require 'spec_helper'

describe Enumerable do

  describe "#difference" do
    it "to be 0" do
      expect([].difference).to eq(0)
    end

    it "to be nil" do
      expect([].difference(nil)).to eq(nil)
    end

    it "to be -4" do
      expect([1, 2, 3].difference).to eq(-4)
    end
  end

  describe "#divisible" do
    it "to be 0" do
      expect([].divisible).to eq(0)
    end

    it "to be nil" do
      expect([].divisible(nil)).to eq(nil)
    end

    it "to be 2" do
      expect([16, 4, 2].divisible).to eq(2)
    end
  end

  describe "#drop_last" do
    it "to be [2, 3]" do
      expect([1, 2, 3].drop_last(1)).to eq([1, 2])
    end

    it "to be []" do
      expect([].drop_last(3)).to eq([])
    end
  end

  describe "#drop_last_while" do
    it "to be [1, 2]" do
      expect([1, 2, 3].drop_last_while(&:odd?)).to eq([1, 2])
    end

    it "to be []" do
      expect([].take_last_while(&:odd?)).to eq([])
    end
  end

  describe "#exactly?" do
    it "to be true" do
      expect([1, false, nil].exactly?(1)).to eq(true)
      expect([false, nil].exactly?(0)).to eq(true)
      expect([1, 2, 3].exactly?(3)).to eq(true)
      expect([1, 2, 3, 4].exactly?(1) { |n| n > 3 }).to eq(true)
      expect([1, 2, 3, 4].exactly?(2, &:even?)).to eq(true)
    end

    it "to be false" do
      expect([].exactly?(1)).to eq(false)
      expect([1, false, nil].exactly?(3)).to eq(false)
      expect([1, 1, 3, 3].exactly?(2, &:even?)).to eq(false)
    end
  end

  describe "#exponential" do
    it "to be 0" do
      expect([].exponential).to eq(0)
    end

    it "to be nil" do
      expect([].exponential(nil)).to eq(nil)
    end

    it "to be 4096" do
      expect([2, 3, 4].exponential).to eq(4096)
    end
  end

  describe "#frequencies" do
    it "to be {}" do
      expect([].frequencies).to eq({})
    end

    it "to be { 1 => 2, :symbol => 2, 'string' => 1, 3 => 1 }" do
      expect([1, :symbol, 'string', 3, :symbol, 1].frequencies).to eq({ 1 => 2, :symbol => 2, 'string' => 1, 3 => 1 })
    end
  end

  describe "#max" do
    it "to be 0" do
      expect([].max).to eq(0)
    end

    it "to be nil" do
      expect([].max(nil)).to eq(nil)
    end

    it "to be 3" do
      expect([2, 3, 1].max).to eq(3)
    end
  end

  describe "#min" do
    it "to be 0" do
      expect([].min).to eq(0)
    end

    it "to be nil" do
      expect([].min(nil)).to eq(nil)
    end

    it "to be 3" do
      expect([2, 3, 1].min).to eq(1)
    end
  end

  describe "#mean" do
    it "to be 0" do
      expect([].mean).to eq(0)
    end

    it "to be nil" do
      expect([].mean(nil)).to eq(nil)
    end

    it "to be 2" do
      expect([1, 2, 3].mean).to eq(2)
    end

    it "to be 2.5" do
      expect([1, 2, 3, 4].mean).to eq(2.5)
    end
  end

  describe '#median' do
    it 'to be 0' do
      expect([].median).to eq(0)
    end

    it 'to be nil' do
      expect([].median(nil)).to eq(nil)
    end

    it 'to be 2' do
      expect([1,2,6].median).to eq(2)
    end

    it 'to be 2.5' do
      expect([1,2,3,6].median).to eq(2.5)
    end
  end

  describe '#mode' do
    it 'to be 0' do
      expect([].mode).to eq(0)
    end

    it 'to be nil' do
      expect([].mode(nil)).to eq(nil)
      expect([1,2,3].mode).to eq(nil)
    end

    it 'to be 1' do
      expect([1,1,2,46].mode).to eq(1)
    end

    it 'to be 3.5' do
      expect([3.5].mode).to eq(3.5)
    end
  end

  describe "#multiple" do
    it "to be 0" do
      expect([].multiple).to eq(0)
    end

    it "to be nil" do
      expect([].multiple(nil)).to eq(nil)
    end

    it "to be 6" do
      expect([1, 2, 3].multiple).to eq(6)
    end
  end

  describe '#range' do
    it 'to be 0' do
      expect([].range).to eq(0)
    end

    it 'to be nil' do
      expect([].range(nil)).to eq(nil)
    end

    it 'to be 5' do
      expect([1,2,6].range).to eq(5)
    end
  end

  describe "#several?" do
    it "to be true" do
      expect([1, 2, 3].several?).to eq(true)
      expect([1, 2, 3, 4].several?(&:even?)).to eq(true)
    end

    it "to be false" do
      expect([].several?).to eq(false)
      expect([1, false, nil].several?).to eq(false)
      expect([1, 1, 3, 3].several?(&:even?)).to eq(false)
    end
  end

  describe '#standard_deviation' do
    it 'to be the square root of the #variance' do
      expect([1,2,6].standard_deviation).to eq(2.6457513110645907)
    end

    it 'to be nil for single element arrays' do
      expect([1].standard_deviation).to eq(0)
    end

    it 'to be nil if empty' do
      expect([].standard_deviation).to eq(0)
    end
  end

  describe "#sum" do
    it "to be 0" do
      expect([].sum).to eq(0)
    end

    it "to be nil" do
      expect([].sum(nil)).to eq(nil)
    end

    it "to be 6" do
      expect([1, 2, 3].sum).to eq(6)
    end
  end

  describe "#take_last" do
    it "to be [2, 3]" do
      expect([1, 2, 3].take_last(2)).to eq([2, 3])
    end

    it "to be []" do
      expect([].take_last(3)).to eq([])
    end
  end

  describe "#take_last_while" do
    it "to be [3, 5]" do
      expect([1, 2, 3, 5].take_last_while(&:odd?)).to eq([3, 5])
    end

    it "to be []" do
      expect([].take_last_while(&:odd?)).to eq([])
    end
  end

  describe '#variance' do
    it 'to be the mean squared deviation of the sample (n - 1 denominator)' do
      expect([1,2,6].variance).to eq(7)
    end

    it 'to be nil if empty' do
      expect([].variance).to eq(0)
    end
  end

end