// See also https://www.alexedwards.net/blog/validation-snippets-for-go
// for more validation snippets
//
// A NonFieldError for example would be "Your email or password is incorrect".
// more secure because it does not leak which field was in error. Used in the login
// form

package validator

import (
	"regexp"
	"slices"
	"strings"
	"unicode/utf8"
)

type Validator struct {
	NonFieldErrors []string
	FieldErrors    map[string]string
}

// Valid() returns true if the FieldErrors map doesn't contain any entries.
func (v *Validator) Valid() bool {
	return len(v.FieldErrors) == 0 && len(v.NonFieldErrors) == 0
}

func (v *Validator) AddNonFieldError(message string) {
	v.NonFieldErrors = append(v.NonFieldErrors, message)
}

// AddFieldError() adds an error message to the FieldErrors map (so long as no
// entry already exists for the given key).
func (v *Validator) AddFieldError(key, message string) {
	if v.FieldErrors == nil {
		v.FieldErrors = make(map[string]string)
	}

	if _, exists := v.FieldErrors[key]; !exists {
		v.FieldErrors[key] = message
	}
}

// CheckField() adds an error message to the FieldErrors map only if a
// validation check is not 'ok'.
func (v *Validator) CheckField(ok bool, key, message string) {
	if !ok {
		v.AddFieldError(key, message)
	}
}

// NotBlank() returns true if a value is not an empty string.
func NotBlank(value string) bool {
	return strings.TrimSpace(value) != ""
}

// MinChars() returns true if the value contains equal to or greater than n characters
func MinChars(value string, n int) bool {
	return utf8.RuneCountInString(value) >= n
}

// MaxChars() returns true if a value contains no more than n characters.
func MaxChars(value string, n int) bool {
	return utf8.RuneCountInString(value) <= n
}

// PermittedValue() returns true if a value is in a list of specific permitted
// values.
func PermittedValue[T comparable](value T, permittedValues ...T) bool {
	return slices.Contains(permittedValues, value)
}

// Use the regexp.MustCompile() function to parse a regular expression pattern
// for sanity checking the format of an email address. This returns a pointer to
// a 'compiled' regexp.Regexp type, or panics in the event of an error. Parsing
// this pattern once at startup and storing the compiled *regexp.Regexp in a
// variable is more performant than re-parsing the pattern each time we need it.
// This pattern is recommended by the W3C and Web Hypertext Application Technology Working Group for validating email addresses
// https://html.spec.whatwg.org/multipage/input.html#valid-e-mail-address
// Because the EmailRX regexp pattern is written as an interpreted string literal, we need to double-escape special characters in the regexp with \\ for it to work correctly
var EmailRX = regexp.MustCompile("^[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$")

// Matches() returns true if a value matches a provided compiled regular
// expression pattern.
func Matches(value string, rx *regexp.Regexp) bool {
	return rx.MatchString(value)
}