#!/usr/bin/env python

import os.path
import sys
import shlex
import traceback
import time

from optparse import OptionParser

CONFIG_FILE = os.environ.get("JOBDAEMON_CFG", "jobdaemon.cfg") 

SLEEP = int(os.environ.get("JOBDAEMON_SLEEP", "60"))

def fork(job):
    pid = os.fork()
    if pid: return pid
    os.execv(job[0], job)
    return -1 # never reached

class Jobs(object):

    def __init__(self, filename):
        self.load_config(filename)

    def load_config(self, filename):
        print >> sys.stderr, "loading config file '%s'" % filename
        plan, jobs = [], []
        f = open(filename, "r")
        try:
            while True:
                line = f.readline()
                if not line: break
                line = line.strip()
                if not line or line.startswith("#"): 
                    continue
                if line.startswith("BLOCKER:"):
                    line = line[len("BLOCKER:"):].strip()
                    plan.append((jobs, line))
                    jobs = []
                    continue
                jobs.append(shlex.split(line))
        finally:
            f.close()

        if jobs: plan.append((jobs, None))

        self.plan = plan

    def run_jobs(self, jobs):
        pids = []
        for job in jobs:
            try:
                pids.append(fork(job))
            except:
                traceback.print_exc()

        for pid in pids:
            try:
                os.waitpid(pid, 0)
            except:
                traceback.print_exc()

    def run(self):
        for jobs, blocker in self.plan:
            self.run_jobs(jobs)
            if blocker:
                try:
                    os.system(blocker)
                except:
                    traceback.print_exc()
        
def main():

    global config_changed

    parser = OptionParser()

    parser.add_option(
        "-c", "--config", dest="config",
        help="load configuration from file", 
        metavar="FILE", default=CONFIG_FILE)

    parser.add_option(
        "-s", "--sleep", dest="sleep_time",
        help="sleep time between runs",
        type="int",
        metavar="TIME", default=SLEEP)

    (options, _) = parser.parse_args()

    if not os.path.isfile(options.config):
        print >> sys.stderr, "config file '%s' does not exists."
        sys.exit(1)

    modtime = os.stat(options.config).st_mtime

    jobs = Jobs(options.config)

    while True:
        if os.path.isfile(options.config):
            nmodtime = os.stat(options.config).st_mtime
            if nmodtime > modtime:
                modtime = nmodtime
                jobs = Jobs(options.config)
        jobs.run()
        time.sleep(options.sleep_time)

if __name__ == '__main__':
    main()