Prevent deletion of last admin account

api/user.go

@@ -17,6 +17,7 @@ type UserDatabase interface {
 	GetUserByID(ID uint) (*model.User, error)
 	GetUserByName(name string) (*model.User, error)
 	GetApplications(user *model.User) ([]model.Application, error)
+	AdminUserCount() (int64, error)
 }
 
 // The UserDispatcher interface for relaying notifications.
@@ -70,6 +71,16 @@ func (h *UserHandler) DeleteUser(ctx *gin.Context) {
 		return
 	}
 
+	if user.IsAdmin {
+		if count, err := h.DB.AdminUserCount(); err != nil {
+			ctx.AbortWithError(http.StatusInternalServerError, err)
+			return
+		} else if count == 1 {
+			ctx.AbortWithError(http.StatusBadRequest, errors.New("cannot delete last admin user"))
+			return
+		}
+	}
+
 	log.Printf("Deleting user %s.\n", user.Name)
 
 	applications, err := h.DB.GetApplications(user)

database/user.go

@@ -56,3 +56,12 @@ func (d *Database) GetApplications(user *model.User) ([]model.Application, error
 
 	return applications, err
 }
+
+// AdminUserCount returns the number of admins or an error.
+func (d *Database) AdminUserCount() (int64, error) {
+	var users []model.User
+
+	query := d.gormdb.Where("is_admin = ?", true).Find(&users)
+
+	return query.RowsAffected, query.Error
+}