refactor(shared): rename Org to Instance

shared/provision/instance.go

@@ -0,0 +1,74 @@
+package provision
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/mrhid6/vantage/shared/models"
+	"go.mongodb.org/mongo-driver/v2/bson"
+	"go.mongodb.org/mongo-driver/v2/mongo"
+)
+
+// ErrNameRejected wraps every reason a name cannot become an instance.
+var ErrNameRejected = errors.New("organisation name rejected")
+
+const maxSlugAttempts = 50
+
+// CreateInstance inserts an instance under the first free slug derived from name.
+//
+// The count-then-insert loop is racy on its own. It is safe only because
+// instances.slug carries a unique index: a lost race surfaces as a duplicate-key
+// error, which we treat as "that slug is taken" and retry. Do not remove the
+// duplicate-key branch, and do not remove the index.
+func CreateInstance(ctx context.Context, db *mongo.Database, name string) (*models.Instance, error) {
+	base, err := BaseSlug(name)
+	if err != nil {
+		return nil, fmt.Errorf("%w: %s", ErrNameRejected, err.Error())
+	}
+
+	for attempt := 1; attempt <= maxSlugAttempts; attempt++ {
+		slug := NextSlug(base, attempt)
+
+		n, err := db.Collection("instances").CountDocuments(ctx, bson.M{"slug": slug})
+		if err != nil {
+			return nil, err
+		}
+		if n > 0 {
+			continue
+		}
+
+		inst := models.Instance{
+			InstanceID: uuid.NewString(),
+			Name:       name,
+			Slug:       slug,
+			CreatedAt:  time.Now().UTC(),
+		}
+		if _, err := db.Collection("instances").InsertOne(ctx, inst); err != nil {
+			if mongo.IsDuplicateKeyError(err) {
+				continue // lost the race; try the next slug
+			}
+			return nil, err
+		}
+		return &inst, nil
+	}
+	return nil, fmt.Errorf("%w: could not find a free slug for %q", ErrNameRejected, name)
+}
+
+// RollbackInstance deletes an instance that has no users.
+//
+// It refuses an instance that has users. Rollback exists to clean up a
+// half-finished signup, and an instance with users is not half-finished.
+func RollbackInstance(ctx context.Context, db *mongo.Database, instanceID string) error {
+	n, err := db.Collection("users").CountDocuments(ctx, bson.M{"instance_id": instanceID})
+	if err != nil {
+		return err
+	}
+	if n > 0 {
+		return fmt.Errorf("refusing to roll back instance %s: it has %d user(s)", instanceID, n)
+	}
+	_, err = db.Collection("instances").DeleteOne(ctx, bson.M{"instance_id": instanceID})
+	return err
+}