require 'tempfile'
require 'net/http'
require 'fileutils'

module Html
  module Test
    class Validator
      @@tidy_ignore_list = []
      cattr_accessor :tidy_ignore_list

      # For local validation you might change this to http://localhost/validator/htdocs/check
      DEFAULT_W3C_URL = "http://validator.w3.org/check"
      @@w3c_url = DEFAULT_W3C_URL
      cattr_accessor :w3c_url
      
      # Whether the W3C validator should show the HTML document being validated in
      # its response. Set to 0 to disable.
      @@w3c_show_source = "1"
      cattr_accessor :w3c_show_source

      DEFAULT_DTD = File.join(File.dirname(__FILE__), 'DTD', 'xhtml1-strict.dtd')

      # Path to DTD file that the xmllint validator uses
      def self.dtd(document)
        DEFAULT_DTD
      end
      
      # Validate an HTML document string using tidy.
      # Code excerpted from the rails_tidy plugin
      def self.tidy_errors(body)
        tidy = RailsTidy.tidy_factory
        tidy.clean(body)
        errors = tidy.errors.empty? ? nil :
          tidy.errors.delete_if { |e| tidy_ignore_list.select { |p| e =~ p }.size > 0 }.join("\n")
        tidy.release
        errors.blank? ? nil : errors
      end

      # Validate an HTML document string by going to the online W3C validator.
      # Credit for the original code goes to Scott Baron (htonl)
      def self.w3c_errors(body)
        response = Net::HTTP.post_form(URI.parse(w3c_url),
                              {'ss'=>w3c_show_source, 'fragment'=>body})
        error = response['x-w3c-validator-status'] == 'Valid' ? nil : response.body
        if error
          # Reference in the stylesheets
          error.sub!(%r{@import "./base.css"}, %Q{@import "#{File.dirname(w3c_url)}/base.css"})
          response_file = File.join(Dir::tmpdir, "w3c_last_response.html")
          open(response_file, "w") { |f| f.puts(error) }
          "Response from W3C was written to the file #{response_file}: " + error
        else
          nil
        end
      end

      # Validate an HTML document string using the xmllint command line validator tool.
      # Returns nil if validation passes and an error message otherwise.
      # Original code taken from the book "Enterprise Integration with Ruby"
      def self.xmllint_errors(body)
        error_file = create_tmp_file("xmllint_error")
        doc_file = command = nil
        if dtd(body) =~ /^doctype$/i
          # Use the DOCTYPE declaration
          doc_file = create_tmp_file("xmllint", body)
          command = "xmllint --noout --valid #{doc_file} &> #{error_file}"
        else
          # Override the DOCTYPE declaration
          doc_file = create_tmp_file("xmllint", body.sub(/<!DOCTYPE[^>]+>/m, ""))
          command = "xmllint --noout --dtdvalid #{dtd(body)} #{doc_file} &> #{error_file}"
        end
        system(command)
        status = $?.exitstatus
        if status == 0
          return nil
        else
          failure_doc = File.join(Dir::tmpdir, "xmllint_last_response.html")
          FileUtils.cp doc_file, failure_doc
          return ("command='#{command}'. HTML document at '#{failure_doc}'. " +
            IO.read(error_file))
        end
      end
      
      private
      def self.create_tmp_file(name, contents = "")
        tmp_file = Tempfile.new(name)
        tmp_file.puts(contents)
        tmp_file.close
        tmp_file.path
      end
    end
  end
end