#    Back In Time
#    Copyright (C) 2008-2009 Oprea Dan, Bart de Koning, Richard Bailey
#
#    This program is free software; you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation; either version 2 of the License, or
#    (at your option) any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License along
#    with this program; if not, write to the Free Software Foundation, Inc.,
#    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.


import os
import os.path
import time


#class used to handle one application instance mechanism
class GUIApplicationInstance:

    #specify the base for control files
    def __init__( self, base_control_file, raise_cmd = '' ):
        self.pid_file = base_control_file + '.pid'
        self.raise_file = base_control_file + '.raise'
        self.raise_cmd = raise_cmd

        #remove raise_file is already exists
        try:
            os.remove( self.raise_file )
        except:
            pass

        self.check( raise_cmd )
        self.start_application()

    #check if the current application is already running
    def check( self, raise_cmd ):
        #check if the pidfile exists
        if not os.path.isfile( self.pid_file ):
            return

        #read the pid from the file
        pid = 0
        try:
            file = open( self.pid_file, 'rt' )
            data = file.read()
            file.close()
            pid = int( data )
        except:
            pass

        #check if the process with specified by pid exists
        if 0 == pid:
            return

        try:
            os.kill( pid, 0 )	#this will raise an exception if the pid is not valid
        except:
            return

        #exit the application
        print("The application is already running ! (pid: %s)" % pid)

        #notify raise
        try:
            file = open( self.raise_file, 'wt' )
            file.write( raise_cmd )
            file.close()
        except:
            pass

        exit(0) #exit raise an exception so don't put it in a try/except block

    #called when the single instance starts to save it's pid
    def start_application( self ):
        file = open( self.pid_file, 'wt' )
        file.write( str( os.getpid() ) )
        file.close()

    #called when the single instance exit ( remove pid file )
    def exit_application( self ):
        try:
            os.remove( self.pid_file )
        except:
            pass

    #check if the application must to be raised
    #return None if no raise needed, or a string command to raise
    def raise_command( self ):
        ret_val = None

        try:
            if os.path.isfile( self.raise_file ):
                file = open( self.raise_file, 'rt' )
                ret_val = file.read()
                file.close()
                os.remove( self.raise_file )
        except:
            pass

        return ret_val

