request_expressions.rb

# Stripped-down version of Consent's expression language

module Consent
  
  class Expression
    def initialize(controller, params = {})
      @controller, @params = controller.to_s, params.dup
    end
    
    def +(expression)
      Group.new + self + expression
    end
    
    def *(expression)
      @format = expression.instance_eval { @controller }
      @action = nil
      self
    end
    
    def /(expression)
      expression.nesting = @controller
      expression
    end
    
    def nesting=(name)
      @controller = "#{ name }/#{ @controller }"
    end
    
    def method_missing(name, params = {})
      @format = name.to_s if @action
      @action ||= name.to_s
      @params.update(params)
      self
    end
    
    class Group
      include Enumerable
      
      def initialize
        @exprs = []
      end
      
      def each(&block)
        @exprs.each(&block)
      end
      
      def +(expression)
        expression.is_a?(Enumerable) ?
            expression.each { |exp| @exprs << exp } :
            @exprs << expression
        self
      end
    end
    
    module Generator
      def method_missing(name, params = {})
        Expression.new(name, params)
      end
    end
  end
  
end