queryxml.rb

require 'xml/libxml'

# Generates 'QueryXML' for use with AutoTask Web Services API
module QueryXML
  def _if(field_name, op, compare, udf = false)
    f_xml = (XML::Node.new('field') << field_name)
    f_xml << (e_xml = XML::Node.new('expression') << compare)
    e_xml['op'] = op
    f_xml['udf'] = true.to_s if udf
    f_xml # return field comparison XML
  end
  
  def _or(*args)
    o_xml = XML::Node.new('condition')
    o_xml['operator'] = 'or'
    args.each { |se| o_xml << se }
    o_xml
  end
  
  def _and(*args)
    o_xml = XML::Node.new('condition')
    args.each { |se| o_xml << se }
    o_xml
  end
  
  def queryxml(entity)
    Query.new(entity)
  end
  
  # Storage object for our XML document
  class Query
    def initialize(entity)
      n_entity = XML::Node.new('entity')
      n_entity << entity
      n_query = XML::Node.new('query')
      
      @doc = XML::Document.new
      @doc.root = XML::Node.new('queryxml')
      @doc.root << n_entity
      @doc.root << n_query
      
      @query = n_query
    end
  
    def to_s
      @doc.root.to_s(indent: true)
    end

    def <<(value)
      @query << value
    end
  end
end

include QueryXML
q = queryxml('Ticket')
q << _if('id', 'equals', 1)
q << _or(
  _and(
    _or(
      _if('id', 'greaterthan', 100),
      _if('id', 'lessthan', 199)
    ),
    _or(
      _if('id', 'greaterthan', 200),
      _if('id', 'lessthan', 299)
    )
  ),
  _and(
    _if('udfField', 'equals', 200, true)
  )
)

puts q.to_s