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

      def memoize_apply_visibility(id)
        visibility = instance_eval do
          case
          when private_method_defined?(id)
            :private
          when protected_method_defined?(id)
            :protected
          end
        end
        yield
      ensure
        visibility and __send__(visibility, id)
      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
          memoize_apply_visibility method_id do
            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
        method_ids.size == 1 ? method_ids.first : method_ids
      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 |function_id|
          function_id = function_id.to_s.to_sym
          memoize_apply_visibility function_id do
            orig_function = instance_method(function_id)
            __send__(:define_method, function_id) do |*args|
              if mc.key?(function_id) and result = mc[function_id][args]
                result
              else
                (mc[function_id] ||= {})[args] = result = orig_function.bind(self).call(*args)
                opts[:freeze] and result.freeze
                $DEBUG and warn "#{self.class} cached function #{function_id}(#{args.inspect unless args.empty?}) = #{result.inspect}"
              end
              result
            end
          end
        end
        function_ids.size == 1 ? function_ids.first : function_ids
      end
    end
  end
end

require 'tins/alias'