#!/usr/bin/python
# Run a command with a lock held.
# Copyright 2009 Adam Sampson <ats@offog.org>

import sys, os, getopt, fcntl, time, curses

def usage(rc):
	print """Usage: with-lock [OPTIONS] LOCKFILE COMMAND ...
Run COMMAND with the file LOCKFILE locked.

  -q                       don't print a message while waiting
  --help                   display this help and exit

Report bugs to <ats@offog.org>."""
	sys.exit(rc)

def main(args):
	try:
		opts, args = getopt.getopt(args, "q", ["help"])
	except getopt.GetoptError:
		usage(1)
	if len(args) < 2:
		usage(1)

	quiet = False
	for o, a in opts:
		if o == "-q":
			quiet = True
		elif o == "--help":
			usage(0)

	if not os.isatty(sys.stdout.fileno()):
		quiet = True

	if not quiet:
		curses.setupterm()
		ti_el = curses.tigetstr("el")
		ti_cr = curses.tigetstr("cr")
		if ti_el is None or ti_cr is None:
			quiet = True

	progress = "/-\\|"

	fd = os.open(args[0], os.O_WRONLY | os.O_CREAT, 0600)
	while True:
		try:
			fcntl.lockf(fd, fcntl.LOCK_EX | fcntl.LOCK_NB)
			break
		except IOError:
			pass

		if not quiet:
			sys.stdout.write("%s(waiting for lock %s... %s)"
			                 % (ti_cr, args[0], progress[0]))
			progress = progress[1:] + progress[0]
			sys.stdout.flush()

		time.sleep(0.2)

		if not quiet:
			sys.stdout.write("%s%s" % (ti_cr, ti_el))
			sys.stdout.flush()

	os.execvp(args[1], args[1:])

if __name__ == "__main__":
	main(sys.argv[1:])