package locale

import (
	"encoding/json"
	"fmt"
	"io/fs"
	"path/filepath"
	"strings"

	"github.com/cloudfoundry/jibber_jabber"
	"github.com/evcc-io/evcc/server/assets"
	"github.com/evcc-io/evcc/util/locale/internal"
	"github.com/nicksnyder/go-i18n/v2/i18n"
	"golang.org/x/text/language"
)

type Config = i18n.LocalizeConfig

var (
	Locale internal.ContextKey

	Bundle    *i18n.Bundle
	Language  string
	Localizer *i18n.Localizer
)

// Init initializes the localization bundle and loads all JSON message files.
func Init() error {
	Bundle = i18n.NewBundle(language.English)
	Bundle.RegisterUnmarshalFunc("json", json.Unmarshal)

	dir, err := fs.ReadDir(assets.I18n, ".")
	if err != nil {
		panic(err)
	}

	// Iterate over each file and process only .json files
	for _, d := range dir {
		if filepath.Ext(d.Name()) != ".json" {
			continue
		}

		b, err := fs.ReadFile(assets.I18n, d.Name())
		if err != nil {
			return fmt.Errorf("reading locale file %s failed: %w", d.Name(), err)
		}

		var s struct {
			Sessions struct {
				CSV map[string]string `json:"csv"`
			} `json:"sessions"`
		}

		if err := json.Unmarshal(b, &s); err != nil {
			return err
		}

		if len(s.Sessions.CSV) > 0 {
			m := make([]*i18n.Message, 0, len(s.Sessions.CSV))
			for k, v := range s.Sessions.CSV {
				m = append(m, &i18n.Message{
					ID:    "sessions.csv." + k,
					Other: v,
				})
			}

			languageTag := language.Make(strings.TrimSuffix(d.Name(), filepath.Ext(d.Name())))
			if err := Bundle.AddMessages(languageTag, m...); err != nil {
				return fmt.Errorf("loading locales failed: %w", err)
			}
		}
	}

	// Detect system language; default to German on failure
	Language, err = jibber_jabber.DetectLanguage()
	if err != nil {
		Language = language.German.String()
	}

	// Create a localizer for the detected language
	Localizer = i18n.NewLocalizer(Bundle, Language)

	return nil
}