/**
 * RSS search backend — supplements keyless web search with structured feeds.
 *
 * The keyless search chain (Bing → Baidu → DuckDuckGo) returns unstructured
 * HTML results — titles + snippets + URLs. RSS feeds return structured
 * entries with **title, link, publication date, and full or summary content**,
 * which gives the LLM:
 *
 * 1. **Timeliness**: every entry has a pubDate — the LLM can filter by
 *    recency without relying on search-engine time filters (which are often
 *    unreliable for keyless backends).
 * 2. **Accuracy**: RSS content comes directly from the source (no search-engine
 *    snippet truncation or anti-bot interference). The LLM sees the actual
 *    article summary, not a scraped fragment.
 * 3. **Source authority**: RSS feeds are curated by the publisher — no SEO
 *    spam, no content farms. Results are from named sources (blogs, news
 *    sites, project release feeds).
 *
 * Design:
 * - Pluggable into the existing `WebSearchBackend` interface (same signature).
 * - No external dependency beyond global `fetch` (Node 18+).
 * - Supports a built-in catalog of tech/robotics news feeds + user-configurable
 *   feeds via `MOSS_RSS_FEEDS` env var.
 * - Filters by recency (day/week/month) using pubDate.
 * - Falls back gracefully on parse errors (malformed XML, network failures).
 *
 * @public
 */
import type { WebSearchBackend } from './web-search.js';
export interface RssFeed {
    url: string;
    category?: string;
    lang?: 'en' | 'zh';
}
export interface RssSearchOptions {
    /** Custom feeds to search (in addition to or instead of built-ins). */
    feeds?: RssFeed[];
    /** Whether to include built-in feeds. Default true. */
    includeBuiltin?: boolean;
    /** Per-feed timeout in ms. Default 10_000. */
    timeoutMs?: number;
    /**
     * Override the SSRF private-host check. Production leaves this undefined so
     * the real `isPrivateHost` (DNS-based) guards every feed fetch. Tests inject
     * a stub so mock feed hosts (e.g. `rss-mock.test`) don't get rejected by
     * DNS resolution failure.
     *
     * @internal
     */
    isPrivateHostCheck?: (hostname: string) => Promise<boolean>;
}
export declare function normalizeFreshNewsQuery(query: string): string;
export declare function buildGoogleNewsRssUrl(query: string, recency?: 'day' | 'week' | 'month' | 'year'): string;
export declare function createGoogleNewsRssBackend(options?: Omit<RssSearchOptions, 'feeds' | 'includeBuiltin'>): WebSearchBackend;
/**
 * Create an RSS search backend that fits the `WebSearchBackend` interface.
 *
 * The backend fetches configured RSS feeds in parallel, filters entries by
 * the query (case-insensitive substring match on title + content), filters
 * by recency if specified, and returns `WebSearchResult[]`.
 */
export declare function createRssSearchBackend(options?: RssSearchOptions): WebSearchBackend;
/** Get the built-in feed list (for testing / configuration). */
export declare function getBuiltinFeeds(): RssFeed[];
/** Parse user-configured feeds from MOSS_RSS_FEEDS env var (comma-separated URLs). */
export declare function parseUserFeeds(env?: NodeJS.ProcessEnv): RssFeed[];
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