if Daru.has_gsl?
  module Daru
    module Accessors
      module GSLStatistics
        def vector_standardized_compute(m,sd)
          Daru::Vector.new @data.collect { |x| (x.to_f - m).quo(sd) }, dtype: :gsl,
                                                                       index: @context.index, name: @context.name
        end

        def vector_centered_compute(m)
          Daru::Vector.new @data.collect { |x| (x.to_f - m) }, dtype: :gsl,
                                                               index: @context.index, name: @context.name
        end

        def sample_with_replacement(sample=1)
          r = GSL::Rng.alloc(GSL::Rng::MT19937,rand(10_000))
          Daru::Vector.new(r.sample(@data, sample).to_a, dtype: :gsl,
                                                         index: @context.index, name: @context.name)
        end

        def sample_without_replacement(sample=1)
          r = GSL::Rng.alloc(GSL::Rng::MT19937,rand(10_000))
          r.choose(@data, sample).to_a
        end

        def median
          GSL::Stats.median_from_sorted_data(@data.sort)
        end

        def variance_sample(m)
          @data.variance(m)
        end

        def standard_deviation_sample(m)
          @data.sd(m)
        end

        def variance_population(m)
          @data.variance_with_fixed_mean(m)
        end

        def standard_deviation_population m
          @data.sd_with_fixed_mean(m)
        end

        def skew
          @data.skew
        end

        def kurtosis
          @data.kurtosis
        end
      end

      class GSLWrapper
        include Enumerable
        extend Forwardable
        include Daru::Accessors::GSLStatistics

        def_delegators :@data, :[], :size, :to_a, :each

        attr_reader :data

        def compact
          ::GSL::Vector.alloc(@data.to_a - [Float::NAN])
        end

        %i[mean min max prod sum].each do |method|
          define_method(method) do
            compact.send(method.to_sym) rescue nil
          end
        end

        alias :product :prod

        def each(&block)
          @data.each(&block)
          self
        end

        def map!(&block)
          @data.map!(&block)
          self
        end

        def initialize data, context
          @data = ::GSL::Vector.alloc(data)
          @context = context
        end

        def []= index, element
          if index == size
            push element
          else
            @data[index] = element
          end
        end

        def delete_at index
          @data.delete_at index
        end

        def index key
          @data.to_a.index key
        end

        def push value
          @data = @data.concat value
          self
        end
        alias :<< :push
        alias :concat :push

        def dup
          GSLWrapper.new(@data.to_a, @context)
        end

        def == other
          @data == other.data
        end
      end
    end
  end
end