django/django/utils/html.py

"""HTML utilities suitable for global use."""

from __future__ import unicode_literals

import re
import sys

from django.utils.encoding import force_text, force_str
from django.utils.functional import allow_lazy
from django.utils.http import RFC3986_GENDELIMS, RFC3986_SUBDELIMS
from django.utils.safestring import SafeData, mark_safe
from django.utils import six
from django.utils.six.moves.urllib.parse import quote, unquote, urlsplit, urlunsplit
from django.utils.text import normalize_newlines

from .html_parser import HTMLParser, HTMLParseError


# Configuration for urlize() function.
TRAILING_PUNCTUATION = ['.', ',', ':', ';', '.)', '"', '\'']
WRAPPING_PUNCTUATION = [('(', ')'), ('<', '>'), ('[', ']'), ('&lt;', '&gt;'), ('"', '"'), ('\'', '\'')]

# List of possible strings used for bullets in bulleted lists.
DOTS = ['&middot;', '*', '\u2022', '&#149;', '&bull;', '&#8226;']

unencoded_ampersands_re = re.compile(r'&(?!(\w+|#\d+);)')
word_split_re = re.compile(r'(\s+)')
simple_url_re = re.compile(r'^https?://\[?\w', re.IGNORECASE)
simple_url_2_re = re.compile(r'^www\.|^(?!http)\w[^@]+\.(com|edu|gov|int|mil|net|org)($|/.*)$', re.IGNORECASE)
simple_email_re = re.compile(r'^\S+@\S+\.\S+$')
link_target_attribute_re = re.compile(r'(<a [^>]*?)target=[^\s>]+')
html_gunk_re = re.compile(r'(?:<br clear="all">|<i><\/i>|<b><\/b>|<em><\/em>|<strong><\/strong>|<\/?smallcaps>|<\/?uppercase>)', re.IGNORECASE)
hard_coded_bullets_re = re.compile(r'((?:<p>(?:%s).*?[a-zA-Z].*?</p>\s*)+)' % '|'.join(re.escape(x) for x in DOTS), re.DOTALL)
trailing_empty_content_re = re.compile(r'(?:<p>(?:&nbsp;|\s|<br \/>)*?</p>\s*)+\Z')


def escape(text):
    """
    Returns the given text with ampersands, quotes and angle brackets encoded for use in HTML.
    """
    return mark_safe(force_text(text).replace('&', '&amp;').replace('<', '&lt;').replace('>', '&gt;').replace('"', '&quot;').replace("'", '&#39;'))
escape = allow_lazy(escape, six.text_type)

_js_escapes = {
    ord('\\'): '\\u005C',
    ord('\''): '\\u0027',
    ord('"'): '\\u0022',
    ord('>'): '\\u003E',
    ord('<'): '\\u003C',
    ord('&'): '\\u0026',
    ord('='): '\\u003D',
    ord('-'): '\\u002D',
    ord(';'): '\\u003B',
    ord('\u2028'): '\\u2028',
    ord('\u2029'): '\\u2029'
}

# Escape every ASCII character with a value less than 32.
_js_escapes.update((ord('%c' % z), '\\u%04X' % z) for z in range(32))


def escapejs(value):
    """Hex encodes characters for use in JavaScript strings."""
    return mark_safe(force_text(value).translate(_js_escapes))
escapejs = allow_lazy(escapejs, six.text_type)


def conditional_escape(text):
    """
    Similar to escape(), except that it doesn't operate on pre-escaped strings.
    """
    if hasattr(text, '__html__'):
        return text.__html__()
    else:
        return escape(text)


def format_html(format_string, *args, **kwargs):
    """
    Similar to str.format, but passes all arguments through conditional_escape,
    and calls 'mark_safe' on the result. This function should be used instead
    of str.format or % interpolation to build up small HTML fragments.
    """
    args_safe = map(conditional_escape, args)
    kwargs_safe = dict((k, conditional_escape(v)) for (k, v) in six.iteritems(kwargs))
    return mark_safe(format_string.format(*args_safe, **kwargs_safe))


def format_html_join(sep, format_string, args_generator):
    """
    A wrapper of format_html, for the common case of a group of arguments that
    need to be formatted using the same format string, and then joined using
    'sep'. 'sep' is also passed through conditional_escape.

    'args_generator' should be an iterator that returns the sequence of 'args'
    that will be passed to format_html.

    Example:

      format_html_join('\n', "<li>{0} {1}</li>", ((u.first_name, u.last_name)
                                                  for u in users))

    """
    return mark_safe(conditional_escape(sep).join(
        format_html(format_string, *tuple(args))
        for args in args_generator))


def linebreaks(value, autoescape=False):
    """Converts newlines into <p> and <br />s."""
    value = normalize_newlines(value)
    paras = re.split('\n{2,}', value)
    if autoescape:
        paras = ['<p>%s</p>' % escape(p).replace('\n', '<br />') for p in paras]
    else:
        paras = ['<p>%s</p>' % p.replace('\n', '<br />') for p in paras]
    return '\n\n'.join(paras)
linebreaks = allow_lazy(linebreaks, six.text_type)


class MLStripper(HTMLParser):
    def __init__(self):
        # The strict parameter was added in Python 3.2 with a default of True.
        # The default changed to False in Python 3.3 and was deprecated.
        if sys.version_info[:2] == (3, 2):
            HTMLParser.__init__(self, strict=False)
        else:
            HTMLParser.__init__(self)
        self.reset()
        self.fed = []

    def handle_data(self, d):
        self.fed.append(d)

    def handle_entityref(self, name):
        self.fed.append('&%s;' % name)

    def handle_charref(self, name):
        self.fed.append('&#%s;' % name)

    def get_data(self):
        return ''.join(self.fed)


def _strip_once(value):
    """
    Internal tag stripping utility used by strip_tags.
    """
    s = MLStripper()
    try:
        s.feed(value)
    except HTMLParseError:
        return value
    try:
        s.close()
    except (HTMLParseError, UnboundLocalError):
        # UnboundLocalError because of http://bugs.python.org/issue17802
        # on Python 3.2, triggered by strict=False mode of HTMLParser
        return s.get_data() + s.rawdata
    else:
        return s.get_data()


def strip_tags(value):
    """Returns the given HTML with all tags stripped."""
    # Note: in typical case this loop executes _strip_once once. Loop condition
    # is redundant, but helps to reduce number of executions of _strip_once.
    while '<' in value and '>' in value:
        new_value = _strip_once(value)
        if new_value == value:
            # _strip_once was not able to detect more tags
            break
        value = new_value
    return value
strip_tags = allow_lazy(strip_tags)


def remove_tags(html, tags):
    """Returns the given HTML with given tags removed."""
    tags = [re.escape(tag) for tag in tags.split()]
    tags_re = '(%s)' % '|'.join(tags)
    starttag_re = re.compile(r'<%s(/?>|(\s+[^>]*>))' % tags_re, re.U)
    endtag_re = re.compile('</%s>' % tags_re)
    html = starttag_re.sub('', html)
    html = endtag_re.sub('', html)
    return html
remove_tags = allow_lazy(remove_tags, six.text_type)


def strip_spaces_between_tags(value):
    """Returns the given HTML with spaces between tags removed."""
    return re.sub(r'>\s+<', '><', force_text(value))
strip_spaces_between_tags = allow_lazy(strip_spaces_between_tags, six.text_type)


def strip_entities(value):
    """Returns the given HTML with all entities (&something;) stripped."""
    return re.sub(r'&(?:\w+|#\d+);', '', force_text(value))
strip_entities = allow_lazy(strip_entities, six.text_type)


def smart_urlquote(url):
    "Quotes a URL if it isn't already quoted."
    # Handle IDN before quoting.
    try:
        scheme, netloc, path, query, fragment = urlsplit(url)
        try:
            netloc = netloc.encode('idna').decode('ascii')  # IDN -> ACE
        except UnicodeError:  # invalid domain part
            pass
        else:
            url = urlunsplit((scheme, netloc, path, query, fragment))
    except ValueError:
        # invalid IPv6 URL (normally square brackets in hostname part).
        pass

    url = unquote(force_str(url))
    # See http://bugs.python.org/issue2637
    url = quote(url, safe=RFC3986_SUBDELIMS + RFC3986_GENDELIMS + str('~'))

    return force_text(url)


def urlize(text, trim_url_limit=None, nofollow=False, autoescape=False):
    """
    Converts any URLs in text into clickable links.

    Works on http://, https://, www. links, and also on links ending in one of
    the original seven gTLDs (.com, .edu, .gov, .int, .mil, .net, and .org).
    Links can have trailing punctuation (periods, commas, close-parens) and
    leading punctuation (opening parens) and it'll still do the right thing.

    If trim_url_limit is not None, the URLs in the link text longer than this
    limit will be truncated to trim_url_limit-3 characters and appended with
    an ellipsis.

    If nofollow is True, the links will get a rel="nofollow" attribute.

    If autoescape is True, the link text and URLs will be autoescaped.
    """
    def trim_url(x, limit=trim_url_limit):
        if limit is None or len(x) <= limit:
            return x
        return '%s...' % x[:max(0, limit - 3)]
    safe_input = isinstance(text, SafeData)
    words = word_split_re.split(force_text(text))
    for i, word in enumerate(words):
        if '.' in word or '@' in word or ':' in word:
            # Deal with punctuation.
            lead, middle, trail = '', word, ''
            for punctuation in TRAILING_PUNCTUATION:
                if middle.endswith(punctuation):
                    middle = middle[:-len(punctuation)]
                    trail = punctuation + trail
            for opening, closing in WRAPPING_PUNCTUATION:
                if middle.startswith(opening):
                    middle = middle[len(opening):]
                    lead = lead + opening
                # Keep parentheses at the end only if they're balanced.
                if (middle.endswith(closing)
                        and middle.count(closing) == middle.count(opening) + 1):
                    middle = middle[:-len(closing)]
                    trail = closing + trail

            # Make URL we want to point to.
            url = None
            nofollow_attr = ' rel="nofollow"' if nofollow else ''
            if simple_url_re.match(middle):
                url = smart_urlquote(middle)
            elif simple_url_2_re.match(middle):
                url = smart_urlquote('http://%s' % middle)
            elif ':' not in middle and simple_email_re.match(middle):
                local, domain = middle.rsplit('@', 1)
                try:
                    domain = domain.encode('idna').decode('ascii')
                except UnicodeError:
                    continue
                url = 'mailto:%s@%s' % (local, domain)
                nofollow_attr = ''

            # Make link.
            if url:
                trimmed = trim_url(middle)
                if autoescape and not safe_input:
                    lead, trail = escape(lead), escape(trail)
                    url, trimmed = escape(url), escape(trimmed)
                middle = '<a href="%s"%s>%s</a>' % (url, nofollow_attr, trimmed)
                words[i] = mark_safe('%s%s%s' % (lead, middle, trail))
            else:
                if safe_input:
                    words[i] = mark_safe(word)
                elif autoescape:
                    words[i] = escape(word)
        elif safe_input:
            words[i] = mark_safe(word)
        elif autoescape:
            words[i] = escape(word)
    return ''.join(words)
urlize = allow_lazy(urlize, six.text_type)


def avoid_wrapping(value):
    """
    Avoid text wrapping in the middle of a phrase by adding non-breaking
    spaces where there previously were normal spaces.
    """
    return value.replace(" ", "\xa0")