/**
 * Importance Decay Calculation
 *
 * Implements time-based decay for memory importance, accounting for
 * access frequency and recency.
 */
/**
 * Decay parameters
 */
export interface DecayParams {
    baseDecayRate?: number;
    halfLifeDays?: number;
    accessBoostFactor?: number;
    maxAccessBoost?: number;
    minDecayScore?: number;
}
/**
 * Calculate the decay score for a memory
 *
 * The decay score represents how "fresh" a memory is, decreasing over time
 * but being boosted by access frequency.
 *
 * Formula:
 *   decay = importance * e^(-rate * days) * (1 + min(accessBoost * accessCount, maxBoost))
 *
 * @param importance - Initial importance (0-1)
 * @param daysSinceAccess - Days since last access
 * @param accessCount - Number of times this memory has been accessed
 * @param params - Optional decay parameters
 * @returns Decay score (0-1 range)
 */
export declare function calculateDecayScore(importance: number, daysSinceAccess: number, accessCount: number, params?: DecayParams): number;
/**
 * Calculate exponential decay with half-life
 *
 * Uses the formula: score = initial * (1/2)^(days / halfLife)
 *
 * @param initial - Initial score
 * @param days - Days elapsed
 * @param halfLife - Half-life in days
 * @returns Decayed score
 */
export declare function exponentialDecay(initial: number, days: number, halfLife?: number): number;
/**
 * Calculate decay rate from half-life
 *
 * @param halfLife - Half-life in days
 * @returns Decay rate
 */
export declare function halfLifeToDecayRate(halfLife: number): number;
/**
 * Calculate days until score drops below threshold
 *
 * @param initialScore - Initial score
 * @param threshold - Target threshold
 * @param decayRate - Decay rate per day
 * @returns Number of days until threshold is reached
 */
export declare function daysUntilThreshold(initialScore: number, threshold: number, decayRate?: number): number;
/**
 * Boost decay score on access
 *
 * @param currentScore - Current decay score
 * @param boostAmount - Amount to boost (default: restore to 80% of original)
 * @returns Boosted decay score
 */
export declare function boostOnAccess(currentScore: number, boostAmount?: number): number;
/**
 * Multi-factor decay combining time, importance, and usage patterns
 *
 * @param params - Memory parameters
 * @returns Combined decay score
 */
export declare function multiFactorDecay(params: {
    importance: number;
    daysSinceCreation: number;
    daysSinceAccess: number;
    accessCount: number;
    userWeight?: number;
    decayParams?: DecayParams;
}): number;
/**
 * Calculate effective decay for search ranking
 *
 * This combines the stored decay score with a query-time recency boost.
 *
 * @param storedDecayScore - Pre-computed decay score from storage
 * @param documentTimestamp - When the document was created
 * @param currentTime - Current time (default: now)
 * @param recencyBoostWeight - How much to boost recent items (0-1)
 * @returns Adjusted decay score for ranking
 */
export declare function searchTimeDecay(storedDecayScore: number, documentTimestamp: Date, currentTime?: Date, recencyBoostWeight?: number): number;
/**
 * Batch update decay scores for multiple memories
 *
 * @param memories - Array of memories with decay metadata
 * @param params - Decay parameters
 * @returns Updated decay scores
 */
export declare function batchUpdateDecayScores(memories: Array<{
    id: string;
    importance: number;
    lastAccessed: Date;
    accessCount: number;
}>, params?: DecayParams): Array<{
    id: string;
    newDecayScore: number;
}>;
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