package link

import (
	"context"
	"encoding/json"
	"os"
	"testing"
	"time"

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

// novox/hq issue 213: while a machine hands its controller over, the new controller (the process)
// is started while the old one (the container) still holds the controller's consumers. It must not
// exit — the host would read that as a replacement that did not come up and never remove the
// container — and must not act on what the old one is handed. It stands by, and takes the consumers
// when the old one lets go.
func TestNatsASecondControllerStandsByAndTakesOverWhenTheFirstLetsGo(t *testing.T) {
	js := aBus(t)
	was := StandbyPoll
	StandbyPoll = 50 * time.Millisecond
	defer func() { StandbyPoll = was }()

	old := &counted{}
	_, stopOld := servingOn(t, js, old)
	eventually(t, "the first controller binding its consumer", func() bool {
		info, err := js.Context().ConsumerInfo("CONTROL", broker.ControllerName)
		return err == nil && info.PushBound
	})

	// The new one, on a connection of its own as the process would have.
	second, err := broker.Dial(os.Getenv("MESH_TEST_NATS"))
	if err != nil {
		t.Fatal(err)
	}
	t.Cleanup(second.Close)
	fresh := &counted{}
	s := &Server{inbound: Nats(second), bus: OverNATS{Conn: second.Conn(), JS: second.Context()},
		listener: fresh, log: quiet()}
	ctx, stopNew := context.WithCancel(context.Background())
	defer stopNew()
	ended := make(chan error, 1)
	go func() { ended <- s.Serve(ctx) }()

	select {
	case err := <-ended:
		t.Fatalf("the second controller stopped instead of standing by: %v", err)
	case <-time.After(500 * time.Millisecond):
	}

	report := func(declared string) {
		body, _ := json.Marshal(Report{Node: "anchor", Declared: declared, Applied: []string{"store"}})
		if _, err := js.Context().Publish(ReportSubject("anchor"), body); err != nil {
			t.Fatal(err)
		}
	}
	report("d1")
	eventually(t, "the holding controller hearing the report", func() bool { return old.count() == 1 })
	if fresh.count() != 0 {
		t.Fatal("the controller standing by acted on a report the holder was handed")
	}

	stopOld()
	report("d2")
	eventually(t, "the second controller taking over once the first let go", func() bool { return fresh.count() == 1 })
	if old.count() != 1 {
		t.Errorf("the first controller heard %d reports", old.count())
	}
}