import os

import sys

import time

import errno

from warnings import warn

from multiprocessing.util import Finalize

from rhodecode.lib.compat import kill

class LockHeld(Exception):

    pass

class DaemonLock(object):

    """daemon locking

    USAGE:

    try:

        l = DaemonLock(file_='/path/tolockfile',desc='test lock')

        main()

        l.release()

    except LockHeld:

        sys.exit(1)

    """

    def __init__(self, file_=None, callbackfn=None,

                 desc='daemon lock', debug=False):

        self.pidfile = file_ if file_ else os.path.join(

                                                    os.path.dirname(__file__),

                                                    'running.lock')

        self.callbackfn = callbackfn

        self.desc = desc

        self.debug = debug

        self.held = False

        #run the lock automatically !

        self.lock()

        self._finalize = Finalize(self, DaemonLock._on_finalize,

                                    args=(self, debug), exitpriority=10)

    @staticmethod

    def _on_finalize(lock, debug):

        if lock.held:

            if debug:

                print 'leck held finilazing and running lock.release()'

            lock.release()

    def lock(self):

        """

        locking function, if lock is present it

        will raise LockHeld exception

        """

        lockname = '%s' % (os.getpid())

        if self.debug:

            print 'running lock'

        self.trylock()

        self.makelock(lockname, self.pidfile)

        return True

                    kill(running_pid, 0)

                except OSError, exc:

                    if exc.errno in (errno.ESRCH, errno.EPERM):

                        print ("Lock File is there but"

                               " the program is not running")

                        print "Removing lock file for the: %s" % running_pid

                        self.release()

                    else:

                        raise

                else:

                    print "You already have an instance of the program running"

                    print "It is running as process %s" % running_pid

                    raise LockHeld()

        except IOError, e:

            if e.errno != 2:

                raise

    def release(self):

        """releases the pid by removing the pidfile

        """

        if self.debug:

            print 'trying to release the pidlock'

        if self.callbackfn:

            #execute callback function on release

            if self.debug:

                print 'executing callback function %s' % self.callbackfn

            self.callbackfn()

        try:

            if self.debug:

                print 'removing pidfile %s' % self.pidfile

            os.remove(self.pidfile)

            self.held = False

        except OSError, e:

            if self.debug:

                print 'removing pidfile failed %s' % e

            pass

    def makelock(self, lockname, pidfile):

        """

        this function will make an actual lock

        :param lockname: acctual pid of file

        :param pidfile: the file to write the pid in

        """

        if self.debug:

            print 'creating a file %s and pid: %s' % (pidfile, lockname)

        pidfile = open(self.pidfile, "wb")

        pidfile.write(lockname)

        pidfile.close

        self.held = True