Simplest rack app

config.ru

require 'rack'

map '/' do
  use Rack::Static, urls: ['/assets', '/templates'], root: File.expand_path('../public', __FILE__)
  app = lambda do |env|
    headers = {
      'Content-Type' => 'text/html',
      'Cache-Control' => 'no-cache'
    }

    body = File.open(File.expand_path('../public/index.html', __FILE__), File::RDONLY).read

    [200, headers, [body]]
  end

  run app
end