import re
import sys
import argparse

def offset_timestamp(timestamp, offset):
    hours, minutes, seconds, microseconds = map(float, re.split('[:.]', timestamp))
    total_seconds = hours * 3600 \
        + minutes * 60 \
        + seconds  \
        + (microseconds * 0.001) \
        + offset
    new_hours = int(total_seconds // 3600)
    new_minutes = int((total_seconds % 3600) // 60)
    new_seconds = total_seconds % 60
    return f"{new_hours:02}:{new_minutes:02}:{new_seconds:.3f}"

def update_webvtt(file_path, offset):
    with open(file_path, 'r', encoding='utf-8') as file:
        lines = file.readlines()

    updated_lines = []
    for line in lines:
        ts = line[:line.find("align")]
        if '-->' in ts:
            start, end = ts.split(' --> ')
            updated_start = offset_timestamp(start.strip(), offset)
            updated_end = offset_timestamp(end.strip(), offset)
            updated_lines.append(f"{updated_start} --> {updated_end}\n")
        else:
            updated_lines.append(line)

    with open('updated_' + file_path, 'w', encoding='utf-8') as file:
        file.writelines(updated_lines)

if __name__ == "__main__":
    parser = argparse.ArgumentParser()
    parser.add_argument('input_file', type=str, help='The input file name')
    parser.add_argument('time_offset', type=str, help='The output file name')
    args = parser.parse_args()

    vtt = args.input_file
    t   = args.time_offset
    
    minutes, seconds = map(float, re.split('[:.]', t))
    offset = minutes * 60 + seconds

    print("bumping timestamps in file %s by %f seconds" % (vtt,  offset))
    update_webvtt(vtt, -offset)  # Use -40 to offset back by 40 seconds