import type { ExistsOptions, ExistsResult } from './npm.js';
interface PurlObject {
    name: string;
    namespace?: string | undefined;
    qualifiers?: Record<string, string> | undefined;
    subpath?: string | undefined;
    type?: string | undefined;
    version?: string | undefined;
}
/**
 * Normalize Docker package URL.
 * Lowercases name only (namespace is case-sensitive for registry hosts).
 */
export declare function normalize(purl: PurlObject): PurlObject;
/**
 * Validate Docker package URL.
 * Name and namespace must not contain injection characters.
 */
export declare function validate(purl: PurlObject, throws: boolean): boolean;
/**
 * Check if a Docker image exists in Docker Hub.
 *
 * Queries Docker Hub API at https://hub.docker.com/v2/repositories to verify
 * image existence and optionally validate a specific tag. Returns the latest
 * tag if no specific tag is requested.
 *
 * **Note:** Docker Hub has rate limits for unauthenticated requests.
 *
 * **Caching:** Responses can be cached using a TTL cache to reduce registry
 * requests. Pass `{ cache }` option with a cache instance from `createTtlCache()`.
 *
 * @param name - Image name (e.g., 'nginx', 'redis')
 * @param namespace - Optional namespace/repository (e.g., 'library' for official images)
 * @param version - Optional tag to validate (e.g., 'latest', '1.25.3')
 * @param options - Optional configuration including cache
 * @returns Promise resolving to existence result with latest tag
 *
 * @example
 * ```typescript
 * // Check if official image exists
 * const result = await dockerExists('nginx', 'library')
 * // -> { exists: true, latestVersion: 'latest' }
 *
 * // Check user image
 * const result = await dockerExists('myapp', 'myuser')
 * // -> { exists: true, latestVersion: 'v1.0.0' }
 *
 * // Validate specific tag
 * const result = await dockerExists('nginx', 'library', '1.25.3')
 * // -> { exists: true, latestVersion: 'latest' }
 *
 * // With caching
 * import { createTtlCache } from '@socketsecurity/lib/cache-with-ttl'
 * const cache = createTtlCache({ ttl: 5 * 60 * 1000, prefix: 'docker' })
 * const result = await dockerExists('nginx', 'library', undefined, { cache })
 *
 * // Non-existent image
 * const result = await dockerExists('this-image-does-not-exist', 'library')
 * // -> { exists: false, error: 'Image not found' }
 * ```
 */
export declare function dockerExists(name: string, namespace?: string, version?: string, options?: ExistsOptions): Promise<ExistsResult>;
export {};