feat: migrate to starlight

node_modules/@astrojs/starlight/utils/createTranslationSystem.ts

@@ -0,0 +1,86 @@
+import type { i18nSchemaOutput } from '../schemas/i18n';
+import builtinTranslations from '../translations/index';
+import type { StarlightConfig } from './user-config';
+
+export function createTranslationSystem<T extends i18nSchemaOutput>(
+	userTranslations: Record<string, T>,
+	config: Pick<StarlightConfig, 'defaultLocale' | 'locales'>
+) {
+	/** User-configured default locale. */
+	const defaultLocale = config.defaultLocale?.locale || 'root';
+
+	/** Default map of UI strings based on Starlight and user-configured defaults. */
+	const defaults = buildDictionary(
+		builtinTranslations.en!,
+		userTranslations.en,
+		builtinTranslations[defaultLocale] || builtinTranslations[stripLangRegion(defaultLocale)],
+		userTranslations[defaultLocale]
+	);
+
+	/**
+	 * Generate a utility function that returns UI strings for the given `locale`.
+	 *
+	 * Also includes an `all()` method for getting the entire dictionary.
+	 *
+	 * @param {string | undefined} [locale]
+	 * @example
+	 * const t = useTranslations('en');
+	 * const label = t('search.label');
+	 * // => 'Search'
+	 * const dictionary = t.all();
+	 * // => { 'skipLink.label': 'Skip to content', 'search.label': 'Search', ... }
+	 */
+	return function useTranslations(locale: string | undefined) {
+		const lang = localeToLang(locale, config.locales, config.defaultLocale);
+		const dictionary = buildDictionary(
+			defaults,
+			builtinTranslations[lang] || builtinTranslations[stripLangRegion(lang)],
+			userTranslations[lang]
+		);
+		const t = <K extends keyof typeof dictionary>(key: K) => dictionary[key];
+		t.all = () => dictionary;
+		return t;
+	};
+}
+
+/**
+ * Strips the region subtag from a BCP-47 lang string.
+ * @param {string} [lang]
+ * @example
+ * const lang = stripLangRegion('en-GB'); // => 'en'
+ */
+function stripLangRegion(lang: string) {
+	return lang.replace(/-[a-zA-Z]{2}/, '');
+}
+
+/**
+ * Get the BCP-47 language tag for the given locale.
+ * @param locale Locale string or `undefined` for the root locale.
+ */
+function localeToLang(
+	locale: string | undefined,
+	locales: StarlightConfig['locales'],
+	defaultLocale: StarlightConfig['defaultLocale']
+): string {
+	const lang = locale ? locales?.[locale]?.lang : locales?.root?.lang;
+	const defaultLang = defaultLocale?.lang || defaultLocale?.locale;
+	return lang || defaultLang || 'en';
+}
+
+type BuiltInStrings = (typeof builtinTranslations)['en'];
+
+/** Build a dictionary by layering preferred translation sources. */
+function buildDictionary<T extends Record<string, string | undefined>>(
+	base: BuiltInStrings,
+	...dictionaries: (T | BuiltInStrings | undefined)[]
+): BuiltInStrings & T {
+	const dictionary = { ...base };
+	// Iterate over alternate dictionaries to avoid overwriting preceding values with `undefined`.
+	for (const dict of dictionaries) {
+		for (const key in dict) {
+			const value = dict[key as keyof typeof dict];
+			if (value) dictionary[key as keyof typeof dictionary] = value;
+		}
+	}
+	return dictionary as BuiltInStrings & T;
+}