# encoding: utf-8

require 'spec_helper'

describe Algebra::Restriction::Methods, '#restrict' do
  let(:object)          { described_class.new(header, body)                       }
  let(:header)          { [[:id, Integer], [:name, String]]                       }
  let(:body)            { LazyEnumerable.new([[1, 'Dan Kubb'], [2, 'Alex Kubb']]) }
  let(:described_class) { Relation                                                }
  let(:tautology)       { Function::Proposition::Tautology.instance               }

  context 'with a predicate' do
    subject { object.restrict(predicate) }

    let(:predicate) { object[:id].eq(1) }

    it { should be_instance_of(Algebra::Restriction) }

    it 'sets the predicate' do
      expect(subject.predicate).to be(predicate)
    end

    it 'behaves the same as Enumerable#select' do
      should == object.select { |tuple| tuple[:id] == 1 }
    end
  end

  context 'with a block' do
    subject do
      object.restrict { |context| context.id.eq(1) }
    end

    it { should be_instance_of(Algebra::Restriction) }

    it 'sets the predicate' do
      expect(subject.predicate).to eql(object[:id].eq(1))
    end

    it 'behaves the same as Enumerable#select' do
      should == object.select { |tuple| tuple[:id] == 1 }
    end
  end

  context 'with a Hash' do
    subject { object.restrict(predicate) }

    let(:predicate) { { id: 1, name: 'Dan Kubb' } }

    it { should be_instance_of(Algebra::Restriction) }

    it 'sets the predicate' do
      expect(subject.predicate).to eql(tautology.and(object[:id].eq(1).and(object[:name].eq('Dan Kubb'))))
    end

    it 'behaves the same as Enumerable#select' do
      should == object.select { |tuple| tuple[:id] == 1 && tuple[:name] == 'Dan Kubb' }
    end
  end

  context 'with an Array' do
    subject { object.restrict(predicate) }

    let(:predicate) { [[:id, 1], [:name, 'Dan Kubb']] }

    it { should be_instance_of(Algebra::Restriction) }

    it 'sets the predicate' do
      expect(subject.predicate).to eql(tautology.and(object[:id].eq(1).and(object[:name].eq('Dan Kubb'))))
    end

    it 'behaves the same as Enumerable#select' do
      should == object.select { |tuple| tuple[:id] == 1 && tuple[:name] == 'Dan Kubb' }
    end
  end
end