/**
 * Decay computation — pure function.
 *
 * Applied by retrieval stages to compute an entry's effective relevance at
 * read time. Never mutates the entry; only returns a scaling factor in
 * `[0, +∞)` that stages apply to their existing score.
 *
 * Model:
 *   factor = exp(-ln2 · Δt / halfLife) · min(accessBoost^accessCount, MAX_BOOST)
 *
 * The time term is exponential decay (half after one half-life). The access
 * term is multiplicative — each read of an entry boosts its future
 * relevance. `MAX_BOOST_MULTIPLIER` caps runaway boosting so a frequently-
 * read but old entry doesn't crowd out newer relevant entries indefinitely.
 */
import type { DecayPolicy, MemoryEntry } from './types.js';
/**
 * Compute the decay factor for an entry at a given moment.
 *
 * @param entry   The memory entry to score. Must have `lastAccessedAt` and
 *                `accessCount` set (storage adapters populate these).
 * @param now     The reference time (unix ms). Defaults to `Date.now()`.
 * @param policy  Optional override — when omitted, uses `entry.decayPolicy`.
 *                Stages can pass a stage-wide default so entries without a
 *                per-entry policy still decay consistently. If neither is
 *                set, returns 1.0 (no decay applied).
 *
 * @returns Scaling factor in `[0, MAX_BOOST_MULTIPLIER]` — stages multiply
 *          this against their existing relevance score.
 */
export declare function computeDecayFactor(entry: Pick<MemoryEntry, 'lastAccessedAt' | 'accessCount' | 'decayPolicy'>, now?: number, policy?: DecayPolicy): number;
/**
 * Compute decay for multiple entries in one call. Order-preserving; returns
 * one factor per entry. Convenience for stages that rank whole batches.
 */
export declare function computeDecayFactors(entries: readonly Pick<MemoryEntry, 'lastAccessedAt' | 'accessCount' | 'decayPolicy'>[], now?: number, policy?: DecayPolicy): number[];