package link

import (
	"errors"
	"strings"
	"testing"

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

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

// What a seat's worker gave up on, when the ask is one the controller itself makes (novox/hq issue 334).
//
// The controller already publishes on the accept subjects of the seats it asks (broker's
// seatsTheControllerAsks) and reaches the stream API, so delivering its own ask again needs no grant it
// does not hold: the original is removed from the work queue by its sequence, and the kept copy is
// published on the ask's own subject, where the seat's one worker takes it. An ask to any other seat is
// still refused, and stays kept: delivering it would need a publish the controller is not granted
// (ADR 0264's consequences), in the asker's name (ADR 0259 §3).

// theBuildWorker is the build seat's worker as a holder pulls from it.
func theBuildWorker(t *testing.T, js *broker.JetStream) jetstream.Consumer {
	t.Helper()
	api, err := jetstream.New(js.Conn())
	if err != nil {
		t.Fatal(err)
	}
	stream := "SEAT_NODE_BUILD_AGENT"
	worker, err := api.Consumer(t.Context(), stream, stream+"_worker")
	if err != nil {
		t.Fatal(err)
	}
	return worker
}

func TestAnAskTheControllerMadeIsDeliveredAgainToTheSeatsWorker(t *testing.T) {
	js := aBusWithTheBuildRole(t)
	keeping(t, js)
	worker := theBuildWorker(t, js)

	subject := BuildWorkOf(TheBuildMachine)
	ask := &nats.Msg{Subject: subject, Data: []byte(`{"module":"x"}`), Header: nats.Header{}}
	ask.Header.Set(nats.MsgIdHdr, "build-1")
	if _, err := js.Context().PublishMsg(ask); err != nil {
		t.Fatal(err)
	}
	d := givenUp(t, js, worker)
	if d.Stream != "SEAT_NODE_BUILD_AGENT" || d.Subject != subject || d.Lost != "" {
		t.Fatalf("kept as %+v", d)
	}
	if _, err := js.Context().GetMsg(d.Stream, d.Sequence); err != nil {
		t.Fatalf("the original is not in the work queue before it is delivered again: %v", err)
	}

	_, to, err := DeliverAgain(js.Context(), d.ID)
	if err != nil {
		t.Fatal(err)
	}
	if to != subject {
		t.Fatalf("delivered again on %s, not the ask's own subject %s", to, subject)
	}
	if _, err := js.Context().GetMsg(d.Stream, d.Sequence); !errors.Is(err, nats.ErrMsgNotFound) {
		t.Fatalf("the original is still in the work queue beside its copy: %v", err)
	}
	again := next(t, worker)
	if again == nil {
		t.Fatal("the seat's worker was not handed the ask again")
	}
	if string(again.Data()) != `{"module":"x"}` || again.Headers().Get(AgainHeader) == "" {
		t.Fatalf("handed again as %s %v", again.Data(), again.Headers())
	}
	_ = again.Ack()
	if m := next(t, worker); m != nil {
		t.Fatalf("the worker was handed it twice: %s", m.Subject())
	}
	if _, err := DeadLetterNamed(js.Context(), d.ID); !errors.Is(err, ErrNoDeadLetter) {
		t.Fatalf("still kept after it was delivered again: %v", err)
	}
	if _, _, err := DeliverAgain(js.Context(), d.ID); !errors.Is(err, ErrNoDeadLetter) {
		t.Fatalf("a second delivery answered %v", err)
	}
}

// An ask to a seat the controller does not ask is refused, says why, and nothing is done.
func TestAnAskTheControllerDidNotMakeIsStillOnlyDropped(t *testing.T) {
	js := aBus(t)
	for _, d := range []DeadLetter{
		{ID: 2, Stream: "SEAT_TELEGRAM_SENDER", Consumer: "SEAT_TELEGRAM_SENDER_worker",
			Subject: "mesh.seat.telegram-sender.accept.send"},
		// The subject of a seat the controller asks, on a stream that is not that seat's queue.
		{ID: 3, Stream: "SEAT_TELEGRAM_SENDER", Consumer: "SEAT_TELEGRAM_SENDER_worker",
			Subject: "mesh.seat.node-build-agent.accept.build"},
	} {
		if to, err := AgainTo(js.Context(), d); err == nil {
			t.Errorf("%s on %s was given %s to be delivered again on", d.Subject, d.Stream, to)
		} else if !strings.Contains(err.Error(), "Drop it") {
			t.Errorf("refused without saying what to do: %v", err)
		}
	}
}

// aBuildAskGivenUp publishes one build ask and lets the worker give it up.
func aBuildAskGivenUp(t *testing.T, js *broker.JetStream, worker jetstream.Consumer, body string) DeadLetter {
	t.Helper()
	if _, err := js.Context().Publish(BuildWorkOf(TheBuildMachine), []byte(body)); err != nil {
		t.Fatal(err)
	}
	return givenUp(t, js, worker)
}

// A copy that cannot be published: the original is already out of the queue, the dead letter is kept and
// the answer says both; asked again once it can be published, it is delivered once.
func TestAnAskWhoseCopyIsRefusedStaysKeptAndIsDeliveredOnTheNextTry(t *testing.T) {
	js := aBusWithTheBuildRole(t)
	keeping(t, js)
	worker := theBuildWorker(t, js)
	d := aBuildAskGivenUp(t, js, worker, `{"module":"x"}`)

	// The queue stops taking the ask's subject, so the copy's publish is refused by the server.
	info, err := js.Context().StreamInfo(d.Stream)
	if err != nil {
		t.Fatal(err)
	}
	cfg := info.Config
	taking := cfg.Subjects
	cfg.Subjects = []string{"mesh.seat." + TheBuildMachine + ".accept.nothing"}
	if _, err := js.Context().UpdateStream(&cfg); err != nil {
		t.Fatal(err)
	}
	_, _, err = DeliverAgain(js.Context(), d.ID)
	if err == nil || !strings.Contains(err.Error(), "still kept") || !strings.Contains(err.Error(), "was removed") {
		t.Fatalf("a refused copy answered %v", err)
	}
	if _, err := js.Context().GetMsg(d.Stream, d.Sequence); !errors.Is(err, nats.ErrMsgNotFound) {
		t.Fatalf("the original is still in the queue: %v", err)
	}
	if _, err := DeadLetterNamed(js.Context(), d.ID); err != nil {
		t.Fatalf("a refused copy let the dead letter go: %v", err)
	}

	cfg.Subjects = taking
	if _, err := js.Context().UpdateStream(&cfg); err != nil {
		t.Fatal(err)
	}
	retried, _, err := DeliverAgain(js.Context(), d.ID)
	if err != nil {
		t.Fatal(err)
	}
	if !strings.Contains(retried.Original, "no longer held") {
		t.Fatalf("the retry said of the original: %q", retried.Original)
	}
	if again := next(t, worker); again == nil || string(again.Data()) != `{"module":"x"}` {
		t.Fatal("the retry did not hand the ask to the worker")
	} else {
		_ = again.Ack()
	}
	if m := next(t, worker); m != nil {
		t.Fatalf("handed twice: %s", m.Data())
	}
}

// A queue made again numbers from one: the old dead letter's sequence then names a live ask, which is left
// alone.
func TestAnAskWhoseSequenceNamesAnotherMessageLeavesThatOneAlone(t *testing.T) {
	js := aBusWithTheBuildRole(t)
	keeping(t, js)
	d := aBuildAskGivenUp(t, js, theBuildWorker(t, js), `{"module":"old"}`)

	// The build handover's way: the seat's queue deleted and made again, with its worker.
	if err := js.Context().DeleteStream(d.Stream); err != nil {
		t.Fatal(err)
	}
	if err := broker.RaiseSeats(js, []broker.DeclaredSeat{{Name: TheBuildMachine, Accepts: []string{"build"},
		Emits: []string{"built"}}}, map[string]broker.Holder{TheBuildMachine: {Node: "anchor", Module: "builder"}}); err != nil {
		t.Fatal(err)
	}
	live, err := js.Context().Publish(BuildWorkOf(TheBuildMachine), []byte(`{"module":"live"}`))
	if err != nil {
		t.Fatal(err)
	}
	if live.Sequence != d.Sequence {
		t.Fatalf("the live ask is message %d, the dead letter names %d: the test does not set up the collision",
			live.Sequence, d.Sequence)
	}

	delivered, _, err := DeliverAgain(js.Context(), d.ID)
	if err != nil {
		t.Fatal(err)
	}
	if !strings.Contains(delivered.Original, "another message") {
		t.Fatalf("the answer said of the original: %q", delivered.Original)
	}
	if held, err := js.Context().GetMsg(d.Stream, d.Sequence); err != nil || string(held.Data) != `{"module":"live"}` {
		t.Fatalf("the live ask at that sequence was touched: %v", err)
	}
}

// No worker on the seat's queue: refused, kept, and nothing published.
func TestAnAskIsNotDeliveredAgainWhileTheSeatHasNoWorker(t *testing.T) {
	js := aBusWithTheBuildRole(t)
	keeping(t, js)
	d := aBuildAskGivenUp(t, js, theBuildWorker(t, js), `{"module":"x"}`)
	if err := js.Context().DeleteConsumer(d.Stream, d.Consumer); err != nil {
		t.Fatal(err)
	}
	if _, _, err := DeliverAgain(js.Context(), d.ID); err == nil || !strings.Contains(err.Error(), "wait in") {
		t.Fatalf("delivered with no worker: %v", err)
	}
	if _, err := js.Context().GetMsg(d.Stream, d.Sequence); err != nil {
		t.Fatalf("a refusal removed the original: %v", err)
	}
	if _, err := DeadLetterNamed(js.Context(), d.ID); err != nil {
		t.Fatalf("a refusal let the dead letter go: %v", err)
	}
}