An example of proxying a Tumblr blog as a subdirectory in Ruby and Sinatra

tumblrproxy.rb

  get '/blog*' do
    path = params[:splat][0]
    source_url = 'http://yourblog.tumblr.com' + path.gsub(/ /, '+')
    source_content_type = ''
    source_body = open(source_url) do |f|
      source_content_type = f.content_type     # "text/html"
      f.read
    end
    if source_content_type == 'text/html'
      output_base = request.base_url + '/blog'
      output_body = source_body.gsub(/\b(href|src|rel)="\/\//, '\1="https:\/\/')
      output_body = output_body.gsub(/\b(href|src|rel)="\//, '\1="' + output_base + '/')
      output_body = output_body.gsub(/\b(href|src|rel)="http:\/\/yourblog\.tumblr\.com/, '\1="/blog')
    else
      output_body = source_body
    end
    
    content_type source_content_type
    output_body
  end