/**
 * Accepts `zh-TW`, `zh-tw`, `zh_TW`, `zhTW`, `ZH-tw`, `en` etc. Returns
 * canonical BCP 47 form (`zh-TW`, `en`). Throws `InvalidLocaleError` for
 * anything that doesn't shape up.
 */
export declare function toCanonicalLocale(input: string): string;
/** Canonical → URL form (always lowercase). */
export declare function toUrlLocale(canonical: string): string;
/**
 * Best-effort canonicalization. Unlike `toCanonicalLocale`, never
 * throws — returns the original input unchanged when it's malformed.
 * Used for query-side comparisons where a malformed filter value
 * should simply match nothing rather than error.
 */
export declare function safeCanonicalLocale(input: string): string;
/**
 * Canonicalize an array of locale strings, separating valid from
 * invalid in one pass. The caller decides whether to reject (write
 * paths) or warn (read paths) on `invalid.length > 0`.
 *
 * Preserves input order in `valid`; canonicalizes each entry; dedupes
 * the result so `["zh-tw", "zh-TW"]` collapses to `["zh-TW"]`.
 */
export declare function canonicalizeLocaleList(inputs: ReadonlyArray<string>): {
    readonly valid: string[];
    readonly invalid: string[];
};
export declare function containsScriptSubtagLocale(inputs: ReadonlyArray<string>): boolean;
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