require 'spec_helper'

describe Immutable::Set do
  [:select, :find_all].each do |method|
    describe "##{method}" do
      let(:set) { S['A', 'B', 'C'] }

      context 'when everything matches' do
        it 'returns self' do
          set.send(method) { |item| true }.should equal(set)
        end
      end

      context 'when only some things match' do
        context 'with a block' do
          let(:result) { set.send(method) { |item| item == 'A' }}

          it 'preserves the original' do
            result
            set.should eql(S['A', 'B', 'C'])
          end

          it 'returns a set with the matching values' do
            result.should eql(S['A'])
          end
        end

        context 'with no block' do
          it 'returns an Enumerator' do
            set.send(method).class.should be(Enumerator)
            set.send(method).each { |item| item == 'A' }.should eql(S['A'])
          end
        end
      end

      context 'when nothing matches' do
        let(:result) { set.send(method) { |item| false }}

        it 'preserves the original' do
          result
          set.should eql(S['A', 'B', 'C'])
        end

        it 'returns the canonical empty set' do
          result.should equal(Immutable::EmptySet)
        end
      end

      context 'from a subclass' do
        it 'returns an instance of the same class' do
          subclass = Class.new(Immutable::Set)
          instance = subclass.new(['A', 'B', 'C'])
          instance.send(method) { true }.class.should be(subclass)
          instance.send(method) { false }.class.should be(subclass)
          instance.send(method) { rand(2) == 0 }.class.should be(subclass)
        end
      end

      it 'works on a large set, with many combinations of input' do
        items = (1..1000).to_a
        original = S.new(items)
        30.times do
          threshold = rand(1000)
          result    = original.send(method) { |item| item <= threshold }
          result.size.should == threshold
          result.each { |item| item.should <= threshold }
          (threshold+1).upto(1000) { |item| result.include?(item).should == false }
        end
        original.should eql(S.new(items))
      end
    end
  end
end