func TestMultipleConstraintParse(t *testing.T) {
	qs, _ := graph.NewQuadStore("memstore", "", nil)
	w, _ := graph.NewQuadWriter("single", qs, nil)
	for _, tv := range []quad.Quad{
		{"i", "like", "food", ""},
		{"i", "like", "beer", ""},
		{"you", "like", "beer", ""},
	} {
		w.AddQuad(tv)
	}
	query := `(
		$a
		(:like :beer)
		(:like "food")
	)`
	it := BuildIteratorTreeForQuery(qs, query)
	if it.Type() != graph.And {
		t.Errorf("Odd iterator tree. Got: %#v", it.Describe())
	}
	if !graph.Next(it) {
		t.Error("Got no results")
	}
	out := it.Result()
	if out != qs.ValueOf("i") {
		t.Errorf("Got %d, expected %d", out, qs.ValueOf("i"))
	}
	if graph.Next(it) {
		t.Error("Too many results")
	}
}

// Next()ing a LinksTo operates as described above.
func (it *LinksTo) Next() bool {
	graph.NextLogIn(it)
	it.runstats.Next += 1
	if graph.Next(it.nextIt) {
		it.runstats.ContainsNext += 1
		it.result = it.nextIt.Result()
		return graph.NextLogOut(it, it.nextIt, true)
	}

	// If there's an error in the 'next' iterator, we save it and we're done.
	it.err = it.nextIt.Err()
	if it.err != nil {
		return false
	}

	// Subiterator is empty, get another one
	if !graph.Next(it.primaryIt) {
		// Possibly save error
		it.err = it.primaryIt.Err()

		// We're out of nodes in our subiterator, so we're done as well.
		return graph.NextLogOut(it, 0, false)
	}
	it.nextIt.Close()
	it.nextIt = it.qs.QuadIterator(it.dir, it.primaryIt.Result())

	// Recurse -- return the first in the next set.
	return it.Next()
}

func (s *Session) Execute(input string, c chan interface{}, _ int) {
	defer close(c)
	var mqlQuery interface{}
	err := json.Unmarshal([]byte(input), &mqlQuery)
	if err != nil {
		return
	}
	s.currentQuery = NewQuery(s)
	s.currentQuery.BuildIteratorTree(mqlQuery)
	if s.currentQuery.isError() {
		return
	}
	it, _ := s.currentQuery.it.Optimize()
	if glog.V(2) {
		b, err := json.MarshalIndent(it.Describe(), "", "  ")
		if err != nil {
			glog.Infof("failed to format description: %v", err)
		} else {
			glog.Infof("%s", b)
		}
	}
	for graph.Next(it) {
		tags := make(map[string]graph.Value)
		it.TagResults(tags)
		c <- tags
		for it.NextPath() == true {
			tags := make(map[string]graph.Value)
			it.TagResults(tags)
			c <- tags
		}
	}
}

func TestRemoveQuad(t *testing.T) {
	qs, w, _ := makeTestStore(simpleGraph)

	w.RemoveQuad(quad.Quad{
		Subject:   "E",
		Predicate: "follows",
		Object:    "F",
		Label:     "",
	})

	fixed := qs.FixedIterator()
	fixed.Add(qs.ValueOf("E"))

	fixed2 := qs.FixedIterator()
	fixed2.Add(qs.ValueOf("follows"))

	innerAnd := iterator.NewAnd(qs)
	innerAnd.AddSubIterator(iterator.NewLinksTo(qs, fixed, quad.Subject))
	innerAnd.AddSubIterator(iterator.NewLinksTo(qs, fixed2, quad.Predicate))

	hasa := iterator.NewHasA(qs, innerAnd, quad.Object)

	newIt, _ := hasa.Optimize()
	if graph.Next(newIt) {
		t.Error("E should not have any followers.")
	}
}

func (qs *QuadStore) optimizeLinksTo(it *iterator.LinksTo) (graph.Iterator, bool) {
	subs := it.SubIterators()
	if len(subs) != 1 {
		return it, false
	}
	primary := subs[0]
	if primary.Type() == graph.Fixed {
		size, _ := primary.Size()
		if size == 1 {
			if !graph.Next(primary) {
				panic("unexpected size during optimize")
			}
			val := primary.Result()
			newIt := qs.QuadIterator(it.Direction(), val)
			nt := newIt.Tagger()
			nt.CopyFrom(it)
			for _, tag := range primary.Tagger().Tags() {
				nt.AddFixed(tag, val)
			}
			it.Close()
			return newIt, true
		}
	}
	return it, false
}

// Next advances the Or graph.iterator. Because the Or is the union of its
// subiterators, it must produce from all subiterators -- unless it it
// shortcircuiting, in which case, it is the first one that returns anything.
func (it *Or) Next() bool {
	graph.NextLogIn(it)
	var first bool
	for {
		if it.currentIterator == -1 {
			it.currentIterator = 0
			first = true
		}
		curIt := it.internalIterators[it.currentIterator]

		if graph.Next(curIt) {
			it.result = curIt.Result()
			return graph.NextLogOut(it, it.result, true)
		}

		it.err = curIt.Err()
		if it.err != nil {
			return graph.NextLogOut(it, nil, false)
		}

		if it.isShortCircuiting && !first {
			break
		}
		it.currentIterator++
		if it.currentIterator == it.itCount {
			break
		}
	}

	return graph.NextLogOut(it, nil, false)
}

func iterated(it graph.Iterator) []int {
	var res []int
	for graph.Next(it) {
		res = append(res, it.Result().(int))
	}
	return res
}

func TestOptimize(t *testing.T) {
	tmpDir, _ := ioutil.TempDir(os.TempDir(), "cayley_test")
	t.Log(tmpDir)
	defer os.RemoveAll(tmpDir)
	err := createNewLevelDB(tmpDir, nil)
	if err != nil {
		t.Fatalf("Failed to create working directory")
	}
	qs, err := newQuadStore(tmpDir, nil)
	if qs == nil || err != nil {
		t.Error("Failed to create leveldb QuadStore.")
	}

	w, _ := writer.NewSingleReplication(qs, nil)
	w.AddQuadSet(makeQuadSet())

	// With an linksto-fixed pair
	fixed := qs.FixedIterator()
	fixed.Add(qs.ValueOf("F"))
	fixed.Tagger().Add("internal")
	lto := iterator.NewLinksTo(qs, fixed, quad.Object)

	oldIt := lto.Clone()
	newIt, ok := lto.Optimize()
	if !ok {
		t.Errorf("Failed to optimize iterator")
	}
	if newIt.Type() != Type() {
		t.Errorf("Optimized iterator type does not match original, got:%v expect:%v", newIt.Type(), Type())
	}

	newQuads := iteratedQuads(qs, newIt)
	oldQuads := iteratedQuads(qs, oldIt)
	if !reflect.DeepEqual(newQuads, oldQuads) {
		t.Errorf("Optimized iteration does not match original")
	}

	graph.Next(oldIt)
	oldResults := make(map[string]graph.Value)
	oldIt.TagResults(oldResults)
	graph.Next(newIt)
	newResults := make(map[string]graph.Value)
	newIt.TagResults(newResults)
	if !reflect.DeepEqual(newResults, oldResults) {
		t.Errorf("Discordant tag results, new:%v old:%v", newResults, oldResults)
	}
}

func iteratedNames(qs graph.QuadStore, it graph.Iterator) []string {
	var res []string
	for graph.Next(it) {
		res = append(res, qs.NameOf(it.Result()))
	}
	sort.Strings(res)
	return res
}

func iteratedQuads(qs graph.QuadStore, it graph.Iterator) []quad.Quad {
	var res ordered
	for graph.Next(it) {
		res = append(res, qs.Quad(it.Result()))
	}
	sort.Sort(res)
	return res
}

func runTopLevel(path *Path) []string {
	var out []string
	it := path.BuildIterator()
	it, _ = it.Optimize()
	for graph.Next(it) {
		v := path.qs.NameOf(it.Result())
		out = append(out, v)
	}
	return out
}

func (it *Comparison) Next() bool {
	for graph.Next(it.subIt) {
		val := it.subIt.Result()
		if it.doComparison(val) {
			it.result = val
			return true
		}
	}
	it.err = it.subIt.Err()
	return false
}

// Returns advances the And iterator. Because the And is the intersection of its
// subiterators, it must choose one subiterator to produce a candidate, and check
// this value against the subiterators. A productive choice of primary iterator
// is therefore very important.
func (it *And) Next() bool {
	graph.NextLogIn(it)
	it.runstats.Next += 1
	for graph.Next(it.primaryIt) {
		curr := it.primaryIt.Result()
		if it.subItsContain(curr, nil) {
			it.result = curr
			return graph.NextLogOut(it, curr, true)
		}
	}
	it.err = it.primaryIt.Err()
	return graph.NextLogOut(it, nil, false)
}

// Next advances the Not iterator. It returns whether there is another valid
// new value. It fetches the next value of the all iterator which is not
// contained by the primary iterator.
func (it *Not) Next() bool {
	graph.NextLogIn(it)
	it.runstats.Next += 1

	for graph.Next(it.allIt) {
		if curr := it.allIt.Result(); !it.primaryIt.Contains(curr) {
			it.result = curr
			it.runstats.ContainsNext += 1
			return graph.NextLogOut(it, curr, true)
		}
	}
	it.err = it.allIt.Err()
	return graph.NextLogOut(it, nil, false)
}

func iterateResults(qs graph.QuadStore, it graph.Iterator) []string {
	var res []string
	for graph.Next(it) {
		v := it.Result()
		if t, ok := v.(*Token); ok && t.Kind == nodeKind {
			res = append(res, qs.NameOf(it.Result()))
		} else {
			res = append(res, qs.Quad(it.Result()).String())
		}
	}
	sort.Strings(res)
	it.Reset()
	return res
}

// Next advances the subiterator, continuing until it returns a value which it
// has not previously seen.
func (it *Unique) Next() bool {
	graph.NextLogIn(it)
	it.runstats.Next += 1

	for graph.Next(it.subIt) {
		curr := it.subIt.Result()
		if ok := it.seen[curr]; !ok {
			it.result = curr
			it.seen[curr] = true
			return graph.NextLogOut(it, it.result, true)
		}
	}
	it.err = it.subIt.Err()
	return graph.NextLogOut(it, nil, false)
}

// NextContains() is shared code between Contains() and GetNextResult() -- calls next on the
// result iterator (a quad iterator based on the last checked value) and returns true if
// another match is made.
func (it *HasA) NextContains() bool {
	for graph.Next(it.resultIt) {
		it.runstats.ContainsNext += 1
		link := it.resultIt.Result()
		if glog.V(4) {
			glog.V(4).Infoln("Quad is", it.qs.Quad(link))
		}
		if it.primaryIt.Contains(link) {
			it.result = it.qs.QuadDirection(link, it.dir)
			return true
		}
	}
	it.err = it.resultIt.Err()
	return false
}

func runTag(path *Path, tag string) []string {
	var out []string
	it := path.BuildIterator()
	it, _ = it.Optimize()
	for graph.Next(it) {
		tags := make(map[string]graph.Value)
		it.TagResults(tags)
		out = append(out, path.qs.NameOf(tags[tag]))
		for it.NextPath() {
			tags := make(map[string]graph.Value)
			it.TagResults(tags)
			out = append(out, path.qs.NameOf(tags[tag]))
		}
	}
	return out
}

func (wk *worker) runIterator(it graph.Iterator) {
	if wk.wantShape() {
		iterator.OutputQueryShapeForIterator(it, wk.qs, wk.shape)
		return
	}
	it, _ = it.Optimize()
	if glog.V(2) {
		b, err := json.MarshalIndent(it.Describe(), "", "  ")
		if err != nil {
			glog.Infof("failed to format description: %v", err)
		} else {
			glog.Infof("%s", b)
		}
	}
	for {
		select {
		case <-wk.kill:
			return
		default:
		}
		if !graph.Next(it) {
			break
		}
		tags := make(map[string]graph.Value)
		it.TagResults(tags)
		if !wk.send(&Result{actualResults: tags}) {
			break
		}
		for it.NextPath() {
			select {
			case <-wk.kill:
				return
			default:
			}
			tags := make(map[string]graph.Value)
			it.TagResults(tags)
			if !wk.send(&Result{actualResults: tags}) {
				break
			}
		}
	}
	if glog.V(2) {
		bytes, _ := json.MarshalIndent(graph.DumpStats(it), "", "  ")
		glog.V(2).Infoln(string(bytes))
	}
	it.Close()
}

// Next advances the iterator. This is simpler than Contains. We have a
// subiterator we can get a value from, and we can take that resultant quad,
// pull our direction out of it, and return that.
func (it *HasA) Next() bool {
	graph.NextLogIn(it)
	it.runstats.Next += 1
	if it.resultIt != nil {
		it.resultIt.Close()
	}
	it.resultIt = &Null{}

	if !graph.Next(it.primaryIt) {
		it.err = it.primaryIt.Err()
		return graph.NextLogOut(it, 0, false)
	}
	tID := it.primaryIt.Result()
	val := it.qs.QuadDirection(tID, it.dir)
	it.result = val
	return graph.NextLogOut(it, val, true)
}