JezK

Edit File: element.rb

# frozen_string_literal: false
require "rexml/parent"
require "rexml/namespace"
require "rexml/attribute"
require "rexml/cdata"
require "rexml/xpath"
require "rexml/parseexception"

module REXML
  # An implementation note about namespaces:
  # As we parse, when we find namespaces we put them in a hash and assign
  # them a unique ID.  We then convert the namespace prefix for the node
  # to the unique ID.  This makes namespace lookup much faster for the
  # cost of extra memory use.  We save the namespace prefix for the
  # context node and convert it back when we write it.
  @@namespaces = {}

# Represents a tagged XML element. Elements are characterized by
 # having children, attributes, and names, and can themselves be
 # children.
 class Element < Parent
 include Namespace

UNDEFINED = "UNDEFINED";            # The default name

# Mechanisms for accessing attributes and child elements of this
    # element.
    attr_reader :attributes, :elements
    # The context holds information about the processing environment, such as
    # whitespace handling.
    attr_accessor :context

# Constructor
 # arg::
 # if not supplied, will be set to the default value.
 # If a String, the name of this object will be set to the argument.
 # If an Element, the object will be shallowly cloned; name,
 # attributes, and namespaces will be copied. Children will +not+ be
 # copied.
 # parent::
 # if supplied, must be a Parent, and will be used as
 # the parent of this object.
 # context::
 # If supplied, must be a hash containing context items. Context items
 # include:
 # * <tt>:respect_whitespace</tt> the value of this is :+all+ or an array of
 # strings being the names of the elements to respect
 # whitespace for. Defaults to :+all+.
 # * <tt>:compress_whitespace</tt> the value can be :+all+ or an array of
 # strings being the names of the elements to ignore whitespace on.
 # Overrides :+respect_whitespace+.
 # * <tt>:ignore_whitespace_nodes</tt> the value can be :+all+ or an array
 # of strings being the names of the elements in which to ignore
 # whitespace-only nodes. If this is set, Text nodes which contain only
 # whitespace will not be added to the document tree.
 # * <tt>:raw</tt> can be :+all+, or an array of strings being the names of
 # the elements to process in raw mode. In raw mode, special
 # characters in text is not converted to or from entities.
 def initialize( arg = UNDEFINED, parent=nil, context=nil )
 super(parent)

@elements = Elements.new(self)
      @attributes = Attributes.new(self)
      @context = context

if arg.kind_of? String
 self.name = arg
 elsif arg.kind_of? Element
 self.name = arg.expanded_name
 arg.attributes.each_attribute{ |attribute|
 @attributes << Attribute.new( attribute )
 }
 @context = arg.context
 end
 end

def inspect
 rv = "<#@expanded_name"

@attributes.each_attribute do |attr|
 rv << " "
 attr.write( rv, 0 )
 end

if children.size > 0
 rv << "> ... </>"
 else
 rv << "/>"
 end
 end

# Creates a shallow copy of self.
 # d = Document.new "<a><c><d/></c></a>"
 # new_a = d.root.clone
 # puts new_a # => "<a/>"
 def clone
 self.class.new self
 end

# Evaluates to the root node of the document that this element
 # belongs to. If this element doesn't belong to a document, but does
 # belong to another Element, the parent's root will be returned, until the
 # earliest ancestor is found.
 #
 # Note that this is not the same as the document element.
 # In the following example, <a> is the document element, and the root
 # node is the parent node of the document element. You may ask yourself
 # why the root node is useful: consider the doctype and XML declaration,
 # and any processing instructions before the document element... they
 # are children of the root node, or siblings of the document element.
 # The only time this isn't true is when an Element is created that is
 # not part of any Document. In this case, the ancestor that has no
 # parent acts as the root node.
 # d = Document.new '<a><c/></a>'
 # a = d[1] ; c = a[1][1]
 # d.root_node == d # TRUE
 # a.root_node # namely, d
 # c.root_node # again, d
 def root_node
 parent.nil? ? self : parent.root_node
 end

def root
      return elements[1] if self.kind_of? Document
      return self if parent.kind_of? Document or parent.nil?
      return parent.root
    end

# Evaluates to the document to which this element belongs, or nil if this
    # element doesn't belong to a document.
    def document
      rt = root
      rt.parent if rt
    end

# Evaluates to +true+ if whitespace is respected for this element.  This
    # is the case if:
    # 1. Neither :+respect_whitespace+ nor :+compress_whitespace+ has any value
    # 2. The context has :+respect_whitespace+ set to :+all+ or
    #    an array containing the name of this element, and
    #    :+compress_whitespace+ isn't set to :+all+ or an array containing the
    #    name of this element.
    # The evaluation is tested against +expanded_name+, and so is namespace
    # sensitive.
    def whitespace
      @whitespace = nil
      if @context
        if @context[:respect_whitespace]
          @whitespace = (@context[:respect_whitespace] == :all or
                         @context[:respect_whitespace].include? expanded_name)
        end
        @whitespace = false if (@context[:compress_whitespace] and
                                (@context[:compress_whitespace] == :all or
                                 @context[:compress_whitespace].include? expanded_name)
                               )
      end
      @whitespace = true unless @whitespace == false
      @whitespace
    end

def ignore_whitespace_nodes
      @ignore_whitespace_nodes = false
      if @context
        if @context[:ignore_whitespace_nodes]
          @ignore_whitespace_nodes =
            (@context[:ignore_whitespace_nodes] == :all or
             @context[:ignore_whitespace_nodes].include? expanded_name)
        end
      end
    end

# Evaluates to +true+ if raw mode is set for this element.  This
    # is the case if the context has :+raw+ set to :+all+ or
    # an array containing the name of this element.
    #
    # The evaluation is tested against +expanded_name+, and so is namespace
    # sensitive.
    def raw
      @raw = (@context and @context[:raw] and
              (@context[:raw] == :all or
               @context[:raw].include? expanded_name))
               @raw
    end

#once :whitespace, :raw, :ignore_whitespace_nodes

#################################################
    # Namespaces                                    #
    #################################################

# Evaluates to an +Array+ containing the prefixes (names) of all defined
 # namespaces at this context node.
 # doc = Document.new("<a xmlns:x='1' xmlns:y='2'><c xmlns:z='3'/></a>")
 # doc.elements['//b'].prefixes # -> ['x', 'y']
 def prefixes
 prefixes = []
 prefixes = parent.prefixes if parent
 prefixes |= attributes.prefixes
 return prefixes
 end

def namespaces
      namespaces = {}
      namespaces = parent.namespaces if parent
      namespaces = namespaces.merge( attributes.namespaces )
      return namespaces
    end

# Evaluates to the URI for a prefix, or the empty string if no such
 # namespace is declared for this element. Evaluates recursively for
 # ancestors. Returns the default namespace, if there is one.
 # prefix::
 # the prefix to search for. If not supplied, returns the default
 # namespace if one exists
 # Returns::
 # the namespace URI as a String, or nil if no such namespace
 # exists. If the namespace is undefined, returns an empty string
 # doc = Document.new("<a xmlns='1' xmlns:y='2'><c xmlns:z='3'/></a>")
 # b = doc.elements['//b']
 # b.namespace # -> '1'
 # b.namespace("y") # -> '2'
 def namespace(prefix=nil)
 if prefix.nil?
 prefix = prefix()
 end
 if prefix == ''
 prefix = "xmlns"
 else
 prefix = "xmlns:#{prefix}" unless prefix[0,5] == 'xmlns'
 end
 ns = attributes[ prefix ]
 ns = parent.namespace(prefix) if ns.nil? and parent
 ns = '' if ns.nil? and prefix == 'xmlns'
 return ns
 end

# Adds a namespace to this element.
 # prefix::
 # the prefix string, or the namespace URI if +uri+ is not
 # supplied
 # uri::
 # the namespace URI. May be nil, in which +prefix+ is used as
 # the URI
 # Evaluates to: this Element
 # a = Element.new("a")
 # a.add_namespace("xmlns:foo", "bar" )
 # a.add_namespace("foo", "bar") # shorthand for previous line
 # a.add_namespace("twiddle")
 # puts a #-> <a xmlns:foo='bar' xmlns='twiddle'/>
 def add_namespace( prefix, uri=nil )
 unless uri
 @attributes["xmlns"] = prefix
 else
 prefix = "xmlns:#{prefix}" unless prefix =~ /^xmlns:/
 @attributes[ prefix ] = uri
 end
 self
 end

# Removes a namespace from this node. This only works if the namespace is
 # actually declared in this node. If no argument is passed, deletes the
 # default namespace.
 #
 # Evaluates to: this element
 # doc = Document.new "<a xmlns:foo='bar' xmlns='twiddle'/>"
 # doc.root.delete_namespace
 # puts doc # -> <a xmlns:foo='bar'/>
 # doc.root.delete_namespace 'foo'
 # puts doc # -> <a/>
 def delete_namespace namespace="xmlns"
 namespace = "xmlns:#{namespace}" unless namespace == 'xmlns'
 attribute = attributes.get_attribute(namespace)
 attribute.remove unless attribute.nil?
 self
 end

#################################################
    # Elements                                      #
    #################################################

# Adds a child to this element, optionally setting attributes in
    # the element.
    # element::
    #   optional.  If Element, the element is added.
    #   Otherwise, a new Element is constructed with the argument (see
    #   Element.initialize).
    # attrs::
    #   If supplied, must be a Hash containing String name,value
    #   pairs, which will be used to set the attributes of the new Element.
    # Returns:: the Element that was added
    #  el = doc.add_element 'my-tag'
    #  el = doc.add_element 'my-tag', {'attr1'=>'val1', 'attr2'=>'val2'}
    #  el = Element.new 'my-tag'
    #  doc.add_element el
    def add_element element, attrs=nil
      raise "First argument must be either an element name, or an Element object" if element.nil?
      el = @elements.add(element)
      attrs.each do |key, value|
        el.attributes[key]=value
      end       if attrs.kind_of? Hash
      el
    end

# Deletes a child element.
 # element::
 # Must be an +Element+, +String+, or +Integer+. If Element,
 # the element is removed. If String, the element is found (via XPath)
 # and removed. This means that any parent can remove any
 # descendant. If Integer, the Element indexed by that number will be
 # removed.
 # Returns:: the element that was removed.
 # doc.delete_element "/a/b/c[@id='4']"
 # doc.delete_element doc.elements["//k"]
 # doc.delete_element 1
 def delete_element element
 @elements.delete element
 end

# Evaluates to +true+ if this element has at least one child Element
 # doc = Document.new "<a><c>Text</c></a>"
 # doc.root.has_elements # -> true
 # doc.elements["/a/b"].has_elements # -> false
 # doc.elements["/a/c"].has_elements # -> false
 def has_elements?
 !@elements.empty?
 end

# Iterates through the child elements, yielding for each Element that
 # has a particular attribute set.
 # key::
 # the name of the attribute to search for
 # value::
 # the value of the attribute
 # max::
 # (optional) causes this method to return after yielding
 # for this number of matching children
 # name::
 # (optional) if supplied, this is an XPath that filters
 # the children to check.
 #
 # doc = Document.new "<a><c @id='2'/><d @id='1'/><e/></a>"
 # # Yields b, c, d
 # doc.root.each_element_with_attribute( 'id' ) {|e| p e}
 # # Yields b, d
 # doc.root.each_element_with_attribute( 'id', '1' ) {|e| p e}
 # # Yields b
 # doc.root.each_element_with_attribute( 'id', '1', 1 ) {|e| p e}
 # # Yields d
 # doc.root.each_element_with_attribute( 'id', '1', 0, 'd' ) {|e| p e}
 def each_element_with_attribute( key, value=nil, max=0, name=nil, &block ) # :yields: Element
 each_with_something( proc {|child|
 if value.nil?
 child.attributes[key] != nil
 else
 child.attributes[key]==value
 end
 }, max, name, &block )
 end

# Iterates through the children, yielding for each Element that
 # has a particular text set.
 # text::
 # the text to search for. If nil, or not supplied, will iterate
 # over all +Element+ children that contain at least one +Text+ node.
 # max::
 # (optional) causes this method to return after yielding
 # for this number of matching children
 # name::
 # (optional) if supplied, this is an XPath that filters
 # the children to check.
 #
 # doc = Document.new '<a>b<c>b</c><d>d</d><e/></a>'
 # # Yields b, c, d
 # doc.each_element_with_text {|e|p e}
 # # Yields b, c
 # doc.each_element_with_text('b'){|e|p e}
 # # Yields b
 # doc.each_element_with_text('b', 1){|e|p e}
 # # Yields d
 # doc.each_element_with_text(nil, 0, 'd'){|e|p e}
 def each_element_with_text( text=nil, max=0, name=nil, &block ) # :yields: Element
 each_with_something( proc {|child|
 if text.nil?
 child.has_text?
 else
 child.text == text
 end
 }, max, name, &block )
 end

# Synonym for Element.elements.each
    def each_element( xpath=nil, &block ) # :yields: Element
      @elements.each( xpath, &block )
    end

# Synonym for Element.to_a
    # This is a little slower than calling elements.each directly.
    # xpath:: any XPath by which to search for elements in the tree
    # Returns:: an array of Elements that match the supplied path
    def get_elements( xpath )
      @elements.to_a( xpath )
    end

# Returns the next sibling that is an element, or nil if there is
 # no Element sibling after this one
 # doc = Document.new '<a>text<c/></a>'
 # doc.root.elements['b'].next_element #-> <c/>
 # doc.root.elements['c'].next_element #-> nil
 def next_element
 element = next_sibling
 element = element.next_sibling until element.nil? or element.kind_of? Element
 return element
 end

# Returns the previous sibling that is an element, or nil if there is
 # no Element sibling prior to this one
 # doc = Document.new '<a>text<c/></a>'
 # doc.root.elements['c'].previous_element #-> 
 # doc.root.elements['b'].previous_element #-> nil
 def previous_element
 element = previous_sibling
 element = element.previous_sibling until element.nil? or element.kind_of? Element
 return element
 end

#################################################
    # Text                                          #
    #################################################

# Evaluates to +true+ if this element has at least one Text child
    def has_text?
      not text().nil?
    end

# A convenience method which returns the String value of the _first_
 # child text element, if one exists, and +nil+ otherwise.
 #
 # Note that an element may have multiple Text elements, perhaps
 # separated by other children. Be aware that this method only returns
 # the first Text node.
 #
 # This method returns the +value+ of the first text child node, which
 # ignores the +raw+ setting, so always returns normalized text. See
 # the Text::value documentation.
 #
 # doc = Document.new "some text this is bold! more text"
 # # The element 'p' has two text elements, "some text " and " more text".
 # doc.root.text #-> "some text "
 def text( path = nil )
 rv = get_text(path)
 return rv.value unless rv.nil?
 nil
 end

# Returns the first child Text node, if any, or +nil+ otherwise.
 # This method returns the actual +Text+ node, rather than the String content.
 # doc = Document.new "some text this is bold! more text"
 # # The element 'p' has two text elements, "some text " and " more text".
 # doc.root.get_text.value #-> "some text "
 def get_text path = nil
 rv = nil
 if path
 element = @elements[ path ]
 rv = element.get_text unless element.nil?
 else
 rv = @children.find { |node| node.kind_of? Text }
 end
 return rv
 end

# Sets the first Text child of this object. See text() for a
 # discussion about Text children.
 #
 # If a Text child already exists, the child is replaced by this
 # content. This means that Text content can be deleted by calling
 # this method with a nil argument. In this case, the next Text
 # child becomes the first Text child. In no case is the order of
 # any siblings disturbed.
 # text::
 # If a String, a new Text child is created and added to
 # this Element as the first Text child. If Text, the text is set
 # as the first Child element. If nil, then any existing first Text
 # child is removed.
 # Returns:: this Element.
 # doc = Document.new '<a></a>'
 # doc.root.text = 'Sean' #-> '<a>Sean</a>'
 # doc.root.text = 'Elliott' #-> '<a>Elliott</a>'
 # doc.root.add_element 'c' #-> '<a>Elliott<c/></a>'
 # doc.root.text = 'Russell' #-> '<a>Russell<c/></a>'
 # doc.root.text = nil #-> '<a><c/></a>'
 def text=( text )
 if text.kind_of? String
 text = Text.new( text, whitespace(), nil, raw() )
 elsif !text.nil? and !text.kind_of? Text
 text = Text.new( text.to_s, whitespace(), nil, raw() )
 end
 old_text = get_text
 if text.nil?
 old_text.remove unless old_text.nil?
 else
 if old_text.nil?
 self << text
 else
 old_text.replace_with( text )
 end
 end
 return self
 end

# A helper method to add a Text child. Actual Text instances can
 # be added with regular Parent methods, such as add() and <<()
 # text::
 # if a String, a new Text instance is created and added
 # to the parent. If Text, the object is added directly.
 # Returns:: this Element
 # e = Element.new('a') #-> <e/>
 # e.add_text 'foo' #-> <e>foo</e>
 # e.add_text Text.new(' bar') #-> <e>foo bar</e>
 # Note that at the end of this example, the branch has 3 nodes; the 'e'
 # element and 2 Text node children.
 def add_text( text )
 if text.kind_of? String
 if @children[-1].kind_of? Text
 @children[-1] << text
 return
 end
 text = Text.new( text, whitespace(), nil, raw() )
 end
 self << text unless text.nil?
 return self
 end

def node_type
      :element
    end

def xpath
 path_elements = []
 cur = self
 path_elements << __to_xpath_helper( self )
 while cur.parent
 cur = cur.parent
 path_elements << __to_xpath_helper( cur )
 end
 return path_elements.reverse.join( "/" )
 end

#################################################
    # Attributes                                    #
    #################################################

def attribute( name, namespace=nil )
      prefix = nil
      if namespaces.respond_to? :key
        prefix = namespaces.key(namespace) if namespace
      else
        prefix = namespaces.index(namespace) if namespace
      end
      prefix = nil if prefix == 'xmlns'

ret_val =
        attributes.get_attribute( "#{prefix ? prefix + ':' : ''}#{name}" )

return ret_val unless ret_val.nil?
      return nil if prefix.nil?

# now check that prefix'es namespace is not the same as the
      # default namespace
      return nil unless ( namespaces[ prefix ] == namespaces[ 'xmlns' ] )

attributes.get_attribute( name )

end

# Evaluates to +true+ if this element has any attributes set, false
    # otherwise.
    def has_attributes?
      return !@attributes.empty?
    end

# Adds an attribute to this element, overwriting any existing attribute
 # by the same name.
 # key::
 # can be either an Attribute or a String. If an Attribute,
 # the attribute is added to the list of Element attributes. If String,
 # the argument is used as the name of the new attribute, and the value
 # parameter must be supplied.
 # value::
 # Required if +key+ is a String, and ignored if the first argument is
 # an Attribute. This is a String, and is used as the value
 # of the new Attribute. This should be the unnormalized value of the
 # attribute (without entities).
 # Returns:: the Attribute added
 # e = Element.new 'e'
 # e.add_attribute( 'a', 'b' ) #-> <e a='b'/>
 # e.add_attribute( 'x:a', 'c' ) #-> <e a='b' x:a='c'/>
 # e.add_attribute Attribute.new('b', 'd') #-> <e a='b' x:a='c' b='d'/>
 def add_attribute( key, value=nil )
 if key.kind_of? Attribute
 @attributes << key
 else
 @attributes[key] = value
 end
 end

# Add multiple attributes to this element.
    # hash:: is either a hash, or array of arrays
    #  el.add_attributes( {"name1"=>"value1", "name2"=>"value2"} )
    #  el.add_attributes( [ ["name1","value1"], ["name2"=>"value2"] ] )
    def add_attributes hash
      if hash.kind_of? Hash
        hash.each_pair {|key, value| @attributes[key] = value }
      elsif hash.kind_of? Array
        hash.each { |value| @attributes[ value[0] ] = value[1] }
      end
    end

# Removes an attribute
 # key::
 # either an Attribute or a String. In either case, the
 # attribute is found by matching the attribute name to the argument,
 # and then removed. If no attribute is found, no action is taken.
 # Returns::
 # the attribute removed, or nil if this Element did not contain
 # a matching attribute
 # e = Element.new('E')
 # e.add_attribute( 'name', 'Sean' ) #-> <E name='Sean'/>
 # r = e.add_attribute( 'sur:name', 'Russell' ) #-> <E name='Sean' sur:name='Russell'/>
 # e.delete_attribute( 'name' ) #-> <E sur:name='Russell'/>
 # e.delete_attribute( r ) #-> <E/>
 def delete_attribute(key)
 attr = @attributes.get_attribute(key)
 attr.remove unless attr.nil?
 end

#################################################
    # Other Utilities                               #
    #################################################

# Get an array of all CData children.
    # IMMUTABLE
    def cdatas
      find_all { |child| child.kind_of? CData }.freeze
    end

# Get an array of all Comment children.
    # IMMUTABLE
    def comments
      find_all { |child| child.kind_of? Comment }.freeze
    end

# Get an array of all Instruction children.
    # IMMUTABLE
    def instructions
      find_all { |child| child.kind_of? Instruction }.freeze
    end

# Get an array of all Text children.
    # IMMUTABLE
    def texts
      find_all { |child| child.kind_of? Text }.freeze
    end

# == DEPRECATED
 # See REXML::Formatters
 #
 # Writes out this element, and recursively, all children.
 # output::
 # output an object which supports '<< string'; this is where the
 # document will be written.
 # indent::
 # An integer. If -1, no indenting will be used; otherwise, the
 # indentation will be this number of spaces, and children will be
 # indented an additional amount. Defaults to -1
 # transitive::
 # If transitive is true and indent is >= 0, then the output will be
 # pretty-printed in such a way that the added whitespace does not affect
 # the parse tree of the document
 # ie_hack::
 # This hack inserts a space before the /> on empty tags to address
 # a limitation of Internet Explorer. Defaults to false
 #
 # out = ''
 # doc.write( out ) #-> doc is written to the string 'out'
 # doc.write( $stdout ) #-> doc written to the console
 def write(output=$stdout, indent=-1, transitive=false, ie_hack=false)
 Kernel.warn("#{self.class.name}.write is deprecated. See REXML::Formatters")
 formatter = if indent > -1
 if transitive
 require "rexml/formatters/transitive"
 REXML::Formatters::Transitive.new( indent, ie_hack )
 else
 REXML::Formatters::Pretty.new( indent, ie_hack )
 end
 else
 REXML::Formatters::Default.new( ie_hack )
 end
 formatter.write( self, output )
 end

private
 def __to_xpath_helper node
 rv = node.expanded_name.clone
 if node.parent
 results = node.parent.find_all {|n|
 n.kind_of?(REXML::Element) and n.expanded_name == node.expanded_name
 }
 if results.length > 1
 idx = results.index( node )
 rv << "[#{idx+1}]"
 end
 end
 rv
 end

# A private helper method
    def each_with_something( test, max=0, name=nil )
      num = 0
      @elements.each( name ){ |child|
        yield child if test.call(child) and num += 1
        return if max>0 and num == max
      }
    end
  end

########################################################################
  # ELEMENTS                                                             #
  ########################################################################

# A class which provides filtering of children for Elements, and
 # XPath search support. You are expected to only encounter this class as
 # the <tt>element.elements</tt> object. Therefore, you are
 # _not_ expected to instantiate this yourself.
 class Elements
 include Enumerable
 # Constructor
 # parent:: the parent Element
 def initialize parent
 @element = parent
 end

# Fetches a child element. Filters only Element children, regardless of
 # the XPath match.
 # index::
 # the search parameter. This is either an Integer, which
 # will be used to find the index'th child Element, or an XPath,
 # which will be used to search for the Element. Because
 # of the nature of XPath searches, any element in the connected XML
 # document can be fetched through any other element. The
 # Integer index is 1-based, not 0-based. This means that the first
 # child element is at index 1, not 0, and the +n+th element is at index
 # +n+, not <tt>n-1</tt>. This is because XPath indexes element children
 # starting from 1, not 0, and the indexes should be the same.
 # name::
 # optional, and only used in the first argument is an
 # Integer. In that case, the index'th child Element that has the
 # supplied name will be returned. Note again that the indexes start at 1.
 # Returns:: the first matching Element, or nil if no child matched
 # doc = Document.new '<a><c id="1"/><c id="2"/><d/></a>'
 # doc.root.elements[1] #-> 
 # doc.root.elements['c'] #-> <c id="1"/>
 # doc.root.elements[2,'c'] #-> <c id="2"/>
 def []( index, name=nil)
 if index.kind_of? Integer
 raise "index (#{index}) must be >= 1" if index < 1
 name = literalize(name) if name
 num = 0
 @element.find { |child|
 child.kind_of? Element and
 (name.nil? ? true : child.has_name?( name )) and
 (num += 1) == index
 }
 else
 return XPath::first( @element, index )
 #{ |element|
 # return element if element.kind_of? Element
 #}
 #return nil
 end
 end

# Sets an element, replacing any previous matching element. If no
 # existing element is found ,the element is added.
 # index:: Used to find a matching element to replace. See []().
 # element::
 # The element to replace the existing element with
 # the previous element
 # Returns:: nil if no previous element was found.
 #
 # doc = Document.new '<a/>'
 # doc.root.elements[10] = Element.new('b') #-> <a></a>
 # doc.root.elements[1] #-> 
 # doc.root.elements[1] = Element.new('c') #-> <a><c/></a>
 # doc.root.elements['c'] = Element.new('d') #-> <a><d/></a>
 def []=( index, element )
 previous = self[index]
 if previous.nil?
 @element.add element
 else
 previous.replace_with element
 end
 return previous
 end

# Returns +true+ if there are no +Element+ children, +false+ otherwise
    def empty?
      @element.find{ |child| child.kind_of? Element}.nil?
    end

# Returns the index of the supplied child (starting at 1), or -1 if
    # the element is not a child
    # element:: an +Element+ child
    def index element
      rv = 0
      found = @element.find do |child|
        child.kind_of? Element and
        (rv += 1) and
        child == element
      end
      return rv if found == element
      return -1
    end

# Deletes a child Element
 # element::
 # Either an Element, which is removed directly; an
 # xpath, where the first matching child is removed; or an Integer,
 # where the n'th Element is removed.
 # Returns:: the removed child
 # doc = Document.new '<a><c/><c id="1"/></a>'
 # b = doc.root.elements[1]
 # doc.root.elements.delete b #-> <a><c/><c id="1"/></a>
 # doc.elements.delete("a/c[@id='1']") #-> <a><c/></a>
 # doc.root.elements.delete 1 #-> <a/>
 def delete element
 if element.kind_of? Element
 @element.delete element
 else
 el = self[element]
 el.remove if el
 end
 end

# Removes multiple elements. Filters for Element children, regardless of
 # XPath matching.
 # xpath:: all elements matching this String path are removed.
 # Returns:: an Array of Elements that have been removed
 # doc = Document.new '<a><c/><c/><c/><c/></a>'
 # deleted = doc.elements.delete_all 'a/c' #-> [<c/>, <c/>, <c/>, <c/>]
 def delete_all( xpath )
 rv = []
 XPath::each( @element, xpath) {|element|
 rv << element if element.kind_of? Element
 }
 rv.each do |element|
 @element.delete element
 element.remove
 end
 return rv
 end

# Adds an element
 # element::
 # if supplied, is either an Element, String, or
 # Source (see Element.initialize). If not supplied or nil, a
 # new, default Element will be constructed
 # Returns:: the added Element
 # a = Element.new('a')
 # a.elements.add(Element.new('b')) #-> <a></a>
 # a.elements.add('c') #-> <a><c/></a>
 def add element=nil
 if element.nil?
 Element.new("", self, @element.context)
 elsif not element.kind_of?(Element)
 Element.new(element, self, @element.context)
 else
 @element << element
 element.context = @element.context
 element
 end
 end

alias :<< :add

# Iterates through all of the child Elements, optionally filtering
 # them by a given XPath
 # xpath::
 # optional. If supplied, this is a String XPath, and is used to
 # filter the children, so that only matching children are yielded. Note
 # that XPaths are automatically filtered for Elements, so that
 # non-Element children will not be yielded
 # doc = Document.new '<a><c/><d/>sean<c/><d/></a>'
 # doc.root.elements.each {|e|p e} #-> Yields b, c, d, b, c, d elements
 # doc.root.elements.each('b') {|e|p e} #-> Yields b, b elements
 # doc.root.elements.each('child::node()') {|e|p e}
 # #-> Yields , <c/>, <d/>, , <c/>, <d/>
 # XPath.each(doc.root, 'child::node()', &block)
 # #-> Yields , <c/>, <d/>, sean, , <c/>, <d/>
 def each( xpath=nil )
 XPath::each( @element, xpath ) {|e| yield e if e.kind_of? Element }
 end

def collect( xpath=nil )
 collection = []
 XPath::each( @element, xpath ) {|e|
 collection << yield(e) if e.kind_of?(Element)
 }
 collection
 end

def inject( xpath=nil, initial=nil )
      first = true
      XPath::each( @element, xpath ) {|e|
        if (e.kind_of? Element)
          if (first and initial == nil)
            initial = e
            first = false
          else
            initial = yield( initial, e ) if e.kind_of? Element
          end
        end
      }
      initial
    end

# Returns the number of +Element+ children of the parent object.
 # doc = Document.new '<a>seanelliottrussell</a>'
 # doc.root.size #-> 6, 3 element and 3 text nodes
 # doc.root.elements.size #-> 3
 def size
 count = 0
 @element.each {|child| count+=1 if child.kind_of? Element }
 count
 end

# Returns an Array of Element children. An XPath may be supplied to
 # filter the children. Only Element children are returned, even if the
 # supplied XPath matches non-Element children.
 # doc = Document.new '<a>seanelliott<c/></a>'
 # doc.root.elements.to_a #-> [ , <c/> ]
 # doc.root.elements.to_a("child::node()") #-> [ , <c/> ]
 # XPath.match(doc.root, "child::node()") #-> [ sean, , elliott, <c/> ]
 def to_a( xpath=nil )
 rv = XPath.match( @element, xpath )
 return rv.find_all{|e| e.kind_of? Element} if xpath
 rv
 end

private
    # Private helper class.  Removes quotes from quoted strings
    def literalize name
      name = name[1..-2] if name[0] == ?' or name[0] == ?"               #'
      name
    end
  end

########################################################################
  # ATTRIBUTES                                                           #
  ########################################################################

# A class that defines the set of Attributes of an Element and provides
 # operations for accessing elements in that set.
 class Attributes < Hash
 # Constructor
 # element:: the Element of which this is an Attribute
 def initialize element
 @element = element
 end

# Fetches an attribute value. If you want to get the Attribute itself,
 # use get_attribute()
 # name:: an XPath attribute name. Namespaces are relevant here.
 # Returns::
 # the String value of the matching attribute, or +nil+ if no
 # matching attribute was found. This is the unnormalized value
 # (with entities expanded).
 #
 # doc = Document.new "<a foo:att='1' bar:att='2' att='&lt;'/>"
 # doc.root.attributes['att'] #-> '<'
 # doc.root.attributes['bar:att'] #-> '2'
 def [](name)
 attr = get_attribute(name)
 return attr.value unless attr.nil?
 return nil
 end

def to_a
      enum_for(:each_attribute).to_a
    end

# Returns the number of attributes the owning Element contains.
 # doc = Document "<a x='1' y='2' foo:x='3'/>"
 # doc.root.attributes.length #-> 3
 def length
 c = 0
 each_attribute { c+=1 }
 c
 end
 alias :size :length

# Iterates over the attributes of an Element. Yields actual Attribute
 # nodes, not String values.
 #
 # doc = Document.new '<a x="1" y="2"/>'
 # doc.root.attributes.each_attribute {|attr|
 # p attr.expanded_name+" => "+attr.value
 # }
 def each_attribute # :yields: attribute
 each_value do |val|
 if val.kind_of? Attribute
 yield val
 else
 val.each_value { |atr| yield atr }
 end
 end
 end

# Iterates over each attribute of an Element, yielding the expanded name
 # and value as a pair of Strings.
 #
 # doc = Document.new '<a x="1" y="2"/>'
 # doc.root.attributes.each {|name, value| p name+" => "+value }
 def each
 each_attribute do |attr|
 yield [attr.expanded_name, attr.value]
 end
 end

# Fetches an attribute
 # name::
 # the name by which to search for the attribute. Can be a
 # <tt>prefix:name</tt> namespace name.
 # Returns:: The first matching attribute, or nil if there was none. This
 # value is an Attribute node, not the String value of the attribute.
 # doc = Document.new '<a x:foo="1" foo="2" bar="3"/>'
 # doc.root.attributes.get_attribute("foo").value #-> "2"
 # doc.root.attributes.get_attribute("x:foo").value #-> "1"
 def get_attribute( name )
 attr = fetch( name, nil )
 if attr.nil?
 return nil if name.nil?
 # Look for prefix
 name =~ Namespace::NAMESPLIT
 prefix, n = $1, $2
 if prefix
 attr = fetch( n, nil )
 # check prefix
 if attr == nil
 elsif attr.kind_of? Attribute
 return attr if prefix == attr.prefix
 else
 attr = attr[ prefix ]
 return attr
 end
 end
 element_document = @element.document
 if element_document and element_document.doctype
 expn = @element.expanded_name
 expn = element_document.doctype.name if expn.size == 0
 attr_val = element_document.doctype.attribute_of(expn, name)
 return Attribute.new( name, attr_val ) if attr_val
 end
 return nil
 end
 if attr.kind_of? Hash
 attr = attr[ @element.prefix ]
 end
 return attr
 end

# Sets an attribute, overwriting any existing attribute value by the
 # same name. Namespace is significant.
 # name:: the name of the attribute
 # value::
 # (optional) If supplied, the value of the attribute. If
 # nil, any existing matching attribute is deleted.
 # Returns::
 # Owning element
 # doc = Document.new "<a x:foo='1' foo='3'/>"
 # doc.root.attributes['y:foo'] = '2'
 # doc.root.attributes['foo'] = '4'
 # doc.root.attributes['x:foo'] = nil
 def []=( name, value )
 if value.nil? # Delete the named attribute
 attr = get_attribute(name)
 delete attr
 return
 end

unless value.kind_of? Attribute
        if @element.document and @element.document.doctype
          value = Text::normalize( value, @element.document.doctype )
        else
          value = Text::normalize( value, nil )
        end
        value = Attribute.new(name, value)
      end
      value.element = @element
      old_attr = fetch(value.name, nil)
      if old_attr.nil?
        store(value.name, value)
      elsif old_attr.kind_of? Hash
        old_attr[value.prefix] = value
      elsif old_attr.prefix != value.prefix
        # Check for conflicting namespaces
        raise ParseException.new(
          "Namespace conflict in adding attribute \"#{value.name}\": "+
          "Prefix \"#{old_attr.prefix}\" = "+
          "\"#{@element.namespace(old_attr.prefix)}\" and prefix "+
          "\"#{value.prefix}\" = \"#{@element.namespace(value.prefix)}\"") if
          value.prefix != "xmlns" and old_attr.prefix != "xmlns" and
          @element.namespace( old_attr.prefix ) ==
            @element.namespace( value.prefix )
          store value.name, { old_attr.prefix   => old_attr,
            value.prefix                => value }
      else
        store value.name, value
      end
      return @element
    end

# Returns an array of Strings containing all of the prefixes declared
 # by this set of # attributes. The array does not include the default
 # namespace declaration, if one exists.
 # doc = Document.new("<a xmlns='foo' xmlns:x='bar' xmlns:y='twee' "+
 # "z='glorp' p:k='gru'/>")
 # prefixes = doc.root.attributes.prefixes #-> ['x', 'y']
 def prefixes
 ns = []
 each_attribute do |attribute|
 ns << attribute.name if attribute.prefix == 'xmlns'
 end
 if @element.document and @element.document.doctype
 expn = @element.expanded_name
 expn = @element.document.doctype.name if expn.size == 0
 @element.document.doctype.attributes_of(expn).each {
 |attribute|
 ns << attribute.name if attribute.prefix == 'xmlns'
 }
 end
 ns
 end

def namespaces
      namespaces = {}
      each_attribute do |attribute|
        namespaces[attribute.name] = attribute.value if attribute.prefix == 'xmlns' or attribute.name == 'xmlns'
      end
      if @element.document and @element.document.doctype
        expn = @element.expanded_name
        expn = @element.document.doctype.name if expn.size == 0
        @element.document.doctype.attributes_of(expn).each {
          |attribute|
          namespaces[attribute.name] = attribute.value if attribute.prefix == 'xmlns' or attribute.name == 'xmlns'
        }
      end
      namespaces
    end

# Removes an attribute
 # attribute::
 # either a String, which is the name of the attribute to remove --
 # namespaces are significant here -- or the attribute to remove.
 # Returns:: the owning element
 # doc = Document.new "<a y:foo='0' x:foo='1' foo='3' z:foo='4'/>"
 # doc.root.attributes.delete 'foo' #-> <a y:foo='0' x:foo='1' z:foo='4'/>"
 # doc.root.attributes.delete 'x:foo' #-> <a y:foo='0' z:foo='4'/>"
 # attr = doc.root.attributes.get_attribute('y:foo')
 # doc.root.attributes.delete attr #-> <a z:foo='4'/>"
 def delete( attribute )
 name = nil
 prefix = nil
 if attribute.kind_of? Attribute
 name = attribute.name
 prefix = attribute.prefix
 else
 attribute =~ Namespace::NAMESPLIT
 prefix, name = $1, $2
 prefix = '' unless prefix
 end
 old = fetch(name, nil)
 if old.kind_of? Hash # the supplied attribute is one of many
 old.delete(prefix)
 if old.size == 1
 repl = nil
 old.each_value{|v| repl = v}
 store name, repl
 end
 elsif old.nil?
 return @element
 else # the supplied attribute is a top-level one
 super(name)
 end
 @element
 end

# Adds an attribute, overriding any existing attribute by the
    # same name.  Namespaces are significant.
    # attribute:: An Attribute
    def add( attribute )
      self[attribute.name] = attribute
    end

alias :<< :add

# Deletes all attributes matching a name. Namespaces are significant.
 # name::
 # A String; all attributes that match this path will be removed
 # Returns:: an Array of the Attributes that were removed
 def delete_all( name )
 rv = []
 each_attribute { |attribute|
 rv << attribute if attribute.expanded_name == name
 }
 rv.each{ |attr| attr.remove }
 return rv
 end

# The +get_attribute_ns+ method retrieves a method by its namespace
    # and name. Thus it is possible to reliably identify an attribute
    # even if an XML processor has changed the prefix.
    #
    # Method contributed by Henrik Martensson
    def get_attribute_ns(namespace, name)
      result = nil
      each_attribute() { |attribute|
        if name == attribute.name &&
          namespace == attribute.namespace() &&
          ( !namespace.empty? || !attribute.fully_expanded_name.index(':') )
          # foo will match xmlns:foo, but only if foo isn't also an attribute
          result = attribute if !result or !namespace.empty? or
                                !attribute.fully_expanded_name.index(':')
        end
      }
      result
    end
  end
end

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