package i18n

import "strings"

func T(lang Lang, key string, args map[string]string) string {
	if key == "" {
		return ""
	}
	if lang == "" {
		lang = Default
	}
	s := lookup(lang, key)
	if s == "" && lang != En {
		s = lookup(En, key)
	}
	if s == "" && lang != ZhCN {
		s = lookup(ZhCN, key)
	}
	if s == "" {
		return key
	}
	return apply(s, args)
}

func lookup(lang Lang, key string) string {
	byLang, ok := catalog[key]
	if !ok {
		return ""
	}
	return byLang[lang]
}

func apply(s string, args map[string]string) string {
	for k, v := range args {
		s = strings.ReplaceAll(s, "{"+k+"}", v)
	}
	return s
}

// ErrorMsg is the user-visible envelope msg for a business code.
func ErrorMsg(lang Lang, code string) string {
	if code == "" || code == "0" {
		return T(lang, KeyOK, nil)
	}
	return T(lang, "err."+code, nil)
}

// Notify returns title and body for a notification type. Missing ".body" falls back to the type key.
func Notify(lang Lang, typ string, args map[string]string) (title, body string) {
	title = T(lang, typ+".title", args)
	if title == typ+".title" {
		title = ""
	}
	body = T(lang, typ+".body", args)
	if body == typ+".body" {
		body = T(lang, typ, args)
		if body == typ {
			body = ""
		}
	}
	return title, body
}