katex-html/convert.rb

require "open3"
require "nokogiri"
require "net/http"
require "json"
require "cgi"

def render_cached(cache, display, string, render_comment = nil)
  string = CGI.unescapeHTML string
  cache.fetch(string) do |new|
    puts "  Rendering #{render_comment || new}"
    res = Net::HTTP.post URI("http://localhost:8000/render"),
      { :equations => [ { :str => string, :display => display } ] }.to_json,
       "Content-Type" => "application/json"
    cache[string] = JSON.parse(res.body)[0]
  end
end

def perform_katex_sub(inline_cache, display_cache, content)
  rendered = content.gsub /\\\(((?:[^\\]|\\[^\)])*)\\\)/ do |match|
    render_cached(inline_cache, false, $~[1])
  end
  rendered = rendered.gsub /\$\$((?:[^\$]|$[^\$])*)\$\$/ do |match|
    render_cached(display_cache, true, $~[1], "display")
  end
  return rendered
end

files = ARGV[0..-1]
inline_cache, display_cache = {}, {}

files.each do |file|
  puts "Rendering file: #{file}"
  document = Nokogiri::HTML.parse(File.open(file))
  document.search('//*[not(ancestor-or-self::code or ancestor-or-self::script)]/text()').each do |t|
    t.replace(perform_katex_sub(inline_cache, display_cache, t.content))
  end
  File.write(file, document.to_html(encoding: 'UTF-8'))
end