refactor: unit testable units and cleaner dep injection

go/internal/livestore/membershippublisher.go

@@ -0,0 +1,42 @@
+package livestore
+
+import (
+	"context"
+
+	"cloud.google.com/go/firestore"
+)
+
+//go:generate mockgen -source ./membershippublisher.go -destination ./mocks/membershippublisher.go
+
+// MembershipPublisher publishes network membership changes to the live store
+// (Firestore) that clients subscribe to. Postgres remains the source of truth;
+// the membership reconciler heals any drift, so callers may log and ignore
+// publish failures.
+type MembershipPublisher interface {
+	Add(ctx context.Context, humanId, networkID string) error
+	Remove(ctx context.Context, humanId, networkID string) error
+}
+
+func NewMembershipPublisher(fs *firestore.Client) MembershipPublisher {
+	return &firestoreMembershipPublisher{fs: fs}
+}
+
+type firestoreMembershipPublisher struct {
+	fs *firestore.Client
+}
+
+func (p *firestoreMembershipPublisher) Add(ctx context.Context, humanId, networkID string) error {
+	_, err := p.fs.Collection("humans").Doc(humanId).Set(ctx, map[string]any{
+		"networks":   firestore.ArrayUnion(networkID),
+		"updated_at": firestore.ServerTimestamp,
+	}, firestore.MergeAll)
+	return err
+}
+
+func (p *firestoreMembershipPublisher) Remove(ctx context.Context, humanId, networkID string) error {
+	_, err := p.fs.Collection("humans").Doc(humanId).Set(ctx, map[string]any{
+		"networks":   firestore.ArrayRemove(networkID),
+		"updated_at": firestore.ServerTimestamp,
+	}, firestore.MergeAll)
+	return err
+}