# ~*~ encoding: utf-8 ~*~
module Gollum
  # Encapsulate sanitization options.
  #
  # This class does not yet support all options of Sanitize library.
  # See http://github.com/rgrove/sanitize/.
  class Sanitization

    # Default whitelisted elements required for MathML. See https://developer.mozilla.org/en-US/docs/Web/MathML/Element
    # For some help on generating MATHML_ELEMENTS and MATHML_ATTRS, see https://gist.github.com/dometto/52d9cb8b45d68bfc7665e5e6683b75a0
    MATHML_ELEMENTS = [
      'math', 'maction', 'maligngroup', 'malignmark', 'menclose',
      'merror', 'mfenced', 'mfrac', 'mglyph', 'mi', 'mlabeledtr',
      'mlongdiv', 'mmultiscripts', 'mn', 'mo', 'mover', 'mpadded',
      'mphantom', 'mroot', 'mrow', 'ms', 'mscarries', 'mscarry',
      'msgroup', 'msline', 'mspace', 'msqrt', 'msrow', 'mstack',
      'mstyle', 'msub', 'msup', 'msubsup', 'mtable', 'mtd',
      'mtext', 'mtr', 'munder', 'munderover', 'semantics'
    ].freeze


    # Default whitelisted attributes required for MathML. See https://developer.mozilla.org/en-US/docs/Web/MathML/Attribute 
    MATHML_ATTRS = {
     'math'=>
        ['altimg',
         'altimg-width',
         'altimg-height',
         'altimg-valign',
         'alttext',
         'dir',
         'display',
         'xmlns',
         'href',
         'id',
         'mathbackground',
         'mathcolor'],
     'maction'=>
        ['actiontype', 'selection', 'href', 'id', 'mathbackground', 'mathcolor'],
     'maligngroup'=>['href', 'id', 'mathbackground', 'mathcolor'],
     'malignmark'=>['href', 'id', 'mathbackground', 'mathcolor'],
     'menclose'=>['notation', 'href', 'id', 'mathbackground', 'mathcolor'],
     'merror'=>['href', 'id', 'mathbackground', 'mathcolor'],
     'mfenced'=>
        ['close', 'open', 'separators', 'href', 'id', 'mathbackground', 'mathcolor'],
     'mfrac'=>
        ['bevelled',
         'denomalign',
         'linethickness',
         'numalign',
         'href',
         'id',
         'mathbackground',
         'mathcolor'],
     'mglyph'=>['height', 'width', 'href', 'id', 'mathbackground', 'mathcolor'],
     'mi'=>
        ['dir',
         'mathbackground',
         'mathcolor',
         'mathsize',
         'mathvariant',
         'href',
         'id',
         'mathbackground',
         'mathcolor'],
     'mlabeledtr'=>['columnalign', 'href', 'id', 'mathbackground', 'mathcolor'],
     'mlongdiv'=>['href', 'id', 'mathbackground', 'mathcolor'],
     'mmultiscripts'=>
        ['subscriptshift',
         'supscriptshift',
         'href',
         'id',
         'mathbackground',
         'mathcolor'],
     'mn'=>
        ['mathbackground',
         'mathcolor',
         'mathsize',
         'mathvariant',
         'href',
         'id',
         'mathbackground',
         'mathcolor'],
     'mo'=>
        ['accent',
         'dir',
         'fence',
         'href',
         'id',
         'largeop',
         'lspace',
         'mathbackground',
         'mathcolor',
         'mathsize',
         'mathvariant',
         'maxsize',
         'minsize',
         'movablelimits',
         'rspace',
         'separator',
         'stretchy',
         'symmetric',
         'href',
         'id',
         'mathbackground',
         'mathcolor'],
     'mover'=>['accent', 'align', 'href', 'id', 'mathbackground', 'mathcolor'],
     'mpadded'=>
        ['depth',
         'height',
         'lspace',
         'voffset',
         'width',
         'href',
         'id',
         'mathbackground',
         'mathcolor'],
     'mphantom'=>['href', 'id', 'mathbackground', 'mathcolor'],
     'mroot'=>['href', 'id', 'mathbackground', 'mathcolor'],
     'mrow'=>['dir', 'href', 'id', 'mathbackground', 'mathcolor'],
     'ms'=>
        ['dir',
         'lquote',
         'mathbackground',
         'mathcolor',
         'mathsize',
         'mathvariant',
         'rquote',
         'href',
         'id',
         'mathbackground',
         'mathcolor'],
     'mscarries'=>['href', 'id', 'mathbackground', 'mathcolor'],
     'mscarry'=>['href', 'id', 'mathbackground', 'mathcolor'],
     'msgroup'=>['href', 'id', 'mathbackground', 'mathcolor'],
     'msline'=>['length', 'href', 'id', 'mathbackground', 'mathcolor'],
     'mspace'=>['height', 'width', 'href', 'id', 'mathbackground', 'mathcolor'],
     'msqrt'=>['href', 'id', 'mathbackground', 'mathcolor'],
     'msrow'=>['href', 'id', 'mathbackground', 'mathcolor'],
     'mstack'=>['align', 'href', 'id', 'mathbackground', 'mathcolor'],
     'mstyle'=>
        ['displaystyle',
         'scriptlevel',
         'scriptminsize',
         'scriptsizemultiplier',
         'href',
         'id',
         'mathbackground',
         'mathcolor'],
     'msub'=>['subscriptshift', 'href', 'id', 'mathbackground', 'mathcolor'],
     'msup'=>['supscriptshift', 'href', 'id', 'mathbackground', 'mathcolor'],
     'msubsup'=>
        ['subscriptshift',
         'supscriptshift',
         'href',
         'id',
         'mathbackground',
         'mathcolor'],
     'mtable'=>
        ['align',
         'columnalign',
         'columnlines',
         'columnspacing',
         'displaystyle',
         'frame',
         'framespacing',
         'rowalign',
         'rowlines',
         'rowspacing',
         'width',
         'href',
         'id',
         'mathbackground',
         'mathcolor'],
     'mtd'=>
        ['columnalign',
         'columnspan',
         'rowalign',
         'rowspan',
         'href',
         'id',
         'mathbackground',
         'mathcolor'],
     'mtext'=>
        ['dir',
         'mathbackground',
         'mathcolor',
         'mathsize',
         'mathvariant',
         'href',
         'id',
         'mathbackground',
         'mathcolor'],
     'mtr'=>
        ['columnalign', 'rowalign', 'href', 'id', 'mathbackground', 'mathcolor'],
     'munder'=>
        ['accentunder', 'align', 'href', 'id', 'mathbackground', 'mathcolor'],
     'munderover'=>
        ['accent',
         'accentunder',
         'align',
         'href',
         'id',
         'mathbackground',
         'mathcolor'],
     'semantics'=>['href', 'id', 'mathbackground', 'mathcolor']
    }.freeze

    # Default whitelisted elements.
    ELEMENTS   = ([
      'a', 'abbr', 'acronym', 'address', 'area', 'b', 'big',
      'blockquote', 'br', 'button', 'caption', 'center', 'cite',
      'code', 'col', 'colgroup', 'dd', 'del', 'dfn', 'dir', 'div',
      'dl', 'dt', 'em', 'fieldset', 'font', 'form', 'h1', 'h2', 'h3',
      'h4', 'h5', 'h6', 'hr', 'i', 'img', 'input', 'ins', 'kbd', 'label',
      'legend', 'li', 'map', 'mark', 'math', 'menu', 'mfrac', 'mi', 'mn',
      'mo', 'mrow', 'msqrt', 'msubsup', 'msup', 'mtext', 'ol', 'optgroup',
      'option', 'p', 'pre', 'q', 's', 'samp', 'select', 'small', 'span',
      'strike', 'strong', 'sub', 'sup', 'table', 'tbody', 'td', 'textarea',
      'tfoot', 'th', 'thead', 'tr', 'tt', 'u', 'ul', 'var'
    ] + MATHML_ELEMENTS).freeze


    # Default whitelisted attributes.
    ATTRIBUTES = ({
        'a'   => ['href'],
        'img' => ['src'],
        :all  => ['abbr', 'accept', 'accept-charset',
                  'accesskey', 'action', 'align', 'alt', 'axis',
                  'border', 'cellpadding', 'cellspacing', 'char',
                  'charoff', 'class', 'charset', 'checked', 'cite',
                  'clear', 'cols', 'colspan', 'color',
                  'compact', 'coords', 'datetime', 'dir',
                  'disabled', 'enctype', 'for', 'frame',
                  'headers', 'height', 'hreflang',
                  'hspace', 'id', 'ismap', 'label', 'lang',
                  'longdesc', 'maxlength', 'media', 'method',
                  'multiple', 'name', 'nohref', 'noshade',
                  'nowrap', 'prompt', 'readonly', 'rel', 'rev',
                  'rows', 'rowspan', 'rules', 'scope',
                  'selected', 'shape', 'size', 'span',
                  'start', 'summary', 'tabindex', 'target',
                  'title', 'type', 'usemap', 'valign', 'value',
                  'vspace', 'width']
    }.merge(MATHML_ATTRS)).freeze

    # Default whitelisted protocols for URLs.
    PROTOCOLS  = {
        'a'    => { 'href' => ['http', 'https', 'mailto', 'ftp', 'irc', 'apt', :relative] },
        'img'  => { 'src' => ['http', 'https', :relative] },
        'form' => { 'action' => ['http', 'https', :relative] }
    }.freeze

    ADD_ATTRIBUTES  = lambda do |env, node|
      if (add = env[:config][:add_attributes][node.name])
        add.each do |key, value|
          node[key] = value
        end
      end
    end

    # Default elements whose contents will be removed in addition
    # to the elements themselve
    REMOVE_CONTENTS = [
        'script',
        'style'
    ].freeze

    # Default transformers to force @id attributes with 'wiki-' prefix
    TRANSFORMERS    = [
        lambda do |env|
          node = env[:node]
          return if env[:is_whitelisted] || !node.element?
          prefix      = env[:config][:id_prefix]
          found_attrs = %w(id name).select do |key|
            if (value = node[key])
              node[key] = value.gsub(/\A(#{prefix})?/, prefix)
            end
          end
          if found_attrs.size > 0
            ADD_ATTRIBUTES.call(env, node)
            {}
          end
        end,
        lambda do |env|
          node = env[:node]
          return unless (value = node['href'])
          prefix       = env[:config][:id_prefix]
          node['href'] = value.gsub(/\A\#(#{prefix})?/, '#'+prefix)
          ADD_ATTRIBUTES.call(env, node)
          {}
        end
    ].freeze

    # Gets an Array of whitelisted HTML elements.  Default: ELEMENTS.
    attr_reader :elements

    # Gets a Hash describing which attributes are allowed in which HTML
    # elements.  Default: ATTRIBUTES.
    attr_reader :attributes

    # Gets a Hash describing which URI protocols are allowed in HTML
    # attributes.  Default: PROTOCOLS
    attr_reader :protocols

    # Gets a Hash describing which URI protocols are allowed in HTML
    # attributes.  Default: TRANSFORMERS
    attr_reader :transformers

    # Gets or sets a String prefix which is added to ID attributes.
    # Default: ''
    attr_accessor :id_prefix

    # Gets a Hash describing HTML attributes that Sanitize should add.
    # Default: {}
    attr_reader :add_attributes

    # Gets an Array of element names whose contents will be removed in addition
    # to the elements themselves. Default: REMOVE_CONTENTS
    attr_reader :remove_contents

    # Sets a boolean determining whether Sanitize allows HTML comments in the
    # output.  Default: false.
    attr_writer :allow_comments

    def initialize
      @elements        = ELEMENTS.dup
      @attributes      = ATTRIBUTES.dup
      @protocols       = PROTOCOLS.dup
      @transformers    = TRANSFORMERS.dup
      @add_attributes  = {}
      @remove_contents = REMOVE_CONTENTS.dup
      @allow_comments  = false
      @id_prefix       = ''
      yield self if block_given?
    end

    # Determines if Sanitize should allow HTML comments.
    #
    # Returns True if comments are allowed, or False.
    def allow_comments?
      !!@allow_comments
    end

    # Modifies the current Sanitization instance to sanitize older revisions
    # of pages.
    #
    # Returns a Sanitization instance.
    def history_sanitization
      self.class.new do |sanitize|
        sanitize.add_attributes['a'] = { 'rel' => 'nofollow' }
      end
    end

    # Builds a Hash of options suitable for Sanitize.clean.
    #
    # Returns a Hash.
    def to_hash
      { :elements        => elements,
        :attributes      => attributes,
        :protocols       => protocols,
        :add_attributes  => add_attributes,
        :remove_contents => remove_contents,
        :allow_comments  => allow_comments?,
        :transformers    => transformers,
        :id_prefix       => id_prefix
      }
    end

    # Builds a Sanitize instance from the current options.
    #
    # Returns a Sanitize instance.
    def to_sanitize
      Sanitize.new(to_hash)
    end
  end
end