アイヌ語追加 (#428) (#433)

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

frontend/src/lib/users.ts

@@ -1,6 +1,70 @@
+import { apiGet, apiPost, isApiError } from '@/lib/api'
+
 import type { User, UserRole } from '@/types'
 
 const CONTENT_EDITOR_ROLES: readonly UserRole[] = ['admin', 'member']
+let pendingSession: Promise<User> | null = null
+
+
+const storedUserCode = (): string | null => {
+  try
+  {
+    return localStorage.getItem ('user_code')
+  }
+  catch
+  {
+    return null
+  }
+}
+
+
+export const rememberUserCode = (code: string): void => {
+  try
+  {
+    localStorage.setItem ('user_code', code)
+  }
+  catch
+  {
+    // A missing recovery copy must not invalidate the authenticated Cookie.
+  }
+}
+
+
+const restoreUserSession = async (): Promise<User> => {
+  try
+  {
+    return await apiGet<User> ('/users/me')
+  }
+  catch (error)
+  {
+    if (!isApiError (error) || error.response?.status !== 401)
+      throw error
+  }
+
+  const code = storedUserCode ()
+  if (code)
+  {
+    const data = await apiPost<{ valid: boolean; user: User }> (
+	'/users/verify', { code, restore: true })
+    if (data.valid)
+      return data.user
+  }
+  const data = await apiPost<{ code: string; user: User }> ('/users')
+  return data.user
+}
+
+
+export const initialiseUserSession = (): Promise<User> => {
+  if (typeof window === 'undefined')
+    throw new Error ('Browser session initialisation is client-only')
+  pendingSession ??= restoreUserSession ().then (user => {
+    rememberUserCode (user.inheritanceCode)
+    return user
+  }).finally (() => {
+    pendingSession = null
+  })
+  return pendingSession
+}
 
 
 export const canEditContent = (