#! /usr/bin/env python

"""A front-end interface to the pyzor daemon."""

import os
import sys
import optparse
import traceback
import ConfigParser

import pyzor.config
import pyzor.server
import pyzor.engines

def detach(stdout="/dev/null", stderr=None, stdin="/dev/null", pidfile=None):
    """This forks the current process into a daemon.

    The stdin, stdout, and stderr arguments are file names that
    will be opened and be used to replace the standard file descriptors
    in sys.stdin, sys.stdout, and sys.stderr.
    These arguments are optional and default to /dev/null.
    Note that stderr is opened unbuffered, so if it shares a file with
    stdout then interleaved output may not appear in the order that you
    expect."""
    # Do first fork.
    try:
        pid = os.fork()
        if pid > 0:
            # Exit first parent.
            sys.exit(0)
    except OSError as err:
        print >> sys.stderr, "Fork #1 failed: (%d) %s" % \
              (err.errno, err.strerror)
        sys.exit(1)

    # Decouple from parent environment.
    os.chdir("/")
    os.umask(0)
    os.setsid()

    # Do second fork.
    try:
        pid = os.fork()
        if pid > 0:
            # Exit second parent.
            sys.exit(0)
    except OSError as err:
        print >> sys.stderr, "Fork #2 failed: (%d) %s" % \
              (err.errno, err.strerror)
        sys.exit(1)

    # Open file descriptors and print start message.
    if not stderr:
        stderr = stdout
    stdi = open(stdin, "r")
    stdo = open(stdout, "a+")
    stde = open(stderr, "a+", 0)
    pid = str(os.getpid())
    if pidfile:
        open(pidfile, "w+").write("%s\n" % pid)

    # Redirect standard file descriptors.
    os.dup2(stdi.fileno(), sys.stdin.fileno())
    os.dup2(stdo.fileno(), sys.stdout.fileno())
    os.dup2(stde.fileno(), sys.stderr.fileno())


def load_configuration():
    """Load the configuration for the server.

    The configuration comes from three sources: the default values, the
    configuration file, and command-line options."""
    # Work out the default directory for configuration files.
    # If $HOME is defined, then use $HOME/.pyzor, otherwise use /etc/pyzor.
    userhome = os.getenv("HOME")
    if userhome:
        homedir = os.path.join(userhome, '.pyzor')
    else:
        homedir = os.path.join("/etc", "pyzor")

    # Configuration defaults.  The configuration file overrides these, and
    # then the command-line options override those.
    defaults = {
        "Port" : "24441",
        "ListenAddress" : "0.0.0.0",

        "Engine" : "gdbm",
        "DigestDB" : "pyzord.db",
        "CleanupAge" : str(60 * 60 * 24 * 30 * 4),  # approximately 4 months

        "Threads": "False",
        "MaxThreads": "0",
        "Processes": "False",
        "MaxProcesses": "40",
        "DBConnections": "0",
        "Gevent": "False",

        "PasswdFile" : "pyzord.passwd",
        "AccessFile" : "pyzord.access",
        "LogFile" : "",
        "UsageLogFile": "",
        "PidFile": "pyzord.pid"
    }

    # Process any command line options.
    description = "Listen for and process incoming Pyzor connections."
    opt = optparse.OptionParser(description=description)
    opt.add_option("-n", "--nice", dest="nice", type="int",
                   help="'nice' level", default=0)
    opt.add_option("-d", "--debug", action="store_true", default=False,
                   dest="debug", help="enable debugging output")
    opt.add_option("--homedir", action="store", default=homedir,
                   dest="homedir", help="configuration directory")
    opt.add_option("-a", "--address", action="store", default=None,
                   dest="ListenAddress", help="listen on this IP")
    opt.add_option("-p", "--port", action="store", type="int", default=None,
                   dest="Port", help="listen on this port")
    opt.add_option("-e", "--database-engine", action="store", default=None,
                   dest="Engine", help="select database backend")
    opt.add_option("--dsn", action="store", default=None, dest="DigestDB",
                   help="data source name (filename for gdbm, host,user,"
                   "password,database,table for MySQL)")
    opt.add_option("--gevent", action="store", default=None, dest="Gevent",
                   help="set to true to use the gevent library")
    opt.add_option("--threads", action="store", default=None, dest="Threads",
                   help="set to true if multi-threading should be used"
                   " (this may not apply to all engines)")
    opt.add_option("--max-threads", action="store", default=None, type="int",
                   dest="MaxThreads", help="the maximum number of concurrent "
                   "threads (defaults to 0 which is unlimited)")
    opt.add_option("--processes", action="store", default=None,
                   dest="Processes", help="set to true if multi-processing "
                   "should be used (this may not apply to all engines)")
    opt.add_option("--max-processes", action="store", default=None, type="int",
                   dest="MaxProcesses", help="the maximum number of concurrent "
                   "processes (defaults to 40)")
    opt.add_option("--db-connections", action="store", default=None, type="int",
                   dest="DBConnections", help="the number of db connections "
                   "that will be kept by the server. This only applies if "
                   "threads are used. Defaults to 0 which means a new "
                   "connection is used for every thread. (this may not apply "
                   "all engines)")
    opt.add_option("--password-file", action="store", default=None,
                   dest="PasswdFile", help="name of password file")
    opt.add_option("--access-file", action="store", default=None,
                   dest="AccessFile", help="name of ACL file")
    opt.add_option("--cleanup-age", action="store", default=None,
                   dest="CleanupAge",
                   help="time before digests expire (in seconds)")
    opt.add_option("--log-file", action="store", default=None,
                   dest="LogFile", help="name of the log file")
    opt.add_option("--usage-log-file", action="store", default=None,
                   dest="UsageLogFile", help="name of the usage log file")
    opt.add_option("--pid-file", action="store", default=None,
                   dest="PidFile", help="save the pid in this file after the "
                   "server is daemonized")
    opt.add_option("--detach", action="store", default=None,
                   dest="detach", help="daemonizes the server and redirects "
                   "any output to the specified file")
    opt.add_option("-V", "--version", action="store_true", default=False,
                   dest="version", help="print version and exit")
    options, args = opt.parse_args()

    if options.version:
        print "%s %s" % (sys.argv[0], pyzor.__version__)
        sys.exit(0)

    if len(args):
        opt.print_help()
        sys.exit()
    os.nice(options.nice)

    # Create the configuration directory if it doesn't already exist.
    if not os.path.exists(options.homedir):
        os.mkdir(options.homedir)

    # Load the configuration.
    config = ConfigParser.ConfigParser()
    # Set the defaults.
    config.add_section("server")
    for key, value in defaults.iteritems():
        config.set("server", key, value)
    # Override with the configuration.
    config.read(os.path.join(options.homedir, "config"))
    # Override with the command-line options.
    for key in defaults:
        value = getattr(options, key)
        if value is not None:
            config.set("server", key, str(value))
    return config, options


def main():
    """Run the pyzor daemon."""
    # Set umask - this restricts this process from granting any world access
    # to files/directories created by this process.
    os.umask(0077)

    config, options = load_configuration()

    homefiles = ["LogFile", "UsageLogFile", "PasswdFile", "AccessFile",
                 "PidFile"]

    engine = config.get("server", "Engine")
    database_classes = pyzor.engines.database_classes[engine]
    use_gevent = config.get("server", "Gevent").lower() == "true"
    use_threads = config.get("server", "Threads").lower() == "true"
    use_processes = config.get("server", "Processes").lower() == "true"

    if use_threads and use_processes:
        print "You cannot use both processes and threads at the same time"
        sys.exit(1)

    # We prefer to use the threaded server, but some database engines
    # cannot handle it.
    if use_threads and database_classes.multi_threaded:
        use_processes = False
        database_class = database_classes.multi_threaded
    elif use_processes and database_classes.multi_processing:
        use_threads = False
        database_class = database_classes.multi_processing
    else:
        use_threads = False
        use_processes = False
        database_class = database_classes.single_threaded

    # If the DSN is a filename, then we make it absolute.
    if database_class.absolute_source:
        homefiles.append("DigestDB")

    pyzor.config.expand_homefiles(homefiles, "server", options.homedir, config)

    logger = pyzor.config.setup_logging("pyzord",
                                        config.get("server", "LogFile"),
                                        options.debug)
    pyzor.config.setup_logging("pyzord-usage",
                               config.get("server", "UsageLogFile"),
                               options.debug)

    db_file = config.get("server", "DigestDB")
    passwd_fn = config.get("server", "PasswdFile")
    access_fn = config.get("server", "AccessFile")
    pidfile_fn = config.get("server", "PidFile")
    address = (config.get("server", "ListenAddress"),
               int(config.get("server", "port")))
    cleanup_age = int(config.get("server", "CleanupAge"))

    if use_gevent:
        # Monkey patch the std libraries with gevent ones
        try:
            import signal
            import gevent
            import gevent.monkey
        except ImportError as e:
            logger.critical("Gevent library not found: %s", e)
            sys.exit(1)
        gevent.monkey.patch_all()
        # The signal method does not get patched in patch_all
        signal.signal = gevent.signal
        # XXX The gevent libary might already be doing this.
        # Enssure that all modules are reloaded so they benefit from
        # the gevent library.
        for module in (os, sys, pyzor, pyzor.server, pyzor.engines):
            reload(module)

    if options.detach:
        detach(stdout=options.detach, pidfile=pidfile_fn)

    if use_threads:
        max_threads = int(config.get("server", "MaxThreads"))
        bound = int(config.get("server", "DBConnections"))

        database = database_class(db_file, "c", cleanup_age, bound)
        if max_threads == 0:
            logger.info("Starting multi-threaded pyzord server.")
            server = pyzor.server.ThreadingServer(address, database, passwd_fn,
                                                  access_fn)
        else:
            logger.info("Starting bounded (%s) multi-threaded pyzord server.",
                        max_threads)
            server = pyzor.server.BoundedThreadingServer(address, database,
                                                         passwd_fn, access_fn,
                                                         max_threads)
    elif use_processes:
        max_children = int(config.get("server", "MaxProcesses"))
        database = database_class(db_file, "c", cleanup_age)
        logger.info("Starting bounded (%s) multi-processing pyzord server.",
                    max_children)
        server = pyzor.server.ProcessServer(address, database, passwd_fn, access_fn,
                                            max_children)
    else:
        database = database_class(db_file, "c", cleanup_age)
        logger.info("Starting pyzord server.")
        server = pyzor.server.Server(address, database, passwd_fn, access_fn)

    try:
        server.serve_forever()
    except:
        logger.critical("Failure: %s", traceback.format_exc())
    finally:
        logger.info("Server shutdown.")
        server.server_close()
        if options.detach and os.path.exists(pidfile_fn):
            try:
                os.remove(pidfile_fn)
            except Exception as e:
                logger.warning("Unable to remove pidfile %r: %s",
                               pidfile_fn, e)


if __name__ == "__main__":
    main()
