# -*- coding: UTF-8 -*-

"""

some input filters, for regularising the html fragments from screen scraping and 

browser-based editors into some semblance of sanity

TODO: turn the messy setting[method_name]=True filter syntax into a list of cleaning methods to invoke, so that they can be invoked in a specific order and multiple times.

AUTHORS:

Dan MacKinlay - https://launchpad.net/~dan-possumpalace

Collin Grady - http://launchpad.net/~collin-collingrady

Andreas Gustafsson - https://bugs.launchpad.net/~gson

Håkan W - https://launchpad.net/~hwaara-gmail

"""

import BeautifulSoup

import re

import sys

# Python 2.4 compatibility

try: any

except NameError:

    def any(iterable):

        for element in iterable:

            if element:

                return True

        return False

"""

html5lib compatibility. Basically, we need to know that this still works whether html5lib

is imported or not. Should run complete suites of tests for both possible configs -

or test in virtual environments, but for now a basic sanity check will do.

>>> if html5:

>>>     c=Cleaner(html5=False)

>>>     c(u'<p>foo</p>)

u'<p>foo</p>'

"""

try:

    import html5lib

    from html5lib import sanitizer, treebuilders

    parser = html5lib.HTMLParser(

        tree=treebuilders.getTreeBuilder("beautifulsoup"),

        tokenizer=sanitizer.HTMLSanitizer

    )

    html5 = True

except ImportError:

    html5 = False

ANTI_JS_RE=re.compile('j\s*a\s*v\s*a\s*s\s*c\s*r\s*i\s*p\s*t\s*:', re.IGNORECASE)

#These tags and attrs are sufficently liberal to let microformats through...

#it ruthlessly culls all the rdf, dublin core metadata and so on.

valid_tags = dict.fromkeys('p i em strong b u a h1 h2 h3 pre abbr br img dd dt ol ul li span sub sup ins del blockquote table tr td th address cite'.split()) #div?

valid_attrs = dict.fromkeys('href src rel title'.split())

valid_schemes = dict.fromkeys('http https'.split())

elem_map = {'b' : 'strong', 'i': 'em'}

attrs_considered_links = dict.fromkeys("src href".split()) #should include

#courtesy http://developer.mozilla.org/en/docs/HTML:Block-level_elements

block_elements = dict.fromkeys(["p", "h1","h2", "h3", "h4", "h5", "h6", "ol", "ul", "pre", "address", "blockquote", "dl", "div", "fieldset", "form", "hr", "noscript", "table"])

#convenient default filter lists.

paranoid_filters = ["strip_comments", "strip_tags", "strip_attrs",

  "strip_schemes", "rename_tags", "wrap_string", "strip_empty_tags", "strip_empty_tags", ]

complete_filters = ["strip_comments", "rename_tags", "strip_tags", "strip_attrs",

    "strip_cdata", "strip_schemes",  "wrap_string", "strip_empty_tags", "rebase_links", "reparse"]

#set some conservative default string processings

default_settings = {

    "filters" : paranoid_filters,

    "block_elements" : block_elements, #xml or None for a more liberal version

    "convert_entities" : "html", #xml or None for a more liberal version

    "valid_tags" : valid_tags,

    "valid_attrs" : valid_attrs,

    "valid_schemes" : valid_schemes,

    "attrs_considered_links" : attrs_considered_links,

    "elem_map" : elem_map,

    "wrapping_element" : "p",

    "auto_clean" : False,

    "original_url" : "",

    "new_url" : "",

    "html5" : html5

}

#processes I'd like but haven't implemented            

#"encode_xml_specials", "ensure complete xhtml doc", "ensure_xhtml_fragment_only"

# and some handling of permitted namespaces for tags. for RDF, say. maybe.

XML_ENTITIES = { u"'" : u"'",

                 u'"' : u""",

                 u"&" : u"&",

                 u"<" : u"&lt;",

                 u">" : u">"

               }

LINE_EXTRACTION_RE = re.compile(".+", re.MULTILINE)

BR_EXTRACTION_RE = re.compile("</?br ?/?>", re.MULTILINE)

class Stop:

    """

    handy class that we use as a stop input for our state machine in lieu of falling

    off the end of lists

    """

    pass

class Cleaner(object):

    r"""

    powerful and slow arbitrary HTML sanitisation. can deal (i hope) with most XSS

    vectors and layout-breaking badness.

    Probably overkill for content from trusted sources; defaults are accordingly

    set to be paranoid.

    >>> bad_html = '<p style="forbidden markup"><!-- XSS attach -->content</p'

    >>> good_html = u'<p>content</p>'

    >>> c = Cleaner()

    >>> c.string = bad_html

    >>> c.clean()

    >>> c.string == good_html

    True

    Also supports shorthand syntax:

    >>> c = Cleaner()

    >>> c(bad_html) == c(good_html)

    True

    """

    def __init__(self, string_or_soup="", *args,  **kwargs):

        self.settings=default_settings.copy()

        self.settings.update(kwargs)

        if args :

            self.settings['filters'] = args

        self.string = string_or_soup

    def __call__(self, string = None, **kwargs):

        """

        convenience method allowing one-step calling of an instance and returning

        a cleaned string.

        TODO: make this method preserve internal state- perhaps by creating a new

        instance.

        >>> s = 'input string'

        >>> c1 = Cleaner(s, auto_clean=True)

        >>> c2 = Cleaner("")

        >>> c1.string == c2(s)

        True

        """

        self.settings.update(kwargs)

        if not string == None :

            self.string = string

        self.clean()

        return self.string

    def _set_contents(self, string_or_soup):

        if isinstance(string_or_soup, BeautifulSoup.BeautifulSoup) :

            self._set_soup(string_or_soup)

        else :

            self._set_string(string_or_soup)

    def _set_string(self, html_fragment_string):

        if self.settings['html5']:

            s = parser.parse(html_fragment_string).body

        else:

            s = BeautifulSoup.BeautifulSoup(

                    html_fragment_string,

                    convertEntities=self.settings['convert_entities'])

        self._set_soup(s)

    def _set_soup(self, soup):

        """

        Does all the work of set_string, but bypasses a potential autoclean to avoid 

        loops upon internal string setting ops.

        """

        self._soup = BeautifulSoup.BeautifulSoup(

            '<rootrootroot></rootrootroot>'

        )

        self.root=self._soup.contents[0]

        if len(soup.contents) :

            backwards_soup = [i for i in soup.contents]

            backwards_soup.reverse()

        else :

            backwards_soup = []

        for i in backwards_soup :

            i.extract()

            self.root.insert(0, i)

    def set_string(self, string) :

        ur"""

            sets the string to process and does the necessary input encoding too

        really intended to be invoked as a property.

        note the godawful rootrootroot element which we need because the

        BeautifulSoup object has all the same methods as a Tag, but

        behaves differently, silently failing on some inserts and appends

        >>> c = Cleaner(convert_entities="html")

        >>> c.string = 'é'

        >>> c.string

        u'\xe9'

        >>> c = Cleaner(convert_entities="xml")

        >>> c.string = u'é'

        >>> c.string

        u'é'

        """

        self._set_string(string)

        if len(string) and self.settings['auto_clean'] : self.clean()

    def get_string(self):

        return self.root.renderContents().decode('utf-8')

    string = property(get_string, set_string)

    def clean(self):

        """

        invoke all cleaning processes stipulated in the settings

        """

        for method in self.settings['filters'] :

            try :

                getattr(self, method)()

            except NotImplementedError :

                sys.stderr.write('Warning, called unimplemented method %s' % method + '\n')

    def strip_comments(self):

        r"""

        XHTML comments are used as an XSS attack vector. they must die.

        >>> c = Cleaner("", "strip_comments")

        >>> c('<p>text<!-- comment --> More text</p>')

        u'<p>text More text</p>'

        """

        for comment in self.root.findAll(

            text = lambda text: isinstance(text, BeautifulSoup.Comment)):

            comment.extract()

    def strip_cdata(self):

        for cdata in self.root.findAll(

          text = lambda text: isinstance(text, BeautifulSoup.CData)):

            cdata.extract()

    def strip_tags(self):

        r"""

        ill-considered tags break our layout. they must die.

        >>> c = Cleaner("", "strip_tags", auto_clean=True)

        >>> c.string = '<div>A <strong>B C</strong></div>'

        >>> c.string

        u'A <strong>B C</strong>'

        >>> c.string = '<div>A <div>B C</div></div>'

        >>> c.string

        u'A B C'

        >>> c.string = '<div>A <br /><div>B C</div></div>'

        >>> c.string

        u'A <br />B C'

        >>> c.string = '<p>A <div>B C</div></p>'

        >>> c.string

        u'<p>A B C</p>'

        >>> c.string = 'A<div>B<div>C<div>D</div>E</div>F</div>G'

        >>> c.string

        u'ABCDEFG'

        >>> c.string = '<div>B<div>C<div>D</div>E</div>F</div>'

        >>> c.string

        u'BCDEF'

        """

        # Beautiful Soup doesn't support dynamic .findAll results when the tree is

        # modified in place.

        # going backwards doesn't seem to help.

        # so find one at a time

        while True :

            next_bad_tag = self.root.find(

              lambda tag : not tag.name in (self.settings['valid_tags'])

            )

            if next_bad_tag :                

                self.disgorge_elem(next_bad_tag)

            else:

                break

    def strip_attrs(self):

        """

        preserve only those attributes we need in the soup

        >>> c = Cleaner("", "strip_attrs")

        >>> c('<div title="v" bad="v">A <strong title="v" bad="v">B C</strong></div>')

        u'<div title="v">A <strong title="v">B C</strong></div>'

        """

        for tag in self.root.findAll(True):

            tag.attrs = [(attr, val) for attr, val in tag.attrs

                         if attr in self.settings['valid_attrs']]

    def _all_links(self):

        """

        finds all tags with link attributes sequentially. safe against modification

        of said attributes in-place.

        """

        start = self.root

        while True: 

            tag = start.findNext(

              lambda tag : any(

                [(tag.get(i) for i in self.settings['attrs_considered_links'])]

              ))

            if tag: 

                start = tag

                yield tag

            else :

                break

    def strip_schemes(self):

        """

        >>> c = Cleaner("", "strip_schemes")

        >>> c('<img src="javascript:alert();" />')

        u'<img />'

        >>> c('<a href="javascript:alert();">foo</a>')

        u'<a>foo</a>'

        """

        for tag in self._all_links() :

            for key in self.settings['attrs_considered_links'] :

                scheme_bits = tag.get(key, u"").split(u':',1)

                if len(scheme_bits) == 1 : 

                    pass #relative link

                else:

		    if not scheme_bits[0] in self.settings['valid_schemes'] :

			del(tag[key])

    def br_to_p(self):

        """

        >>> c = Cleaner("", "br_to_p")

        >>> c('<p>A<br />B</p>')

        u'<p>A</p><p>B</p>'

        >>> c('A<br />B')

        u'<p>A</p><p>B</p>'

        """

        block_elems = self.settings['block_elements']

        block_elems['br'] = None

        block_elems['p'] = None

        while True :

            next_br = self.root.find('br')

            if not next_br: break

            parent = next_br.parent

            self.wrap_string('p', start_at=parent, block_elems = block_elems)

            while True:

                useless_br=parent.find('br', recursive=False)

                if not useless_br: break

                useless_br.extract()        

            if parent.name == 'p':

                self.disgorge_elem(parent)

    def rename_tags(self):

        """

        >>> c = Cleaner("", "rename_tags", elem_map={'i': 'em'})

        >>> c('<b>A<i>B</i></b>')

        u'<b>A<em>B</em></b>'

        """

        for tag in self.root.findAll(self.settings['elem_map']) :

            tag.name = self.settings['elem_map'][tag.name]

    def wrap_string(self, wrapping_element = None, start_at=None, block_elems=None):

        """

        takes an html fragment, which may or may not have a single containing element,

        and guarantees what the tag name of the topmost elements are.

        TODO: is there some simpler way than a state machine to do this simple thing?

        >>> c = Cleaner("", "wrap_string")

        >>> c('A <strong>B C</strong>D')

        u'<p>A <strong>B C</strong>D</p>'

        >>> c('A <p>B C</p>D')

        u'<p>A </p><p>B C</p><p>D</p>'

        """

        if not start_at : start_at = self.root

        if not block_elems : block_elems = self.settings['block_elements']

        e = (wrapping_element or self.settings['wrapping_element'])

        paragraph_list = []

        children = [elem for elem in start_at.contents]

        children.append(Stop())

        last_state = 'block'

        paragraph = BeautifulSoup.Tag(self._soup, e)

        for node in children :

            if isinstance(node, Stop) :

                state = 'end'

            elif hasattr(node, 'name') and node.name in block_elems:

                state = 'block'

            else:

                state = 'inline'

            if last_state == 'block' and state == 'inline':

                #collate inline elements

                paragraph = BeautifulSoup.Tag(self._soup, e)

            if state == 'inline' :

                paragraph.append(node)

            if ((state <> 'inline') and last_state == 'inline') :

                paragraph_list.append(paragraph)

            if state == 'block' :

                paragraph_list.append(node)

            last_state = state

        #can't use append since it doesn't work on empty elements...

        paragraph_list.reverse()

        for paragraph in paragraph_list:

            start_at.insert(0, paragraph)

    def strip_empty_tags(self):

        """

        strip out all empty tags

        TODO: depth-first search

        >>> c = Cleaner("", "strip_empty_tags")

        >>> c('<p>A</p><p></p><p>B</p><p></p>')

        u'<p>A</p><p>B</p>'

        >>> c('<p><a></a></p>')

        u'<p></p>'

        """

        tag = self.root

        while True:

            next_tag = tag.findNext(True)

            if not next_tag: break

            if next_tag.contents or next_tag.attrs:

                tag = next_tag

                continue

            next_tag.extract()

    def rebase_links(self, original_url="", new_url ="") :

        if not original_url : original_url = self.settings.get('original_url', '')

        if not new_url : new_url = self.settings.get('new_url', '')

        raise NotImplementedError

    # Because of its internal character set handling,

    # the following will not work in Beautiful soup and is hopefully redundant.

    # def encode_xml_specials(self, original_url="", new_url ="") :

    #     """

    #     BeautifulSoup will let some dangerous xml entities hang around

    #     in the navigable strings. destroy all monsters.

    #     >>> c = Cleaner(auto_clean=True, encode_xml_specials=True)

    #     >>> c('<<<<<')

    #     u'<<<<'

    #     """

    #     for string in self.root.findAll(text=True) :

    #         sys.stderr.write("root" +"\n")

    #         sys.stderr.write(str(self.root) +"\n")

    #         sys.stderr.write("parent" +"\n")

    #         sys.stderr.write(str(string.parent) +"\n")

    #         new_string = unicode(string)

    #         sys.stderr.write(string +"\n")

    #         for special_char in XML_ENTITIES.keys() :

    #             sys.stderr.write(special_char +"\n")

    #         string.replaceWith(

    #           new_string.replace(special_char, XML_ENTITIES[special_char])

    #         )

    def disgorge_elem(self, elem):

        """

        remove the given element from the soup and replaces it with its own contents

        actually tricky, since you can't replace an element with an list of elements

        using replaceWith

        >>> disgorgeable_string = '<body>A <em>B</em> C</body>'

        >>> c = Cleaner()

        >>> c.string = disgorgeable_string

        >>> elem = c._soup.find('em')

        >>> c.disgorge_elem(elem)

        >>> c.string

        u'<body>A B C</body>'

        >>> c.string = disgorgeable_string

        >>> elem = c._soup.find('body')

        >>> c.disgorge_elem(elem)

        >>> c.string

        u'A <em>B</em> C'

        >>> c.string = '<div>A <div id="inner">B C</div></div>'

        >>> elem = c._soup.find(id="inner")

        >>> c.disgorge_elem(elem)

        >>> c.string

        u'<div>A B C</div>'

        """

        if elem == self.root :

            raise AttributeError, "Can't disgorge root"  

        # With in-place modification, BeautifulSoup occasionally can return

        # elements that think they are orphans

        # this lib is full of workarounds, but it's worth checking

        parent = elem.parent

        if parent == None: 

            raise AttributeError, "AAAAAAAAGH! NO PARENTS! DEATH!"

        i = None

        for i in range(len(parent.contents)) :

            if parent.contents[i] == elem :

                index = i

                break

        elem.extract()

        #the proceeding method breaks horribly, sporadically.

        # for i in range(len(elem.contents)) :

        #     elem.contents[i].extract()

        #     parent.contents.insert(index+i, elem.contents[i])

        # return

        self._safe_inject(parent, index, elem.contents)

    def _safe_inject(self, dest, dest_index, node_list):

        #BeautifulSoup result sets look like lists but don't behave right

        # i.e. empty ones are still True,

        if not len(node_list) : return

        node_list = [i for i in node_list]

        node_list.reverse()

        for i in node_list :

            dest.insert(dest_index, i)

class Htmlator(object) :

    """

    converts a string into a series of html paragraphs

    """

    settings = {

        "encode_xml_specials" : True,

        "is_plaintext" : True,

        "convert_newlines" : False,

        "make_links" : True,

        "auto_convert" : False,

        "valid_schemes" : valid_schemes,

    }

    def __init__(self, string = "",  **kwargs):

        self.settings.update(kwargs)

        super(Htmlator, self).__init__(string, **kwargs)

        self.string = string

    def _set_string(self, string):

        self.string = string

        if self.settings['auto_convert'] : self.convert()

    def _get_string(self):

        return unicode(self._soup)