niki/vendor/github.com/go-ozzo/ozzo-validation/struct.go

// Copyright 2016 Qiang Xue. 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

import (
	"errors"
	"fmt"
	"reflect"
	"strings"
)

var (

	// ErrStructPointer is the error that a struct being validated is not specified as a pointer.

	ErrStructPointer = errors.New("only a pointer to a struct can be validated")
)

type (

	// ErrFieldPointer is the error that a field is not specified as a pointer.

	ErrFieldPointer int

	// ErrFieldNotFound is the error that a field cannot be found in the struct.

	ErrFieldNotFound int

	// FieldRules represents a rule set associated with a struct field.

	FieldRules struct {
		fieldPtr interface{}

		rules []Rule
	}
)

// Error returns the error string of ErrFieldPointer.

func (e ErrFieldPointer) Error() string {

	return fmt.Sprintf("field #%v must be specified as a pointer", int(e))

}

// Error returns the error string of ErrFieldNotFound.

func (e ErrFieldNotFound) Error() string {

	return fmt.Sprintf("field #%v cannot be found in the struct", int(e))

}

// ValidateStruct validates a struct by checking the specified struct fields against the corresponding validation rules.

// Note that the struct being validated must be specified as a pointer to it. If the pointer is nil, it is considered valid.

// Use Field() to specify struct fields that need to be validated. Each Field() call specifies a single field which

// should be specified as a pointer to the field. A field can be associated with multiple rules.

// For example,

//

//	value := struct {

//	    Name  string

//	    Value string

//	}{"name", "demo"}

//	err := validation.ValidateStruct(&value,

//	     validation.Field(&a.Name, validation.Required),

//	     validation.Field(&a.Value, validation.Required, validation.Length(5, 10)),

//	)

//	fmt.Println(err)

//	// Value: the length must be between 5 and 10.

//

// An error will be returned if validation fails.

func ValidateStruct(structPtr interface{}, fields ...*FieldRules) error {

	value := reflect.ValueOf(structPtr)

	if value.Kind() != reflect.Ptr || !value.IsNil() && value.Elem().Kind() != reflect.Struct {

		// must be a pointer to a struct

		return NewInternalError(ErrStructPointer)

	}

	if value.IsNil() {

		// treat a nil struct pointer as valid

		return nil

	}

	value = value.Elem()

	errs := Errors{}

	for i, fr := range fields {

		fv := reflect.ValueOf(fr.fieldPtr)

		if fv.Kind() != reflect.Ptr {

			return NewInternalError(ErrFieldPointer(i))

		}

		ft := findStructField(value, fv)

		if ft == nil {

			return NewInternalError(ErrFieldNotFound(i))

		}

		if err := Validate(fv.Elem().Interface(), fr.rules...); err != nil {

			if ie, ok := err.(InternalError); ok && ie.InternalError() != nil {

				return err

			}

			if ft.Anonymous {

				// merge errors from anonymous struct field

				if es, ok := err.(Errors); ok {

					for name, value := range es {

						errs[name] = value

					}

					continue

				}

			}

			errs[getErrorFieldName(ft)] = err

		}

	}

	if len(errs) > 0 {

		return errs

	}

	return nil

}

// Field specifies a struct field and the corresponding validation rules.

// The struct field must be specified as a pointer to it.

func Field(fieldPtr interface{}, rules ...Rule) *FieldRules {

	return &FieldRules{

		fieldPtr: fieldPtr,

		rules: rules,
	}

}

// findStructField looks for a field in the given struct.

// The field being looked for should be a pointer to the actual struct field.

// If found, the field info will be returned. Otherwise, nil will be returned.

func findStructField(structValue reflect.Value, fieldValue reflect.Value) *reflect.StructField {

	ptr := fieldValue.Pointer()

	for i := structValue.NumField() - 1; i >= 0; i-- {

		sf := structValue.Type().Field(i)

		if ptr == structValue.Field(i).UnsafeAddr() {

			// do additional type comparison because it's possible that the address of

			// an embedded struct is the same as the first field of the embedded struct

			if sf.Type == fieldValue.Elem().Type() {

				return &sf

			}

		}

		if sf.Anonymous {

			// delve into anonymous struct to look for the field

			fi := structValue.Field(i)

			if sf.Type.Kind() == reflect.Ptr {

				fi = fi.Elem()

			}

			if fi.Kind() == reflect.Struct {

				if f := findStructField(fi, fieldValue); f != nil {

					return f

				}

			}

		}

	}

	return nil

}

// getErrorFieldName returns the name that should be used to represent the validation error of a struct field.

func getErrorFieldName(f *reflect.StructField) string {

	if tag := f.Tag.Get(ErrorTag); tag != "" {

		if cps := strings.SplitN(tag, ",", 2); cps[0] != "" {

			return cps[0]

		}

	}

	return f.Name

}