laravel_like_validation.go

package utils

import (
	"regexp"
	"strings"

	"github.com/go-playground/validator/v10"
)

// Convert field names from CamelCase to snake_case
func toSnakeCase(input string) string {
	// Use a regular expression to insert underscores before uppercase letters
	re := regexp.MustCompile("([a-z0-9])([A-Z])")
	snake := re.ReplaceAllString(input, "${1}_${2}")
	// Convert the entire string to lowercase
	return strings.ToLower(snake)
}

// Map validation tags to custom error messages
func getErrorMessage(tag string) string {
	switch tag {
	case "required":
		return "Field must be filled"
	case "unique":
		return "This value already exists"
	case "gt": // greater than
		return "Value must be greater than the minimum allowed"
	case "gte": // greater than or equal
		return "Value must be greater than or equal to the minimum allowed"
	case "lt": // less than
		return "Value must be less than the maximum allowed"
	case "lte": // less than or equal
		return "Value must be less than or equal to the maximum allowed"
	case "email":
		return "Invalid email format"
	case "min":
		return "Value is too short"
	case "max":
		return "Value is too long"
	default:
		return "Invalid input"
	}
}

// ParseValidationErrors converts validation errors into JSON format
func LaravelLikeValidatorErrors(err error) map[string][]string {
	validationErrors := make(map[string][]string)

	// Handle go-playground/validator errors
	if errs, ok := err.(validator.ValidationErrors); ok {
		for _, e := range errs {
			fieldName := toSnakeCase(e.Field()) // Convert to snake_case
			validationErrors[fieldName] = append(validationErrors[fieldName], getErrorMessage(e.Tag()))
		}
	} else {
		// Handle generic errors (manual validation)
		re := regexp.MustCompile(`Key: '([^']+)'.+?failed on the '([^']+)' tag`)
		matches := re.FindStringSubmatch(err.Error())
		if len(matches) == 3 {
			fieldName := toSnakeCase(matches[1]) // Convert to snake_case
			validationErrors[fieldName] = append(validationErrors[fieldName], getErrorMessage(matches[2]))
		} else {
			validationErrors["error"] = []string{err.Error()}
		}
	}

	return validationErrors
}