require 'puppet'
require 'puppet/simple_graph'

# A module that handles the small amount of graph stuff in Puppet.
module Puppet::Util::Graph
  # Make a graph where each of our children gets converted to
  # the receiving end of an edge.  Call the same thing on all
  # of our children, optionally using a block
  def to_graph(graph = nil, &block)
    # Allow our calling function to send in a graph, so that we
    # can call this recursively with one graph.
    graph ||= Puppet::SimpleGraph.new

    self.each do |child|
      unless block_given? and ! yield(child)
        graph.add_edge(self, child)

        child.to_graph(graph, &block) if child.respond_to?(:to_graph)
      end
    end

    # Do a topsort, which will throw an exception if the graph is cyclic.

    graph
  end
end