gistfile1.rb

module TypoFixer
  def self.included(base)
    base.class_eval do
      alias_method :method_missing_without_fix_typo, :method_missing
      alias_method :method_missing, :method_missing_with_fix_typo
    end
  end

  def method_missing_with_fix_typo(name, *args)
    if name && method = find_method(name)
      $stderr.puts "WARNING: execute `#{name}` as `#{method}` for #{self}"
      return send(method, *args)
    elsif method = find_method_with_only_one_typo(name)
      $stdout.print "WARNING: execute `#{name}` as `#{method}`? [Y/n] "
      return send(method, *args) if ($stdin.getc == 'Y')
    end

    method_missing_without_fix_typo(name, *args)
  end

  private
  def find_method_with_only_one_typo name
    self.class.instance_methods.each do |method|
      next unless method.size == name.size
      return method if(method.to_s.split(//) - name.to_s.split(//)).size == 1
    end
    nil
  end

  def find_method name
    name.to_s.split(//).permutation.each do |candidate|
      _candidate = candidate.join
      return _candidate if respond_to?(_candidate, true)
    end
    nil
  end
end