/**
 * SMI-915: Metrics Aggregator
 *
 * Aggregates skill usage events into actionable metrics for value measurement.
 * Provides:
 * - Per-skill metrics aggregation
 * - Global metrics across all skills
 * - Retention rate calculation
 * - Time-period filtering
 */
import type { Database as DatabaseType } from '../db/database-interface.js';
import type { SkillMetrics } from './types.js';
/**
 * Time period for aggregation queries
 */
export interface AggregationPeriod {
    /** Start timestamp in milliseconds */
    start: number;
    /** End timestamp in milliseconds */
    end: number;
}
/**
 * Global metrics across all skills
 */
export interface GlobalMetrics {
    /** Total number of skill invocations */
    totalInvocations: number;
    /** Count of unique users */
    uniqueUsers: number;
    /** Overall success rate (0-1) */
    overallSuccessRate: number;
    /** Average task duration in milliseconds */
    avgTaskDuration: number;
    /** Top skills by invocation count */
    topSkills: Array<{
        skillId: string;
        invocations: number;
    }>;
}
/**
 * Aggregates skill usage metrics from the database
 */
export declare class MetricsAggregator {
    private db;
    /**
     * Create a metrics aggregator
     *
     * @param db - SQLite database instance
     */
    constructor(db: DatabaseType);
    /**
     * Get metrics for a specific skill
     *
     * @param skillId - The skill identifier
     * @param period - Optional time period filter
     * @returns Aggregated metrics for the skill
     */
    getSkillMetrics(skillId: string, period?: AggregationPeriod): SkillMetrics;
    /**
     * Get metrics for all skills
     *
     * @param period - Optional time period filter
     * @returns Array of metrics for each skill
     */
    getAllSkillMetrics(period?: AggregationPeriod): SkillMetrics[];
    /**
     * Get global metrics across all skills
     *
     * @param period - Optional time period filter
     * @returns Aggregated metrics for all skills
     */
    getGlobalMetrics(period?: AggregationPeriod): GlobalMetrics;
    /**
     * Calculate retention rate (users who used skill again within N days)
     *
     * @param skillId - The skill identifier
     * @param days - Retention window in days (default: 7)
     * @returns Retention rate (0-1)
     */
    getRetentionRate(skillId: string, days?: number): number;
    /**
     * Get skills with usage in the specified period
     *
     * @param period - Time period filter
     * @returns Array of skill IDs with usage
     */
    getActiveSkills(period: AggregationPeriod): string[];
    /**
     * Get the date range of available data
     *
     * @returns Object with min and max timestamps, or null if no data
     */
    getDataRange(): {
        minTimestamp: number;
        maxTimestamp: number;
    } | null;
}
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