Name the pulls buckets of the seat's claimants on the check, so the build agent reads them (issue 1212)

internal/link/pull_buckets_test.go

@@ -0,0 +1,113 @@
+package link
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"reflect"
+	"strings"
+	"testing"
+
+	"github.com/nats-io/nats.go/jetstream"
+
+	"github.com/novox/mesh-controller/internal/broker"
+)
+
+// The build agent reads and watches the pull requests' keys in the buckets the check request names (novox/hq ADR 0437
+// §3, issue 1212): the controller knows the seat's claimants, the build agent holds no catalogue.
+
+// 1212/AC4: a request naming no bucket reads mesh-delivery's, as before; the field is optional on the wire.
+func TestARequestNamingNoPullsBucketUsesMeshDeliverys(t *testing.T) {
+	if got := PullBucketsOf(&CheckRequest{}); !reflect.DeepEqual(got, []string{broker.PullsBucket}) {
+		t.Errorf("buckets %v", got)
+	}
+	if got := PullBucketsOf(nil); !reflect.DeepEqual(got, []string{broker.PullsBucket}) {
+		t.Errorf("buckets of no check %v", got)
+	}
+	named := &CheckRequest{Pulls: []string{"mesh-delivery-gate_pulls"}}
+	if got := PullBucketsOf(named); !reflect.DeepEqual(got, named.Pulls) {
+		t.Errorf("buckets %v", got)
+	}
+	raw := mustJSON(t, CheckRequest{Owner: "o"})
+	if contains(string(raw), "pulls") {
+		t.Errorf("an empty field is written: %s", raw)
+	}
+}
+
+// opened is a set of buckets by name, each holding keys; a bucket not in it does not exist.
+func opened(buckets map[string]map[string]string, opens *[]string) func(context.Context, string) (func(context.Context, string) ([]byte, error), error) {
+	return func(_ context.Context, bucket string) (func(context.Context, string) ([]byte, error), error) {
+		*opens = append(*opens, bucket)
+		keys, ok := buckets[bucket]
+		if !ok {
+			return nil, jetstream.ErrBucketNotFound
+		}
+		return func(_ context.Context, key string) ([]byte, error) {
+			v, ok := keys[key]
+			if !ok {
+				return nil, jetstream.ErrKeyNotFound
+			}
+			return []byte(v), nil
+		}, nil
+	}
+}
+
+// 1212/AC3: the buckets are read in turn, the first holding the key answers, a missing bucket is passed over, and
+// none holding it is no key.
+func TestThePullKeyIsReadFromTheNamedBucketsInTurn(t *testing.T) {
+	key := PullKeyOf("novox", "a", 7)
+	both := map[string]map[string]string{
+		"mesh-delivery_pulls":      {key: `{"head":"old"}`},
+		"mesh-delivery-gate_pulls": {key: `{"head":"new"}`},
+	}
+	var opens []string
+	got, found, err := readPullKeyIn(t.Context(), []string{"mesh-delivery-gate_pulls", "mesh-delivery_pulls"}, opened(both, &opens), "novox", "a", 7)
+	if err != nil || !found || got.Head != "new" || len(opens) != 1 {
+		t.Errorf("first holding answers: %+v %v %v, opened %v", got, found, err, opens)
+	}
+	opens = nil
+	only := map[string]map[string]string{"mesh-delivery_pulls": {key: `{"head":"old"}`}, "mesh-delivery-gate_pulls": {}}
+	got, found, err = readPullKeyIn(t.Context(), []string{"mesh-delivery-gate_pulls", "mesh-delivery_pulls"}, opened(only, &opens), "novox", "a", 7)
+	if err != nil || !found || got.Head != "old" || len(opens) != 2 {
+		t.Errorf("a bucket without the key is passed over: %+v %v %v, opened %v", got, found, err, opens)
+	}
+	opens = nil
+	got, found, err = readPullKeyIn(t.Context(), []string{"gone_pulls", "mesh-delivery_pulls"}, opened(only, &opens), "novox", "a", 7)
+	if err != nil || !found || got.Head != "old" {
+		t.Errorf("a missing bucket is passed over: %+v %v %v", got, found, err)
+	}
+	_, found, err = readPullKeyIn(t.Context(), []string{"gone_pulls", "mesh-delivery-gate_pulls"}, opened(only, &opens), "novox", "a", 8)
+	if err != nil || found {
+		t.Errorf("none holding it: found %v, %v", found, err)
+	}
+	boom := errors.New("bus away")
+	_, _, err = readPullKeyIn(t.Context(), []string{"x"}, func(context.Context, string) (func(context.Context, string) ([]byte, error), error) {
+		return nil, boom
+	}, "novox", "a", 7)
+	if !errors.Is(err, boom) {
+		t.Errorf("a real failure is an error: %v", err)
+	}
+	// The watch takes the first named bucket that exists.
+	opens = nil
+	bucket, err := firstBucketThatExists(t.Context(), []string{"gone_pulls", "mesh-delivery-gate_pulls", "mesh-delivery_pulls"}, func(_ context.Context, b string) error {
+		opens = append(opens, b)
+		if b == "gone_pulls" {
+			return jetstream.ErrBucketNotFound
+		}
+		return nil
+	})
+	if err != nil || bucket != "mesh-delivery-gate_pulls" || len(opens) != 2 {
+		t.Errorf("watch bucket %q %v, tried %v", bucket, err, opens)
+	}
+}
+
+func mustJSON(t *testing.T, v any) string {
+	t.Helper()
+	raw, err := json.Marshal(v)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return string(raw)
+}
+
+func contains(s, sub string) bool { return strings.Contains(s, sub) }