require 'spec_helper'

describe Helper do
  include Helper
  context '#is_n?' do
    it{ expect(0.is_0?).to be_true }
    it{ expect(_(0).is_0?).to be_true }
    it{ expect(inverse(0, :+).is_0?).to be_true }
    it{ expect(1.is_1?).to be_true }
    it{ expect(_(1).is_1?).to be_true }
    it{ expect(inverse(1, :*).is_1?).to be_true }
    it{ expect(-1.is_minus1?).to be_true }
    it{ expect(_(-1).is_minus1?).to be_true }
  end

  context '#is_multiple_of' do
    it{ expect(0.is_multiple_of(:x).to_s).to eq('0') }
    it{ expect(_(0).is_multiple_of(:y).to_s).to eq('0')}

    it{ expect(:x.is_multiple_of(:x).to_s).to eq('1') }
    it{ expect(:x.is_multiple_of(:y)).to be_false }

    it{ expect((:x * :y).is_multiple_of(:x)).to eq(:y) }
    it{ expect((:x * :y).is_multiple_of(:y)).to eq(:x) }
    it{ expect((:x * :y).is_multiple_of(:z)).to be_false }
  end

  context '#combinable?' do
    it{ expect(:x.combinable?(:x, :+)).to be_true }
    it{ expect(:x.combinable?(2 * :x, :+)).to be_true }
    it{ expect((2 * :x).combinable?(:x, :+)).to be_true }
    it{ expect((2 * :x).combinable?(2 * :x, :+)).to be_true }
    it{ expect(:x.combinable?(:y, :+)).to be_false }
    it{ expect(1.combinable?(2, :+)).to be_true }
    it{ expect(:x.combinable?(:x, :*)).to be_true }
    it{ expect(:x.combinable?(:y, :*)).to be_false }
    it{ expect(1.combinable?(2, :*)).to be_true }
    it{ expect(0.combinable?(:x, :^)).to be_true }
    it{ expect(1.combinable?(:y, :^)).to be_true }
  end

  context '#distributive?' do
    it{ expect(distributive?(:+, :*)).to be_true }
    it{ expect(distributive?(:+, :/)).to be_true }
    it{ expect(distributive?(:-, :*)).to be_true }
    it{ expect(distributive?(:-, :/)).to be_true }
    it{ expect(distributive?(:*, :^)).to be_true }
    it{ expect(distributive?(:/, :^)).to be_true }
    it{ expect(distributive?(:*, :+)).to be_false }
    it{ expect(distributive?(:^, :*)).to be_false }
  end

  let(:addition)      { (:x + :y) }
  let(:subtraction)   { (:x - :y) }
  let(:multiplication){ (:x * :y) }
  let(:division)      { (:x / :y) }
  let(:exponentiation){ (:x ^ :y) }

  it{ expect(addition.addition?).to be_true }
  it{ expect(multiplication.multiplication?).to be_true }
  it{ expect(exponentiation.exponentiation?).to be_true }

  it{ expect(inverse(:x, :+).inverse?(:+, :x)).to be_true }
  it{ expect(:x.inverse?(:+, inverse(:x, :+))).to be_true }
  it{ expect(inverse(:x, :*).inverse?(:*, :x)).to be_true }
  it{ expect(:x.inverse?(:*, inverse(:x, :*))).to be_true }
end