require 'asciidoctor'
require 'asciidoctor-pdf'
require 'securerandom'

class SnippetToImageFilter < Asciidoctor::Extensions::Preprocessor
  def process(document, reader)
    new_lines = []
    image_id = nil
    capture = false
    html_content = ""

    reader.lines.each do |line|
      if line.strip == "<!--image-->"
        capture = true
        image_id = SecureRandom.hex(10)
        next
      elsif line.strip == "<!--/image-->" && capture
        output_path = "generated_images/#{image_id}.png"
        `node saveAsImage.js "#{html_content}" "#{output_path}"`
        new_lines << "image::#{output_path}[Generated Image, scaledwidth=75%]"
        capture = false
        html_content = ""
        next
      elsif capture
        html_content += line
      else
        new_lines << line
      end
    end

    # Ensure all lines are added if the document doesn't end properly
    if capture
      new_lines.concat(html_content.split("\n"))
    end

    Asciidoctor::PreprocessorReader.new(document, new_lines)
  end
end

Asciidoctor::Extensions.register do
  preprocessor SnippetToImageFilter
end