commandor.rb

module Commandor

  private

  class Command
    def self.match?(arg); end
    def self.parse(argv) end
    def self.execute(*args); end
    def self.help_msg; ''; end
  end

  module ClassMethods

    def process argv, *args
      argv << '-h' if argv.empty?
      command = argv.shift
      self.each do |cmd|
        if cmd.match? command
          opts = cmd.parse(argv)
          cmd.execute opts, *args
          break
        end
      end
    end

    def help_msg
      self.inject("") {|out, cmd| out << cmd.help_msg << "\n"}
    end

    ### Command creation methods
    
    private

    def command name
      command_name = name.capitalize+'Command'
      @new_class = self.const_set(command_name, Class.new(Command))

      yield

      @commands << @new_class
      @new_class = nil
    end

    def match *args
      block = block_given? ? lambda{|arg| yield(arg)} : lambda{|arg| args.include? arg}
      @new_class.instance_variable_set(:@match_list, args)

      @new_class.define_singleton_method(:match?) do |arg|
        block.call(arg)
      end
    end

    def parse &block
      @new_class.define_singleton_method(:parse) do |argv|
        block.call(argv)
      end
    end

    def execute &block
      @new_class.define_singleton_method(:execute) do |*args|
        block.call(*args)
      end
    end

    def help arg_names, help_txt
      @new_class.define_singleton_method(:help_msg) do
        "  #{@match_list.join(', ')} #{arg_names}#{help_txt}"
      end
    end

  end

  def self.included(klass)
    klass.extend(ClassMethods)
    klass.instance_variable_set(:@commands, [])

    klass.extend Enumerable
    def klass.each
      @commands.each do |cmd|
        yield cmd
      end
    end
  end

end