validate.go

// Copyright 2020 Daniel G. Taylor
//
// Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
package openapi

import (
	"errors"
	"fmt"
	"math"
	"net"
	"net/mail"
	"net/url"
	"reflect"
	"regexp"
	"strconv"
	"strings"
	"time"
	"unicode/utf8"
	"unsafe"
)

// ValidateMode describes the direction of validation (server -> client or
// client -> server). It impacts things like how read-only or write-only fields
// are handled.
type ValidateMode int

const (
	// ModeReadFromServer is a read mode (response output) that may ignore or
	// reject write-only fields that are non-zero, as these write-only fields
	// are meant to be sent by the client.
	ModeReadFromServer ValidateMode = iota

	// ModeWriteToServer is a write mode (request input) that may ignore or
	// reject read-only fields that are non-zero, as these are owned by the
	// server and the client should not try to modify them.
	ModeWriteToServer
)

var rxHostname = regexp.MustCompile(`^([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\-]{0,61}[a-zA-Z0-9])(\.([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\-]{0,61}[a-zA-Z0-9]))*$`)
var rxURITemplate = regexp.MustCompile("^([^{]*({[^}]*})?)*$")
var rxJSONPointer = regexp.MustCompile("^(?:/(?:[^~/]|~0|~1)*)*$")
var rxRelJSONPointer = regexp.MustCompile("^(?:0|[1-9][0-9]*)(?:#|(?:/(?:[^~/]|~0|~1)*)*)$")
var rxBase64 = regexp.MustCompile(`^[a-zA-Z0-9+/_-]+=*$`)

func mapTo[A, B any](s []A, f func(A) B) []B {
	r := make([]B, len(s))
	for i, v := range s {
		r[i] = f(v)
	}
	return r
}

// PathBuffer is a low-allocation helper for building a path string like
// `foo.bar.baz`. It is not goroutine-safe. Combined with `sync.Pool` it can
// result in zero allocations, and is used for validation. It is significantly
// better than `strings.Builder` and `bytes.Buffer` for this use case.
//
// Path buffers can be converted to strings for use in responses or printing
// using either the `pb.String()` or `pb.With("field")` methods.
//
//	pb := NewPathBuffer([]byte{}, 0)
//	pb.Push("foo")  // foo
//	pb.PushIndex(1) // foo[1]
//	pb.Push("bar")  // foo[1].bar
//	pb.Pop()        // foo[1]
//	pb.Pop()        // foo
type PathBuffer struct {
	buf []byte
	off int
}

// Push an entry onto the path, adding a `.` separator as needed.
//
//	pb.Push("foo") // foo
//	pb.Push("bar") // foo.bar
func (b *PathBuffer) Push(s string) {
	if b.off > 0 {
		b.buf = append(b.buf, '.')
		b.off++
	}
	b.buf = append(b.buf, s...)
	b.off += len(s)
}

// PushIndex pushes an entry onto the path surrounded by `[` and `]`.
//
//	pb.Push("foo")  // foo
//	pb.PushIndex(1) // foo[1]
func (b *PathBuffer) PushIndex(i int) {
	l := len(b.buf)
	b.buf = append(b.buf, '[')
	b.buf = append(b.buf, strconv.Itoa(i)...)
	b.buf = append(b.buf, ']')
	b.off += len(b.buf) - l
}

// Pop the latest entry off the path.
//
//	pb.Push("foo")  // foo
//	pb.PushIndex(1) // foo[1]
//	pb.Push("bar")  // foo[1].bar
//	pb.Pop()        // foo[1]
//	pb.Pop()        // foo
func (b *PathBuffer) Pop() {
	for b.off > 0 {
		b.off--
		if b.buf[b.off] == '.' || b.buf[b.off] == '[' {
			break
		}
	}
	b.buf = b.buf[:b.off]
}

// With is shorthand for push, convert to string, and pop. This is useful
// when you want the location of a field given a path buffer as a prefix.
//
//	pb.Push("foo")
//	pb.With("bar") // returns foo.bar
func (b *PathBuffer) With(s string) string {
	b.Push(s)
	tmp := b.String()
	b.Pop()
	return tmp
}

// Len returns the length of the current path.
func (b *PathBuffer) Len() int {
	return b.off
}

// Bytes returns the underlying slice of bytes of the path.
func (b *PathBuffer) Bytes() []byte {
	return b.buf[:b.off]
}

// String converts the path buffer to a string.
func (b *PathBuffer) String() string {
	return string(b.buf[:b.off])
}

// Reset the path buffer to empty, keeping and reusing the underlying bytes.
func (b *PathBuffer) Reset() {
	b.buf = b.buf[:0]
	b.off = 0
}

// NewPathBuffer creates a new path buffer given an existing byte slice.
// Tip: using `sync.Pool` can significantly reduce buffer allocations.
//
//	pb := NewPathBuffer([]byte{}, 0)
//	pb.Push("foo")
func NewPathBuffer(buf []byte, offset int) *PathBuffer {
	return &PathBuffer{buf: buf, off: offset}
}

// ValidateResult tracks validation errors. It is safe to use for multiple
// validations as long as `Reset()` is called between uses.
type ValidateResult struct {
	Errors []error
}

// Add an error to the validation result at the given path and with the
// given value.
func (r *ValidateResult) Add(path *PathBuffer, v any, msg string) {
	r.Errors = append(r.Errors, &ErrorDetail{
		Message:  msg,
		Location: path.String(),
		Value:    v,
	})
}

// Addf adds an error to the validation result at the given path and with
// the given value, allowing for fmt.Printf-style formatting.
func (r *ValidateResult) Addf(path *PathBuffer, v any, format string, args ...any) {
	r.Errors = append(r.Errors, &ErrorDetail{
		Message:  fmt.Sprintf(format, args...),
		Location: path.String(),
		Value:    v,
	})
}

// Reset the validation error so it can be used again.
func (r *ValidateResult) Reset() {
	r.Errors = r.Errors[:0]
}

func validateFormat(path *PathBuffer, str string, s *Schema, res *ValidateResult) {
	switch s.Format {
	case "date-time":
		found := false
		for _, format := range []string{time.RFC3339, time.RFC3339Nano} {
			if _, err := time.Parse(format, str); err == nil {
				found = true
				break
			}
		}
		if !found {
			res.Add(path, str, "expected string to be RFC 3339 date-time")
		}
	case "date-time-http":
		if _, err := time.Parse(time.RFC1123, str); err != nil {
			res.Add(path, str, "expected string to be RFC 1123 date-time")
		}
	case "date":
		if _, err := time.Parse("2006-01-02", str); err != nil {
			res.Add(path, str, "expected string to be RFC 3339 date")
		}
	case "time":
		if _, err := time.Parse("15:04:05", str); err != nil {
			if _, err := time.Parse("15:04:05Z07:00", str); err != nil {
				res.Add(path, str, "expected string to be RFC 3339 time")
			}
		}
		// TODO: duration
	case "email", "idn-email":
		if _, err := mail.ParseAddress(str); err != nil {
			res.Addf(path, str, "expected string to be RFC 5322 email: %v", err)
		}
	case "hostname":
		if !(rxHostname.MatchString(str) && len(str) < 256) {
			res.Add(path, str, "expected string to be RFC 5890 hostname")
		}
	// TODO: proper idn-hostname support... need to figure out how.
	case "ipv4":
		if ip := net.ParseIP(str); ip == nil || ip.To4() == nil {
			res.Add(path, str, "expected string to be RFC 2673 ipv4")
		}
	case "ipv6":
		if ip := net.ParseIP(str); ip == nil || ip.To16() == nil {
			res.Add(path, str, "expected string to be RFC 2373 ipv6")
		}
	case "uri", "uri-reference", "iri", "iri-reference":
		if _, err := url.Parse(str); err != nil {
			res.Addf(path, str, "expected string to be RFC 3986 uri: %v", err)
		}
		// TODO: check if it's actually a reference?
	case "uuid":
		if err := validateUUID(str); err != nil {
			res.Addf(path, str, "expected string to be RFC 4122 uuid: %v", err)
		}
	case "uri-template":
		u, err := url.Parse(str)
		if err != nil {
			res.Addf(path, str, "expected string to be RFC 3986 uri: %v", err)
			return
		}
		if !rxURITemplate.MatchString(u.Path) {
			res.Add(path, str, "expected string to be RFC 6570 uri-template")
		}
	case "json-pointer":
		if !rxJSONPointer.MatchString(str) {
			res.Add(path, str, "expected string to be RFC 6901 json-pointer")
		}
	case "relative-json-pointer":
		if !rxRelJSONPointer.MatchString(str) {
			res.Add(path, str, "expected string to be RFC 6901 relative-json-pointer")
		}
	case "regex":
		if _, err := regexp.Compile(str); err != nil {
			res.Addf(path, str, "expected string to be regex: %v", err)
		}
	}
}

func validateOneOf(r Registry, s *Schema, path *PathBuffer, mode ValidateMode, v any, res *ValidateResult) {
	found := false
	subRes := &ValidateResult{}
	for _, sub := range s.OneOf {
		Validate(r, sub, path, mode, v, subRes)
		if len(subRes.Errors) == 0 {
			if found {
				res.Add(path, v, "expected value to match exactly one schema but matched multiple")
			}
			found = true
		}
		subRes.Reset()
	}
	if !found {
		res.Add(path, v, "expected value to match exactly one schema but matched none")
	}
}

func validateAnyOf(r Registry, s *Schema, path *PathBuffer, mode ValidateMode, v any, res *ValidateResult) {
	matches := 0
	subRes := &ValidateResult{}
	for _, sub := range s.AnyOf {
		Validate(r, sub, path, mode, v, subRes)
		if len(subRes.Errors) == 0 {
			matches++
		}
		subRes.Reset()
	}

	if matches == 0 {
		res.Add(path, v, "expected value to match at least one schema but matched none")
	}
}

// Validate an input value against a schema, collecting errors in the validation
// result object. If successful, `res.Errors` will be empty. It is suggested
// to use a `sync.Pool` to reuse the PathBuffer and ValidateResult objects,
// making sure to call `Reset()` on them before returning them to the pool.
//
//	registry := openapi.NewMapRegistry("#/prefix", openapi.DefaultSchemaNamer)
//	schema := openapi.SchemaFromType(registry, reflect.TypeOf(MyType{}))
//	pb := openapi.NewPathBuffer([]byte(""), 0)
//	res := &openapi.ValidateResult{}
//
//	var value any
//	json.Unmarshal([]byte(`{"foo": "bar"}`), &v)
//	openapi.Validate(registry, schema, pb, openapi.ModeWriteToServer, value, res)
//	for _, err := range res.Errors {
//		fmt.Println(err.Error())
//	}
func Validate(r Registry, s *Schema, path *PathBuffer, mode ValidateMode, v any, res *ValidateResult) {
	// Get the actual schema if this is a reference.
	for s.Ref != "" {
		s = r.SchemaFromRef(s.Ref)
	}

	if s.OneOf != nil {
		validateOneOf(r, s, path, mode, v, res)
	}

	if s.AnyOf != nil {
		validateAnyOf(r, s, path, mode, v, res)
	}

	if s.AllOf != nil {
		for _, sub := range s.AllOf {
			Validate(r, sub, path, mode, v, res)
		}
	}

	if s.Not != nil {
		subRes := &ValidateResult{}
		Validate(r, s.Not, path, mode, v, subRes)
		if len(subRes.Errors) == 0 {
			res.Add(path, v, "expected value to not match schema")
		}
	}

	if s.Nullable && v == nil {
		return
	}

	switch s.Type {
	case TypeBoolean:
		if _, ok := v.(bool); !ok {
			res.Add(path, v, "expected boolean")
			return
		}
	case TypeNumber, TypeInteger:
		var num float64

		switch v := v.(type) {
		case float64:
			num = v
		case float32:
			num = float64(v)
		case int:
			num = float64(v)
		case int8:
			num = float64(v)
		case int16:
			num = float64(v)
		case int32:
			num = float64(v)
		case int64:
			num = float64(v)
		case uint:
			num = float64(v)
		case uint8:
			num = float64(v)
		case uint16:
			num = float64(v)
		case uint32:
			num = float64(v)
		case uint64:
			num = float64(v)
		default:
			res.Add(path, v, "expected number")
			return
		}

		if s.Minimum != nil {
			if num < *s.Minimum {
				res.Addf(path, v, s.msgMinimum)
			}
		}
		if s.ExclusiveMinimum != nil {
			if num <= *s.ExclusiveMinimum {
				res.Addf(path, v, s.msgExclusiveMinimum)
			}
		}
		if s.Maximum != nil {
			if num > *s.Maximum {
				res.Add(path, v, s.msgMaximum)
			}
		}
		if s.ExclusiveMaximum != nil {
			if num >= *s.ExclusiveMaximum {
				res.Addf(path, v, s.msgExclusiveMaximum)
			}
		}
		if s.MultipleOf != nil {
			if math.Mod(num, *s.MultipleOf) != 0 {
				res.Addf(path, v, s.msgMultipleOf)
			}
		}
	case TypeString:
		str, ok := v.(string)
		if !ok {
			if b, ok := v.([]byte); ok {
				str = *(*string)(unsafe.Pointer(&b))
			} else {
				res.Add(path, v, "expected string")
				return
			}
		}

		if s.MinLength != nil {
			if utf8.RuneCountInString(str) < *s.MinLength {
				res.Addf(path, str, s.msgMinLength)
			}
		}
		if s.MaxLength != nil {
			if utf8.RuneCountInString(str) > *s.MaxLength {
				res.Add(path, str, s.msgMaxLength)
			}
		}
		if s.patternRe != nil {
			if !s.patternRe.MatchString(str) {
				res.Add(path, v, s.msgPattern)
			}
		}

		if s.Format != "" {
			validateFormat(path, str, s, res)
		}

		if s.ContentEncoding == "base64" {
			if !rxBase64.MatchString(str) {
				res.Add(path, str, "expected string to be base64 encoded")
			}
		}
	case TypeArray:
		switch arr := v.(type) {
		case []any:
			handleArray(r, s, path, mode, res, arr)
		// Special cases for params which are lists.
		case []string:
			handleArray(r, s, path, mode, res, arr)
		case []int:
			handleArray(r, s, path, mode, res, arr)
		case []int8:
			handleArray(r, s, path, mode, res, arr)
		case []int16:
			handleArray(r, s, path, mode, res, arr)
		case []int32:
			handleArray(r, s, path, mode, res, arr)
		case []int64:
			handleArray(r, s, path, mode, res, arr)
		case []uint:
			handleArray(r, s, path, mode, res, arr)
		case []uint16:
			handleArray(r, s, path, mode, res, arr)
		case []uint32:
			handleArray(r, s, path, mode, res, arr)
		case []uint64:
			handleArray(r, s, path, mode, res, arr)
		case []float32:
			handleArray(r, s, path, mode, res, arr)
		case []float64:
			handleArray(r, s, path, mode, res, arr)
		default:
			res.Add(path, v, "expected array")
			return
		}
	case TypeObject:
		if vv, ok := v.(map[string]any); ok {
			handleMapString(r, s, path, mode, vv, res)
		} else if vv, ok := v.(map[any]any); ok {
			handleMapAny(r, s, path, mode, vv, res)
		} else {
			res.Add(path, v, "expected object")
			return
		}
	}

	if len(s.Enum) > 0 {
		found := false
		for _, e := range s.Enum {
			if e == v {
				found = true
				break
			}
		}
		if !found {
			res.Add(path, v, s.msgEnum)
		}
	}
}

func handleArray[T any](r Registry, s *Schema, path *PathBuffer, mode ValidateMode, res *ValidateResult, arr []T) {
	if s.MinItems != nil {
		if len(arr) < *s.MinItems {
			res.Addf(path, arr, s.msgMinItems)
		}
	}
	if s.MaxItems != nil {
		if len(arr) > *s.MaxItems {
			res.Addf(path, arr, s.msgMaxItems)
		}
	}

	if s.UniqueItems {
		seen := make(map[any]struct{}, len(arr))
		for _, item := range arr {
			if _, ok := seen[item]; ok {
				res.Add(path, arr, "expected array items to be unique")
			}
			seen[item] = struct{}{}
		}
	}

	for i, item := range arr {
		path.PushIndex(i)
		Validate(r, s.Items, path, mode, item, res)
		path.Pop()
	}
}

func handleMapString(r Registry, s *Schema, path *PathBuffer, mode ValidateMode, m map[string]any, res *ValidateResult) {
	if s.MinProperties != nil {
		if len(m) < *s.MinProperties {
			res.Add(path, m, s.msgMinProperties)
		}
	}
	if s.MaxProperties != nil {
		if len(m) > *s.MaxProperties {
			res.Add(path, m, s.msgMaxProperties)
		}
	}

	for _, k := range s.propertyNames {
		v := s.Properties[k]

		// Schemas are generated such that the read/write-only properties are set
		// alongside the `$ref`, if it is present (i.e. for objects). If not,
		// then the read/write-only properties are set directly on the schema and
		// the `for` loop never runs.
		readOnly := v.ReadOnly
		writeOnly := v.WriteOnly
		for v.Ref != "" {
			v = r.SchemaFromRef(v.Ref)
		}

		// We should be permissive by default to enable easy round-trips for the
		// client without needing to remove read-only values.
		// TODO: should we make this configurable?

		// Be stricter for responses, enabling validation of the server if desired.
		if mode == ModeReadFromServer && writeOnly && m[k] != nil && !reflect.ValueOf(m[k]).IsZero() {
			res.Add(path, m[k], "write only property is non-zero")
			continue
		}

		if _, ok := m[k]; !ok {
			if !s.requiredMap[k] {
				continue
			}
			if (mode == ModeWriteToServer && readOnly) ||
				(mode == ModeReadFromServer && writeOnly) {
				// These are not required for the current mode.
				continue
			}
			res.Add(path, m, s.msgRequired[k])
			continue
		}

		if m[k] == nil && (!s.requiredMap[k] || s.Nullable) {
			// This is a non-required field which is null, or a nullable field set
			// to null, so ignore it.
			continue
		}

		if m[k] != nil && s.DependentRequired[k] != nil {
			for _, dependent := range s.DependentRequired[k] {
				if m[dependent] != nil {
					continue
				}

				res.Add(path, m, s.msgDependentRequired[k][dependent])
			}
		}

		path.Push(k)
		Validate(r, v, path, mode, m[k], res)
		path.Pop()
	}

	if addl, ok := s.AdditionalProperties.(bool); ok && !addl {
		for k := range m {
			// No additional properties allowed.
			if _, ok := s.Properties[k]; !ok {
				path.Push(k)
				res.Add(path, m, "unexpected property")
				path.Pop()
			}
		}
	}

	if addl, ok := s.AdditionalProperties.(*Schema); ok {
		// Additional properties are allowed, but must match the given schema.
		for k, v := range m {
			if _, ok := s.Properties[k]; ok {
				continue
			}

			path.Push(k)
			Validate(r, addl, path, mode, v, res)
			path.Pop()
		}
	}
}

func handleMapAny(r Registry, s *Schema, path *PathBuffer, mode ValidateMode, m map[any]any, res *ValidateResult) {
	if s.MinProperties != nil {
		if len(m) < *s.MinProperties {
			res.Add(path, m, s.msgMinProperties)
		}
	}
	if s.MaxProperties != nil {
		if len(m) > *s.MaxProperties {
			res.Add(path, m, s.msgMaxProperties)
		}
	}

	for _, k := range s.propertyNames {
		v := s.Properties[k]

		// Schemas are generated such that the read/write-only properties are set
		// alongside the `$ref`, if it is present (i.e. for objects). If not,
		// then the read/write-only properties are set directly on the schema and
		// the `for` loop never runs.
		readOnly := v.ReadOnly
		writeOnly := v.WriteOnly
		for v.Ref != "" {
			v = r.SchemaFromRef(v.Ref)
		}

		// We should be permissive by default to enable easy round-trips for the
		// client without needing to remove read-only values.
		// TODO: should we make this configurable?

		// Be stricter for responses, enabling validation of the server if desired.
		if mode == ModeReadFromServer && writeOnly && m[k] != nil && !reflect.ValueOf(m[k]).IsZero() {
			res.Add(path, m[k], "write only property is non-zero")
			continue
		}

		if _, ok := m[k]; !ok {
			if !s.requiredMap[k] {
				continue
			}
			if (mode == ModeWriteToServer && readOnly) ||
				(mode == ModeReadFromServer && writeOnly) {
				// These are not required for the current mode.
				continue
			}
			res.Add(path, m, s.msgRequired[k])
			continue
		}

		if m[k] == nil && (!s.requiredMap[k] || s.Nullable) {
			// This is a non-required field which is null, or a nullable field set
			// to null, so ignore it.
			continue
		}

		if m[k] != nil && s.DependentRequired[k] != nil {
			for _, dependent := range s.DependentRequired[k] {
				if m[dependent] != nil {
					continue
				}

				res.Add(path, m, s.msgDependentRequired[k][dependent])
			}
		}

		path.Push(k)
		Validate(r, v, path, mode, m[k], res)
		path.Pop()
	}

	if addl, ok := s.AdditionalProperties.(bool); ok && !addl {
		for k := range m {
			// No additional properties allowed.
			var kStr string
			if s, ok := k.(string); ok {
				kStr = s
			} else {
				kStr = fmt.Sprint(k)
			}
			if _, ok := s.Properties[kStr]; !ok {
				path.Push(kStr)
				res.Add(path, m, "unexpected property")
				path.Pop()
			}
		}
	}

	if addl, ok := s.AdditionalProperties.(*Schema); ok {
		// Additional properties are allowed, but must match the given schema.
		for k, v := range m {
			var kStr string
			if s, ok := k.(string); ok {
				kStr = s
			} else {
				kStr = fmt.Sprint(k)
			}
			path.Push(kStr)
			Validate(r, addl, path, mode, v, res)
			path.Pop()
		}
	}
}

// ModelValidator is a utility for validating e.g. JSON loaded data against a
// Go struct model. It is not goroutine-safe and should not be used in HTTP
// handlers! Schemas are generated on-the-fly on first use and re-used on
// subsequent calls. This utility can be used to easily validate data outside
// of the normal request/response flow, for example on application startup:
//
//	type MyExample struct {
//		Name string `json:"name" maxLength:"5"`
//		Age int `json:"age" minimum:"25"`
//	}
//
//	var value any
//	json.Unmarshal([]byte(`{"name": "abcdefg", "age": 1}`), &value)
//
//	validator := ModelValidator()
//	errs := validator.Validate(reflect.TypeOf(MyExample{}), value)
//	if errs != nil {
//		fmt.Println("Validation error", errs)
//	}
type ModelValidator struct {
	registry Registry
	pb       *PathBuffer
	result   *ValidateResult
}

// NewModelValidator creates a new model validator with all the components
// it needs to create schemas, validate them, and return any errors.
func NewModelValidator() *ModelValidator {
	return &ModelValidator{
		registry: NewMapRegistry("#/components/schemas/", DefaultSchemaNamer),
		pb:       NewPathBuffer([]byte(""), 0),
		result:   &ValidateResult{},
	}
}

// Validate the inputs. The type should be the Go struct with validation field
// tags and the value should be e.g. JSON loaded into an `any`. A list of
// errors is returned if validation failed, otherwise `nil`.
//
//	type MyExample struct {
//		Name string `json:"name" maxLength:"5"`
//		Age int `json:"age" minimum:"25"`
//	}
//
//	var value any
//	json.Unmarshal([]byte(`{"name": "abcdefg", "age": 1}`), &value)
//
//	validator := ModelValidator()
//	errs := validator.Validate(reflect.TypeOf(MyExample{}), value)
//	if errs != nil {
//		fmt.Println("Validation error", errs)
//	}
func (v *ModelValidator) Validate(typ reflect.Type, value any) []error {
	v.pb.Reset()
	v.result.Reset()

	s := v.registry.Schema(typ, true, typ.Name())

	Validate(v.registry, s, v.pb, ModeReadFromServer, value, v.result)

	if len(v.result.Errors) > 0 {
		return v.result.Errors
	}
	return nil
}

// The following is borrowed from the Google UUID package:
// https://github.com/google/uuid/blob/v1.6.0/uuid.go
// Copyright (c) 2009,2014 Google Inc. All rights reserved.
// BSD licensed.

type invalidLengthError struct{ len int }

func (err invalidLengthError) Error() string {
	return fmt.Sprintf("invalid UUID length: %d", err.len)
}

// xvalues returns the value of a byte as a hexadecimal digit or 255.
var xvalues = [256]byte{
	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
	0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 255, 255, 255, 255, 255, 255,
	255, 10, 11, 12, 13, 14, 15, 255, 255, 255, 255, 255, 255, 255, 255, 255,
	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
	255, 10, 11, 12, 13, 14, 15, 255, 255, 255, 255, 255, 255, 255, 255, 255,
	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
}

// xtob converts hex characters x1 and x2 into a byte.
//
//nolint:unparam
func xtob(x1, x2 byte) (byte, bool) {
	b1 := xvalues[x1]
	b2 := xvalues[x2]
	return (b1 << 4) | b2, b1 != 255 && b2 != 255
}

// validateUUID returns an error if s is not a properly formatted UUID in one of the following formats:
//
//	xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
//	urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
//	xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
//	{xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}
//
// It returns an error if the format is invalid, otherwise nil.
func validateUUID(s string) error {
	switch len(s) {
	// Standard UUID format
	case 36:

	// UUID with "urn:uuid:" prefix
	case 36 + 9:
		if !strings.EqualFold(s[:9], "urn:uuid:") {
			return fmt.Errorf("invalid urn prefix: %q", s[:9])
		}
		s = s[9:]

	// UUID enclosed in braces
	case 36 + 2:
		if s[0] != '{' || s[len(s)-1] != '}' {
			return errors.New("invalid bracketed UUID format")
		}
		s = s[1 : len(s)-1]

	// UUID without hyphens
	case 32:
		for i := 0; i < len(s); i += 2 {
			_, ok := xtob(s[i], s[i+1])
			if !ok {
				return errors.New("invalid UUID format")
			}
		}

	default:
		return invalidLengthError{len(s)}
	}

	// Check for standard UUID format
	if len(s) == 36 {
		if s[8] != '-' || s[13] != '-' || s[18] != '-' || s[23] != '-' {
			return errors.New("invalid UUID format")
		}
		for _, x := range []int{0, 2, 4, 6, 9, 11, 14, 16, 19, 21, 24, 26, 28, 30, 32, 34} {
			if _, ok := xtob(s[x], s[x+1]); !ok {
				return errors.New("invalid UUID format")
			}
		}
	}

	return nil
}