# -*- test-case-name: twisted.test.test_twistd -*-
# Copyright (c) 2001-2009 Twisted Matrix Laboratories.
# See LICENSE for details.

import os, errno, sys

from twisted.python import log, syslog, logfile
from twisted.python.util import switchUID, uidFromString, gidFromString
from twisted.application import app, service
from twisted import copyright


def _umask(value):
    return int(value, 8)


class ServerOptions(app.ServerOptions):
    synopsis = "Usage: twistd [options]"

    optFlags = [['nodaemon','n',  "don't daemonize, don't use default umask of 0077"],
                ['originalname', None, "Don't try to change the process name"],
                ['syslog', None,   "Log to syslog, not to file"],
                ['euid', '',
                 "Set only effective user-id rather than real user-id. "
                 "(This option has no effect unless the server is running as "
                 "root, in which case it means not to shed all privileges "
                 "after binding ports, retaining the option to regain "
                 "privileges in cases such as spawning processes. "
                 "Use with caution.)"],
               ]

    optParameters = [
                     ['prefix', None,'twisted',
                      "use the given prefix when syslogging"],
                     ['pidfile','','twistd.pid',
                      "Name of the pidfile"],
                     ['chroot', None, None,
                      'Chroot to a supplied directory before running'],
                     ['uid', 'u', None, "The uid to run as.", uidFromString],
                     ['gid', 'g', None, "The gid to run as.", gidFromString],
                     ['umask', None, None,
                      "The (octal) file creation mask to apply.", _umask],
                    ]
    zsh_altArgDescr = {"prefix":"Use the given prefix when syslogging (default: twisted)",
                       "pidfile":"Name of the pidfile (default: twistd.pid)",}
    #zsh_multiUse = ["foo", "bar"]
    #zsh_mutuallyExclusive = [("foo", "bar"), ("bar", "baz")]
    zsh_actions = {"pidfile":'_files -g "*.pid"', "chroot":'_dirs'}
    zsh_actionDescr = {"chroot":"chroot directory"}

    def opt_version(self):
        """Print version information and exit.
        """
        print 'twistd (the Twisted daemon) %s' % copyright.version
        print copyright.copyright
        sys.exit()


    def postOptions(self):
        app.ServerOptions.postOptions(self)
        if self['pidfile']:
            self['pidfile'] = os.path.abspath(self['pidfile'])


def checkPID(pidfile):
    if not pidfile:
        return
    if os.path.exists(pidfile):
        try:
            pid = int(open(pidfile).read())
        except ValueError:
            sys.exit('Pidfile %s contains non-numeric value' % pidfile)
        try:
            os.kill(pid, 0)
        except OSError, why:
            if why[0] == errno.ESRCH:
                # The pid doesnt exists.
                log.msg('Removing stale pidfile %s' % pidfile, isError=True)
                os.remove(pidfile)
            else:
                sys.exit("Can't check status of PID %s from pidfile %s: %s" %
                         (pid, pidfile, why[1]))
        else:
            sys.exit("""\
Another twistd server is running, PID %s\n
This could either be a previously started instance of your application or a
different application entirely. To start a new one, either run it in some other
directory, or use the --pidfile and --logfile parameters to avoid clashes.
""" %  pid)



class UnixAppLogger(app.AppLogger):
    """
    A logger able to log to syslog, to files, and to stdout.

    @ivar _syslog: A flag indicating whether to use syslog instead of file
        logging.
    @type _syslog: C{bool}

    @ivar _syslogPrefix: If C{sysLog} is C{True}, the string prefix to use for
        syslog messages.
    @type _syslogPrefix: C{str}

    @ivar _nodaemon: A flag indicating the process will not be daemonizing.
    @type _nodaemon: C{bool}
    """

    def __init__(self, options):
        app.AppLogger.__init__(self, options)
        self._syslog = options.get("syslog", False)
        self._syslogPrefix = options.get("prefix", "")
        self._nodaemon = options.get("nodaemon", False)


    def _getLogObserver(self):
        """
        Create and return a suitable log observer for the given configuration.

        The observer will go to syslog using the prefix C{_syslogPrefix} if
        C{_syslog} is true.  Otherwise, it will go to the file named
        C{_logfilename} or, if C{_nodaemon} is true and C{_logfilename} is
        C{"-"}, to stdout.

        @return: An object suitable to be passed to C{log.addObserver}.
        """
        if self._syslog:
            return syslog.SyslogObserver(self._syslogPrefix).emit

        if self._logfilename == '-':
            if not self._nodaemon:
                sys.exit('Daemons cannot log to stdout, exiting!')
            logFile = sys.stdout
        elif self._nodaemon and not self._logfilename:
            logFile = sys.stdout
        else:
            if not self._logfilename:
                self._logfilename = 'twistd.log'
            logFile = logfile.LogFile.fromFullPath(self._logfilename)
            try:
                import signal
            except ImportError:
                pass
            else:
                # Override if signal is set to None or SIG_DFL (0)
                if not signal.getsignal(signal.SIGUSR1):
                    def rotateLog(signal, frame):
                        from twisted.internet import reactor
                        reactor.callFromThread(logFile.rotate)
                    signal.signal(signal.SIGUSR1, rotateLog)
        return log.FileLogObserver(logFile).emit



def daemonize():
    # See http://www.erlenstar.demon.co.uk/unix/faq_toc.html#TOC16
    if os.fork():   # launch child and...
        os._exit(0) # kill off parent
    os.setsid()
    if os.fork():   # launch child and...
        os._exit(0) # kill off parent again.
    null = os.open('/dev/null', os.O_RDWR)
    for i in range(3):
        try:
            os.dup2(null, i)
        except OSError, e:
            if e.errno != errno.EBADF:
                raise
    os.close(null)



def launchWithName(name):
    if name and name != sys.argv[0]:
        exe = os.path.realpath(sys.executable)
        log.msg('Changing process name to ' + name)
        os.execv(exe, [name, sys.argv[0], '--originalname'] + sys.argv[1:])



class UnixApplicationRunner(app.ApplicationRunner):
    """
    An ApplicationRunner which does Unix-specific things, like fork,
    shed privileges, and maintain a PID file.
    """
    loggerFactory = UnixAppLogger

    def preApplication(self):
        """
        Do pre-application-creation setup.
        """
        checkPID(self.config['pidfile'])
        self.config['nodaemon'] = (self.config['nodaemon']
                                   or self.config['debug'])
        self.oldstdout = sys.stdout
        self.oldstderr = sys.stderr


    def postApplication(self):
        """
        To be called after the application is created: start the
        application and run the reactor. After the reactor stops,
        clean up PID files and such.
        """
        self.startApplication(self.application)
        self.startReactor(None, self.oldstdout, self.oldstderr)
        self.removePID(self.config['pidfile'])


    def removePID(self, pidfile):
        """
        Remove the specified PID file, if possible.  Errors are logged, not
        raised.

        @type pidfile: C{str}
        @param pidfile: The path to the PID tracking file.
        """
        if not pidfile:
            return
        try:
            os.unlink(pidfile)
        except OSError, e:
            if e.errno == errno.EACCES or e.errno == errno.EPERM:
                log.msg("Warning: No permission to delete pid file")
            else:
                log.err(e, "Failed to unlink PID file")
        except:
            log.err(None, "Failed to unlink PID file")


    def setupEnvironment(self, chroot, rundir, nodaemon, umask, pidfile):
        """
        Set the filesystem root, the working directory, and daemonize.

        @type chroot: C{str} or L{NoneType}
        @param chroot: If not None, a path to use as the filesystem root (using
            L{os.chroot}).

        @type rundir: C{str}
        @param rundir: The path to set as the working directory.

        @type nodaemon: C{bool}
        @param nodaemon: A flag which, if set, indicates that daemonization
            should not be done.

        @type umask: C{int} or L{NoneType}
        @param umask: The value to which to change the process umask.

        @type pidfile: C{str} or L{NoneType}
        @param pidfile: If not C{None}, the path to a file into which to put
            the PID of this process.
        """
        daemon = not nodaemon

        if chroot is not None:
            os.chroot(chroot)
            if rundir == '.':
                rundir = '/'
        os.chdir(rundir)
        if daemon and umask is None:
            umask = 077
        if umask is not None:
            os.umask(umask)
        if daemon:
            daemonize()
        if pidfile:
            f = open(pidfile,'wb')
            f.write(str(os.getpid()))
            f.close()


    def shedPrivileges(self, euid, uid, gid):
        """
        Change the UID and GID or the EUID and EGID of this process.

        @type euid: C{bool}
        @param euid: A flag which, if set, indicates that only the I{effective}
            UID and GID should be set.

        @type uid: C{int} or C{NoneType}
        @param uid: If not C{None}, the UID to which to switch.

        @type gid: C{int} or C{NoneType}
        @param gid: If not C{None}, the GID to which to switch.
        """
        if uid is not None or gid is not None:
            switchUID(uid, gid, euid)
            extra = euid and 'e' or ''
            log.msg('set %suid/%sgid %s/%s' % (extra, extra, uid, gid))


    def startApplication(self, application):
        """
        Configure global process state based on the given application and run
        the application.

        @param application: An object which can be adapted to
            L{service.IProcess} and L{service.IService}.
        """
        process = service.IProcess(application)
        if not self.config['originalname']:
            launchWithName(process.processName)
        self.setupEnvironment(
            self.config['chroot'], self.config['rundir'],
            self.config['nodaemon'], self.config['umask'],
            self.config['pidfile'])

        service.IService(application).privilegedStartService()

        uid, gid = self.config['uid'], self.config['gid']
        if uid is None:
            uid = process.uid
        if gid is None:
            gid = process.gid

        self.shedPrivileges(self.config['euid'], uid, gid)
        app.startApplication(application, not self.config['no_save'])
