# encoding: utf-8

require 'spec_helper'

describe Relation::Operation::Limit, '#optimize' do
  subject { object.optimize }

  let(:body)       { LazyEnumerable.new([ [ 1 ], [ 2 ], [ 3 ] ]) }
  let(:relation)   { Relation.new([ [ :id, Integer ] ], body)    }
  let(:directions) { [ relation[:id] ]                           }
  let(:order)      { relation.sort_by { directions }             }
  let(:operand)    { order                                       }
  let(:limit)      { 1                                           }
  let(:object)     { described_class.new(operand, limit)         }

  context 'when the limit is 0' do
    let(:limit) { 0 }

    it { should be_kind_of(Relation::Empty) }

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

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

    it_should_behave_like 'an optimize method'
  end

  context 'containing an order operation' do
    it { should equal(object) }

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

    it_should_behave_like 'an optimize method'
  end

  context 'containing an optimizable order operation' do
    let(:operand) { order.rename({}) }

    it { should be_kind_of(described_class) }

    its(:operand) { should equal(order) }

    its(:limit) { should == 1 }

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

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

    it_should_behave_like 'an optimize method'
  end

  context 'containing a more restrictive object operation' do
    let(:operand) { order.take(5) }
    let(:limit)   { 10            }

    it { should be_kind_of(described_class) }

    its(:operand) { should equal(order) }

    it 'uses the more restrictive object' do
      subject.limit.should == 5
    end

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

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

    it_should_behave_like 'an optimize method'
  end

  context 'containing a less restrictive object operation' do
    let(:operand) { order.take(10) }
    let(:limit)   { 5              }

    it { should be_kind_of(described_class) }

    its(:operand) { should equal(order) }

    it 'uses the more restrictive object' do
      subject.limit.should == 5
    end

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

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

    it_should_behave_like 'an optimize method'
  end

  context 'containing a similar object operation' do
    let(:operand) { order.take(10) }
    let(:limit)   { 10             }

    it { should equal(operand) }

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

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

    it_should_behave_like 'an optimize method'
  end

  context 'containing a materialized relation' do
    let(:relation) { Relation.new([ [ :id, Integer ] ], [ [ 1 ], [ 2 ], [ 3 ] ]) }

    it { should eql(Relation::Materialized.new([ [ :id, Integer ] ], [ [ 1 ] ])) }

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

    it_should_behave_like 'an optimize method'
  end
end