package broker

import (
	"fmt"
	"os"
	"strings"
	"testing"
	"time"

	"github.com/nats-io/nats.go"
)

const twoSeconds = 2 * time.Second

// A running mesh already holds consumers made before the delivery subject carried the stream
// (novox/hq 04-ISSUES/146). The server will not change a push consumer's delivery subject in place,
// so bringing one to match must replace it — and must not replay what it already acknowledged
// (novox/hq 04-ISSUES/156).
//
//	docker run -d --rm --name t -p 14231:4222 nats:2.10-alpine -js
//	MESH_TEST_NATS=nats://127.0.0.1:14231 go test ./internal/broker/ -run TestUpgrading
func TestUpgradingAConsumerWhoseDeliverySubjectMoved(t *testing.T) {
	url := os.Getenv("MESH_TEST_NATS")
	if url == "" {
		t.Skip("MESH_TEST_NATS unset")
	}
	js, err := Dial(url)
	if err != nil {
		t.Fatal(err)
	}
	defer js.Close()

	// The stream exactly as the mesh's own is — one declaration per node, always the newest.
	// Reproduced rather than approximated: the first version of this test used a plain stream and
	// a plain consumer, and the server accepted the update it refuses in a running mesh, so the
	// test passed against the very code that was crash-looping on the control node.
	const stream, name = "NODES", "novox"
	subject := "mesh.node." + name + ".declare"
	_ = js.js.DeleteStream(stream)
	if _, err := js.js.AddStream(&nats.StreamConfig{
		Name: stream, Subjects: []string{"mesh.node.*.declare"},
		MaxMsgsPerSubject: 1, Storage: nats.MemoryStorage,
	}); err != nil {
		t.Fatal(err)
	}
	defer func() { _ = js.js.DeleteStream(stream) }()

	for i := 0; i < 6; i++ {
		if _, err := js.js.Publish(subject, []byte(fmt.Sprint(i))); err != nil {
			t.Fatal(err)
		}
	}

	// The consumer as a running mesh holds it: made before the subject carried the stream, and
	// otherwise exactly what NodeConsumer asks for.
	if _, err := js.js.AddConsumer(stream, &nats.ConsumerConfig{
		Durable: name, AckPolicy: nats.AckExplicitPolicy,
		AckWait: 300 * time.Second, MaxDeliver: -1,
		FilterSubject:  subject,
		DeliverSubject: "_DELIVER." + name,
	}); err != nil {
		t.Fatal(err)
	}

	// It acknowledged the first four. Those must not come back.
	sub, err := js.js.SubscribeSync(subject, nats.Bind(stream, name))
	if err != nil {
		t.Fatal(err)
	}
	for i := 0; i < 1; i++ {
		m, err := sub.NextMsg(twoSeconds)
		if err != nil {
			t.Fatalf("message %d never arrived: %v", i, err)
		}
		if err := m.AckSync(); err != nil {
			t.Fatal(err)
		}
	}
	// **The subscription stays up.** In a running mesh the machine is attached to this consumer
	// the whole time — that is what a node listening for its declaration IS. The first version of
	// this test unsubscribed first, and the server then accepted an update it refuses while a
	// subscriber is bound, so the test passed against the code that was crash-looping.
	defer func() { _ = sub.Unsubscribe() }()

	// Now the upgrade: the consumer the controller asserts on every start, with the subject that
	// carries the stream.
	want := NodeConsumer(name)
	var notes []string
	js.Note = func(f string, a ...any) { notes = append(notes, fmt.Sprintf(f, a...)) }

	if err := js.EnsureConsumer(want); err != nil {
		t.Fatalf("a consumer the mesh already held could not be brought to match, which is the "+
			"control plane failing to start: %v", err)
	}

	info, err := js.js.ConsumerInfo(stream, name)
	if err != nil {
		t.Fatal(err)
	}

	// It KEEPS the subject it had. Moving it would need the holder's grant to have widened first,
	// and that grant travels in the bus's user list, which a machine applies minutes later.
	if got := info.Config.DeliverSubject; got != "_DELIVER."+name {
		t.Fatalf("the consumer a machine is bound to was moved to %q; a machine not yet allowed "+
			"to subscribe there is a machine that hears nothing", got)
	}
	if len(notes) != 1 {
		t.Fatalf("keeping it was not reported, so it would be invisible: %v", notes)
	}
	if !strings.Contains(notes[0], "keeps working") {
		t.Fatalf("the note does not say the consumer still works: %q", notes[0])
	}

	// And the machine bound to it is still being delivered to — the point of keeping it.
	if _, err := js.js.Publish(subject, []byte("after the assertion")); err != nil {
		t.Fatal(err)
	}
	m, err := sub.NextMsg(twoSeconds)
	if err != nil {
		t.Fatalf("the machine stopped hearing its declarations after the assertion: %v", err)
	}
	if string(m.Data) != "after the assertion" {
		t.Fatalf("delivered %q", m.Data)
	}

	// Asserting again is a no-op, or the controller crash-loops on its own restart.
	if err := js.EnsureConsumer(want); err != nil {
		t.Fatalf("the second assertion failed: %v", err)
	}
}

// And where nothing is bound, the subject DOES move — that is 04-ISSUES/146's fix, which this must
// not undo. The controller's own two consumers are in exactly this position: it asserts them before
// it subscribes.
func TestAConsumerNothingIsBoundToDoesMove(t *testing.T) {
	url := os.Getenv("MESH_TEST_NATS")
	if url == "" {
		t.Skip("MESH_TEST_NATS unset")
	}
	js, err := Dial(url)
	if err != nil {
		t.Fatal(err)
	}
	defer js.Close()

	const stream, name = "NODES", "shanks"
	subject := "mesh.node." + name + ".declare"
	_ = js.js.DeleteStream(stream)
	if _, err := js.js.AddStream(&nats.StreamConfig{
		Name: stream, Subjects: []string{"mesh.node.*.declare"},
		MaxMsgsPerSubject: 1, Storage: nats.MemoryStorage,
	}); err != nil {
		t.Fatal(err)
	}
	defer func() { _ = js.js.DeleteStream(stream) }()

	if _, err := js.js.AddConsumer(stream, &nats.ConsumerConfig{
		Durable: name, AckPolicy: nats.AckExplicitPolicy,
		AckWait: 300 * time.Second, MaxDeliver: -1,
		FilterSubject:  subject,
		DeliverSubject: "_DELIVER." + name,
	}); err != nil {
		t.Fatal(err)
	}

	want := NodeConsumer(name)
	if err := js.EnsureConsumer(want); err != nil {
		t.Fatal(err)
	}
	info, err := js.js.ConsumerInfo(stream, name)
	if err != nil {
		t.Fatal(err)
	}
	if got := info.Config.DeliverSubject; got != DeliverSubjectFor(want) {
		t.Fatalf("delivery subject is %q, wanted %q -- issue 146's fix no longer applies to a "+
			"consumer nothing is holding", got, DeliverSubjectFor(want))
	}
}