feat(admin-i18n): add cookie-based locale runtime and switcher baseline

apps/admin/src/i18n/messages.test.ts

@@ -0,0 +1,117 @@
+import { describe, expect, it } from "vitest"
+
+import type { AdminMessages } from "./messages"
+import { translateMessage } from "./messages"
+
+const messages: AdminMessages = {
+  common: {
+    language: "Language",
+    localeNames: {
+      de: "German",
+      en: "English",
+      es: "Spanish",
+      fr: "French",
+    },
+  },
+  auth: {
+    badge: "Admin Auth",
+    titles: {
+      signIn: "Sign in",
+      signUpOwner: "Welcome",
+      signUpUser: "Create account",
+    },
+    descriptions: {
+      signIn: "Sign in description",
+      signUpOwner: "Owner description",
+      signUpUser: "User description",
+    },
+    fields: {
+      name: "Name",
+      emailOrUsername: "Email or username",
+      email: "Email",
+      username: "Username",
+      password: "Password",
+    },
+    actions: {
+      signInIdle: "Sign in",
+      signInBusy: "Signing in...",
+      signUpOwnerIdle: "Create owner account",
+      signUpUserIdle: "Create account",
+      signUpBusy: "Creating account...",
+    },
+    links: {
+      needAccount: "Need an account?",
+      register: "Register",
+      alreadyHaveAccount: "Already have an account?",
+      goToSignIn: "Go to sign in",
+    },
+    messages: {
+      ownerCreated: "Owner account created.",
+      accountCreated: "Account created.",
+    },
+    errors: {
+      nameRequired: "Name is required.",
+      signInFailed: "Sign in failed",
+      signUpFailed: "Sign up failed",
+      networkSignIn: "Network sign in error",
+      networkSignUp: "Network sign up error",
+    },
+  },
+  dashboard: {
+    badge: "Admin App",
+    title: "Content Dashboard",
+    description: "Manage content.",
+    actions: {
+      openRoadmap: "Open roadmap",
+    },
+    notices: {
+      noCrudPermission: "No permission.",
+      crudSandboxTag: "MVP0 functional test",
+    },
+    posts: {
+      title: "Posts CRUD Sandbox",
+      createTitle: "Create post",
+      fields: {
+        title: "Title",
+        slug: "Slug",
+        excerpt: "Excerpt",
+        body: "Body",
+        status: "Status",
+      },
+      status: {
+        draft: "Draft",
+        published: "Published",
+      },
+      actions: {
+        create: "Create post",
+        save: "Save changes",
+        delete: "Delete",
+      },
+      errors: {
+        createFailed: "Create failed.",
+        updateFailed: "Update failed.",
+        updateMissingId: "Missing post id.",
+        deleteFailed: "Delete failed.",
+        deleteMissingId: "Missing post id.",
+      },
+      success: {
+        created: "Post created.",
+        updated: "Post updated.",
+        deleted: "Post deleted.",
+      },
+      fallback: {
+        noExcerpt: "No excerpt",
+      },
+    },
+  },
+}
+
+describe("translateMessage", () => {
+  it("resolves nested keys", () => {
+    expect(translateMessage(messages, "dashboard.title")).toBe("Content Dashboard")
+  })
+
+  it("returns fallback for unknown keys", () => {
+    expect(translateMessage(messages, "dashboard.unknown", "Fallback")).toBe("Fallback")
+  })
+})

apps/admin/src/i18n/messages.ts

@@ -0,0 +1,27 @@
+import type enMessages from "../messages/en.json"
+
+export type AdminMessages = typeof enMessages
+
+function resolveNestedValue(source: unknown, key: string): unknown {
+  let current: unknown = source
+
+  for (const segment of key.split(".")) {
+    if (!current || typeof current !== "object") {
+      return null
+    }
+
+    current = (current as Record<string, unknown>)[segment]
+  }
+
+  return current
+}
+
+export function translateMessage(messages: AdminMessages, key: string, fallback?: string): string {
+  const resolved = resolveNestedValue(messages, key)
+
+  if (typeof resolved === "string") {
+    return resolved
+  }
+
+  return fallback ?? key
+}

apps/admin/src/i18n/server.ts

@@ -0,0 +1,20 @@
+import { type AppLocale, defaultLocale, isAppLocale } from "@cms/i18n"
+import { cookies } from "next/headers"
+
+import type { AdminMessages } from "./messages"
+import { ADMIN_LOCALE_COOKIE } from "./shared"
+
+export async function resolveAdminLocale(): Promise<AppLocale> {
+  const cookieStore = await cookies()
+  const value = cookieStore.get(ADMIN_LOCALE_COOKIE)?.value
+
+  if (value && isAppLocale(value)) {
+    return value
+  }
+
+  return defaultLocale
+}
+
+export async function getAdminMessages(locale: AppLocale): Promise<AdminMessages> {
+  return (await import(`../messages/${locale}.json`)).default as AdminMessages
+}

apps/admin/src/i18n/shared.ts

@@ -0,0 +1 @@
+export const ADMIN_LOCALE_COOKIE = "cms_admin_locale"