#!/usr/bin/env python3

import sys
import argparse
import re
import subprocess


NORMAL_BRANCH_NAME_LINE_PREFIX = "# On branch "
MESSAGE_BRANCH_NAME_LINE_PREFIX = "["
TICKET_NUMBER_REGEX = r'(\d+)-'


if __name__ == '__main__':
    parser = argparse.ArgumentParser()
    parser.add_argument('commit_msg_file')
    parser.add_argument('commit_source', nargs='?')
    parser.add_argument('sha1', nargs='?')
    args = parser.parse_args()

    if args.commit_source in ('merge', 'squash', 'commit'):
        sys.exit()

    content = None
    ticket_number = None

    branch_name_line_prefix = MESSAGE_BRANCH_NAME_LINE_PREFIX \
        if args.commit_source == 'message' \
        else NORMAL_BRANCH_NAME_LINE_PREFIX

    with open(args.commit_msg_file) as f:
        branch_name = subprocess.check_output(
            ['git', 'rev-parse', '--abbrev-ref', 'HEAD']).decode('utf8')
        match = re.match(TICKET_NUMBER_REGEX, branch_name)
        if match:
            f.seek(0)
            content = f.read()
            ticket_number = match.group(1)

    if content is not None and ticket_number is not None:
        if args.commit_source == 'message':
            ticket_number_suffix = " "
        else:
            ticket_number_suffix = " \n"
        content = "{}{}{}".format(ticket_number, ticket_number_suffix, content)
        with open(args.commit_msg_file, 'w') as f:
            f.write(content)