validation.go

// Copyright 2021 Igor Lazarev. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.

// Package validation provides tools for data validation.
// It is designed to create complex validation rules with abilities to hook into the validation process.
package validation

import (
	"context"
)

const DefaultGroup = "default"

// Validatable is interface for creating validatable types on the client side.
// By using it you can build complex validation rules on a set of objects used in other objects.
//
// Example
//
//	type Book struct {
//	    Title    string
//	    Author   string
//	    Keywords []string
//	}
//
//	func (b Book) Validate(ctx context.Context, validator *validation.Validator) error {
//	    return validator.Validate(
//	        ctx,
//	        validation.StringProperty("title", &b.Title, it.IsNotBlank()),
//	        validation.StringProperty("author", &b.Author, it.IsNotBlank()),
//	        validation.CountableProperty("keywords", len(b.Keywords), it.HasCountBetween(1, 10)),
//	        validation.EachStringProperty("keywords", b.Keywords, it.IsNotBlank()),
//	    )
//	}
type Validatable interface {
	Validate(ctx context.Context, validator *Validator) error
}

// ValidatableFunc is a functional adapter for the [Validatable] interface.
type ValidatableFunc func(ctx context.Context, validator *Validator) error

// Validate runs validation process on function.
func (f ValidatableFunc) Validate(ctx context.Context, validator *Validator) error {
	return f(ctx, validator)
}

// Filter is used for processing the list of errors to return a single [ViolationList].
// If there is at least one non-violation error it will return it instead.
func Filter(violations ...error) error {
	list := &ViolationList{}

	for _, violation := range violations {
		err := list.AppendFromError(violation)
		if err != nil {
			return err
		}
	}

	return list.AsError()
}