// Package i18n holds gitfed-web's translation strings and looks them up by
// key. Every page's copy lives here instead of being hardcoded in the Go
// templates, so the web UI can be served in more than one language.
package i18n

import "fmt"

// Lang is a supported UI language. New languages are added by defining a
// constant here and a dictionary for it in dict().
type Lang string

const (
	EN Lang = "en"
	FR Lang = "fr"
)

// Default is used whenever a request carries no usable language signal
// (no cookie, no matching Accept-Language tag).
const Default = EN

// ParseLang validates a language tag from a cookie or path segment,
// returning ok=false for anything gitfed doesn't have a dictionary for.
func ParseLang(v string) (Lang, bool) {
	switch Lang(v) {
	case EN, FR:
		return Lang(v), true
	default:
		return "", false
	}
}

func dict(l Lang) map[string]string {
	if l == FR {
		return fr
	}
	return en
}

// T looks up key in lang's dictionary, falling back to English and then to
// the key itself so a missing translation shows up as an obviously-wrong
// string instead of a blank. With extra args, the result is passed through
// fmt.Sprintf.
func T(lang Lang, key string, args ...any) string {
	s, ok := dict(lang)[key]
	if !ok {
		s, ok = en[key]
	}
	if !ok {
		s = key
	}
	if len(args) > 0 {
		return fmt.Sprintf(s, args...)
	}
	return s
}