def extract_filenames(json):
    def get_filename(reply_json):
        hashed_name = reply_json['tim'] + reply_json['ext']
        original_name = reply_json['filename'] + reply_json['ext']

        return [dict(hashed_name=hashed_name, original_name=original_name)]

    filenames = []
    for p in json['posts']:
        if 'filename' in p:
            filenames += get_filename(p)

            if 'extra_files' in p:
                for e in p['extra_files']:
                    filenames += get_filename(e)

    return filenames


def time_of_last_reply(json):
    t = int(json['posts'][-1]['last_modified'])
    return t


def get_oldest_reply(replies):
    oldest_reply = min(replies, key=lambda x: int(x['last_modified']))
    return oldest_reply['no']