stitcher.rb

if ENV["STITCH"] == "1"
  require "rack-proxy"

  class Stitcher < Rack::Proxy
    EXACT = %w(/ /terms /privacy)
    PREFIX = %w(/pricing /about /support /gateways /assets)

    def initialize(app)
      @app = app
    end

    def call(env)
      original_host = env["HTTP_HOST"]
      rewrite_env(env)
      if env["HTTP_HOST"] != original_host
        rewrite_response(perform_request(env))
      else
        @app.call(env)
      end
    end

    def rewrite_env(env)
      request = Rack::Request.new(env)

      return env unless(request.host == ENV["PUBLIC_FULL_DOMAIN"])

      unless(
          EXACT.include?(request.path) ||
          EXACT.include?(request.path + "/") ||
          PREFIX.include?(request.path) ||
          PREFIX.any?{|prefix| request.path.starts_with?(prefix + "/")})
        env["HTTP_HOST"] = ENV["SUBSCRIPTIONS_INTERNAL_DOMAIN"]
      end

      env
    end

    def extract_http_request_headers(env)
      headers = super
      headers["Host"] = ENV["PUBLIC_FULL_DOMAIN"]
      headers
    end
  end

  Rails.application.middleware.insert_before ActionDispatch::Static, Stitcher
end