Rewritten

Rewritten is a lookup-based rewriting engine that rewrites requested URLs on the fly. The URL manipulations depend on translations found in a redis database. URLs without translations are passed through while URLs with translations result in a either redirection or ultimatively in a modification of path and request parameters. The gem is compromised of several parts:

1. A Ruby library for creating, modifying and querying translations.
2. A Sinatra app for displaying and managing translations
3. A Rack app for rewriting and redirecting requests (Rack::Rewritten::Url)
4. A Rack app for substituting URLs in HTML pages with their current translation (Rack::Rewritten::Html)
5. A Rack app for recording requests (Rack::Rewritten::Record)
6. A Rack app for identifying subdomains (Rack::Rewritten::Subdomain)

Part 1. and 2. are based heavily on parts from the Resque codebase.

gem install rewritten

On Rails add Rewritten to your Gemfile:

gem 'rewritten'

Rewritten works completely transparent and decoupled as Rack middleware. Add it to your rack stack.

# config.ru
require 'rewritten'

Rewritten.redis = Redis.new(host: 'host', port: 'port', password: 'password' )

map "/" do
  use Rack::Rewritten::Url
  use Rack::Rewritten::Html
  run MyApp::Application
end

This will translate pretty/SEO requests to the language that MyApp speaks and translate the HTML-Output of MyApp to the desired pretty/SEO language.

On Rails the HTML translation can also be achieved by including the following to your application_controller.rb:

require 'rewritten/rails'

class ApplicationController < Action:Controller::Base

  include Rewritten::Rails::UrlHelper

  # ....
  #

end

This way all routes helpers will be translated.

To manage the vocabulary from within your Rack app you need to establish a connection to the same redis db (on Rails put this into an initializer).

include 'rewritten'
Rewritten.redis = Redis.new(host: 'host', port: 'port', password: 'password' )

The ruby library allows you to successively add and remove vocabulary:

Rewritten.add_translation('/apple-computer/newton', '/products/4e4d3c6a1d41c811e8000009')
Rewritten.add_translation('/apple/ipad', '/products/4e4d3c6a1d41c811e8000009')

Rewritten.remove_translation('/failed-computer/newton', '/products/4e4d3c6a1d41c811e8000009')

To query for the current "trade language" use:

Rewritten.get_current_translation('/products/4e4d3c6a1d41c811e8000009')         # => "/apple/ipad"

Rewritten comes with a Sinatra-based front end for dislaying and managing your URL translations (layout taken from Resque). Include it in your Rack stack with:

require 'rewritten/server'

map "/rewritten" do
  use Rack::Auth::Basic do |username, password|
    username == 'user' and password == 'password'
  end
  run Rewritten::Server
end

Running the gem in standalone mode is easy as well:

$ rewritten-web 

It's based on Vegas, a thin layer around rackup, and as such configurable as well:

$ rewritten-web -p 8282