From: Robert Klemme <shortcutter@...>
Date: 2010-10-26T16:48:12+09:00
Subject: Re: DSL and indirection question

On Mon, Oct 25, 2010 at 10:30 PM, Matt Lawrence <matt@technoronin.com> wrote:
> On Tue, 26 Oct 2010, James Edward Gray II wrote:
>
>> On Oct 25, 2010, at 2:20 PM, Matt Lawrence wrote:
>>
>>> I'm trying to figure out the best way of writing a script that describes
>>> various requirements in the form of "12.34.56" (from a requirement document)
>>> that I can then create methods for reporting, verifying and remediating the
>>> requirment on a system.
>>>
>>> This is script for checking and fixing systems based on a bunch of
>>> security requirements.  There are a couple of hundred rules and a few
>>> hundred systems.  I am thinking about building a hash of Procs, but I think
>>> it is going to be too ugly.  Any suggestions on a clean and easy to read way
>>> of doing this?
>>
>> This almost sounds like a job for Chef or Puppet, if I understood
>> correctly.
>
> Chef or Puppet would not be practical in this environment for various
> reasons.  This place is not in the Stone Age like my last job, they're more
> like the Bronze Age.  I am campaigning to at least get Cfengine set up.
>
>> I'm not really getting what you are aiming for here.  Can you show a
>> simple example or two?
>
> I have a directory full of results from a security scan, on file per system.
>  In that file each line starts with a rule number, like "12.34" and has a
> pass/fail/skipped result.
>
> What I probably want to do is to create a class for rules with each rule
> having methods for testing and fixing each issue found.  I know I can brute
> force the script and it will look ugly or I can ask for help on doing a
> nifty DSL in the new favoured Ruby style.

Rule = Struct.new :name do
  def test(&b)
    if b
      @test = b
    else
      @test
    end
  end

  # same for fix
end

AllRules = Hash.new {|h,k| h[k.freeze] = Rule[k]}

AllRules["12.34"].test |system| puts "Testing rule on system #{system}"}
AllRules["12.34"].fix {|system| puts "Fixing rule on system #{system}"}

or

AllRules["12.34"].tap do |rule|
  rule.test do |system|
    puts "Testing rule on system #{system}"
  end

  rule.fix do |system|
      puts "Fixing rule on system #{system}"
  end
end


RuleResult = Struct.new :rule, :result do
  def self.parse(str)
    raise ArgumentError, "Cannot parse %p" % str unless
/^(\d+(?:\.\d+)*).*(pass|fail|skip)/
    self[AllRules[$1], $2.to_sym]
  end

  alias __result= result=

  def result=(x)
    __result= x.to_sym
  end

  def ok?
    result == :pass
  end
end

Something like this?

Cheers

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/