#--
# Copyright (c) 2009 Ryan Grove <ryan@wonko.com>
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the 'Software'), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.
#++

# Append this file's directory to the include path if it's not there already.
$:.unshift(File.dirname(File.expand_path(__FILE__)))
$:.uniq!

require 'rubygems'

gem 'hpricot',      '~> 0.6'
gem 'htmlentities', '~> 4.0.0'

require 'hpricot'
require 'htmlentities'
require 'sanitize/config'
require 'sanitize/config/restricted'
require 'sanitize/config/basic'
require 'sanitize/config/relaxed'
require 'sanitize/monkeypatch/hpricot'

class Sanitize

  # Matches an attribute value that could be treated by a browser as a URL
  # with a protocol prefix, such as "http:" or "javascript:". Any string of one
  # or more characters followed by a colon is considered a match, even if the
  # colon is encoded as an entity and even if it's an incomplete entity (which
  # IE6 and Opera will still parse).
  REGEX_PROTOCOL = /^([^:]+)(?:\:|&#0*58|&#x0*3a)(?:[^0-9a-f]|$)/i

  #--
  # Class Methods
  #++

  # Returns a sanitized copy of _html_, using the settings in _config_ if
  # specified.
  def self.clean(html, config = {})
    sanitize = Sanitize.new(config)
    sanitize.clean(html)
  end

  # Performs Sanitize#clean in place, returning _html_, or +nil+ if no changes
  # were made.
  def self.clean!(html, config = {})
    sanitize = Sanitize.new(config)
    sanitize.clean!(html)
  end

  #--
  # Instance Methods
  #++

  # Returns a new Sanitize object initialized with the settings in _config_.
  def initialize(config = {})
    @config = Config::DEFAULT.merge(config)
  end

  # Returns a sanitized copy of _html_.
  def clean(html)
    dupe = html.dup
    clean!(dupe) || dupe
  end

  # Performs clean in place, returning _html_, or +nil+ if no changes were
  # made.
  def clean!(html)
    fragment = Hpricot(html)

    fragment.search('*') do |node|
      if node.bogusetag? || node.doctype? || node.procins? || node.xmldecl?
        node.swap('')
        next
      end

      if node.comment?
        node.swap('') unless @config[:allow_comments]
      elsif node.elem?
        name = node.name.to_s.downcase

        # Delete any element that isn't in the whitelist.
        unless @config[:elements].include?(name)
          node.parent.replace_child(node, node.children)
          next
        end

        if @config[:attributes].has_key?(name)
          # Delete any attribute that isn't in the whitelist for this element.
          node.raw_attributes.delete_if do |key, value|
            !@config[:attributes][name].include?(key.to_s.downcase)
          end

          # Delete remaining attributes that use unacceptable protocols.
          if @config[:protocols].has_key?(name)
            protocol = @config[:protocols][name]

            node.raw_attributes.delete_if do |key, value|
              next false unless protocol.has_key?(key)
              next true if value.nil?

              if value.to_s.downcase =~ REGEX_PROTOCOL
                !protocol[key].include?($1.downcase)
              else
                !protocol[key].include?(:relative)
              end
            end
          end
        else
          # Delete all attributes from elements with no whitelisted
          # attributes.
          node.raw_attributes = {}
        end

        # Add required attributes.
        if @config[:add_attributes].has_key?(name)
          node.raw_attributes.merge!(@config[:add_attributes][name])
        end
      end
    end

    # Make one last pass through the fragment and encode all special HTML chars
    # and non-ASCII chars as entities. This eliminates certain types of
    # maliciously-malformed nested tags and also compensates for Hpricot's
    # burning desire to decode all entities.
    coder = HTMLEntities.new

    fragment.traverse_element do |node|
      if node.text?
        node.swap(coder.encode(node.inner_text, :named))
      end
    end

    result = fragment.to_s
    return result == html ? nil : html[0, html.length] = result
  end
end