package link

import (
	"context"
	"sync"
	"testing"
	"time"

	"github.com/novox/mesh-controller/internal/broker"
)

// A provider's standing (novox/hq ADR 0224): who said it is read from the subject the bus let it
// publish on, a failing one is kept and a recovery cleared, and a recovery is never lost to a store
// that is away — said once, it would leave status naming a consumer that is fine.

type keptStandings struct {
	kept []Standing
	err  error
}

func (k *keptStandings) Stood(_ context.Context, s Standing) (bool, error) {
	if k.err != nil {
		return false, k.err
	}
	k.kept = append(k.kept, s)
	return !s.Failing, nil
}

func standingSays(t *testing.T, in *fakeInbound, to *settled, subject string, body map[string]any) Control {
	t.Helper()
	m := in.sends(t, to, KindProvisioner, body).(*fakeControl)
	m.subject = subject
	return m
}

func TestTheControllerFollowsEveryProvidersStandingAndNothingElse(t *testing.T) {
	for subject, want := range map[string]string{
		"mesh.mod.keycloak.event.provisioner.failing":   "keycloak",
		"mesh.mod.postgres.event.provisioner.recovered": "postgres",
		"mesh.mod.*.event.provisioner.failing":          "*",
	} {
		got, ok := ProvisionerEmitter(subject)
		if !ok || got != want {
			t.Errorf("%s: %q %v", subject, got, ok)
		}
		if kind, _ := kindOfSubject(subject); kind != KindProvisioner {
			t.Errorf("%s decodes to %q", subject, kind)
		}
	}
	for _, subject := range []string{
		"mesh.mod.keycloak.event.provisioner.other",
		"mesh.mod.keycloak.event.client.created",
		"mesh.mod.a.b.event.provisioner.failing",
		"mesh.seat.keycloak.event.provisioner.failing",
	} {
		if _, ok := ProvisionerEmitter(subject); ok {
			t.Errorf("%s read as a provider's standing", subject)
		}
	}
	var follows int
	for _, s := range broker.ControllerFollows {
		if kind, _ := kindOfSubject(s); kind == KindProvisioner {
			follows++
		}
	}
	if follows != 2 {
		t.Fatalf("the controller follows %d standing subjects, want failing and recovered", follows)
	}
}

func TestAFailingStandingIsKeptNamingTheEmitterFromTheSubject(t *testing.T) {
	s, in := serving()
	kept := &keptStandings{}
	if err := s.Watches(kept); err != nil {
		t.Fatal(err)
	}
	to := &settled{}
	since := time.Date(2026, 10, 5, 0, 49, 0, 0, time.UTC)
	s.act(t.Context(), standingSays(t, in, to, "mesh.mod.keycloak.event.provisioner.failing", map[string]any{
		"provider": "oidc-client", "provider-node": "anchor", "consumer": "mesh_home_grafana",
		"node": "home-server", "class": "credentials-rejected", "error": "401 invalid_grant",
		"since": since, "attempts": 31000,
		// A body naming another module is not believed: the subject is the bus's word.
		"module": "postgres",
	}))
	if !to.acked || len(kept.kept) != 1 {
		t.Fatalf("settled %+v, kept %+v", to, kept.kept)
	}
	got := kept.kept[0]
	if got.Module != "keycloak" || !got.Failing || got.Consumer != "mesh_home_grafana" || got.Node != "home-server" ||
		got.ProviderNode != "anchor" || got.Class != "credentials-rejected" || got.Attempts != 31000 || !got.Since.Equal(since) {
		t.Fatalf("%+v", got)
	}

	to = &settled{}
	s.act(t.Context(), standingSays(t, in, to, "mesh.mod.keycloak.event.provisioner.recovered", map[string]any{
		"provider": "oidc-client", "provider-node": "anchor", "consumer": "mesh_home_grafana",
	}))
	if !to.acked || len(kept.kept) != 2 || kept.kept[1].Failing {
		t.Fatalf("settled %+v, kept %+v", to, kept.kept)
	}
}

func TestARecoveryIsHeldWhileTheStoreIsAway(t *testing.T) {
	s, in := serving()
	kept := &keptStandings{err: restarting}
	if err := s.Watches(kept); err != nil {
		t.Fatal(err)
	}
	to := &settled{}
	s.act(t.Context(), standingSays(t, in, to, "mesh.mod.keycloak.event.provisioner.recovered",
		map[string]any{"consumer": "mesh_home_grafana"}))
	if !to.unsettled() || len(in.held) != 1 {
		t.Fatalf("a recovery was settled while the store was away: %+v", to)
	}
	kept.err = nil
	in.retries(t.Context(), s)
	if !to.acked || len(kept.kept) != 1 {
		t.Fatalf("the held recovery was not kept when the store came back: %+v %+v", to, kept.kept)
	}
}

func TestAStandingThatNamesNoConsumerIsTakenAndForgotten(t *testing.T) {
	s, in := serving()
	kept := &keptStandings{}
	if err := s.Watches(kept); err != nil {
		t.Fatal(err)
	}
	to := &settled{}
	s.act(t.Context(), standingSays(t, in, to, "mesh.mod.keycloak.event.provisioner.failing", map[string]any{}))
	if !to.acked || len(kept.kept) != 0 {
		t.Fatalf("%+v %+v", to, kept.kept)
	}
}

func TestAStandingWithNothingKeepingItIsTaken(t *testing.T) {
	s, in := serving()
	to := &settled{}
	s.act(t.Context(), standingSays(t, in, to, "mesh.mod.keycloak.event.provisioner.failing",
		map[string]any{"consumer": "x"}))
	if !to.acked {
		t.Fatal("a standing nothing keeps was left for the bus to hand over again")
	}
}

// Over a real bus: a provider's standing published under its own module's namespace reaches the
// controller through the events consumer's filter — the one wildcard filter on it — names the emitter
// from the subject, and is acknowledged.
func TestNatsAProvidersStandingReachesTheController(t *testing.T) {
	js := aBus(t)
	kept := &lockedStandings{}
	s := &Server{inbound: Nats(js), bus: OverNATS{Conn: js.Conn(), JS: js.Context()}, log: quiet()}
	if err := s.Follows(&toldAbout{}); err != nil {
		t.Fatal(err)
	}
	if err := s.Watches(kept); err != nil {
		t.Fatal(err)
	}
	ctx, stop := context.WithCancel(context.Background())
	defer stop()
	go func() { _ = s.Serve(ctx) }()
	eventually(t, "the controller's event consumer being made", func() bool {
		_, err := js.Context().ConsumerInfo("EVENTS", broker.ControllerName)
		return err == nil
	})

	for _, event := range []string{broker.ProvisionerFailing, broker.ProvisionerRecovered} {
		if _, err := js.Context().Publish("mesh.mod.keycloak.event."+event,
			[]byte(`{"consumer":"mesh_home_grafana","provider-node":"anchor","class":"credentials-rejected"}`)); err != nil {
			t.Fatal(err)
		}
	}
	// Somebody else's event under the same prefix is not the controller's to hear.
	if _, err := js.Context().Publish("mesh.mod.keycloak.event.client.created", []byte(`{}`)); err != nil {
		t.Fatal(err)
	}
	eventually(t, "both standings being kept, in order, naming the emitter", func() bool {
		got := kept.all()
		return len(got) == 2 && got[0].Module == "keycloak" && got[0].Failing && !got[1].Failing
	})
	eventually(t, "both being acknowledged and nothing else delivered", func() bool {
		info, err := js.Context().ConsumerInfo("EVENTS", broker.ControllerName)
		return err == nil && info.NumAckPending == 0 && info.Delivered.Consumer == 2
	})
}

type lockedStandings struct {
	mu   sync.Mutex
	kept []Standing
}

func (l *lockedStandings) Stood(_ context.Context, s Standing) (bool, error) {
	l.mu.Lock()
	defer l.mu.Unlock()
	l.kept = append(l.kept, s)
	return !s.Failing, nil
}

func (l *lockedStandings) all() []Standing {
	l.mu.Lock()
	defer l.mu.Unlock()
	return append([]Standing(nil), l.kept...)
}