module Rdbc
  class Contract
    class << self
      include Translating
    
      def pre(method, &block)
        define_method(method_pre(method), &block)
      end

      def post(method, &block)
        define_method(method_post(method), &block)
      end

      def invariant(&block)
        define_method(:invariant, &block)
      end
    end

    include Translating
    
    class AssertionFailed < RuntimeError
    end

    def assert(condition)
      raise AssertionFailed unless condition
    end
    
    def send_method_pre(method, object, *args)
      method_pre = method_pre(method)
      if respond_to?(method_pre)
        send(method_pre, object, *args)
      end
    end
    
    def send_invariant(object)
      if respond_to?(:invariant)
        invariant(object)
      end
    end
    
    def send_method_post(method, object_pre, object, exception, result, *args)
      method_post = method_post(method)
      if respond_to?(method_post)
        send(method_post, object_pre, object, exception, result, *args)
      end
    end
  end
end