# frozen_string_literal: true

# name: discourse-graphviz
# about: Provides the ability to add graphs to posts using the DOT language.
# meta_topic_id: 97554
# version: 0.0.1
# authors: Maja Komel, Joffrey Jaffeux
# url: https://github.com/discourse/discourse/tree/main/plugins/discourse-graphviz

enabled_site_setting :discourse_graphviz_enabled

register_svg_icon "diagram-project"
register_asset "stylesheets/common/graphviz.scss"

module ::DiscourseGraphviz
  ALLOWED_URL_SCHEMES = %w[http https].freeze

  def self.context
    context = MiniRacer::Context.new
    context.load("#{Rails.root}/plugins/discourse-graphviz/public/javascripts/viz-3.0.1.js")
    context
  end

  def self.allowed_svg_xpath
    @@allowed_svg_xpath ||=
      "//*[#{UploadCreator::ALLOWED_SVG_ELEMENTS.map { |e| "name()!='#{e}'" }.join(" and ")}]"
  end

  def self.sanitize_svg_links(svg_node)
    svg_node
      .css("a")
      .each do |anchor|
        href = anchor["href"] || anchor["xlink:href"]
        next unless href

        begin
          uri = URI.parse(href)
          scheme = uri.scheme&.downcase

          if scheme && !ALLOWED_URL_SCHEMES.include?(scheme)
            anchor.replace(anchor.children)
          elsif scheme.nil? && href.strip.match?(/\A\s*javascript:/i)
            anchor.replace(anchor.children)
          end
        rescue URI::InvalidURIError
          anchor.replace(anchor.children)
        end
      end
  end
end

after_initialize do
  on(:before_post_process_cooked) do |doc, post|
    if SiteSetting.discourse_graphviz_enabled
      doc
        .css("div.graphviz")
        .each do |graph|
          engine = graph.attribute("data-engine").value
          svg_graph =
            begin
              DiscourseGraphviz.context.eval(
                "vizRenderStringSync(#{graph.children[0].content.inspect}, {engine: '#{engine}'})",
              )
            rescue StandardError
              nil
            end
          next if svg_graph.nil?

          should_use_svg = SiteSetting.graphviz_default_svg
          should_use_svg ||= graph.classes.include?("graphviz-svg")
          should_use_svg &&= !graph.classes.include?("graphviz-no-svg")

          if should_use_svg
            # Changing to Nokogiri::HTML5.fragment returns `nil` for `.css('svg')`
            # rubocop:todo Discourse/NoNokogiriHtmlFragment
            new_graph_node = Nokogiri::HTML.fragment(svg_graph).css("svg").first
            # rubocop:enable Discourse/NoNokogiriHtmlFragment
            new_graph_node["class"] = "graphviz-svg-render"
            DiscourseGraphviz.sanitize_svg_links(new_graph_node)
            new_graph_node.xpath(DiscourseGraphviz.allowed_svg_xpath).remove
            graph.replace new_graph_node
            next
          end

          tmp_svg = Tempfile.new(%w[svgfile .svg])
          tmp_png = Tempfile.new(%w[vizgraph- .png])

          tmp_svg.write(svg_graph)
          tmp_svg.rewind

          graph_title =
            Nokogiri
              .parse(svg_graph)
              .at("//comment()[contains(.,'Title')]")
              &.content
              &.match(/Title:\s(?<title>.+)\sPages:/)
              &.[](:title)
          filename = graph_title != "%0" ? graph_title : File.basename(tmp_png.path)

          Discourse::Utils.execute_command("convert", "-density", "300", tmp_svg.path, tmp_png.path)

          upload = UploadCreator.new(tmp_png, filename).create_for(-1)

          # replace div.graphviz with image node
          new_graph_node = Nokogiri::XML::Node.new("img", doc)
          new_graph_node["src"] = upload.url
          new_graph_node["alt"] = filename
          graph.replace new_graph_node

          tmp_svg.close!
          tmp_png.close!
        end
    end
  end
end