORE_STATE_DIR,
                "logfile": "%s/log/core-daemon.log" % constants.CORE_STATE_DIR,
                "xmlfilever": "1.0",
                "numthreads": "1",
                "verbose": "False",
                "daemonize": "False",
                "debug": "False",
                "execfile": None,
                "aux_request_handler": None,
                }

    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("-d", "--daemonize", dest="daemonize",
                      action="store_true",
                      help="run in background as daemon; default=%s" % \
                           defaults["daemonize"])
    parser.add_option("-e", "--execute", dest="execfile", type="string",
                      help="execute a Python/XML-based session")
    parser.add_option("-l", "--logfile", dest="logfile", type="string",
                      help="log output to specified file; default = %s" %
                           defaults["logfile"])
    parser.add_option("-p", "--port", dest="port", type=int,
                      help="port number to listen on; default = %s" % \
                           defaults["port"])
    parser.add_option("-i", "--pidfile", dest="pidfile",
                      help="filename to write pid to; default = %s" % \
                           defaults["pidfile"])
    parser.add_option("-t", "--numthreads", dest="numthreads", type=int,
                      help="number of server threads; default = %s" % \
                           defaults["numthreads"])
    parser.add_option("-v", "--verbose", dest="verbose", action="store_true",
                      help="enable verbose logging; default = %s" % \
                           defaults["verbose"])
    parser.add_option("-g", "--debug", dest="debug", action="store_true",
                      help="enable debug logging; default = %s" % \
                           defaults["debug"])

    # 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)
    # gracefully support legacy configs (cored.py/cored now core-daemon)
    if cfg.has_section("cored.py"):
        for name, val in cfg.items("cored.py"):
            if name == "pidfile" or name == "logfile":
                bn = os.path.basename(val).replace("coredpy", "core-daemon")
                val = os.path.join(os.path.dirname(val), bn)
            cfg.set(section, name, val)
    if cfg.has_section("cored"):
        for name, val in cfg.items("cored"):
            if name == "pidfile" or name == "logfile":
                bn = os.path.basename(val).replace("cored", "core-daemon")
                val = os.path.join(os.path.dirname(val), bn)
            cfg.set(section, name, val)

    # 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 exec_file(cfg):
    """
    Send a Register Message to execute a new session based on XML or Python script file.

    :param dict cfg: configuration settings
    :return: 0
    """
    filename = cfg["execfile"]
    logger.info("Telling daemon to execute file: %s...", filename)
    tlvdata = coreapi.CoreRegisterTlv.pack(RegisterTlvs.EXECUTE_SERVER.value, filename)
    msg = coreapi.CoreRegMessage.pack(MessageFlags.ADD.value, tlvdata)
    sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    # TODO: connect address option
    sock.connect(("localhost", int(cfg["port"])))
    sock.sendall(msg)
    return 0


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:
        logger.error("ignoring command line argument: %s", a)

    if cfg["daemonize"] == "True":
        daemonize(rootdir=None, umask=0, close_fds=False,
                  stdin=os.devnull,
                  stdout=cfg["logfile"], stderr=cfg["logfile"],
                  pidfilename=cfg["pidfile"],
                  defaultmaxfd=DEFAULT_MAXFD)
        signal.signal(signal.SIGUSR1, lambda signum, stackframe:
        logrotate(stdout=cfg["logfile"], stderr=cfg["logfile"]))

    banner()
    if cfg["execfile"]:
        cfg["execfile"] = os.path.abspath(cfg["execfile"])
        sys.exit(exec_file(cfg))
    try:
        cored(cfg)
    except KeyboardInterrupt:
        logger.info("keyboard interrupt, stopping core daemon")

    sys.exit(0)


if __name__ == "__main__":
    # configure nodes to use
    node_map = nodemaps.NODES
    if len(sys.argv) == 2 and sys.argv[1] == "ovs":
        from core.netns.openvswitch import OVS_NODES
        node_map.update(OVS_NODES)

    # update with BSD based nodes
    if os.uname()[0] == "FreeBSD":
        from core.bsd.nodes import BSD_NODES
        node_map.update(BSD_NODES)

    nodeutils.set_node_map(node_map)

    # load default services
    services.load()

    main()