turash/bugulma/backend/internal/middleware/i18n.go

package middleware

import (
	"bugulma/backend/internal/service"
	"strings"

	"github.com/gin-gonic/gin"
)

// LocaleKey is the context key for locale
const LocaleKey = "locale"

// I18nMiddleware extracts locale from Accept-Language header or query parameter
// Sets locale in context for use by handlers
func I18nMiddleware(i18nService *service.I18nService) gin.HandlerFunc {
	return func(c *gin.Context) {
		locale := service.DefaultLocale

		// Check query parameter first (highest priority)
		if queryLocale := c.Query("locale"); queryLocale != "" {
			if i18nService.ValidateLocale(queryLocale) {
				locale = queryLocale
			}
		} else if headerLocale := c.GetHeader("Accept-Language"); headerLocale != "" {
			// Parse Accept-Language header
			locale = parseAcceptLanguage(headerLocale, i18nService)
		}

		// Set locale in context
		c.Set(LocaleKey, locale)
		c.Next()
	}
}

// parseAcceptLanguage parses Accept-Language header and returns best match
func parseAcceptLanguage(header string, i18nService *service.I18nService) string {
	// Parse header like "en-US,en;q=0.9,ru;q=0.8"
	languages := strings.Split(header, ",")

	for _, lang := range languages {
		// Extract language code (e.g., "en" from "en-US" or "en;q=0.9")
		parts := strings.Split(strings.TrimSpace(lang), ";")
		langCode := strings.ToLower(strings.Split(parts[0], "-")[0])

		if i18nService.ValidateLocale(langCode) {
			return langCode
		}
	}

	return service.DefaultLocale
}

// GetLocaleFromContext extracts locale from context
func GetLocaleFromContext(c *gin.Context) string {
	if locale, exists := c.Get(LocaleKey); exists {
		if loc, ok := locale.(string); ok {
			return loc
		}
	}
	return service.DefaultLocale
}