#!/usr/bin/env python

import urllib2
import argparse
import socket
import os
import signal
import sys

def parseArgs():
    parser = argparse.ArgumentParser(description='Distributex client')
    parser.add_argument('command', type=str, nargs='?',
                       help='Command to execute when lock is obtained')

    parser.add_argument('-H', dest='host', required=False, help='Server hostname')
    parser.add_argument('-r', dest='pool', required=True, help='Resource pool')
    parser.add_argument('-p', dest='port', default=9889, type=int,
        help='Server port (default 9889)')
    parser.add_argument('-l', dest='lock', default=False, action="store_true", help='Don\'t use local locking')

    return parser.parse_args()

if __name__ == "__main__": 
    args = parseArgs()

    if args.lock and not args.host:
        print "You must specify a server hostname or use local locking"
        sys.exit(1)

    if not args.command:
        print "You must specify a command to run"
        sys.exit(1)

    host = socket.gethostbyaddr(socket.gethostname())[0]

    lockfile = '/tmp/dx-%s.lock' % args.pool

    if args.host:
        # Build a reusable URI for the server
        server_uri = "http://%s:%s/%%s/?pool=%s&host=%s" % (
                args.host,
                args.port,
                args.pool,
                host
            )
    else:
        server_uri = None

    def cleanup():
        if not args.lock:
            try:
                os.unlink(lockfile)
            except:
                pass

    def exitClean(signal, frame):
        cleanup()
        if server_uri:
            urllib2.urlopen(server_uri % 'release').read()
        sys.exit(1)

    signal.signal(signal.SIGINT, exitClean)
    signal.signal(signal.SIGTERM, exitClean)

    # Look for a local lock
    if not args.lock:
        if os.path.exists(lockfile):
            try:
                pid = int(open(lockfile).read())
                os.kill(pid, 0)
            except OSError:
                print "Cleaning stale lockfile"
                cleanup()
            except Exception:
                print "Broken lock file %s. Please remove it" % lockfile
                sys.exit(1)
            else:
                print ("Another instance of distributex is running for this"
                    "pool (pid %s). Wait for it to end or remove %s" % (
                    pid, lockfile))

                sys.exit(1)

        f = open(lockfile, 'wt')
        f.write(str(os.getpid()))
        f.close()

    try:
        if server_uri:
            lock = urllib2.urlopen(server_uri % 'wait').read()
            
            if lock == "YES":
                os.system(args.command)
                
                cleanup()
                urllib2.urlopen(server_uri % 'release').read()
            else:
                print "Error obtaining lock, server said", lock
                cleanup()
                sys.exit(1)
        else:
            cleanup()

    except (KeyboardInterrupt, SystemExit):
        print "Exiting"

        cleanup()
        if server_uri:
            urllib2.urlopen(server_uri % 'release').read()
    except:
        cleanup()
        if server_uri:
            urllib2.urlopen(server_uri % 'release').read()