NDOJ/judge/lxml_tree.py

import logging

from django.utils.safestring import SafeData, mark_safe
from lxml import html
from lxml.etree import ParserError, XMLSyntaxError

logger = logging.getLogger("judge.html")


class HTMLTreeString(SafeData):
    def __init__(self, str):
        try:
            self._tree = html.fromstring(str, parser=html.HTMLParser(recover=True))
        except (XMLSyntaxError, ParserError) as e:
            if str and (
                not isinstance(e, ParserError) or e.args[0] != "Document is empty"
            ):
                logger.exception("Failed to parse HTML string")
            self._tree = html.Element("div")

    def __getattr__(self, attr):
        try:
            return getattr(self._tree, attr)
        except AttributeError:
            return getattr(str(self), attr)

    def __setattr__(self, key, value):
        if key[0] == "_":
            super(HTMLTreeString, self).__setattr__(key, value)
        setattr(self._tree, key, value)

    def __repr__(self):
        return "<HTMLTreeString %r>" % str(self)

    def __str__(self):
        return mark_safe(html.tostring(self._tree, encoding="unicode"))

    def __radd__(self, other):
        return other + str(self)

    def __add__(self, other):
        return str(self) + other

    def __getitem__(self, item):
        return str(self)[item]

    def __getstate__(self):
        return str(self)

    def __setstate__(self, state):
        self._tree = html.fromstring(state)

    @property
    def tree(self):
        return self._tree


def fromstring(str):
    if isinstance(str, HTMLTreeString):
        return str
    return HTMLTreeString(str)