Don't delete a user if its the last one

models/error.go

@@ -94,6 +94,19 @@ func (err ErrCouldNotGetUserID) Error() string {
 	return fmt.Sprintf("could not get user ID")
 }
 
+// ErrCannotDeleteLastUser represents a "ErrCannotDeleteLastUser" kind of error.
+type ErrCannotDeleteLastUser struct{}
+
+// IsErrCannotDeleteLastUser checks if an error is a ErrCannotDeleteLastUser.
+func IsErrCannotDeleteLastUser(err error) bool {
+	_, ok := err.(ErrCannotDeleteLastUser)
+	return ok
+}
+
+func (err ErrCannotDeleteLastUser) Error() string {
+	return fmt.Sprintf("cannot delete last user")
+}
+
 // ===================
 // Empty things errors
 // ===================

models/user_delete.go

@@ -1,5 +1,7 @@
 package models
 
+import "fmt"
+
 // DeleteUserByID deletes a user by its ID
 func DeleteUserByID(id int64) error {
 	// Check if the id is 0
@@ -7,8 +9,18 @@ func DeleteUserByID(id int64) error {
 		return ErrIDCannotBeZero{}
 	}
 
+	// Check if there is > 1 user
+	total, err := x.Count(User{})
+	if err != nil {
+		return err
+	}
+
+	if total < 2 {
+		return ErrCannotDeleteLastUser{}
+	}
+
 	// Delete the user
-	_, err := x.Id(id).Delete(&User{})
+	_, err = x.Id(id).Delete(&User{})
 
 	if err != nil {
 		return err

routes/api/v1/user_delete.go

@@ -42,6 +42,11 @@ func UserDelete(c echo.Context) error {
 		if models.IsErrIDCannotBeZero(err) {
 			return c.JSON(http.StatusBadRequest, models.Message{"Id cannot be 0"})
 		}
+
+		if models.IsErrCannotDeleteLastUser(err) {
+			return c.JSON(http.StatusBadRequest, models.Message{"Cannot delete last user."})
+		}
+
 		return c.JSON(http.StatusInternalServerError, models.Message{"Could not delete user."})
 	}