#!/usr/bin/python

import os
from os.path import expanduser
from pwd import getpwnam
from grp import getgrnam

import glob
import syslog
from string import split

import usb.core

####### Start User Edits #########

# Controller USB parms
control_vid = 0x0763
control_pid = 0x0160

# Mustang USB parms
mustang_vid = 0x1ed8

# Mustang III (original)
# mustang_pid = 0x0005

# Mustang III v2
mustang_pid = 0x0016

# Controller MIDI device
midi_device = 1

# MIDI listen channel
midi_channel = 1

######## End User Edits ##########

rundir = "/var/run/mustang/"

# Look for devices
controller = usb.core.find( idVendor=control_vid, idProduct=control_pid )
mustang = usb.core.find( idVendor=mustang_vid, idProduct=mustang_pid )

pid = os.getpid()
# syslog.syslog( "%d: Starting" % pid )

# was it found?
if controller and mustang:
    os.chdir( rundir )
    filelist = glob.glob( 'mustang_*' )

    if len( filelist ) == 1:
        lockfile = filelist[0]
        oldpid = split( lockfile, '_' )[1]

        # syslog.syslog( "%d: Check for path /proc/%s" % (pid, oldpid) )
        if not os.path.exists( "/proc/%s" % oldpid ):
            # No such process, ok to start ours
            # syslog.syslog( "%d: Renaming %s to mustang_%d" % (pid, lockfile, pid) )
            try:
                os.rename( lockfile, "mustang_%d" % os.getpid() ) 
            except Exception, e:
                pass
                # syslog.syslog( "%d: Unable to rename file" % pid )
            else:
                # syslog.syslog( "%d: About to exec" % pid )
                # Drop privileges and start the program
                pwObj = getpwnam('mustang-user')
                os.setgid( pwObj.pw_gid )
                
                # Need secondary groups to access MIDI and USB devices
                sec_gids = ( getgrnam('plugdev').gr_gid, getgrnam('audio').gr_gid )
                os.setgroups( sec_gids )
                
                os.setuid( pwObj.pw_uid )
                os.execl( "/usr/local/bin/mustang_midi", "mustang_midi", "%s" % midi_device, "%s" % midi_channel )
    else:
        syslog.syslog( "%d: /var/run/mustang is not properly setup" % pid )