#!/usr/bin/python
# Hotplug script for gpsd by Eric S. Raymond, March 2005
# This script is part of the gpsd distribution: see http://gpsd.berlios.de
# Can be called like "gpsd.hotplug [add|remove] /dev/ttyUSB0" for test
# purposes.
import sys, os, syslog, glob, socket, stat

CONTROL_SOCKET = "/var/run/gpsd.sock"

def gpsd_control_connect():
    "Acquire a connection to the GPSD control socket."
    try:
        sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM, 0)
        sock.connect(CONTROL_SOCKET)
        sockfile = sock.makefile()
    except socket.error, msg:
        if sock:
            sock.close()
        sock = None
        sockfile = None
    if not sock:
        syslog.syslog("gpsd is not running or %s is unreachable" % CONTROL_SOCKET)
        return None
    else:
        return sockfile

def gpsd_control(action, argument):
    "Pass a command to gpsd; start the daemon if not already running."
    connect = gpsd_control_connect()
    if connect:
        syslog.syslog("reached a running gpsd")
    elif action == 'add':
        syslog.syslog("attempting to launch gpsd")
        os.system("gpsd -F " + CONTROL_SOCKET)
        connect = gpsd_control_connect()
    if not connect:
        return None
    # We've got a live connection to the gpsd control socket.  No
    # need to parse the response, because gpsd will lock on to the
    # device if it's really a GPS and ignore it if it's not.
    if action == 'add':
        # Force the group-read & group-write bits on, so gpsd will still be
        # able to use this device after dropping root privileges.
        os.chmod(argument, stat.S_IMODE(os.stat(argument)[stat.ST_MODE])|0660)
        connect.write("+%s\r\n" % argument)
    elif action == 'remove':
        connect.write("-%s\r\n" % argument)
    connect.close()
    return action

def hotplug(action, devpath):
    syslog.openlog('gpsd.hotplug', 0, syslog.LOG_DAEMON)
    syslog.syslog("gpsd.hotplug begins with action: %s" % action)
    if not devpath:
        syslog.syslog("No device")
    else:
        subnodes = glob.glob("/sys" + devpath + "/*")
        subnodes = map(os.path.basename, subnodes)
        subnodes = filter(lambda s: s.startswith("ttyUSB"), subnodes) 
        if len(subnodes) == 0:
            syslog.syslog("no ttyUSB device under " + devpath)
            return
        elif len(subnodes) > 1:
            syslog.syslog("too many ttyUSB devices under " + devpath)
            return
        else:
            tty = "/dev/" + subnodes[0]
            syslog.syslog(tty + " has gone active")

            gpsd_control(action, tty)
            return
    syslog.syslog("gpsd.hotplug ends")
    syslog.closelog()

if __name__ == '__main__':
    try: 
        if len(sys.argv) == 1:	# Called as hotplug script
            hotplug(os.getenv("ACTION"), os.getenv("DEVPATH"))
        else:			# Called by hand for testing
            gpsd_control(sys.argv[1], sys.argv[2])
    except:
        (exc_type, exc_value, exc_traceback) = sys.exc_info()
        syslog.syslog("gpsd.hotplug: exception %s yields %s" % (exc_type, exc_value))
        raise exc_type, exc_value, exc_traceback