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

	err := w.RemoveQuad(quad.Make(
		"E",
		"follows",
		"F",
		"",
	))

	if err != nil {
		t.Error("Couldn't remove quad", err)
	}

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

	fixed2 := qs.FixedIterator()
	fixed2.Add(qs.ValueOf(quad.Raw("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 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()
	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 hasMorphism(via interface{}, nodes ...string) morphism {
	return morphism{
		Name:     "has",
		Reversal: func() morphism { return hasMorphism(via, nodes...) },
		Apply: func(qs graph.QuadStore, it graph.Iterator) graph.Iterator {
			var sub graph.Iterator
			if len(nodes) == 0 {
				sub = qs.NodesAllIterator()
			} else {
				fixed := qs.FixedIterator()
				for _, n := range nodes {
					fixed.Add(qs.ValueOf(n))
				}
				sub = fixed
			}
			var viaPath *Path
			if via != nil {
				viaPath = buildViaPath(qs, via)
			} else {
				viaPath = buildViaPath(qs)
			}
			subAnd := iterator.NewAnd(qs)
			subAnd.AddSubIterator(iterator.NewLinksTo(qs, sub, quad.Object))
			subAnd.AddSubIterator(iterator.NewLinksTo(qs, viaPath.BuildIterator(), quad.Predicate))
			hasa := iterator.NewHasA(qs, subAnd, quad.Subject)
			and := iterator.NewAnd(qs)
			and.AddSubIterator(it)
			and.AddSubIterator(hasa)
			return and
		},
	}
}

func buildSave(
	qs graph.QuadStore, via interface{},
	tag string, from graph.Iterator, reverse bool, optional bool,
) graph.Iterator {

	allNodes := qs.NodesAllIterator()
	allNodes.Tagger().Add(tag)

	start, goal := quad.Subject, quad.Object
	if reverse {
		start, goal = goal, start
	}
	viaIter := buildViaPath(qs, via).
		BuildIterator()

	dest := iterator.NewLinksTo(qs, allNodes, goal)
	trail := iterator.NewLinksTo(qs, viaIter, quad.Predicate)

	route := join(qs, trail, dest)
	save := graph.Iterator(iterator.NewHasA(qs, route, start))

	if optional {
		save = iterator.NewOptional(save)
	}
	return join(qs, from, save)
}

func TestIteratorsAndNextResultOrderA(t *testing.T) {
	glog.Info("\n-----------\n")
	inst, opts, err := createInstance()
	defer inst.Close()

	if err != nil {
		t.Fatalf("failed to create instance: %v", err)
	}
	qs, _, _ := makeTestStore(simpleGraph, opts)
	if qs.Size() != 11 {
		t.Fatal("Incorrect number of quads")
	}

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

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

	all := qs.NodesAllIterator()

	innerAnd := iterator.NewAnd(qs)
	innerAnd.AddSubIterator(iterator.NewLinksTo(qs, fixed2, quad.Predicate))
	innerAnd.AddSubIterator(iterator.NewLinksTo(qs, all, quad.Object))

	hasa := iterator.NewHasA(qs, innerAnd, quad.Subject)
	outerAnd := iterator.NewAnd(qs)
	outerAnd.AddSubIterator(fixed)
	outerAnd.AddSubIterator(hasa)

	if !outerAnd.Next() {
		t.Error("Expected one matching subtree")
	}
	val := outerAnd.Result()
	if qs.NameOf(val) != "C" {
		t.Errorf("Matching subtree should be %s, got %s", "barak", qs.NameOf(val))
	}

	var (
		got    []string
		expect = []string{"B", "D"}
	)
	for {
		got = append(got, qs.NameOf(all.Result()))
		if !outerAnd.NextPath() {
			break
		}
	}
	sort.Strings(got)

	if !reflect.DeepEqual(got, expect) {
		t.Errorf("Unexpected result, got:%q expect:%q", got, expect)
	}

	if outerAnd.Next() {
		t.Error("More than one possible top level output?")
	}
}

func buildInOutPredicateIterator(obj *otto.Object, qs graph.QuadStore, base graph.Iterator, isReverse bool) graph.Iterator {
	dir := quad.Subject
	if isReverse {
		dir = quad.Object
	}
	lto := iterator.NewLinksTo(qs, base, dir)
	hasa := iterator.NewHasA(qs, lto, quad.Predicate)
	return iterator.NewUnique(hasa)
}

func inOutIterator(viaPath *Path, it graph.Iterator, reverse bool) graph.Iterator {
	in, out := quad.Subject, quad.Object
	if reverse {
		in, out = out, in
	}
	lto := iterator.NewLinksTo(viaPath.qs, it, in)
	and := iterator.NewAnd(viaPath.qs)
	and.AddSubIterator(iterator.NewLinksTo(viaPath.qs, viaPath.BuildIterator(), quad.Predicate))
	and.AddSubIterator(lto)
	return iterator.NewHasA(viaPath.qs, and, out)
}

// hasMorphism is the set of nodes that is reachable via either a *Path, a
// single node.(string) or a list of nodes.([]string).
func hasMorphism(via interface{}, nodes ...string) morphism {
	return morphism{
		Name:     "has",
		Reversal: func(ctx *context) (morphism, *context) { return hasMorphism(via, nodes...), ctx },
		Apply: func(qs graph.QuadStore, in graph.Iterator, ctx *context) (graph.Iterator, *context) {
			viaIter := buildViaPath(qs, via).
				BuildIterator()
			ends := func() graph.Iterator {
				if len(nodes) == 0 {
					return qs.NodesAllIterator()
				}

				fixed := qs.FixedIterator()
				for _, n := range nodes {
					fixed.Add(qs.ValueOf(n))
				}
				return fixed
			}()

			trail := iterator.NewLinksTo(qs, viaIter, quad.Predicate)
			dest := iterator.NewLinksTo(qs, ends, quad.Object)

			// If we were given nodes, intersecting with them first will
			// be extremely cheap-- otherwise, it will be the most expensive
			// (requiring iteration over all nodes). We have enough info to
			// make this optimization now since intersections are commutative
			if len(nodes) == 0 { // Where dest involves an All iterator.
				route := join(qs, trail, dest)
				has := iterator.NewHasA(qs, route, quad.Subject)
				return join(qs, in, has), ctx
			}

			// This looks backwards. That's OK-- see the note above.
			route := join(qs, dest, trail)
			has := iterator.NewHasA(qs, route, quad.Subject)
			return join(qs, has, in), ctx
		},
	}
}

func buildHas(qs graph.QuadStore, via interface{}, in graph.Iterator, reverse bool, nodes []quad.Value) graph.Iterator {
	viaIter := buildViaPath(qs, via).
		BuildIterator()
	ends := func() graph.Iterator {
		if len(nodes) == 0 {
			return qs.NodesAllIterator()
		}

		fixed := qs.FixedIterator()
		for _, n := range nodes {
			fixed.Add(qs.ValueOf(n))
		}
		return fixed
	}()

	start, goal := quad.Subject, quad.Object
	if reverse {
		start, goal = goal, start
	}

	trail := iterator.NewLinksTo(qs, viaIter, quad.Predicate)
	dest := iterator.NewLinksTo(qs, ends, goal)

	// If we were given nodes, intersecting with them first will
	// be extremely cheap-- otherwise, it will be the most expensive
	// (requiring iteration over all nodes). We have enough info to
	// make this optimization now since intersections are commutative
	if len(nodes) == 0 { // Where dest involves an All iterator.
		route := join(qs, trail, dest)
		has := iterator.NewHasA(qs, route, start)
		return join(qs, in, has)
	}

	// This looks backwards. That's OK-- see the note above.
	route := join(qs, dest, trail)
	has := iterator.NewHasA(qs, route, start)
	return join(qs, has, in)
}

func TestIteratorsAndNextResultOrderA(t *testing.T) {
	ts, _ := makeTestStore(simpleGraph)

	fixed := ts.FixedIterator()
	fixed.Add(ts.ValueOf("C"))

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

	all := ts.NodesAllIterator()

	innerAnd := iterator.NewAnd()
	innerAnd.AddSubIterator(iterator.NewLinksTo(ts, fixed2, graph.Predicate))
	innerAnd.AddSubIterator(iterator.NewLinksTo(ts, all, graph.Object))

	hasa := iterator.NewHasA(ts, innerAnd, graph.Subject)
	outerAnd := iterator.NewAnd()
	outerAnd.AddSubIterator(fixed)
	outerAnd.AddSubIterator(hasa)

	val, ok := outerAnd.Next()
	if !ok {
		t.Error("Expected one matching subtree")
	}
	if ts.NameOf(val) != "C" {
		t.Errorf("Matching subtree should be %s, got %s", "barak", ts.NameOf(val))
	}

	var (
		got    []string
		expect = []string{"B", "D"}
	)
	for {
		got = append(got, ts.NameOf(all.Result()))
		if !outerAnd.NextResult() {
			break
		}
	}
	sort.Strings(got)

	if !reflect.DeepEqual(got, expect) {
		t.Errorf("Unexpected result, got:%q expect:%q", got, expect)
	}

	val, ok = outerAnd.Next()
	if ok {
		t.Error("More than one possible top level output?")
	}
}

func inOutIterator(viaPath *Path, from graph.Iterator, inIterator bool) graph.Iterator {
	start, goal := quad.Subject, quad.Object
	if inIterator {
		start, goal = goal, start
	}

	viaIter := viaPath.BuildIterator()

	source := iterator.NewLinksTo(viaPath.qs, from, start)
	trail := iterator.NewLinksTo(viaPath.qs, viaIter, quad.Predicate)

	route := join(viaPath.qs, source, trail)

	return iterator.NewHasA(viaPath.qs, route, goal)
}

func TestIteratorsAndNextResultOrderA(t testing.TB, gen DatabaseFunc) {
	qs, opts, closer := gen(t)
	defer closer()

	MakeWriter(t, qs, opts, MakeQuadSet()...)

	require.Equal(t, int64(11), qs.Size(), "Incorrect number of quads")

	fixed := qs.FixedIterator()
	fixed.Add(qs.ValueOf(quad.Raw("C")))

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

	all := qs.NodesAllIterator()

	innerAnd := iterator.NewAnd(qs)
	innerAnd.AddSubIterator(iterator.NewLinksTo(qs, fixed2, quad.Predicate))
	innerAnd.AddSubIterator(iterator.NewLinksTo(qs, all, quad.Object))

	hasa := iterator.NewHasA(qs, innerAnd, quad.Subject)
	outerAnd := iterator.NewAnd(qs)
	outerAnd.AddSubIterator(fixed)
	outerAnd.AddSubIterator(hasa)

	require.True(t, outerAnd.Next(), "Expected one matching subtree")

	val := outerAnd.Result()
	require.Equal(t, quad.Raw("C"), qs.NameOf(val))

	var (
		got    []string
		expect = []string{"B", "D"}
	)
	for {
		got = append(got, qs.NameOf(all.Result()).String())
		if !outerAnd.NextPath() {
			break
		}
	}
	sort.Strings(got)

	require.Equal(t, expect, got)

	require.True(t, !outerAnd.Next(), "More than one possible top level output?")
}

func inOutIterator(viaPath *Path, from graph.Iterator, inIterator bool, tags []string) graph.Iterator {
	start, goal := quad.Subject, quad.Object
	if inIterator {
		start, goal = goal, start
	}

	viaIter := viaPath.BuildIterator()
	for _, tag := range tags {
		viaIter.Tagger().Add(tag)
	}

	source := iterator.NewLinksTo(viaPath.qs, from, start)
	trail := iterator.NewLinksTo(viaPath.qs, viaIter, quad.Predicate)

	route := join(viaPath.qs, source, trail)

	return iterator.NewHasA(viaPath.qs, route, goal)
}

func TestIteratorsAndNextResultOrderA(t *testing.T) {
	ts := MakeTestingMemstore()
	fixed := ts.FixedIterator()
	fixed.AddValue(ts.GetIdFor("C"))
	all := ts.GetNodesAllIterator()
	lto := iterator.NewLinksTo(ts, all, graph.Object)
	innerAnd := iterator.NewAnd()

	fixed2 := ts.FixedIterator()
	fixed2.AddValue(ts.GetIdFor("follows"))
	lto2 := iterator.NewLinksTo(ts, fixed2, graph.Predicate)
	innerAnd.AddSubIterator(lto2)
	innerAnd.AddSubIterator(lto)
	hasa := iterator.NewHasA(ts, innerAnd, graph.Subject)
	outerAnd := iterator.NewAnd()
	outerAnd.AddSubIterator(fixed)
	outerAnd.AddSubIterator(hasa)
	val, ok := outerAnd.Next()
	if !ok {
		t.Error("Expected one matching subtree")
	}
	if ts.GetNameFor(val) != "C" {
		t.Errorf("Matching subtree should be %s, got %s", "barak", ts.GetNameFor(val))
	}
	expected := make([]string, 2)
	expected[0] = "B"
	expected[1] = "D"
	actualOut := make([]string, 2)
	actualOut[0] = ts.GetNameFor(all.LastResult())
	nresultOk := outerAnd.NextResult()
	if !nresultOk {
		t.Error("Expected two results got one")
	}
	actualOut[1] = ts.GetNameFor(all.LastResult())
	nresultOk = outerAnd.NextResult()
	if nresultOk {
		t.Error("Expected two results got three")
	}
	CompareStringSlices(t, expected, actualOut)
	val, ok = outerAnd.Next()
	if ok {
		t.Error("More than one possible top level output?")
	}
}

func TestRemoveTriple(t *testing.T) {
	ts := MakeTestingMemstore()
	ts.RemoveTriple(&graph.Triple{"E", "follows", "F", ""})
	fixed := ts.FixedIterator()
	fixed.AddValue(ts.GetIdFor("E"))
	lto := iterator.NewLinksTo(ts, fixed, graph.Subject)
	fixed2 := ts.FixedIterator()
	fixed2.AddValue(ts.GetIdFor("follows"))
	lto2 := iterator.NewLinksTo(ts, fixed2, graph.Predicate)
	innerAnd := iterator.NewAnd()
	innerAnd.AddSubIterator(lto2)
	innerAnd.AddSubIterator(lto)
	hasa := iterator.NewHasA(ts, innerAnd, graph.Object)
	newIt, _ := hasa.Optimize()
	_, ok := newIt.Next()
	if ok {
		t.Error("E should not have any followers.")
	}
}

// predicatesMorphism iterates to the uniqified set of predicates from
// the given set of nodes in the path.
func predicatesMorphism(isIn bool) morphism {
	m := morphism{
		Name: "out_predicates",
		Reversal: func(ctx *context) (morphism, *context) {
			panic("not implemented: need a function from predicates to their associated edges")
		},
		Apply: func(qs graph.QuadStore, in graph.Iterator, ctx *context) (graph.Iterator, *context) {
			dir := quad.Subject
			if isIn {
				dir = quad.Object
			}
			lto := iterator.NewLinksTo(qs, in, dir)
			hasa := iterator.NewHasA(qs, lto, quad.Predicate)
			return iterator.NewUnique(hasa), ctx
		},
	}
	if isIn {
		m.Name = "in_predicates"
	}
	return m
}

func buildInOutIterator(obj *otto.Object, ts graph.TripleStore, base graph.Iterator, isReverse bool) graph.Iterator {
	argList, _ := obj.Get("_gremlin_values")
	if argList.Class() != "GoArray" {
		glog.Errorln("How is arglist not an array? Return nothing.", argList.Class())
		return iterator.NewNull()
	}
	argArray := argList.Object()
	lengthVal, _ := argArray.Get("length")
	length, _ := lengthVal.ToInteger()
	var predicateNodeIterator graph.Iterator
	if length == 0 {
		predicateNodeIterator = ts.NodesAllIterator()
	} else {
		zero, _ := argArray.Get("0")
		predicateNodeIterator = buildIteratorFromValue(zero, ts)
	}
	if length >= 2 {
		var tags []string
		one, _ := argArray.Get("1")
		if one.IsString() {
			s, _ := one.ToString()
			tags = append(tags, s)
		} else if one.Class() == "Array" {
			tags = makeListOfStringsFromArrayValue(one.Object())
		}
		for _, tag := range tags {
			predicateNodeIterator.Tagger().Add(tag)
		}
	}

	in, out := quad.Subject, quad.Object
	if isReverse {
		in, out = out, in
	}
	lto := iterator.NewLinksTo(ts, base, in)
	and := iterator.NewAnd()
	and.AddSubIterator(iterator.NewLinksTo(ts, predicateNodeIterator, quad.Predicate))
	and.AddSubIterator(lto)
	return iterator.NewHasA(ts, and, out)
}

func TestRemoveTriple(t *testing.T) {
	ts, _ := makeTestStore(simpleGraph)

	ts.RemoveTriple(&graph.Triple{"E", "follows", "F", ""})

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

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

	innerAnd := iterator.NewAnd()
	innerAnd.AddSubIterator(iterator.NewLinksTo(ts, fixed, graph.Subject))
	innerAnd.AddSubIterator(iterator.NewLinksTo(ts, fixed2, graph.Predicate))

	hasa := iterator.NewHasA(ts, innerAnd, graph.Object)

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

func buildSave(qs graph.QuadStore, via interface{}, tag string, it graph.Iterator, reverse bool) graph.Iterator {
	all := qs.NodesAllIterator()
	all.Tagger().Add(tag)
	node, allDir := quad.Subject, quad.Object
	var viaPath *Path
	if via != nil {
		viaPath = buildViaPath(qs, via)
	} else {
		viaPath = buildViaPath(qs)
	}
	if reverse {
		node, allDir = allDir, node
	}
	lto := iterator.NewLinksTo(qs, all, allDir)
	subAnd := iterator.NewAnd(qs)
	subAnd.AddSubIterator(iterator.NewLinksTo(qs, viaPath.BuildIterator(), quad.Predicate))
	subAnd.AddSubIterator(lto)
	hasa := iterator.NewHasA(qs, subAnd, node)
	and := iterator.NewAnd(qs)
	and.AddSubIterator(hasa)
	and.AddSubIterator(it)
	return and
}

func inOutIterator(viaPath *Path, from graph.Iterator, inIterator bool, tags []string, ctx *context) graph.Iterator {
	start, goal := quad.Subject, quad.Object
	if inIterator {
		start, goal = goal, start
	}

	viaIter := viaPath.BuildIterator()
	for _, tag := range tags {
		viaIter.Tagger().Add(tag)
	}

	source := iterator.NewLinksTo(viaPath.qs, from, start)
	trail := iterator.NewLinksTo(viaPath.qs, viaIter, quad.Predicate)
	var label graph.Iterator
	if ctx != nil {
		if ctx.labelSet != nil {
			labeliter := ctx.labelSet.BuildIteratorOn(viaPath.qs)
			label = iterator.NewLinksTo(viaPath.qs, labeliter, quad.Label)
		}
	}
	route := join(viaPath.qs, source, trail, label)

	return iterator.NewHasA(viaPath.qs, route, goal)
}