discourse/lib/onebox/preview.rb

# frozen_string_literal: true

module Onebox
  class Preview
    # see https://bugs.ruby-lang.org/issues/14688
    client_exception =
      defined?(Net::HTTPClientException) ? Net::HTTPClientException : Net::HTTPServerException
    WEB_EXCEPTIONS ||= [
      client_exception,
      OpenURI::HTTPError,
      Timeout::Error,
      Net::HTTPError,
      Errno::ECONNREFUSED,
    ]

    def initialize(url, options = Onebox.options)
      @url = url
      @options = options.dup

      allowed_origins = @options[:allowed_iframe_origins] || Onebox::Engine.all_iframe_origins
      @options[:allowed_iframe_regexes] = Engine.origins_to_regexes(allowed_origins)

      @engine_class = Matcher.new(@url, @options).oneboxed
    end

    def to_s
      return "" unless engine
      sanitize process_html engine_html
    rescue *WEB_EXCEPTIONS
      ""
    end

    def placeholder_html
      return "" unless engine
      sanitize process_html engine.placeholder_html
    rescue *WEB_EXCEPTIONS
      ""
    end

    def errors
      return {} unless engine
      engine.errors
    end

    def data
      return {} unless engine
      engine.data
    end

    def verified_data
      return {} unless engine
      engine.verified_data
    end

    def options
      OpenStruct.new(@options)
    end

    private

    def engine_html
      engine.to_html
    end

    def process_html(html)
      return "" unless html

      if @options[:max_width]
        doc = Nokogiri::HTML5.fragment(html)
        if doc
          doc
            .css("[width]")
            .each do |e|
              width = e["width"].to_i

              if width > @options[:max_width]
                height = e["height"].to_i
                if (height > 0)
                  ratio = (height.to_f / width.to_f)
                  e["height"] = (@options[:max_width] * ratio).floor
                end
                e["width"] = @options[:max_width]
              end
            end
          return doc.to_html
        end
      end

      html
    end

    def sanitize(html)
      config = @options[:sanitize_config] || SanitizeConfig::ONEBOX
      config = config.merge(allowed_iframe_regexes: @options[:allowed_iframe_regexes])

      Sanitize.fragment(html, config)
    end

    def engine
      return nil unless @engine_class
      return @engine if defined?(@engine)

      @engine = @engine_class.new(@url)
      @engine.options = @options
      @engine
    end

    class InvalidURI < StandardError
    end
  end
end