#!/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
import os, syslog, glob, socket

def gpsd_connect():
    "Acquire a connection to the GPSD port."
    msg = "getaddrinfo returns an empty list"
    sock = None
    sockfile = None
    for res in socket.getaddrinfo("localhost", 2947, 0, socket.SOCK_STREAM):
        (af, socktype, proto, canonname, sa) = res
        try:
            sock = socket.socket(af, socktype, proto)
            sock.connect(sa)
            sockfile = sock.makefile()
        except socket.error, msg:
            if sock:
                sock.close()
            sock = None
            sockfile = None
            continue
        break
    if not sock:
        syslog.syslog("gpsd is not running or is unreachable")
        return None
    else:
        return sockfile

def wake_up_gpsd(devpath):
    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")

        # Next get a connection to gpsd; start one if not already running
        connect = gpsd_connect()
        if connect:
            syslog.syslog("reached a running gpsd")
        else:
            syslog.syslog("attempting to launch gpsd")
            os.system("gpsd")
            connect = gpsd_connect()
        if not connect:
            return

        # We've got a live connection to gpsd. Ship it the right F command.
        # No need to look at the response; gpsd will lock on to the device
        # if it's really a GPS and ignore it if it's not.
        connect.write("F=%s\r\n" % tty)
        connect.close()
        return

syslog.openlog('gpsdplug', 0, syslog.LOG_DAEMON)
syslog.syslog("gpsdplug begins with action: %s" % os.getenv("ACTION"))
devpath = os.getenv("DEVPATH")
if not devpath:
    syslog.syslog("No DEVPATH")
else:
    # First, discover the device
    #syslog.syslog("DEVPATH = %s" % devpath)
    wake_up_gpsd(devpath)

syslog.syslog("gpsdplug ends")
syslog.closelog()