router.rb

module Murray
  class Router
    class << self
      attr_reader :mapping
      
      def map &block
        @mapping = []
        instance_eval &block
        self
      end
      
      def method_missing meth, &block
        super unless meth.to_s[0,1] =~ /[A-Z]/
        @mapping << Scope.new(meth, &block)
      end
      
      def describe
        @mapping.each do |scope|
          puts "#{scope.name}:"
          scope.contents.each do |flake|
            puts "\t+ /#{flake.to_path}"
          end
          puts "\n"
        end
      end
    end
    
    class Scope
      undef :id
      
      attr_accessor :name, :contents
      
      def initialize name, &block
        @name = name
        @contents = []
        instance_eval &block
      end
      
      def method_missing meth, *args, &block
        super if meth.to_s[0,1] =~ /[A-Z]/
        case args.length
        when 0
          Flake.new self, meth
        when 1
          Parameter.new meth, args.first
        else
          super
        end
      end
      
      def f name
        Flake.new self, name
      end
      
      def << flake
        @contents << flake
      end
      
      def inspect
        "#<Scope " + @contents.join(', ') + ">"
      end
    end
    
    class Flake
      attr_reader :contents
      
      def initialize scope, first
        @scope = scope
        @contents = [first]
      end
      
      def / other
        if Flake === other
          @contents.concat other.contents
        else
          @contents << other
        end
        self
      end
      
      def +@
        @scope << self
      end
      
      def inspect
        "#<Flake #{@contents.join('/')}>"
      end
      alias_method :to_s, :inspect
      
      def to_path
        "#{@contents.map{|f| Symbol === f ? f.to_s : f.to_path}.join('/')}"
      end
    end
    
    class Parameter
      attr_reader :name, :type
      
      def initialize name, type
        @name, @type = name, type
      end
      
      def to_path
        ":#@name"
      end
      
      def inspect
        "(#@name #@type)"
      end
      alias_method :to_s, :inspect
    end
  end
end

if $0 == __FILE__
  Murray::Router.map do
    Establishments do
      + (list / (zip_code:integer)) # "http://example.org/establishments/2639"
      + (index / (id:integer) / bar / (foo:array))
      + (show / (short_name:string))
    end
    
    People do
      +(show / (guy:integer))
    end
  end
  
  Murray::Router.describe
end