package validation

import (
	"errors"
	"fmt"
	"strings"

	"github.com/go-playground/locales/en"
	"github.com/go-playground/locales/id"
	ut "github.com/go-playground/universal-translator"
	v10 "github.com/go-playground/validator/v10"
	entranslations "github.com/go-playground/validator/v10/translations/en"
	idtranslations "github.com/go-playground/validator/v10/translations/id"
)

// Constants for supported locales
const (
	LocaleID = "id"
	LocaleEN = "en"
)

// ErrorMessage represents a validation error message
type ErrorMessage struct {
	Field   string `json:"field"`
	Message string `json:"-"`
}

type validator struct {
	validate   *v10.Validate
	translator ut.Translator
}

// validatorInstance adalah instance global dari validator.
var validatorInstance *validator

// New creates a new validation instance with the specified locale
// dan menginisialisasi instance global validatorInstance.
func New(locale string) error {
	v := &validator{}
	parsedLocale := parseLocale(locale)

	uni := ut.New(en.New(), id.New(), en.New())
	translator, found := uni.GetTranslator(parsedLocale)
	if !found {
		return fmt.Errorf("translator not found for locale: %s", parsedLocale)
	}

	validate := v10.New()

	if err := setupValidations(validate); err != nil {
		return fmt.Errorf("failed to setup validations: %w", err)
	}

	if err := setupTranslations(validate, translator, parsedLocale); err != nil {
		return fmt.Errorf("failed to setup translations for locale %s: %w", parsedLocale, err)
	}

	v.validate = validate
	v.translator = translator

	validatorInstance = v // Inisialisasi instance global
	return nil
}

func parseLocale(locale string) string {
	switch strings.ToLower(locale) {
	case "id":
		return LocaleID
	case "en":
		return LocaleEN
	default:
		return LocaleID // Default to Indonesian
	}
}

// setupValidations configures custom validation rules.
func setupValidations(validate *v10.Validate) error {
	rules := NewValidatorRules(&InMemoryOptionSource{})
	if err := rules.RegisterAllCustomRules(validate); err != nil {
		return err
	}
	return nil
}

// setupTranslations configures translations for validation messages.
func setupTranslations(validate *v10.Validate, translator ut.Translator, locale string) error {
	// Register default translations based on locale
	if err := registerDefaultTranslations(validate, translator, locale); err != nil {
		return fmt.Errorf("failed to register default translations for locale %s: %w", locale, err)
	}

	// Register custom password validation translation
	err := validate.RegisterTranslation("password", translator,
		func(ut ut.Translator) error {
			return ut.Add("password", "harus mengandung minimal 8 karakter, huruf besar, huruf kecil, dan angka.", true)
		},
		func(ut ut.Translator, fe v10.FieldError) string {
			translated, err := ut.T(fe.Tag(), fe.Field())
			if err != nil {
				return fe.Field() + " is invalid"
			}
			return translated
		},
	)
	if err != nil {
		return fmt.Errorf("failed to register password translation: %w", err)
	}

	return nil
}

// registerDefaultTranslations sets up default translations for the specified locale.
func registerDefaultTranslations(validate *v10.Validate, translator ut.Translator, locale string) error {
	switch locale {
	case LocaleID:
		return idtranslations.RegisterDefaultTranslations(validate, translator)
	case LocaleEN:
		return entranslations.RegisterDefaultTranslations(validate, translator)
	default:
		// Fallback to English if the locale is not supported
		return entranslations.RegisterDefaultTranslations(validate, translator)
	}
}

// Validate validates a struct using the global validator instance
// and returns a slice of ErrorMessage.
func Validate(s any) []ErrorMessage {
	if validatorInstance == nil {
		return []ErrorMessage{{Field: "", Message: "Validator belum diinisialisasi. Panggil validation.New() terlebih dahulu."}}
	}
	err := validatorInstance.validate.Struct(s)
	if err != nil {
		return TranslateError(err)
	}
	return nil
}

// TranslateError takes a validation error and translates it using the global translator.
func TranslateError(err error) []ErrorMessage {
	if validatorInstance == nil {
		return nil
	}

	var validationErrors v10.ValidationErrors
	if !errors.As(err, &validationErrors) {
		return nil
	}

	errorMessages := make([]ErrorMessage, 0, len(validationErrors))
	for _, e := range validationErrors {
		fieldLabel := e.Field()
		msg, err := validatorInstance.translator.T(e.Tag(), fieldLabel)
		if err != nil {
			msg = fieldLabel + " is Invalid"
		}

		errorMessages = append(errorMessages, ErrorMessage{
			Field:   e.Tag(),
			Message: msg,
		})
	}

	return errorMessages
}