import { type RemotePattern } from '@astrojs/internal-helpers/remote';
/**
 * Parses a potentially comma-separated multi-value header (as produced by
 * proxy chains) and returns the first value, trimmed of whitespace.
 * Returns `undefined` when the header is absent or empty.
 */
export declare function getFirstForwardedValue(multiValueHeader: string | string[] | undefined): string | undefined;
/**
 * Validate a host against allowedDomains.
 * Returns the host only if it matches an allowed pattern; otherwise, undefined.
 * This prevents SSRF attacks by ensuring the Host header is trusted.
 */
export declare function validateHost(host: string | undefined, protocol: string, allowedDomains?: Partial<RemotePattern>[]): string | undefined;
/**
 * Validate forwarded headers (proto, host, port) against allowedDomains.
 * Returns validated values or undefined for rejected headers.
 * Uses strict defaults: http/https only for proto, rejects port if not in allowedDomains.
 */
export declare function validateForwardedHeaders(forwardedProtocol?: string, forwardedHost?: string, forwardedPort?: string, allowedDomains?: Partial<RemotePattern>[]): {
    protocol?: string;
    host?: string;
    port?: string;
};