module RailsConnector
  #
  # This module provides an interface for generating PDF files.
  #
  module FopOnRails
    #
    # Is raised if the response was not 200.
    #
    class DownloadError < RuntimeError; end

    READ_TIMEOUT = 300

    #
    # Generates a PDF from <code>xml_location</code> and <code>xsl_location</code> and returns its
    # path in the file system.
    #
    # If the file <code>xml_location</code> doesn't already exist, then <code>xml_location</code>
    # and <code>xsl_location</code> are interpreted as URLs and will be downloaded before
    # the PDF is generated.
    #
    # If the download of <code>xml_location</code> or <code>xsl_location</code> fails, then
    # the {RailsConnector::FopOnRails::DownloadError} is raised.
    #
    # To generate a PDF, the given XML <b>must</b> be valid. If for some reasons it is not, then you can use the
    # <code>tidy</code> option to repair it.
    #
    # If the PDF generation fails, then the {RailsConnector::Fop::GenerationFailed} error
    # is raised.
    #
    # Example:
    #
    #   RailsConnector::FopOnRails.generate_pdf('/tmp/test.xml', '/tmp/test.xsl')
    #   # This will generate a PDF and return its path
    #
    #   RailsConnector::FopOnRails.generate_pdf('http://mywebsite.com/test.xml', 'http://mywebsite.com/test.xsl', true)
    #   # This will download both files, repair the XML, generate a PDF, and return its path
    #
    def self.generate_pdf(xml_location, xsl_location, tidy = false)
      log("\nStarting PDF generation...")

      w_dir = File.join(Rails.root, %w(tmp fop_on_rails), $$.to_s)
      FileUtils.rm_rf(w_dir)
      FileUtils.mkdir_p(w_dir)

      pdf = "#{w_dir}/pdf"

      if File.exist?(xml_location)
        xml = xml_location
        xsl = xsl_location
        log("\trepairing XML")
        FopOnRails::Document.repair(xml)
      else
        xml = "#{w_dir}/xml"
        xsl = "#{w_dir}/xsl"

        log("\tgetting XSL source from #{xsl_location}")
        download(xml_location, xml)
        log("\tgetting XML source from #{xml_location}")
        download(xsl_location, xsl)
      end

      if tidy
        log("\trepairing XML")
        FopOnRails::Document.repair(xml, xml_location)
      end

      log("\tgenerating PDF\n\n")
      Fop.generate_pdf(xml, xsl, pdf)

      return pdf
    end

    private

    def self.download(src, dest)
      url = URI.parse(src)
      http = Net::HTTP.new(url.host, url.port)
      http.read_timeout = READ_TIMEOUT
      resp = http.get(url.request_uri)
      unless resp.kind_of?(Net::HTTPSuccess)
        raise DownloadError, "Could not download #{src}"
      end
      File.open dest, 'w' do |f|
        f.write resp.body
      end
    end

    def self.log(msg)
      Rails.logger.info(msg)
    end
  end
end