mesh-sdk/go/process/binding_test.go

package process

import (
	"encoding/json"
	"errors"
	"strings"
	"sync"
	"testing"

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

type bindMsg struct {
	jetstream.Msg
	subject string
	data    string
	acked   bool
}

func (m *bindMsg) Subject() string { return m.subject }
func (m *bindMsg) Data() []byte    { return []byte(m.data) }
func (m *bindMsg) Ack() error      { m.acked = true; return nil }

// design 47 G §577: a process reaches the kept data its `requires` declares through its Binding: `show` of the seat
// mesh-broker at the start, asked again on `recreated` and `dropped` of the entry, and a wait naming the entry until it answers.
func TestABindingAsksShowAndAgainOnRecreatedAndDropped(t *testing.T) {
	var mu sync.Mutex
	bucket, answers := "m_performed", true
	var asked []string
	call := func(key string, body any) (json.RawMessage, error) {
		mu.Lock()
		defer mu.Unlock()
		asked = append(asked, key+" "+toJSON(body))
		if !answers {
			return nil, errors.New("no responders")
		}
		return json.RawMessage(`{"binding":{"local":"performed","storage":"key-value","bucket":"` + bucket + `"}}`), nil
	}
	b := NewBinding("mesh-broker", "m", call, nil, "performed", "events")
	b.spawn = func(f func()) { f() }
	if _, err := b.Names("performed"); err == nil || !strings.Contains(err.Error(), `"performed"`) {
		t.Fatalf("before show answered: %v", err)
	}
	if w := b.Waiting(); !strings.Contains(w, `"performed"`) || !strings.Contains(w, `"events"`) {
		t.Fatalf("waiting words %q name neither entry", w)
	}
	if _, err := b.Names("nope"); err == nil {
		t.Fatal("an entry this Binding was not made for was answered")
	}
	b.Ask("performed")
	b.Ask("events")
	got, err := b.Names("performed")
	if err != nil || got.Bucket != "m_performed" || b.Waiting() != "" {
		t.Fatalf("after show: %+v, %v, waiting %q", got, err, b.Waiting())
	}
	if !strings.Contains(asked[0], `seat:mesh-broker.show {"local-name":"performed","module":"m"}`) {
		t.Fatalf("asked %v", asked)
	}
	// recreated for this module's entry: asked again, the new names kept
	mu.Lock()
	bucket = "m_performed2"
	mu.Unlock()
	for _, m := range []*bindMsg{
		{subject: "mesh.seat.mesh-broker.event.recreated", data: `{"module":"other","local-name":"performed"}`},
		{subject: "mesh.seat.mesh-broker.event.recreated", data: `{"module":"m","local-name":"performed"}`},
	} {
		b.Hear(m)
		if !m.acked {
			t.Errorf("%s not acknowledged", m.data)
		}
	}
	if n, _ := b.Names("performed"); n.Bucket != "m_performed2" {
		t.Fatalf("recreated was not asked again: %+v", n)
	}
	// dropped: unbound until show answers, which it does not
	mu.Lock()
	answers = false
	mu.Unlock()
	b.Hear(&bindMsg{subject: "mesh.seat.mesh-broker.event.dropped", data: `{"module":"m","local-name":"performed"}`})
	if _, err := b.Names("performed"); err == nil || !strings.Contains(err.Error(), "no responders") {
		t.Fatalf("dropped left it bound: %v", err)
	}
	// an entry the bus holds no objects for is waited for, not bound
	b2 := NewBinding("mesh-broker", "m", func(string, any) (json.RawMessage, error) {
		return json.RawMessage(`{"state":"waiting","why":"not made"}`), nil
	}, nil, "x")
	b2.Ask("x")
	if _, err := b2.Names("x"); err == nil || !strings.Contains(err.Error(), "not made") {
		t.Fatalf("an entry with no binding: %v", err)
	}
}

func toJSON(v any) string { d, _ := json.Marshal(v); return string(d) }