require "memoit/version"

module Memoit

  # Memoize the method with the given name.
  #
  # @example
  #   class Foo
  #     memoize def bar(value)
  #       expensive_calculation(value)
  #     end
  #   end
  def memoize(name)
    ivar_name = "@_memo_#{name}".to_sym
    mod = Module.new do
      define_method(name) do |*args, &block|
        return super(*args, &block) if block
        cache = instance_variable_get(ivar_name) || instance_variable_set(ivar_name, {})
        hash = args.hash
        if cache.has_key?(hash)
          cache[hash]
        else
          cache[hash] = super(*args)
        end
      end
    end
    prepend mod
  end
end

Module.send(:include, Memoit)