#!/usr/bin/python 
# Filename: module-lockfile.py

# Author Evuraan Gmail dot com 

import optparse,sys,os,time

def usage():
	print """
Usage   : lockfile.py <lockfile>
Usage   : lockfile.py -l <timeout> <lockfile>
Example : lockfile.py -l 1300 /tmp/my.lockfile.txt
Example : lockfile.py /tmp/my.lockfile.txt

"""


def remove_lockfile(lock_file):
	os.remove(lock_file)


def set_lockfile(lock_file):
	write_file = open(lock_file,"w",)
	write_file.write(str(time.time()))
	write_file.close()
	if os.path.isfile(lock_file):
		# file exists, good enough for us. 
		return 0
	else:
		return 1
		


#if the lockfile exists, check for locktimeout
def checklock(lock_file):
	if os.path.isfile(lock_file):
		# lock file exists. check how old etc. 
		mtime = float(os.path.getmtime(lock_file))
		delta = time.time() - mtime 
		if float(delta) >= float(locktimeout):
			# file is stale, over write it 
			if set_lockfile(lock_file) != 0:
				sys.exit(1)
		else:
			#file is not stale. new. spanking new. 
			sys.exit(1)	
	else:
		# no lock file. 
		if set_lockfile(lock_file) != 0:
			sys.exit(1)
			
				

if __name__ == "__main__":

	parser = optparse.OptionParser()
	parser.add_option('-l', '--locktimeout',
		dest="locktimeout",
		type="int",
		default="3489999999",
		help="""If you specify a locktimeout then a lockfile will be 
removed by force after locktimeout seconds have passed since the lockfile was last
modified/created (most likely by some other program that unexpectedly 
died a long time ago, and hence could not clean up any leftover lockfiles)."""
		)

	options,remainder = parser.parse_args()

	#print "locktimeout       :", options.locktimeout
	#print "remainder         :", remainder

	global locktimeout
	locktimeout = options.locktimeout

	try:
		if len(remainder) == 0:
			print "Invalid usage"
			usage()
			sys.exit(2)
		else:
			global lock_file 
			lock_file = remainder[0]
	except:
		sys.exit(2)

				
	#print "Ahem", lock_file
	checklock(lock_file)