From: Joel VanderWerf <joelvanderwerf@...>
Date: 2010-10-26T05:51:44+09:00
Subject: Re: DSL and indirection question

On 10/25/2010 12:20 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?

Maybe this helps, at least on the syntactic side (it's still a hash of 
procs underneath):


hash_builder = proc {|h,k| h[k] = Hash.new(&hash_builder)}
@rules = Hash.new(&hash_builder)
@stack = []

def section name, &block
   begin
     @stack.push name
     yield
   ensure
     @stack.pop
   end
end

def rule name, &block
   section = @stack.inject(@rules) {|sect,n| sect[n]}
   context = (@stack + [name]).join(".")
   section[name] = proc do
     block.call(context)
   end
end

section 27 do
   section "B" do
     rule 6 do
       puts "this is 27B-6"
     end

     rule "foo" do |name|
       puts "this is #{name}"
     end
   end
end

section 70 do
   section 1 do
     rule 9 do |name|
       puts "this is rule #{name}"
     end
   end
end

require 'pp'
pp @rules
puts
@rules[27]["B"][6].call
@rules[70][1][9].call

__END__

Output:

{27=>
   {"B"=>
     {6=>#<Proc:0x00007f179675e590@-:17>,
      "foo"=>#<Proc:0x00007f179675e590@-:17>}},
  70=>{1=>{9=>#<Proc:0x00007f179675e590@-:17>}}}

this is 27B-6
this is rule 70.1.9