text: import re
  from xml.sax.saxutils import escape, unescape
  
  from .tokenizer import HTMLTokenizer
  from .constants import tokenTypes
  
  class HTMLSanitizerMixin(object):
      """ sanitization of XHTML+MathML+SVG and of inline style attributes."""
  
      acceptable_elements = ['a', 'abbr', 'acronym', 'address', 'area',
          'article', 'aside', 'audio', 'b', 'big', 'blockquote', 'br', 'button',
          'canvas', 'caption', 'center', 'cite', 'code', 'col', 'colgroup',
          'command', 'datagrid', 'datalist', 'dd', 'del', 'details', 'dfn',
          'dialog', 'dir', 'div', 'dl', 'dt', 'em', 'event-source', 'fieldset',
          'figcaption', 'figure', 'footer', 'font', 'form', 'header', 'h1',
          'h2', 'h3', 'h4', 'h5', 'h6', 'hr', 'i', 'img', 'input', 'ins',
          'keygen', 'kbd', 'label', 'legend', 'li', 'm', 'map', 'menu', 'meter',
          'multicol', 'nav', 'nextid', 'ol', 'output', 'optgroup', 'option',
          'p', 'pre', 'progress', 'q', 's', 'samp', 'section', 'select',
          'small', 'sound', 'source', 'spacer', 'span', 'strike', 'strong',
          'sub', 'sup', 'table', 'tbody', 'td', 'textarea', 'time', 'tfoot',
          'th', 'thead', 'tr', 'tt', 'u', 'ul', 'var', 'video']
        
      mathml_elements = ['maction', 'math', 'merror', 'mfrac', 'mi',
          'mmultiscripts', 'mn', 'mo', 'mover', 'mpadded', 'mphantom',
          'mprescripts', 'mroot', 'mrow', 'mspace', 'msqrt', 'mstyle', 'msub',
          'msubsup', 'msup', 'mtable', 'mtd', 'mtext', 'mtr', 'munder',
          'munderover', 'none']
        
      svg_elements = ['a', 'animate', 'animateColor', 'animateMotion',
          'animateTransform', 'clipPath', 'circle', 'defs', 'desc', 'ellipse',
          'font-face', 'font-face-name', 'font-face-src', 'g', 'glyph', 'hkern',
          'linearGradient', 'line', 'marker', 'metadata', 'missing-glyph',
          'mpath', 'path', 'polygon', 'polyline', 'radialGradient', 'rect',
          'set', 'stop', 'svg', 'switch', 'text', 'title', 'tspan', 'use']
          
      acceptable_attributes = ['abbr', 'accept', 'accept-charset', 'accesskey',
          'action', 'align', 'alt', 'autocomplete', 'autofocus', 'axis',
          'background', 'balance', 'bgcolor', 'bgproperties', 'border',
          'bordercolor', 'bordercolordark', 'bordercolorlight', 'bottompadding',
          'cellpadding', 'cellspacing', 'ch', 'challenge', 'char', 'charoff',
          'choff', 'charset', 'checked', 'cite', 'class', 'clear', 'color',
          'cols', 'colspan', 'compact', 'contenteditable', 'controls', 'coords',
          'data', 'datafld', 'datapagesize', 'datasrc', 'datetime', 'default',
          'delay', 'dir', 'disabled', 'draggable', 'dynsrc', 'enctype', 'end',
          'face', 'for', 'form', 'frame', 'galleryimg', 'gutter', 'headers',
          'height', 'hidefocus', 'hidden', 'high', 'href', 'hreflang', 'hspace',
          'icon', 'id', 'inputmode', 'ismap', 'keytype', 'label', 'leftspacing',
          'lang', 'list', 'longdesc', 'loop', 'loopcount', 'loopend',
          'loopstart', 'low', 'lowsrc', 'max', 'maxlength', 'media', 'method',
          'min', 'multiple', 'name', 'nohref', 'noshade', 'nowrap', 'open',
          'optimum', 'pattern', 'ping', 'point-size', 'poster', 'pqg', 'preload',
          'prompt', 'radiogroup', 'readonly', 'rel', 'repeat-max', 'repeat-min',
          'replace', 'required', 'rev', 'rightspacing', 'rows', 'rowspan',
          'rules', 'scope', 'selected', 'shape', 'size', 'span', 'src', 'start',
          'step', 'style', 'summary', 'suppress', 'tabindex', 'target',
          'template', 'title', 'toppadding', 'type', 'unselectable', 'usemap',
          'urn', 'valign', 'value', 'variable', 'volume', 'vspace', 'vrml',
          'width', 'wrap', 'xml:lang']
  
      mathml_attributes = ['actiontype', 'align', 'columnalign', 'columnalign',
          'columnalign', 'columnlines', 'columnspacing', 'columnspan', 'depth',
          'display', 'displaystyle', 'equalcolumns', 'equalrows', 'fence',
          'fontstyle', 'fontweight', 'frame', 'height', 'linethickness', 'lspace',
          'mathbackground', 'mathcolor', 'mathvariant', 'mathvariant', 'maxsize',
          'minsize', 'other', 'rowalign', 'rowalign', 'rowalign', 'rowlines',
          'rowspacing', 'rowspan', 'rspace', 'scriptlevel', 'selection',
          'separator', 'stretchy', 'width', 'width', 'xlink:href', 'xlink:show',
          'xlink:type', 'xmlns', 'xmlns:xlink']
    
      svg_attributes = ['accent-height', 'accumulate', 'additive', 'alphabetic',
          'arabic-form', 'ascent', 'attributeName', 'attributeType',
          'baseProfile', 'bbox', 'begin', 'by', 'calcMode', 'cap-height',
          'class', 'clip-path', 'color', 'color-rendering', 'content', 'cx',
          'cy', 'd', 'dx', 'dy', 'descent', 'display', 'dur', 'end', 'fill',
          'fill-opacity', 'fill-rule', 'font-family', 'font-size',
          'font-stretch', 'font-style', 'font-variant', 'font-weight', 'from',
          'fx', 'fy', 'g1', 'g2', 'glyph-name', 'gradientUnits', 'hanging',
          'height', 'horiz-adv-x', 'horiz-origin-x', 'id', 'ideographic', 'k',
          'keyPoints', 'keySplines', 'keyTimes', 'lang', 'marker-end',
          'marker-mid', 'marker-start', 'markerHeight', 'markerUnits',
          'markerWidth', 'mathematical', 'max', 'min', 'name', 'offset',
          'opacity', 'orient', 'origin', 'overline-position',
          'overline-thickness', 'panose-1', 'path', 'pathLength', 'points',
          'preserveAspectRatio', 'r', 'refX', 'refY', 'repeatCount',
          'repeatDur', 'requiredExtensions', 'requiredFeatures', 'restart',
          'rotate', 'rx', 'ry', 'slope', 'stemh', 'stemv', 'stop-color',
          'stop-opacity', 'strikethrough-position', 'strikethrough-thickness',
          'stroke', 'stroke-dasharray', 'stroke-dashoffset', 'stroke-linecap',
          'stroke-linejoin', 'stroke-miterlimit', 'stroke-opacity',
          'stroke-width', 'systemLanguage', 'target', 'text-anchor', 'to',
          'transform', 'type', 'u1', 'u2', 'underline-position',
          'underline-thickness', 'unicode', 'unicode-range', 'units-per-em',
          'values', 'version', 'viewBox', 'visibility', 'width', 'widths', 'x',
          'x-height', 'x1', 'x2', 'xlink:actuate', 'xlink:arcrole',
          'xlink:href', 'xlink:role', 'xlink:show', 'xlink:title', 'xlink:type',
          'xml:base', 'xml:lang', 'xml:space', 'xmlns', 'xmlns:xlink', 'y',
          'y1', 'y2', 'zoomAndPan']
  
      attr_val_is_uri = ['href', 'src', 'cite', 'action', 'longdesc', 'poster',
          'xlink:href', 'xml:base']
  
      svg_attr_val_allows_ref = ['clip-path', 'color-profile', 'cursor', 'fill',
          'filter', 'marker', 'marker-start', 'marker-mid', 'marker-end',
          'mask', 'stroke']
  
      svg_allow_local_href = ['altGlyph', 'animate', 'animateColor',
          'animateMotion', 'animateTransform', 'cursor', 'feImage', 'filter',
          'linearGradient', 'pattern', 'radialGradient', 'textpath', 'tref',
          'set', 'use']
    
      acceptable_css_properties = ['azimuth', 'background-color',
          'border-bottom-color', 'border-collapse', 'border-color',
          'border-left-color', 'border-right-color', 'border-top-color', 'clear',
          'color', 'cursor', 'direction', 'display', 'elevation', 'float', 'font',
          'font-family', 'font-size', 'font-style', 'font-variant', 'font-weight',
          'height', 'letter-spacing', 'line-height', 'overflow', 'pause',
          'pause-after', 'pause-before', 'pitch', 'pitch-range', 'richness',
          'speak', 'speak-header', 'speak-numeral', 'speak-punctuation',
          'speech-rate', 'stress', 'text-align', 'text-decoration', 'text-indent',
          'unicode-bidi', 'vertical-align', 'voice-family', 'volume',
          'white-space', 'width']
    
      acceptable_css_keywords = ['auto', 'aqua', 'black', 'block', 'blue',
          'bold', 'both', 'bottom', 'brown', 'center', 'collapse', 'dashed',
          'dotted', 'fuchsia', 'gray', 'green', '!important', 'italic', 'left',
          'lime', 'maroon', 'medium', 'none', 'navy', 'normal', 'nowrap', 'olive',
          'pointer', 'purple', 'red', 'right', 'solid', 'silver', 'teal', 'top',
          'transparent', 'underline', 'white', 'yellow']
    
      acceptable_svg_properties = [ 'fill', 'fill-opacity', 'fill-rule',
          'stroke', 'stroke-width', 'stroke-linecap', 'stroke-linejoin',
          'stroke-opacity']
    
      acceptable_protocols = [ 'ed2k', 'ftp', 'http', 'https', 'irc',
          'mailto', 'news', 'gopher', 'nntp', 'telnet', 'webcal',
          'xmpp', 'callto', 'feed', 'urn', 'aim', 'rsync', 'tag',
          'ssh', 'sftp', 'rtsp', 'afs' ]
    
      # subclasses may define their own versions of these constants
      allowed_elements = acceptable_elements + mathml_elements + svg_elements
      allowed_attributes = acceptable_attributes + mathml_attributes + svg_attributes
      allowed_css_properties = acceptable_css_properties
      allowed_css_keywords = acceptable_css_keywords
      allowed_svg_properties = acceptable_svg_properties
      allowed_protocols = acceptable_protocols
  
      # Sanitize the +html+, escaping all elements not in ALLOWED_ELEMENTS, and
      # stripping out all # attributes not in ALLOWED_ATTRIBUTES. Style
      # attributes are parsed, and a restricted set, # specified by
      # ALLOWED_CSS_PROPERTIES and ALLOWED_CSS_KEYWORDS, are allowed through.
      # attributes in ATTR_VAL_IS_URI are scanned, and only URI schemes specified
      # in ALLOWED_PROTOCOLS are allowed.
      #
      #   sanitize_html('<script> do_nasty_stuff() </script>')
      #    => &lt;script> do_nasty_stuff() &lt;/script>
      #   sanitize_html('<a href="javascript: sucker();">Click here for $100</a>')
      #    => <a>Click here for $100</a>
      def sanitize_token(self, token):
  
          # accommodate filters which use token_type differently
          token_type = token["type"]
          if token_type in list(tokenTypes.keys()):
            token_type = tokenTypes[token_type]
  
          if token_type in (tokenTypes["StartTag"], tokenTypes["EndTag"], 
                               tokenTypes["EmptyTag"]):
              if token["name"] in self.allowed_elements:
                  if "data" in token:
                      attrs = dict([(name,val) for name,val in
                                    token["data"][::-1] 
                                    if name in self.allowed_attributes])
                      for attr in self.attr_val_is_uri:
                          if attr not in attrs:
                              continue
                          val_unescaped = re.sub("[`\000-\040\177-\240\s]+", '',
                                                 unescape(attrs[attr])).lower()
                          #remove replacement characters from unescaped characters
                          val_unescaped = val_unescaped.replace("\ufffd", "")
                          if (re.match("^[a-z0-9][-+.a-z0-9]*:",val_unescaped) and
                              (val_unescaped.split(':')[0] not in 
                               self.allowed_protocols)):
                              del attrs[attr]
                      for attr in self.svg_attr_val_allows_ref:
                          if attr in attrs:
                              attrs[attr] = re.sub(r'url\s*\(\s*[^#\s][^)]+?\)',
                                                   ' ',
                                                   unescape(attrs[attr]))
                      if (token["name"] in self.svg_allow_local_href and
                          'xlink:href' in attrs and re.search('^\s*[^#\s].*',
                                                              attrs['xlink:href'])):
                          del attrs['xlink:href']
                      if 'style' in attrs:
                          attrs['style'] = self.sanitize_css(attrs['style'])
                      token["data"] = [[name,val] for name,val in list(attrs.items())]
                  return token
              else:
                  if token_type == tokenTypes["EndTag"]:
                      token["data"] = "</%s>" % token["name"]
                  elif token["data"]:
                      attrs = ''.join([' %s="%s"' % (k,escape(v)) for k,v in token["data"]])
                      token["data"] = "<%s%s>" % (token["name"],attrs)
                  else:
                      token["data"] = "<%s>" % token["name"]
                  if token.get("selfClosing"):
                      token["data"]=token["data"][:-1] + "/>"
  
                  if token["type"] in list(tokenTypes.keys()):
                      token["type"] = "Characters"
                  else:
                      token["type"] = tokenTypes["Characters"]
  
                  del token["name"]
                  return token
          elif token_type == tokenTypes["Comment"]:
              pass
          else:
              return token
  
      def sanitize_css(self, style):
          # disallow urls
          style=re.compile('url\s*\(\s*[^\s)]+?\s*\)\s*').sub(' ',style)
  
          # gauntlet
          if not re.match("""^([:,;#%.\sa-zA-Z0-9!]|\w-\w|'[\s\w]+'|"[\s\w]+"|\([\d,\s]+\))*$""", style): return ''
          if not re.match("^\s*([-\w]+\s*:[^:;]*(;\s*|$))*$", style): return ''
  
          clean = []
          for prop,value in re.findall("([-\w]+)\s*:\s*([^:;]*)",style):
            if not value: continue
            if prop.lower() in self.allowed_css_properties:
                clean.append(prop + ': ' + value + ';')
            elif prop.split('-')[0].lower() in ['background','border','margin',
                                                'padding']:
                for keyword in value.split():
                    if not keyword in self.acceptable_css_keywords and \
                        not re.match("^(#[0-9a-f]+|rgb\(\d+%?,\d*%?,?\d*%?\)?|\d{0,2}\.?\d{0,2}(cm|em|ex|in|mm|pc|pt|px|%|,|\))?)$",keyword):
                        break
                else:
                    clean.append(prop + ': ' + value + ';')
            elif prop.lower() in self.allowed_svg_properties:
                clean.append(prop + ': ' + value + ';')
  
          return ' '.join(clean)
  
  class HTMLSanitizer(HTMLTokenizer, HTMLSanitizerMixin):
      def __init__(self, stream, encoding=None, parseMeta=True, useChardet=True,
                   lowercaseElementName=False, lowercaseAttrName=False, parser=None):
          #Change case matching defaults as we only output lowercase html anyway
          #This solution doesn't seem ideal...
          HTMLTokenizer.__init__(self, stream, encoding, parseMeta, useChardet,
                                 lowercaseElementName, lowercaseAttrName, parser=parser)
  
      def __iter__(self):
          for token in HTMLTokenizer.__iter__(self):
              token = self.sanitize_token(token)
              if token:
                  yield token
  