class Puppet::Parser::Relationship
    attr_accessor :source, :target, :type

    PARAM_MAP = {:relationship => :before, :subscription => :notify}

    def evaluate(catalog)
        if source.is_a?(Puppet::Parser::Collector)
            sources = source.collected.values
        else
            sources = [source]
        end
        if target.is_a?(Puppet::Parser::Collector)
            targets = target.collected.values
        else
            targets = [target]
        end
        sources.each do |s|
            targets.each do |t|
                mk_relationship(s, t, catalog)
            end
        end
    end

    def initialize(source, target, type)
        @source, @target, @type = source, target, type
    end

    def param_name
        PARAM_MAP[type] || raise(ArgumentError, "Invalid relationship type #{type}")
    end

    def mk_relationship(source, target, catalog)
        unless source_resource = catalog.resource(source.to_s)
            raise ArgumentError, "Could not find resource '#{source}' for relationship on '#{target}'"
        end
        unless target_resource = catalog.resource(target.to_s)
            raise ArgumentError, "Could not find resource '#{target}' for relationship from '#{source}'"
        end
        Puppet.debug "Adding relationship from #{source.to_s} to #{target.to_s} with '#{param_name}'"
        source_resource[param_name] ||= []
        source_resource[param_name] << target.to_s
    end
end