import type { BodyType, KeyValue } from './types.js';
import type { ApplyCookieResult, BuildHeadersResult, IHeaders } from './IHeaders.js';
/**
 * Builds request headers and merges cookie jar values for outbound requests.
 */
export declare class Headers implements IHeaders {
    /**
     * Builds request headers from enabled key-value pairs and body type defaults.
     *
     * Rejects hop-by-hop headers and fields containing control characters or CRLF.
     *
     * @param headers - User-defined headers.
     * @param bodyType - Body type used to infer Content-Type when absent.
     * @param options - When `preserveMultipartContentType` is true, keep a user Content-Type
     *   for multipart (used with raw body overrides that own the boundary).
     * @returns Header map ready for fetch, or an error when a field is invalid.
     */
    build(headers: KeyValue[], bodyType: BodyType, options?: {
        preserveMultipartContentType?: boolean;
    }): BuildHeadersResult;
    /**
     * Validates and merges a cookie jar header when no Cookie header is already present.
     *
     * @param headers - Mutable header map to update on success.
     * @param cookieHeader - Optional Cookie header value from the cookie jar.
     */
    applyCookie(headers: Record<string, string>, cookieHeader: string | undefined): ApplyCookieResult;
}
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