feat: add internationalization message platform

src/presentation/i18n/message-contract.ts

@@ -0,0 +1,135 @@
+import {
+  EN_MESSAGES,
+  KO_MESSAGES,
+  MESSAGE_CATALOGS,
+  type MessageKey,
+} from "./catalog.js";
+
+export const SUPPORTED_LOCALES = Object.freeze([
+  "ko-KR",
+  "en-US",
+  "en-XA",
+  "ar-EG",
+] as const);
+export type SupportedLocale = (typeof SUPPORTED_LOCALES)[number];
+export type TextDirection = "ltr" | "rtl";
+
+export type MessageParameters = Readonly<{
+  "action.closeNamed": { title: string };
+  "action.alertCloseNamed": { title: string };
+  "route.loadingNamed": { title: string };
+  "route.documentTitle": { title: string; appName: string };
+  "template.supportReference": { reference: string };
+  "form.remaining": { count: number };
+  "boot.supportReference": { reference: string };
+}>;
+export type ParameterlessMessageKey = Exclude<
+  MessageKey,
+  keyof MessageParameters
+>;
+
+export type MessageArguments<Key extends MessageKey> =
+  Key extends keyof MessageParameters
+    ? [parameters: MessageParameters[Key]]
+    : [parameters?: never];
+
+const PLACEHOLDER_PATTERN = /\{([a-zA-Z][a-zA-Z0-9]*)\}/g;
+const FALLBACK_LOCALE = "ko-KR" as const;
+export const MESSAGE_KEY_ALIASES = Object.freeze({
+  "action.login": "action.reauth",
+  "async.pending": "common.processing",
+} as const satisfies Readonly<Record<string, MessageKey>>);
+
+export function normalizeLocale(locale: string): SupportedLocale {
+  if ((SUPPORTED_LOCALES as readonly string[]).includes(locale)) {
+    return locale as SupportedLocale;
+  }
+  const language = locale.split("-")[0]?.toLowerCase();
+  if (language === "ko") return "ko-KR";
+  if (language === "ar") return "ar-EG";
+  if (language === "en") return "en-US";
+  return FALLBACK_LOCALE;
+}
+
+export function localeDirection(locale: SupportedLocale): TextDirection {
+  return locale === "ar-EG" ? "rtl" : "ltr";
+}
+
+export function messagePlaceholders(template: string): readonly string[] {
+  return Object.freeze(
+    [...template.matchAll(PLACEHOLDER_PATTERN)].map((match) => match[1] ?? ""),
+  );
+}
+
+export function resolveMessage(
+  locale: string,
+  key: string,
+  parameters?: Readonly<Record<string, string | number>>,
+): string {
+  const normalized = normalizeLocale(locale);
+  const sourceLocale: keyof typeof MESSAGE_CATALOGS =
+    normalized === "en-XA" ? "en-US" : normalized;
+  const catalog =
+    MESSAGE_CATALOGS[sourceLocale] ??
+    MESSAGE_CATALOGS[FALLBACK_LOCALE];
+  const fallback = KO_MESSAGES["common.unavailable"];
+  const canonicalKey =
+    MESSAGE_KEY_ALIASES[key as keyof typeof MESSAGE_KEY_ALIASES] ?? key;
+  const template = catalog[canonicalKey as MessageKey] ?? fallback;
+  const placeholders = messagePlaceholders(template);
+  if (
+    placeholders.some(
+      (placeholder) =>
+        parameters?.[placeholder] === undefined ||
+        parameters?.[placeholder] === null,
+    )
+  ) {
+    return fallback;
+  }
+  const formatted = template.replace(
+    PLACEHOLDER_PATTERN,
+    (_, placeholder: string) => String(parameters?.[placeholder] ?? ""),
+  );
+  return normalized === "en-XA" ? pseudoLocalize(formatted) : formatted;
+}
+
+export function formatMessage<Key extends MessageKey>(
+  locale: string,
+  key: Key,
+  ...args: MessageArguments<Key>
+): string {
+  return resolveMessage(
+    locale,
+    key,
+    args[0] as Readonly<Record<string, string | number>> | undefined,
+  );
+}
+
+function pseudoLocalize(value: string): string {
+  const expanded = value.replace(/[A-Za-z]/g, (character) => {
+    const replacements: Readonly<Record<string, string>> = {
+      a: "á",
+      e: "é",
+      i: "í",
+      o: "ó",
+      u: "ú",
+      A: "Á",
+      E: "É",
+      I: "Í",
+      O: "Ó",
+      U: "Ú",
+    };
+    return replacements[character] ?? character;
+  });
+  return `［${expanded} ···］`;
+}
+
+export function catalogKeys(
+  locale: "ko-KR" | "en-US" | "ar-EG",
+): MessageKey[] {
+  return Object.keys(MESSAGE_CATALOGS[locale]).sort() as MessageKey[];
+}
+
+export function fallbackMessage() {
+  return EN_MESSAGES["common.unavailable"];
+}