#!/usr/bin/python3

import argparse
from datetime import datetime, timedelta

parser = argparse.ArgumentParser(description='Tool to adjust srt-file subtitle timing values')
parser.add_argument('source', metavar='source', type=str, nargs=1,
                    help='source srt-file')
parser.add_argument('-a', '--appear', dest='appear', action='store',
                    default=0, type=int, nargs=1,
                    help='Integer value, milliseconds to add to time when subtitle appears (default: 0)')
parser.add_argument('-d', '--disappear', dest='disappear', action='store',
                    default=0, type=int, nargs=1,
                    help='Integer value, milliseconds to add to time when subtitle disappears (default: 0)')

args = parser.parse_args()

try:
  with open(args.source[0]) as fp:
    count = 0
    while True:
        count += 1
        line = fp.readline()
        if not line:
          break
        times = line.strip().split('-->')
        if (len(times) == 2) and (args.appear != 0 or args.disappear != 0):
          if args.appear != 0:
            appears = datetime.strptime(times[0].strip(),'%H:%M:%S,%f')
            appears += timedelta(milliseconds=args.appear[0])
            appears = datetime.strftime(appears, '%H:%M:%S,%f')[:-3]
          else:
            appears = times[0].strip()
          if args.disappear != 0:
            disappears = datetime.strptime(times[1].strip(),'%H:%M:%S,%f')
            disappears += timedelta(milliseconds=args.disappear[0])
            disappears = datetime.strftime(disappears, '%H:%M:%S,%f')[:-3]
          else:
            disappears = times[1].strip()
          print("{} --> {}".format(appears, disappears))
        else:
          print(line.strip())

except FileNotFoundError:
  print('File "{}" not found'.format(args.source[0]))

except Exception as e:
  print(e)