#428

frontend/src/lib/useLocale.ts

@@ -0,0 +1,27 @@
+import { useCallback } from 'react'
+import { useLocation, useNavigate, useParams } from 'react-router-dom'
+
+import { isLocaleCode, localeFromPath, localiseTo } from '@/lib/locales'
+
+import type { NavigateFunction, NavigateOptions, To } from 'react-router-dom'
+
+import type { LocaleCode } from '@/lib/locales'
+
+
+export const useLocale = (): LocaleCode => {
+  const { locale } = useParams ()
+  const location = useLocation ()
+  return isLocaleCode (locale) ? locale : localeFromPath (location.pathname) ?? 'ja'
+}
+
+
+export const useLocaleNavigate = (): NavigateFunction => {
+  const navigate = useNavigate ()
+  const locale = useLocale ()
+  return useCallback ((to: To | number, options?: NavigateOptions) => {
+    if (typeof to === 'number')
+      navigate (to)
+    else
+      navigate (localiseTo (to, locale), options)
+  }, [locale, navigate])
+}