gistfile1.rb

module Factor
  def self.add(name, &block)
    Factor::Resolvers.add(name, block)
  end

  def self.value(name)
    # needs moar delegation
    Factor::Resolvers::RESOLVERS[name].value
  end
end

class Factor::Resolvers
  # resolver table
  RESOLVERS = {}

  def self.add(name, &block)
    RESOLVERS[name] = new.instance_eval(block)
  end

  def exec(command)
    Factor::Resolvers::Exec.new(command)
  end

  def command(&block)
    Factor::Resolvers::Command.new(block)
  end

  def setcode(str=nil, &block)
    exec(str, block) if str
    command(block)
  end
end

# Abstract class used to provide default behavior to resolvers
class Facter::Resolvers::Resolver
  IDENTITY_PROC = lambda {|x| x}

  def value
    raise NotImplementedError, "value must be implemented in subclasses"
  end
end

module Facter
  class Resolvers
    # Execute a shell command and optionally pass STDOUT to a block for
    # processing (similar to a unix pipe).
    #
    # Example:
    #   Exec.new('hostname') do |name|
    #     name and name.match(/^([\w-]+)\.(.+)$/).first
    #   end
    class Exec < Resolver
      def initialize(exec, block=nil)
        @exec = exec
        @block = block || IDENTITY_PROC
      end

      def value
        @value ||= @block.call(`#{@exec}`)
      end
    end
  end
end