import { ApolloLink, Observable, FetchResult, Operation } from '@apollo/client/core';
export interface SSELinkOptions {
    /** SSE endpoint URL */
    url: string;
    /** Optional headers to include with requests */
    headers?: Record<string, string>;
    /** Enable debug logging */
    debug?: boolean;
}
/**
 * SSE Link for GraphQL Yoga subscriptions
 *
 * GraphQL Yoga uses Server-Sent Events (SSE) for subscriptions over HTTP.
 * This is more compatible with serverless and edge deployments than WebSockets.
 *
 * SSE Format:
 * - event: next\ndata: {...}\n\n - Subscription data
 * - event: complete\n\n - Subscription ended
 * - event: error\ndata: {...}\n\n - Error occurred
 *
 * @example
 * ```ts
 * import { SSELink } from '@burdenoff/fe-libs/shared/graphql/links/sse-link';
 *
 * const sseLink = new SSELink({
 *   url: 'https://gw-wspace.local.burdenoff.com/workspaces/graphql/stream',
 *   headers: {
 *     authorization: `Bearer ${token}`,
 *   },
 * });
 * ```
 */
export declare class SSELink extends ApolloLink {
    private url;
    private headers;
    private debug;
    constructor(options: SSELinkOptions);
    /**
     * Update headers (useful for token refresh)
     */
    setHeaders(headers: Record<string, string>): void;
    /**
     * Update the authorization header
     */
    setAuthToken(token: string | null): void;
    request(operation: Operation): Observable<FetchResult>;
}
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