module Loofah::HTML5::Scrub

def allowed_element? element_name
  ::Loofah::HTML5::SafeList::ALLOWED_ELEMENTS_WITH_LIBXML2.include? element_name
end

def force_correct_attribute_escaping! node
  return unless Nokogiri::VersionInfo.instance.libxml2?
  node.attribute_nodes.each do |attr_node|
    next unless LibxmlWorkarounds::BROKEN_ESCAPING_ATTRIBUTES.include?(attr_node.name)
    tag_name = LibxmlWorkarounds::BROKEN_ESCAPING_ATTRIBUTES_QUALIFYING_TAG[attr_node.name]
    next unless tag_name.nil? || tag_name == node.name
    #
    #  this block is just like CGI.escape in Ruby 2.4, but
    #  only encodes space and double-quote, to mimic
    #  pre-2.9.2 behavior
    #
    encoding = attr_node.value.encoding
    attr_node.value = attr_node.value.gsub(/[ "]/) do |m|
      '%' + m.unpack('H2' * m.bytesize).join('%').upcase
    end.force_encoding(encoding)
  end
end

def scrub_attributes node
  node.attribute_nodes.each do |attr_node|
    attr_name = if attr_node.namespace
                  "#{attr_node.namespace.prefix}:#{attr_node.node_name}"
                else
                  attr_node.node_name
                end
    if attr_name =~ /\Adata-[\w-]+\z/
      next
    end
    unless SafeList::ALLOWED_ATTRIBUTES.include?(attr_name)
      attr_node.remove
      next
    end
    if SafeList::ATTR_VAL_IS_URI.include?(attr_name)
      # this block lifted nearly verbatim from HTML5 sanitization
      val_unescaped = CGI.unescapeHTML(attr_node.value).gsub(CONTROL_CHARACTERS,'').downcase
      if val_unescaped =~ /^[a-z0-9][-+.a-z0-9]*:/ && ! SafeList::ALLOWED_PROTOCOLS.include?(val_unescaped.split(SafeList::PROTOCOL_SEPARATOR)[0])
        attr_node.remove
        next
      elsif val_unescaped.split(SafeList::PROTOCOL_SEPARATOR)[0] == 'data'
        # permit only allowed data mediatypes
        mediatype = val_unescaped.split(SafeList::PROTOCOL_SEPARATOR)[1]
        mediatype, _ = mediatype.split(';')[0..1] if mediatype
        if mediatype && !SafeList::ALLOWED_URI_DATA_MEDIATYPES.include?(mediatype)
          attr_node.remove
          next
        end
      end
    end
    if SafeList::SVG_ATTR_VAL_ALLOWS_REF.include?(attr_name)
      attr_node.value = attr_node.value.gsub(/url\s*\(\s*[^#\s][^)]+?\)/m, ' ') if attr_node.value
    end
    if SafeList::SVG_ALLOW_LOCAL_HREF.include?(node.name) && attr_name == 'xlink:href' && attr_node.value =~ /^\s*[^#\s].*/m
      attr_node.remove
      next
    end
  end
  scrub_css_attribute node
  node.attribute_nodes.each do |attr_node|
    node.remove_attribute(attr_node.name) if attr_node.value !~ /[^[:space:]]/
  end
  force_correct_attribute_escaping! node
end

def scrub_css style
  style_tree = Crass.parse_properties style
  sanitized_tree = []
  style_tree.each do |node|
    next unless node[:node] == :property
    next if node[:children].any? do |child|
      [:url, :bad_url].include?(child[:node]) || (child[:node] == :function && !SafeList::ALLOWED_CSS_FUNCTIONS.include?(child[:name].downcase))
    end
    name = node[:name].downcase
    if SafeList::ALLOWED_CSS_PROPERTIES.include?(name) || SafeList::ALLOWED_SVG_PROPERTIES.include?(name)
      sanitized_tree << node << CRASS_SEMICOLON
    elsif SafeList::SHORTHAND_CSS_PROPERTIES.include?(name.split('-').first)
      value = node[:value].split.map do |keyword|
        if SafeList::ALLOWED_CSS_KEYWORDS.include?(keyword) || keyword =~ CSS_KEYWORDISH
          keyword
        end
      end.compact
      unless value.empty?
        propstring = sprintf "%s:%s", name, value.join(" ")
        sanitized_node = Crass.parse_properties(propstring).first
        sanitized_tree << sanitized_node << CRASS_SEMICOLON
      end
    end
  end
  Crass::Parser.stringify sanitized_tree
end

def scrub_css_attribute node
  style = node.attributes['style']
  style.value = scrub_css(style.value) if style
end