strings.rb

require 'parslet'

module Strings
  class Parser < Parslet::Parser
    rule(:spaces)  { match['\s\n'].repeat }

    rule(:eq)      { str("=") >> spaces }
    rule(:colon)   { str(";") >> spaces }

    rule(:string)  { str('"') >> (str('\\') >> any | str('"').absent? >> any).repeat.as(:internal) >> str('"') >> spaces }
    rule(:comment) { str("/*") >> (str("*/").absent? >> any).repeat >> str("*/") >> spaces                               }

    rule(:keyval)  { string.as(:key) >> eq >> string.as(:value) >> colon }
    rule(:line)    { keyval.as(:keyval) | comment.as(:comment)           }
    rule(:file)    { (spaces >> line.repeat).as(:file)                   }

    root(:file)
  end

  class Transform < Parslet::Transform
    rule(internal: simple(:i))     { i.str                               }
    rule(key:      subtree(:key))  { key                                 }
    rule(value:    subtree(:val))  { val                                 } 
    rule(keyval:   subtree(:kv))   { {kv[:key] => kv[:value]}            }
    rule(comment:  simple(:c))     { {}                                  }
    rule(file:     subtree(:file)) { file.reduce({}) {|a,b| a.merge(b) } }
  end

  def self.parse(source)
    Transform.new.apply(Parser.new.parse(source))
  end
end