novel_decode.py

import base64, math, re
from html.parser import HTMLParser

class MyHTMLParser(HTMLParser):
    def __init__(self):
        super().__init__()
        self.line = []
        self.table = []
        self.c = 0

    def handle_starttag(self, tag, attrs):
        if tag == 'meta' and attrs[0][1] == 'client':
            self.table = re.split('[A-Z]+%', base64.b64decode(attrs[1][1]).decode())

    def handle_data(self, data):
        if self.get_starttag_text() == '<p>':
            self.line.append(data.replace('\xa0', ' ') + '\n')
        elif self.get_starttag_text() == '<script type="text/javascript">' and 'codeurl' in data:
            self.c = int(re.search('codeurl="([\d]+)"', data).group(1))


def decode(table, c, line):
    t_line = [''] * len(line)
    for i,code in enumerate(table):
        k = math.ceil((i+1) % c)
        k = math.ceil(int(code) - k)
        t_line[k] = line[i]
    return t_line


parser = MyHTMLParser()
with open('test.html') as f:
    parser.feed(f.read())
line = decode(parser.table, parser.c, parser.line)
with open('test.txt', 'w') as f:
    f.writelines(line)