#!/usr/bin/python
#
# do-until - run a command until it succeeds
# Copyright (C) 2008  Lars Wirzenius
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.


"""Run a command until it succeeds.

Lars Wirzenius <liw@liw.fi>
"""


import optparse
import subprocess
import sys
import time


def do_until(options, argv):
    tries = 0
    while options.max_tries == 0 or tries < options.max_tries:
        tries += 1
        if options.verbose:
            sys.stderr.write("do-until: attempt #%d: %s\n" % 
                             (tries, " ".join(argv)))
        if options.no_act:
            sys.stderr.write("do-until: not running command, pretending it "
                             "works anyway\n")
            break
        else:
            p = subprocess.Popen(argv)
            p.communicate()
            if p.returncode == 0:
                break
        sys.stderr.write("do-until: command failed, "
                         "trying again in %d second(s)\n" % options.sleep)
        time.sleep(options.sleep)


def parse_args(args):
    parser = optparse.OptionParser()
    parser.add_option("-n", "--no-act", action="store_true",
                      help="Do not run command, just pretend to do it, and "
                           "pretend that it succeeds.")
    parser.add_option("-v", "--verbose", action="store_true",
                      help="Print command before executing it.")
    parser.add_option("--sleep", type="int", default=1, metavar="SECS",
                      help="Wait SECS seconds before re-trying a command. "
                           "(Default is %default.)")
    parser.add_option("--max-tries", type="int", default=0, metavar="COUNT",
                      help="Try at most COUNT times, with 0 meaning forever. "
                           "(Default is %default.)")
    
    options, argv = parser.parse_args(args)

    return options, argv


def main():
    try:
        options, argv = parse_args(sys.argv[1:])
        if argv:
            do_until(options, argv)
    except KeyboardInterrupt:
        sys.exit(1)


if __name__ == "__main__":
    main()