package i18n

import (
	"embed"
	"fmt"
	"strings"

	"github.com/nicksnyder/go-i18n/v2/i18n"
	"golang.org/x/text/language"
	"gopkg.in/yaml.v3"

	"git.wxccs.org/iceking2nd/winauth-go/internal/global"
)

//go:embed locales/*.toml
var localeFS embed.FS

var (
	bundle    *i18n.Bundle
	localizer *i18n.Localizer
)

// Init loads bundled locales and selects a localizer based on the requested
// language tag. Pass an empty string to use the system default (currently
// English).
func Init(lang string) error {
	const fn = "internal.i18n.Init"

	bundle = i18n.NewBundle(language.English)
	bundle.RegisterUnmarshalFunc("toml", tomlUnmarshal)
	bundle.RegisterUnmarshalFunc("yaml", yaml.Unmarshal)

	entries, err := localeFS.ReadDir("locales")
	if err != nil {
		return fmt.Errorf("read locales: %w", err)
	}
	for _, e := range entries {
		if e.IsDir() {
			continue
		}
		path := "locales/" + e.Name()
		if _, err := bundle.LoadMessageFileFS(localeFS, path); err != nil {
			global.Log.WithField("func", fn).WithError(err).
				WithField("file", path).Warn("failed to load locale")
		}
	}

	if strings.TrimSpace(lang) == "" {
		lang = "en"
	}
	localizer = i18n.NewLocalizer(bundle, lang, "en")

	global.Log.WithField("func", fn).WithField("lang", lang).Debug("i18n initialized")
	return nil
}

// T translates the given message id using the active localizer. If
// translation fails (missing key or i18n not initialized), it returns the
// id unchanged so the UI still renders something readable.
func T(id string, args ...any) string {
	if localizer == nil {
		return id
	}
	cfg := &i18n.LocalizeConfig{MessageID: id}
	if len(args) > 0 {
		// args are formatted directly via fmt.Sprintf if the message
		// id contains %s/%d-style verbs.
		out, err := localizer.Localize(cfg)
		if err != nil {
			return fmt.Sprintf(id, args...)
		}
		return fmt.Sprintf(out, args...)
	}
	out, err := localizer.Localize(cfg)
	if err != nil {
		return id
	}
	return out
}

// SetLanguage switches the active language at runtime.
func SetLanguage(lang string) {
	const fn = "internal.i18n.SetLanguage"
	localizer = i18n.NewLocalizer(bundle, lang, "en")
	global.Log.WithField("func", fn).WithField("lang", lang).Debug("language changed")
}