#!/usr/bin/env python
#
# .srt subtitle timestamp adjuster, r1 <harjoc at gee mail>

import os, sys, re

if len(sys.argv) < 4:
	print "syntax: %s in out msecs" % os.path.basename(sys.argv[0])
	sys.exit()

fi = open(sys.argv[1], "r")
fo = open(sys.argv[2], "w")
delay = int(sys.argv[3])

#00:00:59,860 --> 00:01:03,730
tsre = "(\\d\\d):(\\d\\d):(\\d\\d),(\\d\\d\\d)"
pat = "%s --> %s[\n\r]+" % (tsre, tsre)

mult = [3600*1000, 60*1000, 1000, 1]
size = [100, 60, 60, 1000]

for line in fi.readlines():
	m = re.match(pat, line)
	if not m:
		fo.write(line)
		continue
	
	g = [int(x) for x in m.groups()]	
	def decode(o):
		return sum([g[o+i] * mult[i] for i in range(4)])

	ts0 = decode(0) + delay
	ts1 = decode(4) + delay

	def encode(ts):
		lst = [ts / mult[i] % size[i] for i in range(4)]
		return "%02d:%02d:%02d,%03d" % tuple(lst)

	fo.write("%s --> %s\n" % (encode(ts0), encode(ts1)))

fi.close()
fo.close()