#!/usr/bin/python

import errno
import os
import socket
import sys
import syslog

MESSAGE_VERS = "GMS:0"
MESSAGE_SIZE = 2048
MESSAGE_FILE = '/var/gms/Message'

addr = None

def die(reason,exit_status=1):
    syslog.syslog(syslog.LOG_INFO, reason)
    sys.exit(exit_status)

def setup_syslog():
    syslog.openlog('pymessaged', syslog.LOG_PID, syslog.LOG_DAEMON)
    
def setup_socket():
    # Create an IPv4 UDP socket from fd0, as passed by inetd
    client = socket.fromfd(0, socket.AF_INET, socket.SOCK_DGRAM)
    # Read up to MESSAGE_SIZE bytes from the client, and record the
    # address so we can then connect to it
    global addr
    buf, addr = client.recvfrom(MESSAGE_SIZE)
    client.connect(addr)
   
    return buf

def ensure_version(buf):
    vers = buf[0:len(MESSAGE_VERS)]
    if MESSAGE_VERS != vers:
        die('GMS bogus version [%s] from %s' % (vers, addr[0]))

def get_message():
    timestamp = 0
    content = ''
    try:
        with open(MESSAGE_FILE, 'r') as msg:
            content = msg.read()
            timestamp = os.fstat(msg.fileno()).st_mtime
    except IOError as e:
        # If it's just ENOENT, there's no message, and that's fine
        if e.errno != errno.ENOENT:
            die('GMS daemon IO error [%s] reading message file <%s>' % \
                    (os.strerror(e.errno), MESSAGE_FILE), exit_status=e.errno)
    return (timestamp, content)

if __name__ == '__main__':
    try:
        setup_syslog()
        ensure_version(setup_socket())
        timestamp, msg = get_message()

        print "%s %ld\n%s" % (MESSAGE_VERS, timestamp, msg),
    except IOError as e:
        die('GMS daemon experienced an unexpected IO error: %s' % \
                (os.strerror(e.errno)), exit_status=e.errno)
    except:
        # Some really weird condition happened
        die('GMS daemon experienced an unknown failure')