#!/usr/bin/python


from __future__ import with_statement

import cjson
import contextlib
import fcntl
import os
import getpass
import select
import socket
import sys


TIMEOUT = 5


@contextlib.contextmanager
def lockfile(path, exclusive=True):
    f = open(path, 'w' if exclusive else 'r')
    fcntl.lockf(f, fcntl.LOCK_EX if self.exclusive else fcntl.LOCK_SH)
    try:
        yield
    finally:
        fcntl.lockf(f, fcntl.LOCK_UN)


def do_send(s, sock_path, change):
    s.sendall(cjson.encode(change))
    s.close()


def do_recv(s, sock_path, change):
    def do_client(cl):
        global changes

        clf = cl.makefile('r')
        change = clf.read()
        changes.append(cjson.decode(change))
        clf.close()
        cl.close()

    def collect_changes(s, timeout):
        global changes

        while True:
            if select.select([s], [], [], timeout) == ([], [], []):
                # Timed out
                break
            else:
                # Something to accept
                cl, _ = s.accept()
                do_client(cl)

    changes = [change]

    collect_changes(s, TIMEOUT)
    # Ok, we've timed out
    os.unlink(sock_path)
    # If anybody connected between when the select() timed out and we
    # unlinked, handle them now
    collect_changes(s, 0)


def main(args):
    change = {}

    change['action'] = args[1]
    change['pocket'] = args[2]
    change['type'] = args[3]
    change['component'] = args[4]
    change['arch'] = args[5]
    change['package'] = args[6]

    args = args[7:]
    if change['action'] in ('add', 'replace'):
        change['new_version'] = args.pop(0)
    if change['action'] in ('remove', 'replace'):
        change['old_version'] = args.pop(0)

    change['args'] = args

    user = getpass.getuser()
    sock_path = os.path.join('/tmp/dagrouper-%s.sock' % user)
    with lockfile('/tmp/dagrouper-%s.lock' % user):
        s = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)

        if os.path.exists(sock_path):
            s.connect(sock_path)
            bound = False
        else:
            s.bind(sock_path)
            bound = True

    if bound:
        do_receive(s, sock_path, change)
    else:
        do_send(s, sock_path, change)


if __name__ == '__main__':
    pid = os.fork()
    if pid:
        os._exit(0)
    else:
        main(sys.argv)