A blog quine and deferred type checks in Ruby

class A
  def foo; "A#foo" end
end

a = A.new
a.foo                                              # => "A#foo"

module B; end

class A
  m = instance_method(:foo)
  B.class_eval{ define_method(:foo, m) }
  remove_method(:foo)
end

a.foo rescue "no method..."                        # => "no method..."

class A; include B end
a.foo                                              # => "A#foo"

class C; include B end
C.new.foo                                          # => 
# ~> -:53:in `foo': bind argument must be an instance of A (TypeError)
# ~> 	from -:53

#!/usr/bin/env ruby


require 'fileutils'

output_lines = []
replacements = {}
snippets = {}

file = ARGV[0] || "defout"
ARGV.replace [] if !File.exist?(file)

dir = "#{file}.files"
state = :begin
current_filename = nil
current_file = nil

ARGF.each do |line|
  case state

  when :begin
    case line
    when /^#(begin|sbegin)\(([^)]+)\)/
      state = :want_end
      current_filename = $2
      if $1 == "begin"
        FileUtils.mkdir_p dir
        current_file = File.open(File.join(dir, current_filename), "w")
      else
        current_file = nil
      end
      output_lines << line
      snippets[$2] = ""
    when %r{^//insert\(([^)]+)\)}
      state = :want_endinsert
      current_filename = $1
      replacements[output_lines.size - 1] = $1
    when %r{^#insert\(([^)]+)\)}
      state = :begin
      current_filename = $1
      replacements[output_lines.size - 1] = $1
    else
      output_lines << line
    end

  when :want_end
    case line
    when /^#end\(#{Regexp.escape(current_filename)}\)/
      current_file.close if current_file
      state = :begin
    else
      snippets[current_filename] << line
      current_file.puts line if current_file
    end
    output_lines << line

  when :want_endinsert
    if md = %r{^//endinsert\(#{Regexp.escape(current_filename)}\)}.match(line)
      state = :begin
    end
  end
end

replacements.each_pair do |idx, snippetname|
  output_lines[idx] << "//insert(#{snippetname})\n" << snippets[snippetname] <<
                       "//endinsert(#{snippetname})"
end
puts output_lines