$:.unshift File.dirname(__FILE__)

require 'template_exception'

module BuildMaster
  class TemplateRunner
    @@NAMESPACE = 'http://buildmaster.rubyforge.org/xtemplate/1.0'
    attr_reader :templatelets
    attr_writer :templatelets

    def initialize(target, template, source, &evaluator)
      @templatelets = Hash.new
      @target = target
      @template = template
      @source_instance = source
      @templatelets = templatelets
      @evaluator = evaluator
    end
        
    def process
      process_children(@target, @template)
    end
        
    private
    def process_children(target, template)
      template.each do |element|
        if (element.kind_of? REXML::Element)
          process_element(target, element)
        else
          target.add(deep_clone(element))
        end
      end
    end
        
    def process_element(target, element)
      if (template_directive?(element))
        process_directive(target, element)
      else
        output_element = clone_element(element)
        target.add(output_element)
        process_children(output_element, element)
      end
    end
        
    def template_directive?(element)
      element.namespace == @@NAMESPACE
    end
        
    def process_directive(target, template_element)
      message = "process_#{template_element.name}_directive"
      templatelet = @templatelets[template_element.name]
      if (not templatelet)
        raise TemplateException, "unable to process element template:#{template_element.name}"
      end
      templatelet.process(target, template_element, @source_instance)
    end

    def clone_element( template_element )
      cloned_element = REXML::Element.new( template_element.expanded_name )
      copy_attributes( template_element, cloned_element )
      cloned_element
    end
        
    def copy_attributes( template_element, expanded_element )
      template_element.attributes.each_attribute do |attribute|
          expanded_element.attributes.add( attribute.clone )
      end
    end
        
    def deep_clone( node )
      if node.kind_of? REXML::Parent
        node.deep_clone
      else
        node.clone
      end
    end
        
  end
end