import type { RequestHandler } from 'express';
export interface CorsOptions {
    /**
     * Allowed origin(s). Pass `'*'` to allow any (incompatible with `credentials: true`),
     * a single origin, an array, or a predicate. Defaults to `'*'`.
     */
    origin?: '*' | string | string[] | ((origin: string | undefined) => boolean);
    /** Allow cookies / Authorization to be sent cross-origin. Default: false. */
    credentials?: boolean;
    /** Methods echoed in `Access-Control-Allow-Methods`. */
    methods?: string[];
    /** Request headers echoed in `Access-Control-Allow-Headers`. */
    headers?: string[];
    /** Response headers exposed to the browser. */
    exposedHeaders?: string[];
    /** Preflight cache TTL in seconds. Default: 86400 (24h). */
    maxAge?: number;
}
/**
 * Minimal CORS middleware. Covers the common needs (allow-list of origins,
 * credentials, preflight). For complex setups, use the `cors` npm package
 * via `mtbREST.app().use(cors())`.
 */
export declare function corsMiddleware(opts?: CorsOptions): RequestHandler;
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