refactor progress

packages/geo_utils/src/RegionCodeValidation.tsx

@@ -0,0 +1,50 @@
+/*
+ * 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/>.
+ */
+
+const ASCII_UPPER_A = 65;
+const ASCII_UPPER_Z = 90;
+const REGION_CODE_LENGTH = 2;
+
+function isAsciiUpperAlpha2(value: string): boolean {
+	return (
+		value.length === REGION_CODE_LENGTH &&
+		value.charCodeAt(0) >= ASCII_UPPER_A &&
+		value.charCodeAt(0) <= ASCII_UPPER_Z &&
+		value.charCodeAt(1) >= ASCII_UPPER_A &&
+		value.charCodeAt(1) <= ASCII_UPPER_Z
+	);
+}
+
+export function normalizeRegionCode(regionCode: string): string | undefined {
+	const trimmedRegionCode = regionCode.trim();
+	if (trimmedRegionCode.length !== REGION_CODE_LENGTH) {
+		return undefined;
+	}
+
+	const upperRegionCode = trimmedRegionCode.toUpperCase();
+	if (!isAsciiUpperAlpha2(upperRegionCode)) {
+		return undefined;
+	}
+
+	return upperRegionCode;
+}
+
+export function isRegionCode(value: string): boolean {
+	return normalizeRegionCode(value) !== undefined;
+}