# encoding: utf-8

require 'spec_helper'

describe Algebra::Join, '#each' do
  subject { object.each { |tuple| yields << tuple } }

  let(:left)   { Relation.new([ [ :id, Integer ] ], [ [ 1 ], [ 2 ] ]) }
  let(:object) { described_class.new(left, right)                     }
  let(:yields) { []                                                   }

  context 'when the attributes are joined' do
    let(:right) { Relation.new([ [ :id, Integer ], [ :name, String ] ], [ [ 2, 'Dan Kubb' ] ]) }

    it_should_behave_like 'an #each method'

    it 'yields each tuple in the join' do
      expect { subject }.to change { yields.dup }.
        from([]).
        to([ [ 2, 'Dan Kubb' ] ])
    end
  end

  context 'when the attributes are disjoint' do
    let(:right) { Relation.new([ [ :name, String ] ], [ [ 'Dan Kubb' ] ]) }

    it_should_behave_like 'an #each method'

    it 'yields each tuple in the product' do
      expect { subject }.to change { yields.dup }.
        from([]).
        to([ [ 1, 'Dan Kubb' ], [ 2, 'Dan Kubb' ] ])
    end
  end

  context 'when the attributes are an intersection' do
    let(:right) { Relation.new([ [ :id, Integer ] ], [ [ 1 ] ]) }

    it_should_behave_like 'an #each method'

    it 'yields each tuple in the intersection' do
      expect { subject }.to change { yields.dup }.
        from([]).
        to([ [ 1 ] ])
    end
  end
end