builder_writer.rb

# An XML writer for Ruby's XML RPC module
require 'rubygems'
require 'builder'

# The default XML serializer in Ruby's XML RPC module is VERY sloppy.
# We use Jim Weirich's excellent Builder to generate clean XML, even though it costs us some extra
# performance
class RPCBuilder
  
  # This is what is going to be lugged around as XML RPC results. It's actually
  # a node element
  class Command
    attr_accessor :text, :name, :children
    
    def initialize
      @text, @name, @children = nil, nil, []
      yield(self) if block_given?
    end
    
    def inspect
      '<#Command @name=%s @text=%s @children=%s' % [ name, text, children.length]
    end
  end
  
  # Should return a prebaked element. It saves us that native Builder uses tag!
  def tag(name, txt)
    Command.new { | c |  c.name = name;  c.text = txt }
  end
  
  def document_to_str(command_tree)
    @builder = Builder::XmlMarkup.new
    @builder.instruct!
    # Play the command tree to builder inside, do not run twice
    command_to_builder_call(command_tree)
    @builder.target!
  end

  # Make a document and stuff things into it. Document is actually a nothing thing.
  def document(*stuff)
    stuff
  end

  # noop, a processing instruction
  def pi(name, *params); end
  
  def ele(name, *children)
    # Make an element with name and attributes
    Command.new { |c| c.name = name; c.children = children }
  end
  
  # Should return the text escaped as XML cdata
  def text(txt)
    Command.new { |c| c.text = txt }
  end
  
  private
  
  # This will convert a tree of commands into XML Builder calls
  def command_to_builder_call(cmd)
    case cmd
      when NilClass
        # pass
      when Array
        cmd.compact.each{|c| command_to_builder_call(c) }
      when Command
        if cmd.name
          @builder.tag!(cmd.name) { @builder.text!(cmd.text.to_s.strip) if cmd.text; command_to_builder_call(cmd.children) }
        else
          @builder.text!(cmd.text)
        end
      when String
        @builder.text!(cmd.strip) unless cmd.empty?
    end
  end
end