package broker

import (
	"errors"
	"strings"
	"testing"
)

type recorder struct {
	seen []Stream
	fail string
}

func (r *recorder) EnsureStream(s Stream) error {
	if s.Name == r.fail {
		return errors.New("refused")
	}
	r.seen = append(r.seen, s)
	return nil
}

// The controller asserts on every start, not only at genesis: a stream that was deleted, or a mesh
// raised from a backup, must converge rather than run without the guarantee its messages assume.
func TestAssertingTwiceIsTheSameAsOnce(t *testing.T) {
	a, b := &recorder{}, &recorder{}
	if err := AssertMeshStreams(a); err != nil {
		t.Fatal(err)
	}
	if err := AssertMeshStreams(a); err != nil {
		t.Fatal(err)
	}
	if err := AssertMeshStreams(b); err != nil {
		t.Fatal(err)
	}
	if len(a.seen) != 2*len(b.seen) {
		t.Fatalf("asserted %d then %d; assertion is not repeatable", len(a.seen), len(b.seen))
	}
}

func TestAFailedAssertionNamesItsStream(t *testing.T) {
	err := AssertMeshStreams(&recorder{fail: "NODES"})
	if err == nil || !strings.Contains(err.Error(), "NODES") {
		t.Fatalf("got %v, which does not say which stream failed", err)
	}
}

// Two streams matching one subject is accepted by NATS and stores the message twice under two
// retentions. Nothing reports that, so it is refused where the set is written.
func TestNoTwoStreamsClaimTheSameSubject(t *testing.T) {
	if clashes := Overlaps(); len(clashes) != 0 {
		t.Fatalf("overlapping subject filters: %v", clashes)
	}
}

// A heartbeat under mesh.control.> must not be persisted: a lost one is the next one, and a
// stream of them competes for retention with the messages that matter.
func TestHeartbeatsAreNotInTheControlStream(t *testing.T) {
	for _, s := range MeshStreams() {
		for _, subject := range s.Subjects {
			if subject == "mesh.control.>" || strings.Contains(subject, "alive") {
				t.Fatalf("stream %s claims %q, which captures heartbeats", s.Name, subject)
			}
		}
	}
}

// The reason the kind token exists: a filter over a module's whole namespace would persist every
// tool call in the mesh.
func TestTheEventsStreamDoesNotCaptureToolCalls(t *testing.T) {
	var events Stream
	for _, s := range MeshStreams() {
		if s.Name == "EVENTS" {
			events = s
		}
	}
	// Nothing a tool call rides may match any of the filters — a module's or a seat's.
	for _, tool := range []string{
		"mesh.mod.billing.tool.status",
		"mesh.seat.telegram-sender.tool.status",
		"mesh.seat.telegram-sender.accept.send", // work, not an event: its own stream
	} {
		for _, f := range events.Subjects {
			if subjectMatches(f, tool) {
				t.Fatalf("%q matches the events filter %q, so it would be persisted here", tool, f)
			}
		}
	}
	// And both kinds of event do match.
	for _, event := range []string{
		"mesh.mod.billing.event.order.placed",
		"mesh.seat.telegram-sender.event.delivered",
	} {
		matched := false
		for _, f := range events.Subjects {
			if subjectMatches(f, event) {
				matched = true
			}
		}
		if !matched {
			t.Fatalf("%q matches no events filter, so nothing would keep it", event)
		}
	}
}

// subjectMatches is NATS subject matching, enough for these filters: `*` is one token, `>` is the
// rest.
func subjectMatches(filter, subject string) bool {
	f, s := strings.Split(filter, "."), strings.Split(subject, ".")
	for i, tok := range f {
		if tok == ">" {
			return i <= len(s)
		}
		if i >= len(s) {
			return false
		}
		if tok != "*" && tok != s[i] {
			return false
		}
	}
	return len(f) == len(s)
}

// Each relationship's retention is the thing that makes it what it is (design 29 §4).
func TestEachStreamCarriesTheRetentionItsShapeNeeds(t *testing.T) {
	want := map[string]Retention{
		"CONTROL": RetentionWorkQueue,
		"NODES":   RetentionLastPerSubject,
		"EVENTS":  RetentionLimits,
	}
	got := map[string]Retention{}
	for _, s := range MeshStreams() {
		got[s.Name] = s.Retention
		if s.Why == "" {
			t.Errorf("stream %s says no reason it exists", s.Name)
		}
	}
	if len(got) != len(want) {
		t.Fatalf("the foundation set is %v", got)
	}
	for name, r := range want {
		if got[name] != r {
			t.Errorf("%s retains as %q, expected %q", name, got[name], r)
		}
	}
}

// The order the bus's objects are asserted in, because getting it wrong is a refusal that names the
// wrong thing: a consumer on a stream that does not exist is refused naming the *stream*, so
// somebody reading it goes looking for a deletion instead of a reversed pair of lines.
func TestTheBusesObjectsAreAssertedStreamsBeforeConsumers(t *testing.T) {
	r := &recording{}
	if err := Raise(r, []string{"anchor", "laptop"}); err != nil {
		t.Fatal(err)
	}

	// Every stream before every consumer.
	firstConsumer := -1
	for i, step := range r.steps {
		if strings.HasPrefix(step, "consumer ") && firstConsumer < 0 {
			firstConsumer = i
		}
		if strings.HasPrefix(step, "stream ") && firstConsumer >= 0 {
			t.Fatalf("a stream was asserted after a consumer: %v", r.steps)
		}
	}
	if firstConsumer < 0 {
		t.Fatalf("no consumer was asserted: %v", r.steps)
	}

	// And every node got one, named after it — without which that node hears nothing while
	// everything else about it looks correct.
	for _, node := range []string{"anchor", "laptop"} {
		if !containsStep(r.steps, "consumer NODES/"+node) {
			t.Errorf("%s was given no way to hear its declaration: %v", node, r.steps)
		}
	}
	// And the controller its own, on both streams it reads.
	for _, want := range []string{"consumer CONTROL/controller", "consumer EVENTS/controller"} {
		if !containsStep(r.steps, want) {
			t.Errorf("the controller is missing %s: %v", want, r.steps)
		}
	}
}

// A seat's work queue is asserted whether or not anybody holds it; the holder's worker only when
// somebody does. **The stream without the consumer is the point**: work queues until a holder
// appears, so installing the module later flushes the backlog instead of having lost it.
func TestASeatsQueueExistsBeforeItsHolderDoes(t *testing.T) {
	seats := []DeclaredSeat{{Name: "telegram-sender", Accepts: []string{"send"}}}

	unheld := &recording{}
	if err := RaiseSeats(unheld, seats, nil); err != nil {
		t.Fatal(err)
	}
	if !containsStep(unheld.steps, "stream SEAT_TELEGRAM_SENDER") {
		t.Fatalf("a declared seat got no work queue: %v", unheld.steps)
	}
	for _, step := range unheld.steps {
		if strings.HasPrefix(step, "consumer ") {
			t.Fatalf("a seat nobody holds got a worker: %v", unheld.steps)
		}
	}

	held := &recording{}
	if err := RaiseSeats(held, seats, map[string]Holder{
		"telegram-sender": {Node: "anchor", Module: "telegram"},
	}); err != nil {
		t.Fatal(err)
	}
	if !containsStep(held.steps, "consumer SEAT_TELEGRAM_SENDER/SEAT_TELEGRAM_SENDER_worker") {
		t.Fatalf("the seat's holder got no worker: %v", held.steps)
	}
}

// recording is a connection to the bus that writes down what it was asked for.
type recording struct{ steps []string }

func (r *recording) EnsureStream(s Stream) error {
	r.steps = append(r.steps, "stream "+s.Name)
	return nil
}

func (r *recording) EnsureConsumer(c Consumer) error {
	r.steps = append(r.steps, "consumer "+c.Stream+"/"+c.Name)
	return nil
}

func containsStep(steps []string, want string) bool {
	for _, s := range steps {
		if s == want {
			return true
		}
	}
	return false
}