package main

import (
	"fmt"
	"math/rand"
	"os"
	"regexp"
	"runtime/debug"
	"sync"
	"testing"
	"time"

	"github.com/nats-io/nats-server/v2/server"
	"github.com/nats-io/nats.go"
)

// The server these tests run is the server the image runs. The image is pinned by a digest, which
// names no release, so the Dockerfile says which release it is, and this keeps the two equal: a
// test of the server below is only worth something about the server the mesh actually runs.
func TestTheImageIsTheServerTestedHere(t *testing.T) {
	raw, err := os.ReadFile("../../Dockerfile")
	if err != nil {
		t.Fatal(err)
	}
	said := regexp.MustCompile(`(?m)^# upstream: nats (\d+\.\d+\.\d+)-alpine$`).FindSubmatch(raw)
	if said == nil {
		t.Fatal("the Dockerfile does not say which nats release its digest is (`# upstream: nats X.Y.Z-alpine`)")
	}
	info, ok := debug.ReadBuildInfo()
	if !ok {
		t.Fatal("no build information to read the tested server's version from")
	}
	for _, dep := range info.Deps {
		if dep.Path == "github.com/nats-io/nats-server/v2" {
			if dep.Version != "v"+string(said[1]) {
				t.Fatalf("the image runs nats %s and these tests run %s: move them together", said[1], dep.Version)
			}
			return
		}
	}
	t.Fatal("these tests run no nats-server")
}

// **A consumer with several filters is handed every message** (novox/hq issue 266).
//
// The controller follows the forge's merges, build outcomes and providers' standings on one durable
// consumer with seven filters, one message at a time. On nats 2.10.29 such a consumer was moved past
// a message now and then without handing it over: nothing pending, nothing redelivered, the message
// on the stream and its consumer never told. On 2026-10-06 that message was a merge, and the modules
// built from that repository were left behind with nobody told. This is that consumer, under traffic
// shaped like the mesh's — a stream mostly of build logs on ever-new subjects, the followed events
// few among them — and it fails on 2.10.29 (a few percent of the followed events never arrive) and
// passes on the release the image pins.
func TestAConsumerWithSeveralFiltersIsHandedEveryMessage(t *testing.T) {
	if testing.Short() {
		t.Skip("runs a server under load for seconds")
	}
	s, err := server.NewServer(&server.Options{Port: -1, JetStream: true, StoreDir: t.TempDir(), NoLog: true, NoSigs: true})
	if err != nil {
		t.Fatal(err)
	}
	go s.Start()
	if !s.ReadyForConnections(5 * time.Second) {
		t.Fatal("the server did not start")
	}
	defer s.Shutdown()

	admin, err := nats.Connect(s.ClientURL())
	if err != nil {
		t.Fatal(err)
	}
	defer admin.Close()
	js, _ := admin.JetStream()
	// The events stream and the controller's consumer on it, as the mesh declares them.
	if _, err := js.AddStream(&nats.StreamConfig{Name: "EVENTS", Subjects: []string{"mesh.mod.*.event.>", "mesh.seat.*.event.>"},
		MaxAge: 168 * time.Hour, MaxMsgsPerSubject: 10000, Storage: nats.FileStorage}); err != nil {
		t.Fatal(err)
	}
	if _, err := js.AddConsumer("EVENTS", &nats.ConsumerConfig{Durable: "controller", DeliverSubject: "_DELIVER.controller.EVENTS",
		FilterSubjects: []string{
			"mesh.mod.mesh-catalog.event.upgraded",
			"mesh.mod.mesh-catalog.event.catching-up",
			"mesh.seat.node-build-agent.event.built",
			"mesh.mod.gitea.event.pull.merged",
			"mesh.seat.mesh-build-machine.event.built",
			"mesh.mod.*.event.provisioner.failing",
			"mesh.mod.*.event.provisioner.recovered",
		},
		AckPolicy: nats.AckExplicitPolicy, AckWait: 30 * time.Second, MaxDeliver: 5, MaxAckPending: 1,
		DeliverPolicy: nats.DeliverNewPolicy}); err != nil {
		t.Fatal(err)
	}

	controller, err := nats.Connect(s.ClientURL())
	if err != nil {
		t.Fatal(err)
	}
	defer controller.Close()
	cjs, _ := controller.JetStream()
	handed := make(chan *nats.Msg, 64)
	if _, err := cjs.ChanSubscribe("", handed, nats.Bind("EVENTS", "controller")); err != nil {
		t.Fatal(err)
	}
	var got sync.Map
	go func() {
		for m := range handed {
			if meta, err := m.Metadata(); err == nil {
				got.Store(meta.Sequence.Stream, true)
			}
			time.Sleep(time.Duration(rand.Intn(20)) * time.Millisecond)
			_ = m.Ack()
		}
	}()

	followed := []string{"mesh.mod.gitea.event.pull.merged", "mesh.seat.node-build-agent.event.built",
		"mesh.mod.postgres.event.provisioner.recovered", "mesh.mod.mesh-catalog.event.catching-up"}
	var mu sync.Mutex
	var sent []uint64
	stop := time.Now().Add(5 * time.Second)
	var wg sync.WaitGroup
	for w := 0; w < 4; w++ {
		wg.Add(1)
		go func(w int) {
			defer wg.Done()
			nc, err := nats.Connect(s.ClientURL())
			if err != nil {
				t.Error(err)
				return
			}
			defer nc.Close()
			pjs, _ := nc.JetStream()
			for i := 0; time.Now().Before(stop); i++ {
				if rand.Intn(40) == 0 {
					if ack, err := pjs.Publish(followed[rand.Intn(len(followed))], []byte(`{}`)); err == nil {
						mu.Lock()
						sent = append(sent, ack.Sequence)
						mu.Unlock()
					}
				} else {
					_, _ = pjs.Publish(fmt.Sprintf("mesh.seat.node-build-agent.event.log.build-%d-%d", w, i/50), make([]byte, 200))
				}
				if rand.Intn(100) == 0 {
					time.Sleep(time.Duration(rand.Intn(300)) * time.Millisecond)
				}
			}
		}(w)
	}
	wg.Wait()

	// Every followed event handed over, given the consumer time to finish.
	deadline := time.Now().Add(20 * time.Second)
	for {
		var missing []uint64
		for _, seq := range sent {
			if _, ok := got.Load(seq); !ok {
				missing = append(missing, seq)
			}
		}
		if len(missing) == 0 {
			return
		}
		info, err := js.ConsumerInfo("EVENTS", "controller")
		if time.Now().After(deadline) || (err == nil && info.NumPending == 0 && info.NumAckPending == 0) {
			t.Fatalf("%d of %d followed events were never handed to the consumer (first at stream sequence %d), "+
				"and it has nothing pending: the server moved past them", len(missing), len(sent), missing[0])
		}
		time.Sleep(200 * time.Millisecond)
	}
}