#test.xml = "<pears><pear id="1254"/><name/><region/></pear><pear id="5656"><name/><region/></pear></pears>"

require 'rexml/document'
include REXML

class Update
  def initialize
  end

  def update_item(doc_p, pelement_name)
    #get the target xml file
    file = File.new('test.xml')
    doc = Document.new(file)

    puts doc
    # get a reference to the record
    id = doc_p.root.elements["parameter[@id]"].attributes.get_attribute('id')
    puts id

    node = doc.root.elements[pelement_name + "[@id='#{id}']"]
    puts node
    rnode = map_record(node, doc_p)
    puts doc
  end

  def map_record(o_node, doc_input)
    # set the element values for each field
    doc_input.elements.each('parameters/parameter') do |in_node|
      field = in_node.attributes.get_attribute('field').to_s
      in_node.elements.each('attributes/attribute') do | attributex|
        attribute_name = attributex.attributes.get_attribute('name').to_s
        attribute_value = attributex.attributes.get_attribute('value').to_s
        o_field = o_node.elements[attribute_name]
        o_field.add_attribute(attribute_name, attribute_value)
      end
      map(o_node, field, in_node.attributes.get_attribute('value').to_s)

    end
    o_node
  end
  
  def map(o_node, field, value)
    o_element = o_node.elements[field]
    o_element.text = value
    o_element
  end
  

end

if __FILE__ == $0
  u = Update.new
  doc = Document.new
  parameters = Element.new('parameters')
  parameter = Element.new('parameter')
  parameter.add_attribute('id', '5656')
  parameters.add_element(parameter)
  parameter = Element.new('parameter')
  parameter.add_attribute('field', 'name')
  parameter.add_attribute('value', 'Harovin Gaia')
  parameters.add_element(parameter)
  parameter = Element.new('parameter')
  parameter.add_attribute('field', 'region')
  parameter.add_attribute('value', 'Niagara')
  parameters.add_element(parameter)
  doc.add_element(parameters)
  u.update_item(doc, 'pear')
  puts doc
end