# strip out a set of nuisance html attributes that can mess up rendering in RSS feeds
import re
from lxml.html.clean import Cleaner

bad_attrs = ["width", "height", "style", "[-a-z]*color", "background[-a-z]*", "on*"]
single_quoted = "'[^']+'"
double_quoted = '"[^"]+"'
non_space = "[^ \"'>]+"
htmlstrip = re.compile(
    "<"  # open
    "([^>]+) "  # prefix
    "(?:%s) *" % ("|".join(bad_attrs),)
    + "= *(?:%s|%s|%s)"  # undesirable attributes
    % (non_space, single_quoted, double_quoted)
    + "([^>]*)"  # value  # postfix
    ">",  # end
    re.I,
)


def clean_attributes(html):
    while htmlstrip.search(html):
        html = htmlstrip.sub("<\\1\\2>", html)
    return html


def normalize_spaces(s):
    if not s:
        return ""
    """replace any sequence of whitespace
    characters with a single space"""
    return " ".join(s.split())


html_cleaner = Cleaner(
    scripts=True,
    javascript=True,
    comments=True,
    style=True,
    links=True,
    meta=False,
    add_nofollow=False,
    page_structure=False,
    processing_instructions=True,
    embedded=False,
    frames=False,
    forms=False,
    annoying_tags=False,
    remove_tags=None,
    remove_unknown_tags=False,
    safe_attrs_only=False,
)