gist_inline.rb

require 'net/http'

module Rack
  class GistInline
    def initialize(app)
      @app = app
    end

    def call(env)
      status, headers, body = @app.call(env)
      body = body.inject("") { |html, part| html += part }

      body.gsub!(/<script[^>]*gist\.github\.com\/(\d+)\.js[^>]*><\/script>/) do |script|
        src = script.match(/src=['"]?([^"']*)["']?/)[1]
        js = Net::HTTP.get(URI.parse(src))
        output = []
        js.each do |line|
          if line.chomp =~/^document\.write\('(.*)'\);?/
            output << $1.gsub(/\\(["'\/])/, '\1').gsub('\n', "\n").gsub('\\\\', '\\')
          end
        end
        output.join("\n")
      end

      headers['Content-Length'] = body.length.to_s
      [status, headers, body]
    end
  end
end