import { Mapping, Transformer } from '@walkeros/core';

/**
 * Fingerprint transformer settings.
 */
interface FingerprintSettings {
    /**
     * Fields to include in hash (order matters!).
     * Each field is resolved via getMappingValue with source object { event, ingest }.
     *
     * String fields use dot notation:
     * - 'ingest.ip' -> context.ingest.ip
     * - 'ingest.userAgent' -> context.ingest.userAgent
     * - 'event.data.userId' -> event.data.userId
     *
     * Function fields via mapping config:
     * - { fn: () => new Date().getDate() } -> day of month
     * - { key: 'ingest.ip', fn: anonymizeIP } -> transform value
     */
    fields: Mapping.Value[];
    /**
     * Dot-notation path where hash is stored on the event.
     * @default 'user.hash'
     */
    output?: string;
    /**
     * Truncate hash to this length.
     * @default undefined (full 64-char SHA-256 hash)
     */
    length?: number;
}

/**
 * Fingerprint transformer - hash configurable fields for session continuity.
 *
 * Resolves fields from { event, ingest } source object using getMappingValue,
 * concatenates values in order, hashes with SHA-256, and stores at output path.
 *
 * @example
 * transformerFingerprint({
 *   config: {
 *     settings: {
 *       fields: [
 *         'ingest.ip',
 *         'ingest.userAgent',
 *         { fn: () => new Date().getDate() },
 *       ],
 *       output: 'user.hash',
 *       length: 16,
 *     },
 *   },
 * })
 */
declare const transformerFingerprint: Transformer.Init<Transformer.Types<FingerprintSettings>>;

export { type FingerprintSettings, transformerFingerprint as default, transformerFingerprint };