アイヌ語追加 (#428) (#433)

Reviewed-on: #433
Co-authored-by: miteruzo <miteruzo@naver.com>

frontend/src/lib/locales.ts

@@ -0,0 +1,83 @@
+import { apiGet } from '@/lib/api'
+import { currentRenderContext } from '@/lib/renderContext'
+
+import type { To } from 'react-router-dom'
+
+export const SUPPORTED_LOCALES = ['ja', 'ain-Kana'] as const
+
+export type LocaleCode = typeof SUPPORTED_LOCALES[number]
+
+export type AvailableLocale = { code: string; name: string }
+
+
+export const fetchLocales = (): Promise<{ locales: AvailableLocale[] }> =>
+    apiGet ('/locales')
+
+
+export const LOCALE_LABELS: Record<LocaleCode, string> = {
+    ja: '日本語', 'ain-Kana': 'ヤウンモシルン アイヌ イタㇰ' }
+
+const LEGACY_ROOTS = [
+    'posts', 'tags', 'nico', 'theatres', 'materials', 'wiki', 'help',
+    'users', 'settings', 'tos', 'gekanator', 'more']
+
+
+export const isLocaleCode = (value: unknown): value is LocaleCode =>
+    SUPPORTED_LOCALES.some (locale => locale === value)
+
+
+export const localeLanguage = (locale: LocaleCode): 'ja' | 'ain' =>
+    locale === 'ja' ? 'ja' : 'ain'
+
+
+export const localeFromPath = (pathname: string): LocaleCode | null => {
+  const segment = pathname.split (/[/?#]/)[1]
+  return isLocaleCode (segment) ? segment : null
+}
+
+
+export const resolveViewingLocale = (
+    pathname: string,
+    routeLocale?: unknown,
+): LocaleCode =>
+    isLocaleCode (routeLocale) ? routeLocale : localeFromPath (pathname) ?? 'ja'
+
+
+export const currentViewingLocale = (): LocaleCode =>
+    resolveViewingLocale (currentRenderContext ()?.pathname ?? '')
+
+
+export const unlocalisedPath = (pathname: string): string => {
+  const locale = localeFromPath (pathname)
+  return locale == null ? pathname : pathname.slice (locale.length + 1) || '/'
+}
+
+
+export const localiseTo = (to: To, locale: LocaleCode): To => {
+  const pathname = typeof to === 'string' ? to : to.pathname
+  if (pathname == null
+      || !(pathname.startsWith ('/'))
+      || pathname.startsWith ('//')
+      || localeFromPath (pathname) != null)
+    return to
+
+  const localised = `/${ locale }${ pathname }`
+  return typeof to === 'string' ? localised : { ...to, pathname: localised }
+}
+
+
+export const switchLocalePath = (
+    location: { pathname: string; search: string; hash: string },
+    locale: LocaleCode,
+): string =>
+    `/${ locale }${ unlocalisedPath (location.pathname) }${ location.search }${ location.hash }`
+
+
+export const legacyLocalePath = (
+    location: { pathname: string; search: string; hash: string },
+): string | null => {
+  const root = location.pathname.split ('/')[1]
+  return (location.pathname === '/' || LEGACY_ROOTS.includes (root))
+      ? `/ja${ location.pathname }${ location.search }${ location.hash }`
+      : null
+}