# -*- coding: utf-8 -*-
# Copyright (c) 2009-2010 Sauce Labs Inc
#
# Portions taken from twistd:
#
# Copyright (c) 2001-2009
# Allen Short
# Andrew Bennetts
# Apple Computer, Inc.
# Benjamin Bruheim
# Bob Ippolito
# Canonical Limited
# Christopher Armstrong
# David Reid
# Donovan Preston
# Eric Mangold
# Itamar Shtull-Trauring
# James Knight
# Jason A. Mobarak
# Jean-Paul Calderone
# Jonathan Lange
# Jonathan D. Simms
# Jürgen Hermann
# Kevin Turner
# Mary Gardiner
# Matthew Lefkowitz
# Massachusetts Institute of Technology
# Moshe Zadka
# Paul Swartz
# Pavel Pergamenshchik
# Ralph Meijer
# Sean Riley
# Software Freedom Conservancy
# Travis B. Hartwell
# Thomas Herve
# Eyal Lotem
# Antoine Pitrou
# Andy Gayton
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

import os
import sys
import errno

def basic_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.
    os.umask(022)   # Don't allow others to write
    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 writePID(pidfile):
    open(pidfile,'wb').write(str(os.getpid()))
    if not os.path.exists(pidfile):
        raise Exception( "pidfile %s does not exist" % 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.
                print('Removing stale pidfile %s' % pidfile)
                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 server is running, PID %s\n" %  pid)

def daemonize(pidfile):
    checkPID(pidfile)
    basic_daemonize()
    writePID(pidfile)