# encoding: utf-8

require 'spec_helper'

describe Algebra::Join, '#optimize' do
  subject { object.optimize }

  let(:left_body)      { LazyEnumerable.new([[1], [2]])                              }
  let(:right_body)     { LazyEnumerable.new([[2, 'Dan Kubb']])                       }
  let(:original_left)  { Relation.new([[:id, Integer]], left_body)                   }
  let(:original_right) { Relation.new([[:id, Integer], [:name, String]], right_body) }
  let(:left)           { original_left                                               }
  let(:right)          { original_right                                              }
  let(:object)         { described_class.new(left, right)                            }

  context 'left is an empty relation' do
    let(:left) { Relation::Empty.new(original_left.header) }

    it { should eql(Relation::Empty.new(right.header)) }

    it 'returns an equivalent relation to the unoptimized operation' do
      should == object
    end

    it 'does not execute right_body#each' do
      right_body.should_not_receive(:each)
      subject
    end

    it_should_behave_like 'an optimize method'
  end

  context 'right is an empty relation' do
    let(:right) { Relation::Empty.new(original_right.header) }

    it { should eql(Relation::Empty.new(right.header)) }

    it 'returns an equivalent relation to the unoptimized operation' do
      should == object
    end

    it 'does not execute left_body#each' do
      left_body.should_not_receive(:each)
      subject
    end

    it_should_behave_like 'an optimize method'
  end

  context 'left is an empty relation when optimized' do
    let(:left) { Algebra::Restriction.new(original_left, Function::Proposition::Contradiction.instance) }

    it { should eql(Relation::Empty.new(right.header)) }

    it 'returns an equivalent relation to the unoptimized operation' do
      should == object
    end

    it 'does not execute right_body#each' do
      right_body.should_not_receive(:each)
      subject
    end

    it_should_behave_like 'an optimize method'
  end

  context 'right is an empty relation when optimized' do
    let(:right) { Algebra::Restriction.new(original_right, Function::Proposition::Contradiction.instance) }

    it { should eql(Relation::Empty.new(right.header)) }

    it 'returns an equivalent relation to the unoptimized operation' do
      should == object
    end

    it 'does not execute left_body#each' do
      left_body.should_not_receive(:each)
      subject
    end

    it_should_behave_like 'an optimize method'
  end

  context 'left and right are not empty relations' do
    it { should be(object) }

    it 'does not execute left_body#each' do
      left_body.should_not_receive(:each)
      subject
    end

    it 'does not execute right_body#each' do
      right_body.should_not_receive(:each)
      subject
    end

    it_should_behave_like 'an optimize method'
  end

  context 'left and right are materialized relations' do
    let(:left)  { Relation.new([[:id, Integer]], [[1], [2]])                         }
    let(:right) { Relation.new([[:id, Integer], [:name, String]], [[2, 'Dan Kubb']]) }

    it { should eql(Relation::Materialized.new([[:id, Integer], [:name, String]], [[2, 'Dan Kubb']])) }

    it 'returns an equivalent relation to the unoptimized operation' do
      should == object
    end

    it_should_behave_like 'an optimize method'
  end
end