require 'tins/extract_last_argument_options'

module Tins
  module Memoize
    module CacheMethods
      # Return the cache object.
      def __memoize_cache__
        @__memoize_cache__ ||= {}
      end

      # Clear cached values for all methods/functions.
      def memoize_cache_clear
         __memoize_cache__.clear
        self
      end
    end

    class ::Module
      # Automatically memoize calls of the the methods +method_ids+. The
      # memoized results do NOT ONLY depend on the arguments, but ALSO on the
      # object the method is called on.
      def memoize_method(*method_ids)
        method_ids.extend(ExtractLastArgumentOptions)
        method_ids, opts = method_ids.extract_last_argument_options
        include CacheMethods
        method_ids.each do |method_id|
          method_id = method_id.to_s.to_sym
          orig_method = instance_method(method_id)
          __send__(:define_method, method_id) do |*args|
            mc = __memoize_cache__
            if mc.key?(method_id) and result = mc[method_id][args]
              result
            else
              (mc[method_id] ||= {})[args] = result = orig_method.bind(self).call(*args)
              $DEBUG and warn "#{self.class} cached method #{method_id}(#{args.inspect unless args.empty?}) = #{result.inspect} [#{__id__}]"
              opts[:freeze] and result.freeze
            end
            result
          end
        end
      end

      include CacheMethods

      # Automatically memoize calls of the functions +function_ids+. The
      # memoized result does ONLY depend on the arguments given to the
      # function.
      def memoize_function(*function_ids)
        function_ids.extend(ExtractLastArgumentOptions)
        function_ids, opts = function_ids.extract_last_argument_options
        mc = __memoize_cache__
        function_ids.each do |method_id|
          method_id = method_id.to_s.to_sym
          orig_method = instance_method(method_id)
          __send__(:define_method, method_id) do |*args|
            if mc.key?(method_id) and result = mc[method_id][args]
              result
            else
              (mc[method_id] ||= {})[args] = result = orig_method.bind(self).call(*args)
              opts[:freeze] and result.freeze
              $DEBUG and warn "#{self.class} cached function #{method_id}(#{args.inspect unless args.empty?}) = #{result.inspect}"
            end
            result
          end
        end
      end
    end
  end
end

require 'tins/alias'