require 'spec_helper'

shared_examples_for "a predicate" do

  let(:w){ [8, 9] }
  let(:x){ 12 }
  let(:y){ 13 }

  it 'can be negated easily' do
    (!subject).should be_a(Predicate)
  end

  it 'detects stupid AND' do
    (subject & Predicate.tautology).should be(subject)
  end

  it 'detects stupid OR' do
    (subject | Predicate.contradiction).should be(subject)
  end

  it 'has free variables' do
    (fv = subject.free_variables).should be_a(Array)
    (fv - [ :w, :x, :y ]).should be_empty
  end

  it 'always splits around and trivially when no free variables are touched' do
    top, down = subject.and_split([:z])
    top.should be_tautology
    down.should eq(subject)
  end

end

describe 'Predicate.tautology' do
  subject{ Predicate.tautology }

  it_should_behave_like "a predicate"
end

describe 'Predicate.contradiction' do
  subject{ Predicate.contradiction }

  it_should_behave_like "a predicate"
end

describe "Predicate.comp" do
  subject{ Predicate.comp(:lt, {:x => 2}) }

  it_should_behave_like "a predicate"
end

describe "Predicate.in" do
  subject{ Predicate.in(:x, [2, 3]) }

  it_should_behave_like "a predicate"

  it 'should lead to a contradiction if value list is empty' do
    expect(Predicate.in(:x, [])).to eql(Predicate.contradiction)
  end
end

describe "Predicate.among" do
  subject{ Predicate.among(:x, [2, 3]) }

  it_should_behave_like "a predicate"
end

describe "Predicate.intersect" do
  subject{ Predicate.intersect(:w, [2, 3]) }

  it_should_behave_like "a predicate"
end

describe "Predicate.eq" do
  subject{ Predicate.eq(:x, 2) }

  it_should_behave_like "a predicate"
end

describe "Predicate.neq" do
  subject{ Predicate.neq(:x, 2) }

  it_should_behave_like "a predicate"
end

describe "Predicate.gt" do
  subject{ Predicate.gt(:x, 2) }

  it_should_behave_like "a predicate"
end

describe "Predicate.gte" do
  subject{ Predicate.gte(:x, 2) }

  it_should_behave_like "a predicate"
end

describe "Predicate.lt" do
  subject{ Predicate.lt(:x, 2) }

  it_should_behave_like "a predicate"
end

describe "Predicate.lte" do
  subject{ Predicate.lte(:x, 2) }

  it_should_behave_like "a predicate"
end

describe "Predicate.between" do
  subject{ Predicate.between(:x, 2, 3) }

  it_should_behave_like "a predicate"
end

describe "Predicate.and" do
  subject{ Predicate.and(Predicate.eq(:x, 12), Predicate.eq(:y, 12)) }

  it_should_behave_like "a predicate"

  it 'detects contraditions' do
    p1 = Predicate.in(:a, [10,11])
    p2 = Predicate.eq(:a, 7)
    expect(p1 & p2).to eq(Predicate.contradiction)
  end
end

describe "Predicate.or" do
  subject{ Predicate.or(Predicate.eq(:x, 12), Predicate.eq(:y, 12)) }

  it_should_behave_like "a predicate"
end

describe "Predicate.not" do
  subject{ Predicate.not(Predicate.in(:x, [12])) }

  it_should_behave_like "a predicate"
end