hq9+.rb

#!/usr/bin/env ruby
# coding: utf-8

module HQ9Plus
  class Interpreter
    NAME = 'RHQ9+'
    
    attr_accessor :interactive

    def initialize
      @acum   = 0 
      @source = ''
      @interactive = false
    end

    def run(source)
      @source << source.upcase
      source.each_char do |c|
        executed = case c
                   when /H/i then print_hello
                   when /Q/i then print_source
                   when /9/i then print_99bottles
                   when /\+/ then increment
                   end
        puts "# @acum => #{@acum}, @source => #{@source.gsub(/[^HQ9\+]/,'')}" if executed && @interactive
      end
    end

    private

    def print_hello
      puts 'Hello, World!'
      true
    end

    def print_source
      puts @source
      true
    end

    def print_99bottles
      a = 'Bottle';b = 'of beer';c = 'on the wall'
      buff = ''
      99.downto(1) do |i|
        ex = i > 1 ? 's' : ''
        buff << "#{i} #{a}#{ex} #{b} #{c}, #{i} #{a}#{ex} #{b}.\nTake one down and pass it around, #{i-1} #{a}#{ex} #{b} #{c}.\n\n"
      end
      puts buff
      true
    end

    def increment
      @acum += 1
      true
    end
  end
end

if $0 == __FILE__
  $0 = File.basename($0)
  interpreter = HQ9Plus::Interpreter.new
  source = case
           when ARGV.size == 2 && ARGV[0] == '-e'
             unless ARGV[1].length > 0
               $stderr.puts 'abort!'
               $stderr.puts "usage: #{$0} -e CODE"
               exit(1)
             end
             ARGV[1]
           when ARGV.size == 1 && (ARGV[0] == '-i' || ARGV[0] == '--interactive')
             interpreter.interactive = true
             loop do
               print 'irhq9p> '
               cmd = $stdin.gets
               if cmd =~ /E/i
                 puts 'Bye!'
                 break
               end
               interpreter.run(cmd)
             end
           else gets
           end
  interpreter.run(source) if !!source
end