mapper.rb

require 'erb'
require 'active_support/core_ext/hash/except'
require 'active_support/core_ext/object/blank'
require 'active_support/core_ext/object/inclusion'
require 'active_support/inflector'
require 'action_dispatch/routing/redirection'

module ActionDispatch
  module Routing
    class Mapper
      class Constraints #:nodoc:
        def self.new(app, constraints, request = Rack::Request)
          if constraints.any?
            super(app, constraints, request)
          else
            app
          end
        end

        attr_reader :app

        def initialize(app, constraints, request)
          @app, @constraints, @request = app, constraints, request
        end

        def matches?(env)
          req = @request.new(env)

          @constraints.each { |constraint|
            if constraint.respond_to?(:matches?) && !constraint.matches?(req)
              return false
            elsif constraint.respond_to?(:call) && !constraint.call(*constraint_args(constraint, req))
              return false
            end
          }

          return true
        end

        def call(env)
          matches?(env) ? @app.call(env) : [ 404, {'X-Cascade' => 'pass'}, [] ]
        end

        private
          def constraint_args(constraint, request)
            constraint.arity == 1 ? [request] : [request.symbolized_path_parameters, request]
          end
      end

      class Mapping #:nodoc:
        IGNORE_OPTIONS = [:to, :as, :via, :on, :constraints, :defaults, :only, :except, :anchor, :shallow, :shallow_path, :shallow_prefix]

        def initialize(set, scope, path, options)
          @set, @scope = set, scope
          @options = (@scope[:options] || {}).merge(options)
          @path = normalize_path(path)
          normalize_options!
        end

        def to_route
          [ app, conditions, requirements, defaults, @options[:as], @options[:anchor] ]
        end

        private

          def normalize_options!
            path_without_format = @path.sub(/\(\.:format\)$/, '')

            if using_match_shorthand?(path_without_format, @options)
              to_shorthand    = @options[:to].blank?
              @options[:to] ||= path_without_format[1..-1].sub(%r{/([^/]*)$}, '#\1')
            end

            @options.merge!(default_controller_and_action(to_shorthand))

            requirements.each do |name, requirement|
              # segment_keys.include?(k.to_s) || k == :controller
              next unless Regexp === requirement && !constraints[name]

              if requirement.source =~ %r{\A(\\A|\^)|(\\Z|\\z|\$)\Z}
                raise ArgumentError, "Regexp anchor characters are not allowed in routing requirements: #{requirement.inspect}"
              end
              if requirement.multiline?
                raise ArgumentError, "Regexp multiline option not allowed in routing requirements: #{requirement.inspect}"
              end
            end
          end

          # match "account/overview"
          def using_match_shorthand?(path, options)
            path && options.except(:via, :anchor, :to, :as).empty? && path =~ %r{^/[\w\/]+$}
          end

          def normalize_path(path)
            raise ArgumentError, "path is required" if path.blank?
            path = Mapper.normalize_path(path)

            if path.match(':controller')
              raise ArgumentError, ":controller segment is not allowed within a namespace block" if @scope[:module]

              # Add a default constraint for :controller path segments that matches namespaced
              # controllers with default routes like :controller/:action/:id(.:format), e.g:
              # GET /admin/products/show/1
              # => { :controller => 'admin/products', :action => 'show', :id => '1' }
              @options.reverse_merge!(:controller => /.+?/)
            end

            # Add a constraint for wildcard route to make it non-greedy and match the
            # optional format part of the route by default
            if path.match(/\*([^\/]+)$/) && @options[:format] != false
              @options.reverse_merge!(:"#{$1}" => /.+?/)
            end

            if @options[:format] == false
              @options.delete(:format)
              path
            elsif path.include?(":format") || path.end_with?('/')
              path
            else
              "#{path}(.:format)"
            end
          end

          def app
            Constraints.new(
              to.respond_to?(:call) ? to : Routing::RouteSet::Dispatcher.new(:defaults => defaults),
              blocks,
              @set.request_class
            )
          end

          def conditions
            { :path_info => @path }.merge(constraints).merge(request_method_condition)
          end

          def requirements
            @requirements ||= (@options[:constraints].is_a?(Hash) ? @options[:constraints] : {}).tap do |requirements|
              requirements.reverse_merge!(@scope[:constraints]) if @scope[:constraints]
              @options.each { |k, v| requirements[k] = v if v.is_a?(Regexp) }
            end
          end

          def defaults
            @defaults ||= (@options[:defaults] || {}).tap do |defaults|
              defaults.reverse_merge!(@scope[:defaults]) if @scope[:defaults]
              @options.each { |k, v| defaults[k] = v unless v.is_a?(Regexp) || IGNORE_OPTIONS.include?(k.to_sym) }
            end
          end

          def default_controller_and_action(to_shorthand=nil)
            if to.respond_to?(:call)
              { }
            else
              if to.is_a?(String)
                controller, action = to.split('#')
              elsif to.is_a?(Symbol)
                action = to.to_s
              end

              controller ||= default_controller
              action     ||= default_action

              unless controller.is_a?(Regexp) || to_shorthand
                controller = [@scope[:module], controller].compact.join("/").presence
              end

              if controller.is_a?(String) && controller =~ %r{\A/}
                raise ArgumentError, "controller name should not start with a slash"
              end

              controller = controller.to_s unless controller.is_a?(Regexp)
              action     = action.to_s     unless action.is_a?(Regexp)

              if controller.blank? && segment_keys.exclude?("controller")
                raise ArgumentError, "missing :controller"
              end

              if action.blank? && segment_keys.exclude?("action")
                raise ArgumentError, "missing :action"
              end

              hash = {}
              hash[:controller] = controller unless controller.blank?
              hash[:action]     = action unless action.blank?
              hash
            end
          end

          def blocks
            block = @scope[:blocks] || []

            if @options[:constraints].present? && !@options[:constraints].is_a?(Hash)
              block << @options[:constraints]
            end

            block
          end

          def constraints
            @constraints ||= requirements.reject { |k, v| segment_keys.include?(k.to_s) || k == :controller }
          end

          def request_method_condition
            if via = @options[:via]
              list = Array(via).map { |m| m.to_s.dasherize.upcase }
              { :request_method => list }
            else
              { }
            end
          end

          def segment_keys
            @segment_keys ||= Rack::Mount::RegexpWithNamedGroups.new(
              Rack::Mount::Strexp.compile(@path, requirements, SEPARATORS)
            ).names
          end

          def to
            @options[:to]
          end

          def default_controller
            if @options[:controller]
              @options[:controller]
            elsif @scope[:controller]
              @scope[:controller]
            end
          end

          def default_action
            if @options[:action]
              @options[:action]
            elsif @scope[:action]
              @scope[:action]
            end
          end
      end

      # Invokes Rack::Mount::Utils.normalize path and ensure that
      # (:locale) becomes (/:locale) instead of /(:locale). Except
      # for root cases, where the latter is the correct one.
      def self.normalize_path(path)
        path = Rack::Mount::Utils.normalize_path(path)
        path.gsub!(%r{/(\(+)/?}, '\1/') unless path =~ %r{^/\(+[^/]+\)$}
        path
      end

      def self.normalize_name(name)
        normalize_path(name)[1..-1].gsub("/", "_")
      end

      module Base
        # You can specify what Rails should route "/" to with the root method:
        #
        #   root :to => 'pages#main'
        #
        # For options, see +match+, as +root+ uses it internally.
        #
        # You should put the root route at the top of <tt>config/routes.rb</tt>,
        # because this means it will be matched first. As this is the most popular route
        # of most Rails applications, this is beneficial.
        def root(options = {})
          match '/', options.reverse_merge(:as => :root)
        end

        # Matches a url pattern to one or more routes. Any symbols in a pattern
        # are interpreted as url query parameters and thus available as +params+
        # in an action:
        #
        #   # sets :controller, :action and :id in params
        #   match ':controller/:action/:id'
        #
        # Two of these symbols are special, +:controller+ maps to the controller
        # and +:action+ to the controller's action. A pattern can also map
        # wildcard segments (globs) to params:
        #
        #   match 'songs/*category/:title' => 'songs#show'
        #
        #   # 'songs/rock/classic/stairway-to-heaven' sets
        #   #  params[:category] = 'rock/classic'
        #   #  params[:title] = 'stairway-to-heaven'
        #
        # When a pattern points to an internal route, the route's +:action+ and
        # +:controller+ should be set in options or hash shorthand. Examples:
        #
        #   match 'photos/:id' => 'photos#show'
        #   match 'photos/:id', :to => 'photos#show'
        #   match 'photos/:id', :controller => 'photos', :action => 'show'
        #
        # A pattern can also point to a +Rack+ endpoint i.e. anything that
        # responds to +call+:
        #
        #   match 'photos/:id' => lambda {|hash| [200, {}, "Coming soon" }
        #   match 'photos/:id' => PhotoRackApp
        #   # Yes, controller actions are just rack endpoints
        #   match 'photos/:id' => PhotosController.action(:show)
        #
        # === Options
        #
        # Any options not seen here are passed on as params with the url.
        #
        # [:controller]
        #   The route's controller.
        #
        # [:action]
        #   The route's action.
        #
        # [:path]
        #   The path prefix for the routes.
        #
        # [:module]
        #   The namespace for :controller.
        #
        #     match 'path' => 'c#a', :module => 'sekret', :controller => 'posts'
        #     #=> Sekret::PostsController
        #
        #   See <tt>Scoping#namespace</tt> for its scope equivalent.
        #
        # [:as]
        #   The name used to generate routing helpers.
        #
        # [:via]
        #   Allowed HTTP verb(s) for route.
        #
        #      match 'path' => 'c#a', :via => :get
        #      match 'path' => 'c#a', :via => [:get, :post]
        #
        # [:to]
        #   Points to a +Rack+ endpoint. Can be an object that responds to
        #   +call+ or a string representing a controller's action.
        #
        #      match 'path', :to => 'controller#action'
        #      match 'path', :to => lambda { [200, {}, "Success!"] }
        #      match 'path', :to => RackApp
        #
        # [:on]
        #   Shorthand for wrapping routes in a specific RESTful context. Valid
        #   values are +:member+, +:collection+, and +:new+. Only use within
        #   <tt>resource(s)</tt> block. For example:
        #
        #      resource :bar do
        #        match 'foo' => 'c#a', :on => :member, :via => [:get, :post]
        #      end
        #
        #   Is equivalent to:
        #
        #      resource :bar do
        #        member do
        #          match 'foo' => 'c#a', :via => [:get, :post]
        #        end
        #      end
        #
        # [:constraints]
        #   Constrains parameters with a hash of regular expressions or an
        #   object that responds to <tt>matches?</tt>
        #
        #     match 'path/:id', :constraints => { :id => /[A-Z]\d{5}/ }
        #
        #     class Blacklist
        #       def matches?(request) request.remote_ip == '1.2.3.4' end
        #     end
        #     match 'path' => 'c#a', :constraints => Blacklist.new
        #
        #   See <tt>Scoping#constraints</tt> for more examples with its scope
        #   equivalent.
        #
        # [:defaults]
        #   Sets defaults for parameters
        #
        #     # Sets params[:format] to 'jpg' by default
        #     match 'path' => 'c#a', :defaults => { :format => 'jpg' }
        #
        #   See <tt>Scoping#defaults</tt> for its scope equivalent.
        #
        # [:anchor]
        #   Boolean to anchor a <tt>match</tt> pattern. Default is true. When set to
        #   false, the pattern matches any request prefixed with the given path.
        #
        #     # Matches any request starting with 'path'
        #     match 'path' => 'c#a', :anchor => false
        def match(path, options=nil)
          mapping = Mapping.new(@set, @scope, path, options || {})
          app, conditions, requirements, defaults, as, anchor = mapping.to_route
          @set.add_route(app, conditions, requirements, defaults, as, anchor)
          self
        end

        # Mount a Rack-based application to be used within the application.
        #
        #   mount SomeRackApp, :at => "some_route"
        #
        # Alternatively:
        #
        #   mount(SomeRackApp => "some_route")
        #
        # For options, see +match+, as +mount+ uses it internally.
        #
        # All mounted applications come with routing helpers to access them.
        # These are named after the class specified, so for the above example
        # the helper is either +some_rack_app_path+ or +some_rack_app_url+.
        # To customize this helper's name, use the +:as+ option:
        #
        #   mount(SomeRackApp => "some_route", :as => "exciting")
        #
        # This will generate the +exciting_path+ and +exciting_url+ helpers
        # which can be used to navigate to this mounted app.
        def mount(app, options = nil)
          if options
            path = options.delete(:at)
          else
            options = app
            app, path = options.find { |k, v| k.respond_to?(:call) }
            options.delete(app) if app
          end

          raise "A rack application must be specified" unless path

          options[:as] ||= app_name(app)

          match(path, options.merge(:to => app, :anchor => false, :format => false))

          define_generate_prefix(app, options[:as])
          self
        end

        def default_url_options=(options)
          @set.default_url_options = options
        end
        alias_method :default_url_options, :default_url_options=

        def with_default_scope(scope, &block)
          scope(scope) do
            instance_exec(&block)
          end
        end

        private
          def app_name(app)
            return unless app.respond_to?(:routes)

            if app.respond_to?(:railtie_name)
              app.railtie_name
            else
              class_name = app.class.is_a?(Class) ? app.name : app.class.name
              ActiveSupport::Inflector.underscore(class_name).gsub("/", "_")
            end
          end

          def define_generate_prefix(app, name)
            return unless app.respond_to?(:routes) && app.routes.respond_to?(:define_mounted_helper)

            _route = @set.named_routes.routes[name.to_sym]
            _routes = @set
            app.routes.define_mounted_helper(name)
            app.routes.class_eval do
              define_method :_generate_prefix do |options|
                prefix_options = options.slice(*_route.segment_keys)
                # we must actually delete prefix segment keys to avoid passing them to next url_for
                _route.segment_keys.each { |k| options.delete(k) }
                _routes.url_helpers.send("#{name}_path", prefix_options)
              end
            end
          end
      end

      module HttpHelpers
        # Define a route that only recognizes HTTP GET.
        # For supported arguments, see <tt>Base#match</tt>.
        #
        # Example:
        #
        # get 'bacon', :to => 'food#bacon'
        def get(*args, &block)
          map_method(:get, *args, &block)
        end

        # Define a route that only recognizes HTTP POST.
        # For supported arguments, see <tt>Base#match</tt>.
        #
        # Example:
        #
        # post 'bacon', :to => 'food#bacon'
        def post(*args, &block)
          map_method(:post, *args, &block)
        end

        # Define a route that only recognizes HTTP PUT.
        # For supported arguments, see <tt>Base#match</tt>.
        #
        # Example:
        #
        # put 'bacon', :to => 'food#bacon'
        def put(*args, &block)
          map_method(:put, *args, &block)
        end

        # Define a route that only recognizes HTTP PUT.
        # For supported arguments, see <tt>Base#match</tt>.
        #
        # Example:
        #
        # delete 'broccoli', :to => 'food#broccoli'
        def delete(*args, &block)
          map_method(:delete, *args, &block)
        end

        private
          def map_method(method, *args, &block)
            options = args.extract_options!
            options[:via] = method
            args.push(options)
            match(*args, &block)
            self
          end
      end

      # You may wish to organize groups of controllers under a namespace.
      # Most commonly, you might group a number of administrative controllers
      # under an +admin+ namespace. You would place these controllers under
      # the <tt>app/controllers/admin</tt> directory, and you can group them
      # together in your router:
      #
      #   namespace "admin" do
      #     resources :posts, :comments
      #   end
      #
      # This will create a number of routes for each of the posts and comments
      # controller. For <tt>Admin::PostsController</tt>, Rails will create:
      #
      #   GET	    /admin/posts
      #   GET	    /admin/posts/new
      #   POST	  /admin/posts
      #   GET	    /admin/posts/1
      #   GET	    /admin/posts/1/edit
      #   PUT	    /admin/posts/1
      #   DELETE  /admin/posts/1
      #
      # If you want to route /posts (without the prefix /admin) to
      # <tt>Admin::PostsController</tt>, you could use
      #
      #   scope :module => "admin" do
      #     resources :posts
      #   end
      #
      # or, for a single case
      #
      #   resources :posts, :module => "admin"
      #
      # If you want to route /admin/posts to +PostsController+
      # (without the Admin:: module prefix), you could use
      #
      #   scope "/admin" do
      #     resources :posts
      #   end
      #
      # or, for a single case
      #
      #   resources :posts, :path => "/admin/posts"
      #
      # In each of these cases, the named routes remain the same as if you did
      # not use scope. In the last case, the following paths map to
      # +PostsController+:
      #
      #   GET	    /admin/posts
      #   GET	    /admin/posts/new
      #   POST	  /admin/posts
      #   GET	    /admin/posts/1
      #   GET	    /admin/posts/1/edit
      #   PUT	    /admin/posts/1
      #   DELETE  /admin/posts/1
      module Scoping
        # Scopes a set of routes to the given default options.
        #
        # Take the following route definition as an example:
        #
        #   scope :path => ":account_id", :as => "account" do
        #     resources :projects
        #   end
        #
        # This generates helpers such as +account_projects_path+, just like +resources+ does.
        # The difference here being that the routes generated are like /:account_id/projects,
        # rather than /accounts/:account_id/projects.
        #
        # === Options
        #
        # Takes same options as <tt>Base#match</tt> and <tt>Resources#resources</tt>.
        #
        # === Examples
        #
        #   # route /posts (without the prefix /admin) to <tt>Admin::PostsController</tt>
        #   scope :module => "admin" do
        #     resources :posts
        #   end
        #
        #   # prefix the posts resource's requests with '/admin'
        #   scope :path => "/admin" do
        #     resources :posts
        #   end
        #
        #   # prefix the routing helper name: +sekret_posts_path+ instead of +posts_path+
        #   scope :as => "sekret" do
        #     resources :posts
        #   end
        def scope(*args)
          options = args.extract_options!
          options = options.dup

          options[:path] = args.first if args.first.is_a?(String)
          recover = {}

          options[:constraints] ||= {}
          unless options[:constraints].is_a?(Hash)
            block, options[:constraints] = options[:constraints], {}
          end

          scope_options.each do |option|
            if value = options.delete(option)
              recover[option] = @scope[option]
              @scope[option]  = send("merge_#{option}_scope", @scope[option], value)
            end
          end

          recover[:block] = @scope[:blocks]
          @scope[:blocks] = merge_blocks_scope(@scope[:blocks], block)

          recover[:options] = @scope[:options]
          @scope[:options]  = merge_options_scope(@scope[:options], options)

          yield
          self
        ensure
          scope_options.each do |option|
            @scope[option] = recover[option] if recover.has_key?(option)
          end

          @scope[:options] = recover[:options]
          @scope[:blocks]  = recover[:block]
        end

        # Scopes routes to a specific controller
        #
        # Example:
        #   controller "food" do
        #     match "bacon", :action => "bacon"
        #   end
        def controller(controller, options={})
          options[:controller] = controller
          scope(options) { yield }
        end

        # Scopes routes to a specific namespace. For example:
        #
        #   namespace :admin do
        #     resources :posts
        #   end
        #
        # This generates the following routes:
        #
        #       admin_posts GET    /admin/posts(.:format)          {:action=>"index", :controller=>"admin/posts"}
        #       admin_posts POST   /admin/posts(.:format)          {:action=>"create", :controller=>"admin/posts"}
        #    new_admin_post GET    /admin/posts/new(.:format)      {:action=>"new", :controller=>"admin/posts"}
        #   edit_admin_post GET    /admin/posts/:id/edit(.:format) {:action=>"edit", :controller=>"admin/posts"}
        #        admin_post GET    /admin/posts/:id(.:format)      {:action=>"show", :controller=>"admin/posts"}
        #        admin_post PUT    /admin/posts/:id(.:format)      {:action=>"update", :controller=>"admin/posts"}
        #        admin_post DELETE /admin/posts/:id(.:format)      {:action=>"destroy", :controller=>"admin/posts"}
        #
        # === Options
        #
        # The +:path+, +:as+, +:module+, +:shallow_path+ and +:shallow_prefix+
        # options all default to the name of the namespace.
        #
        # For options, see <tt>Base#match</tt>. For +:shallow_path+ option, see
        # <tt>Resources#resources</tt>.
        #
        # === Examples
        #
        #   # accessible through /sekret/posts rather than /admin/posts
        #   namespace :admin, :path => "sekret" do
        #     resources :posts
        #   end
        #
        #   # maps to <tt>Sekret::PostsController</tt> rather than <tt>Admin::PostsController</tt>
        #   namespace :admin, :module => "sekret" do
        #     resources :posts
        #   end
        #
        #   # generates +sekret_posts_path+ rather than +admin_posts_path+
        #   namespace :admin, :as => "sekret" do
        #     resources :posts
        #   end
        def namespace(path, options = {})
          path = path.to_s
          options = { :path => path, :as => path, :module => path,
                      :shallow_path => path, :shallow_prefix => path }.merge!(options)
          scope(options) { yield }
        end

        # === Parameter Restriction
        # Allows you to constrain the nested routes based on a set of rules.
        # For instance, in order to change the routes to allow for a dot character in the +id+ parameter:
        #
        #   constraints(:id => /\d+\.\d+) do
        #     resources :posts
        #   end
        #
        # Now routes such as +/posts/1+ will no longer be valid, but +/posts/1.1+ will be.
        # The +id+ parameter must match the constraint passed in for this example.
        #
        # You may use this to also restrict other parameters:
        #
        #   resources :posts do
        #     constraints(:post_id => /\d+\.\d+) do
        #       resources :comments
        #     end
        #   end
        #
        # === Restricting based on IP
        #
        # Routes can also be constrained to an IP or a certain range of IP addresses:
        #
        #   constraints(:ip => /192.168.\d+.\d+/) do
        #     resources :posts
        #   end
        #
        # Any user connecting from the 192.168.* range will be able to see this resource,
        # where as any user connecting outside of this range will be told there is no such route.
        #
        # === Dynamic request matching
        #
        # Requests to routes can be constrained based on specific criteria:
        #
        #    constraints(lambda { |req| req.env["HTTP_USER_AGENT"] =~ /iPhone/ }) do
        #      resources :iphones
        #    end
        #
        # You are able to move this logic out into a class if it is too complex for routes.
        # This class must have a +matches?+ method defined on it which either returns +true+
        # if the user should be given access to that route, or +false+ if the user should not.
        #
        #    class Iphone
        #      def self.matches(request)
        #        request.env["HTTP_USER_AGENT"] =~ /iPhone/
        #      end
        #    end
        #
        # An expected place for this code would be +lib/constraints+.
        #
        # This class is then used like this:
        #
        #    constraints(Iphone) do
        #      resources :iphones
        #    end
        def constraints(constraints = {})
          scope(:constraints => constraints) { yield }
        end

        # Allows you to set default parameters for a route, such as this:
        #   defaults :id => 'home' do
        #     match 'scoped_pages/(:id)', :to => 'pages#show'
        #   end
        # Using this, the +:id+ parameter here will default to 'home'.
        def defaults(defaults = {})
          scope(:defaults => defaults) { yield }
        end

        private
          def scope_options #:nodoc:
            @scope_options ||= private_methods.grep(/^merge_(.+)_scope$/) { $1.to_sym }
          end

          def merge_path_scope(parent, child) #:nodoc:
            Mapper.normalize_path("#{parent}/#{child}")
          end

          def merge_shallow_path_scope(parent, child) #:nodoc:
            Mapper.normalize_path("#{parent}/#{child}")
          end

          def merge_as_scope(parent, child) #:nodoc:
            parent ? "#{parent}_#{child}" : child
          end

          def merge_shallow_prefix_scope(parent, child) #:nodoc:
            parent ? "#{parent}_#{child}" : child
          end

          def merge_module_scope(parent, child) #:nodoc:
            parent ? "#{parent}/#{child}" : child
          end

          def merge_controller_scope(parent, child) #:nodoc:
            child
          end

          def merge_path_names_scope(parent, child) #:nodoc:
            merge_options_scope(parent, child)
          end

          def merge_constraints_scope(parent, child) #:nodoc:
            merge_options_scope(parent, child)
          end

          def merge_defaults_scope(parent, child) #:nodoc:
            merge_options_scope(parent, child)
          end

          def merge_blocks_scope(parent, child) #:nodoc:
            merged = parent ? parent.dup : []
            merged << child if child
            merged
          end

          def merge_options_scope(parent, child) #:nodoc:
            (parent || {}).except(*override_keys(child)).merge(child)
          end

          def merge_shallow_scope(parent, child) #:nodoc:
            child ? true : false
          end

          def override_keys(child) #:nodoc:
            child.key?(:only) || child.key?(:except) ? [:only, :except] : []
          end
      end

      # Resource routing allows you to quickly declare all of the common routes
      # for a given resourceful controller. Instead of declaring separate routes
      # for your +index+, +show+, +new+, +edit+, +create+, +update+ and +destroy+
      # actions, a resourceful route declares them in a single line of code:
      #
      #  resources :photos
      #
      # Sometimes, you have a resource that clients always look up without
      # referencing an ID. A common example, /profile always shows the profile of
      # the currently logged in user. In this case, you can use a singular resource
      # to map /profile (rather than /profile/:id) to the show action.
      #
      #  resource :profile
      #
      # It's common to have resources that are logically children of other
      # resources:
      #
      #   resources :magazines do
      #     resources :ads
      #   end
      #
      # You may wish to organize groups of controllers under a namespace. Most
      # commonly, you might group a number of administrative controllers under
      # an +admin+ namespace. You would place these controllers under the
      # <tt>app/controllers/admin</tt> directory, and you can group them together
      # in your router:
      #
      #   namespace "admin" do
      #     resources :posts, :comments
      #   end
      #
      # By default the +:id+ parameter doesn't accept dots. If you need to
      # use dots as part of the +:id+ parameter add a constraint which
      # overrides this restriction, e.g:
      #
      #   resources :articles, :id => /[^\/]+/
      #
      # This allows any character other than a slash as part of your +:id+.
      #
      module Resources
        # CANONICAL_ACTIONS holds all actions that does not need a prefix or
        # a path appended since they fit properly in their scope level.
        VALID_ON_OPTIONS  = [:new, :collection, :member]
        RESOURCE_OPTIONS  = [:as, :controller, :path, :only, :except]
        CANONICAL_ACTIONS = %w(index create new show update destroy)

        class Resource #:nodoc:
          DEFAULT_ACTIONS = [:index, :create, :new, :show, :update, :destroy, :edit]

          attr_reader :controller, :path, :options

          def initialize(entities, options = {})
            @name       = entities.to_s
            @path       = (options.delete(:path) || @name).to_s
            @controller = (options.delete(:controller) || @name).to_s
            @as         = options.delete(:as)
            @options    = options
          end

          def default_actions
            self.class::DEFAULT_ACTIONS
          end

          def actions
            if only = @options[:only]
              Array(only).map(&:to_sym)
            elsif except = @options[:except]
              default_actions - Array(except).map(&:to_sym)
            else
              default_actions
            end
          end

          def name
            @as || @name
          end

          def plural
            @plural ||= name.to_s
          end

          def singular
            @singular ||= name.to_s.singularize
          end

          alias :member_name :singular

          # Checks for uncountable plurals, and appends "_index" if the plural
          # and singular form are the same.
          def collection_name
            singular == plural ? "#{plural}_index" : plural
          end

          def resource_scope
            { :controller => controller }
          end

          alias :collection_scope :path

          def member_scope
            "#{path}/:id"
          end

          def new_scope(new_path)
            "#{path}/#{new_path}"
          end

          def nested_scope
            "#{path}/:#{singular}_id"
          end

        end

        class SingletonResource < Resource #:nodoc:
          DEFAULT_ACTIONS = [:show, :create, :update, :destroy, :new, :edit]

          def initialize(entities, options)
            @as         = nil
            @name       = entities.to_s
            @path       = (options.delete(:path) || @name).to_s
            @controller = (options.delete(:controller) || plural).to_s
            @as         = options.delete(:as)
            @options    = options
          end

          def plural
            @plural ||= name.to_s.pluralize
          end

          def singular
            @singular ||= name.to_s
          end

          alias :member_name :singular
          alias :collection_name :singular

          alias :member_scope :path
          alias :nested_scope :path
        end

        def resources_path_names(options)
          @scope[:path_names].merge!(options)
        end

        # Sometimes, you have a resource that clients always look up without
        # referencing an ID. A common example, /profile always shows the
        # profile of the currently logged in user. In this case, you can use
        # a singular resource to map /profile (rather than /profile/:id) to
        # the show action:
        #
        #   resource :geocoder
        #
        # creates six different routes in your application, all mapping to
        # the +GeoCoders+ controller (note that the controller is named after
        # the plural):
        #
        #   GET     /geocoder/new
        #   POST    /geocoder
        #   GET     /geocoder
        #   GET     /geocoder/edit
        #   PUT     /geocoder
        #   DELETE  /geocoder
        #
        # === Options
        # Takes same options as +resources+.
        def resource(*resources, &block)
          options = resources.extract_options!

          if apply_common_behavior_for(:resource, resources, options, &block)
            return self
          end

          resource_scope(SingletonResource.new(resources.pop, options)) do
            yield if block_given?

            collection do
              post :create
            end if parent_resource.actions.include?(:create)

            new do
              get :new
            end if parent_resource.actions.include?(:new)

            member do
              get    :edit if parent_resource.actions.include?(:edit)
              get    :show if parent_resource.actions.include?(:show)
              put    :update if parent_resource.actions.include?(:update)
              delete :destroy if parent_resource.actions.include?(:destroy)
            end
          end

          self
        end

        # In Rails, a resourceful route provides a mapping between HTTP verbs
        # and URLs and controller actions. By convention, each action also maps
        # to particular CRUD operations in a database. A single entry in the
        # routing file, such as
        #
        #   resources :photos
        #
        # creates seven different routes in your application, all mapping to
        # the +Photos+ controller:
        #
        #   GET     /photos/new
        #   POST    /photos
        #   GET     /photos/:id
        #   GET     /photos/:id/edit
        #   PUT     /photos/:id
        #   DELETE  /photos/:id
        #
        # Resources can also be nested infinitely by using this block syntax:
        #
        #   resources :photos do
        #     resources :comments
        #   end
        #
        # This generates the following comments routes:
        #
        #   GET     /photos/:id/comments/new
        #   POST    /photos/:id/comments
        #   GET     /photos/:id/comments/:id
        #   GET     /photos/:id/comments/:id/edit
        #   PUT     /photos/:id/comments/:id
        #   DELETE  /photos/:id/comments/:id
        #
        # === Options
        # Takes same options as <tt>Base#match</tt> as well as:
        #
        # [:path_names]
        #   Allows you to change the paths of the seven default actions.
        #   Paths not specified are not changed.
        #
        #     resources :posts, :path_names => { :new => "brand_new" }
        #
        #   The above example will now change /posts/new to /posts/brand_new
        #
        # [:only]
        #   Only generate routes for the given actions.
        #
        #     resources :cows, :only => :show
        #     resources :cows, :only => [:show, :index]
        #
        # [:except]
        #   Generate all routes except for the given actions.
        #
        #     resources :cows, :except => :show
        #     resources :cows, :except => [:show, :index]
        #
        # [:shallow]
        #   Generates shallow routes for nested resource(s). When placed on a parent resource,
        #   generates shallow routes for all nested resources.
        #
        #     resources :posts, :shallow => true do
        #       resources :comments
        #     end
        #
        #   Is the same as:
        #
        #     resources :posts do
        #       resources :comments, :except => [:show, :edit, :update, :destroy]
        #     end
        #     resources :comments, :only => [:show, :edit, :update, :destroy]
        #
        #   This allows URLs for resources that otherwise would be deeply nested such
        #   as a comment on a blog post like <tt>/posts/a-long-permalink/comments/1234</tt>
        #   to be shortened to just <tt>/comments/1234</tt>.
        #
        # [:shallow_path]
        #   Prefixes nested shallow routes with the specified path.
        #
        #     scope :shallow_path => "sekret" do
        #       resources :posts do
        #         resources :comments, :shallow => true
        #       end
        #     end
        #
        #   The +comments+ resource here will have the following routes generated for it:
        #
        #     post_comments    GET    /sekret/posts/:post_id/comments(.:format)
        #     post_comments    POST   /sekret/posts/:post_id/comments(.:format)
        #     new_post_comment GET    /sekret/posts/:post_id/comments/new(.:format)
        #     edit_comment     GET    /sekret/comments/:id/edit(.:format)
        #     comment          GET    /sekret/comments/:id(.:format)
        #     comment          PUT    /sekret/comments/:id(.:format)
        #     comment          DELETE /sekret/comments/:id(.:format)
        #
        # === Examples
        #
        #   # routes call <tt>Admin::PostsController</tt>
        #   resources :posts, :module => "admin"
        #
        #   # resource actions are at /admin/posts.
        #   resources :posts, :path => "admin/posts"
        def resources(*resources, &block)
          options = resources.extract_options!

          if apply_common_behavior_for(:resources, resources, options, &block)
            return self
          end

          resource_scope(Resource.new(resources.pop, options)) do
            yield if block_given?

            collection do
              get  :index if parent_resource.actions.include?(:index)
              post :create if parent_resource.actions.include?(:create)
            end

            new do
              get :new
            end if parent_resource.actions.include?(:new)

            member do
              get    :edit if parent_resource.actions.include?(:edit)
              get    :show if parent_resource.actions.include?(:show)
              put    :update if parent_resource.actions.include?(:update)
              delete :destroy if parent_resource.actions.include?(:destroy)
            end
          end

          self
        end

        # To add a route to the collection:
        #
        #   resources :photos do
        #     collection do
        #       get 'search'
        #     end
        #   end
        #
        # This will enable Rails to recognize paths such as <tt>/photos/search</tt>
        # with GET, and route to the search action of +PhotosController+. It will also
        # create the <tt>search_photos_url</tt> and <tt>search_photos_path</tt>
        # route helpers.
        def collection
          unless resource_scope?
            raise ArgumentError, "can't use collection outside resource(s) scope"
          end

          with_scope_level(:collection) do
            scope(parent_resource.collection_scope) do
              yield
            end
          end
        end

        # To add a member route, add a member block into the resource block:
        #
        #   resources :photos do
        #     member do
        #       get 'preview'
        #     end
        #   end
        #
        # This will recognize <tt>/photos/1/preview</tt> with GET, and route to the
        # preview action of +PhotosController+. It will also create the
        # <tt>preview_photo_url</tt> and <tt>preview_photo_path</tt> helpers.
        def member
          unless resource_scope?
            raise ArgumentError, "can't use member outside resource(s) scope"
          end

          with_scope_level(:member) do
            scope(parent_resource.member_scope) do
              yield
            end
          end
        end

        def new
          unless resource_scope?
            raise ArgumentError, "can't use new outside resource(s) scope"
          end

          with_scope_level(:new) do
            scope(parent_resource.new_scope(action_path(:new))) do
              yield
            end
          end
        end

        def nested
          unless resource_scope?
            raise ArgumentError, "can't use nested outside resource(s) scope"
          end

          with_scope_level(:nested) do
            if shallow?
              with_exclusive_scope do
                if @scope[:shallow_path].blank?
                  scope(parent_resource.nested_scope, nested_options) { yield }
                else
                  scope(@scope[:shallow_path], :as => @scope[:shallow_prefix]) do
                    scope(parent_resource.nested_scope, nested_options) { yield }
                  end
                end
              end
            else
              scope(parent_resource.nested_scope, nested_options) { yield }
            end
          end
        end

        # See ActionDispatch::Routing::Mapper::Scoping#namespace
        def namespace(path, options = {})
          if resource_scope?
            nested { super }
          else
            super
          end
        end

        def shallow
          scope(:shallow => true, :shallow_path => @scope[:path]) do
            yield
          end
        end

        def shallow?
          parent_resource.instance_of?(Resource) && @scope[:shallow]
        end

        def match(*args)
          options = args.extract_options!.dup
          options[:anchor] = true unless options.key?(:anchor)

          if args.length > 1
            args.each { |path| match(path, options.dup) }
            return self
          end

          on = options.delete(:on)
          if VALID_ON_OPTIONS.include?(on)
            args.push(options)
            return send(on){ match(*args) }
          elsif on
            raise ArgumentError, "Unknown scope #{on.inspect} given to :on"
          end

          if @scope[:scope_level] == :resources
            args.push(options)
            return nested { match(*args) }
          elsif @scope[:scope_level] == :resource
            args.push(options)
            return member { match(*args) }
          end

          action = args.first
          path = path_for_action(action, options.delete(:path))

          if action.to_s =~ /^[\w\/]+$/
            options[:action] ||= action unless action.to_s.include?("/")
          else
            action = nil
          end

          if options.key?(:as) && !options[:as]
            options.delete(:as)
          else
            options[:as] = name_for_action(options[:as], action)
          end

          super(path, options)
        end

        def root(options={})
          if @scope[:scope_level] == :resources
            with_scope_level(:root) do
              scope(parent_resource.path) do
                super(options)
              end
            end
          else
            super(options)
          end
        end

        protected

          def parent_resource #:nodoc:
            @scope[:scope_level_resource]
          end

          def apply_common_behavior_for(method, resources, options, &block) #:nodoc:
            if resources.length > 1
              resources.each { |r| send(method, r, options, &block) }
              return true
            end

            if resource_scope?
              nested { send(method, resources.pop, options, &block) }
              return true
            end

            options.keys.each do |k|
              (options[:constraints] ||= {})[k] = options.delete(k) if options[k].is_a?(Regexp)
            end

            scope_options = options.slice!(*RESOURCE_OPTIONS)
            unless scope_options.empty?
              scope(scope_options) do
                send(method, resources.pop, options, &block)
              end
              return true
            end

            unless action_options?(options)
              options.merge!(scope_action_options) if scope_action_options?
            end

            false
          end

          def action_options?(options) #:nodoc:
            options[:only] || options[:except]
          end

          def scope_action_options? #:nodoc:
            @scope[:options].is_a?(Hash) && (@scope[:options][:only] || @scope[:options][:except])
          end

          def scope_action_options #:nodoc:
            @scope[:options].slice(:only, :except)
          end

          def resource_scope? #:nodoc:
            @scope[:scope_level].in?([:resource, :resources])
          end

          def resource_method_scope? #:nodoc:
            @scope[:scope_level].in?([:collection, :member, :new])
          end

          def with_exclusive_scope
            begin
              old_name_prefix, old_path = @scope[:as], @scope[:path]
              @scope[:as], @scope[:path] = nil, nil

              with_scope_level(:exclusive) do
                yield
              end
            ensure
              @scope[:as], @scope[:path] = old_name_prefix, old_path
            end
          end

          def with_scope_level(kind, resource = parent_resource)
            old, @scope[:scope_level] = @scope[:scope_level], kind
            old_resource, @scope[:scope_level_resource] = @scope[:scope_level_resource], resource
            yield
          ensure
            @scope[:scope_level] = old
            @scope[:scope_level_resource] = old_resource
          end

          def resource_scope(resource) #:nodoc:
            with_scope_level(resource.is_a?(SingletonResource) ? :resource : :resources, resource) do
              scope(parent_resource.resource_scope) do
                yield
              end
            end
          end

          def nested_options #:nodoc:
            {}.tap do |options|
              options[:as] = parent_resource.member_name
              options[:constraints] = { "#{parent_resource.singular}_id".to_sym => id_constraint } if id_constraint?
            end
          end

          def id_constraint? #:nodoc:
            @scope[:constraints] && @scope[:constraints][:id].is_a?(Regexp)
          end

          def id_constraint #:nodoc:
            @scope[:constraints][:id]
          end

          def canonical_action?(action, flag) #:nodoc:
            flag && resource_method_scope? && CANONICAL_ACTIONS.include?(action.to_s)
          end

          def shallow_scoping? #:nodoc:
            shallow? && @scope[:scope_level] == :member
          end

          def path_for_action(action, path) #:nodoc:
            prefix = shallow_scoping? ?
              "#{@scope[:shallow_path]}/#{parent_resource.path}/:id" : @scope[:path]

            path = if canonical_action?(action, path.blank?)
              prefix.to_s
            else
              "#{prefix}/#{action_path(action, path)}"
            end
          end

          def action_path(name, path = nil) #:nodoc:
            # Ruby 1.8 can't transform empty strings to symbols
            name = name.to_sym if name.is_a?(String) && !name.empty?
            path || @scope[:path_names][name] || name.to_s
          end

          def prefix_name_for_action(as, action) #:nodoc:
            if as
              as.to_s
            elsif !canonical_action?(action, @scope[:scope_level])
              action.to_s
            end
          end

          def name_for_action(as, action) #:nodoc:
            prefix = prefix_name_for_action(as, action)
            prefix = Mapper.normalize_name(prefix) if prefix
            name_prefix = @scope[:as]

            if parent_resource
              return nil if as.nil? && action.nil?

              collection_name = parent_resource.collection_name
              member_name = parent_resource.member_name
            end

            name = case @scope[:scope_level]
            when :nested
              [name_prefix, prefix]
            when :collection
              [prefix, name_prefix, collection_name]
            when :new
              [prefix, :new, name_prefix, member_name]
            when :member
              [prefix, shallow_scoping? ? @scope[:shallow_prefix] : name_prefix, member_name]
            when :root
              [name_prefix, collection_name, prefix]
            else
              [name_prefix, member_name, prefix]
            end

            candidate = name.select(&:present?).join("_").presence
            candidate unless as.nil? && @set.routes.find { |r| r.name == candidate }
          end
      end

      module Shorthand #:nodoc:
        def match(*args)
          if args.size == 1 && args.last.is_a?(Hash)
            options  = args.pop
            path, to = options.find { |name, value| name.is_a?(String) }
            options.merge!(:to => to).delete(path)
            super(path, options)
          else
            super
          end
        end
      end

      def initialize(set) #:nodoc:
        @set = set
        @scope = { :path_names => @set.resources_path_names }
      end

      include Base
      include HttpHelpers
      include Redirection
      include Scoping
      include Resources
      include Shorthand
    end
  end
end