refactor progress

packages/geo_utils/src/RegionDisplayNameResolver.tsx

@@ -0,0 +1,75 @@
+/*
+ * Copyright (C) 2026 Fluxer Contributors
+ *
+ * This file is part of Fluxer.
+ *
+ * Fluxer is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Fluxer is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with Fluxer. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+import {Locales} from '@fluxer/constants/src/Locales';
+import {normalizeRegionCode} from '@fluxer/geo_utils/src/RegionCodeValidation';
+
+const DISPLAY_NAME_TYPE: Intl.DisplayNamesOptions['type'] = 'region';
+const DISPLAY_NAME_FALLBACK: Intl.DisplayNamesOptions['fallback'] = 'none';
+
+const displayNamesByLocale = new Map<string, Intl.DisplayNames>();
+
+function resolveLocale(locale?: string): string {
+	const trimmedLocale = locale?.trim();
+	if (trimmedLocale && trimmedLocale.length > 0) {
+		return trimmedLocale;
+	}
+
+	return Locales.EN_US;
+}
+
+function getDisplayNames(locale?: string): Intl.DisplayNames {
+	const localeCode = resolveLocale(locale);
+	const cachedDisplayNames = displayNamesByLocale.get(localeCode);
+	if (cachedDisplayNames) {
+		return cachedDisplayNames;
+	}
+
+	const displayNames = new Intl.DisplayNames([localeCode], {
+		type: DISPLAY_NAME_TYPE,
+		fallback: DISPLAY_NAME_FALLBACK,
+	});
+	displayNamesByLocale.set(localeCode, displayNames);
+	return displayNames;
+}
+
+function resolveRegionDisplayNameFromFormatter(
+	regionCode: string,
+	displayNames: Intl.DisplayNames,
+): string | undefined {
+	const normalizedRegionCode = normalizeRegionCode(regionCode);
+	if (!normalizedRegionCode) {
+		return undefined;
+	}
+
+	return displayNames.of(normalizedRegionCode) ?? undefined;
+}
+
+export function resolveRegionDisplayName(regionCode: string, locale?: string): string | undefined {
+	const displayNames = getDisplayNames(locale);
+	return resolveRegionDisplayNameFromFormatter(regionCode, displayNames);
+}
+
+export function resolveRegionDisplayNames(
+	regionCodes: ReadonlyArray<string>,
+	locale?: string,
+): Array<string | undefined> {
+	const displayNames = getDisplayNames(locale);
+	return regionCodes.map((regionCode) => resolveRegionDisplayNameFromFormatter(regionCode, displayNames));
+}