start working on struct validation for gtsmodel

internal/gtsmodel/validate.go

@@ -0,0 +1,78 @@
+/*
+   GoToSocial
+   Copyright (C) 2021 GoToSocial Authors admin@gotosocial.org
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Affero General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Affero General Public License for more details.
+
+   You should have received a copy of the GNU Affero General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package gtsmodel
+
+import (
+	"reflect"
+
+	"github.com/go-playground/validator/v10"
+	"github.com/superseriousbusiness/gotosocial/internal/util"
+)
+
+var v *validator.Validate
+
+const (
+	PointerValidationPanic = "validate function was passed pointer"
+	InvalidValidationPanic = "validate function was passed invalid item"
+)
+
+var ulidValidator = func(fl validator.FieldLevel) bool {
+	value, kind, _ := fl.ExtractType(fl.Field())
+
+	if kind != reflect.String {
+		return false
+	}
+
+	// we want either an empty string, or a proper ULID, nothing else
+	// if the string is empty, the `required` tag will take care of it so we don't need to worry about it here
+	s := value.String()
+	if len(s) == 0 {
+		return true
+	}
+	return util.ValidateULID(s)
+}
+
+func init() {
+	v = validator.New()
+	v.RegisterValidation("ulid", ulidValidator)
+}
+
+func ValidateStruct(s interface{}) error {
+	switch reflect.ValueOf(s).Kind() {
+	case reflect.Invalid:
+		panic(InvalidValidationPanic)
+	case reflect.Ptr:
+		panic(PointerValidationPanic)
+	}
+
+	err := v.Struct(s)
+	return processValidationError(err)
+}
+
+func processValidationError(err error) error {
+	if err == nil {
+		return nil
+	}
+
+	if ive, ok := err.(*validator.InvalidValidationError); ok {
+		panic(ive)
+	}
+
+	return err.(validator.ValidationErrors)
+}