Katgut is a Rails Engine for adding simple url redirection features to your apps.

The gem provides:

• Dynamic redirection rules on DB
• After redirection callbacks

• Ruby 2.3 or later
• Rails 4.2.6 or later

Add katgut to your Gemfile

gem 'katgut', '~> 0.0.1'

Then install the migration files by running:

$ rake katgut:install:migrations

And apply them to your database.

$ rake db:migrate

Katgut is implemented as an Rails Engine. You can mount it anywhere you like:

# config/routes.rb

Rails.application.routes.draw do
  mount Katgut::Engine => "/katgut"  # /katgut/xxxxxx will be the redirection path
end

The redirection rules will be stored in katgut_rules table. A rule is a set of following parameters:

• source
• destination
• active

Set a unique key to determine which rule should be used to redirect the request. Only word characters and hyphens([^a-zA-Z0-9_\-]) are allowed and at least 5 characters needed. If you don't give any value for the source attribute, katgut generates a random value automatically.

/mount_point/:source

Set the desination url.

• You can omit http:// scheme.
• Only http and https schemes are allowed.
• Urls begin with / will be assumed as a same-origin path.

Set false to ignore the rule.

# Define a rule...
Katgut::Rule.new(source: "go-to-google", destination: "https://www.google.co.jp/").save

# ... to create this redirection
# GET /katgut/go-to-google => GET https://www.google.co.jp/

Katgut defines url helpers to generate redirection urls.

Suppose the engine is mounted to your app in this way:

# config/routes.rb
Rails.application.routes.draw do
  mount Katgut::Engine => "/katgut"
end

Then you can access predefined url helpers like this:

# app/controllers/xxxx_controller.rb

katgut.rule_path("source_string")  # => "/katgut/source_string"

You can see all the predefined helpers in Routes for Katgut::Engine section in the list that rake routes generates.

$ rake routes | grep --ignore-case katgut

Routes for Katgut::Engine:
  rule GET  /:id(.:format) katgut/rules#show

You can customize the behavour of the gem through the initializer script.

$ rails g katgut:initializer
# => config/initializers/katgut.rb

You can set a alternative destination url for the case the given source url does not exist.

Katgut.configure do |config|
  config.fall_back_path = '/not_found.html'  # default: '/'
end

You can define a custom block that will be called after every redirection. The block should have 3 argumets: request, parameters and rule. The rule will be nil when the specified source url on the request was not valid.

Katgut.configure do |config|
  config.after_refirection_callback = proc do |request, parameters, rule|
    # add custom behaviour here, such as logging, overwriting the rule, etc...
    # this block will be called in the context of Katgut::RulesController.
  end
end