validate_test.rb

#!/usr/bin/env ruby -w

require_relative '../lib/ctools/validator.rb'

class Tool_test
  puts $LOAD_PATH 
  @html = File.new('/Users/carlos/experiment/code/conversion_tools/test/index.html').read
  Ctools.Validator.validate_text(@html)
end

validator.rb

#!/usr/bin/env ruby -w
require 'json'
require 'rest_client'

module Ctools
  class Validator
  # Based on the code from https://github.com/damian/html5_validator/blob/master/lib/html5_validator.rb

    attr_reader :errors
    BASE_URI = 'http://html5.validator.nu'
    HEADERS = { 'Content-Type' => 'text/html; charset=utf-8', 'Content-Encoding' => 'UTF-8' }
  
    def initialize(proxy = nil)
      RestClient.proxy = proxy unless proxy.nil?
    end
  
    # Validate the markup of a String
    def validate_text(text)
      response = RestClient.post "#{BASE_URI}/?out=json", text, HEADERS
      @json = JSON.parse(response.body)
      @errors = retrieve_errors
    end
  
    # Validate the markup of a URI
    def validate_uri(uri)
      response = RestClient.get BASE_URI, :params => { :doc => uri, :out => 'json' }
      @json = JSON.parse(response.body)
      @errors = retrieve_errors
    end
  
    def inspect
    @errors.map do |err|
      "- Error: #{err['message']}"
      end.join("\n")
    end

    def valid?
      @errors.length == 0
    end

    private
  
    def retrieve_errors
      @json['messages'].select { |mssg| mssg['type'] == 'error' }
    end
  end #class
end # module