/**
 * Spaced Repetition Scheduler (SM-2 Algorithm)
 *
 * Implements the SuperMemo SM-2 algorithm for optimal review scheduling.
 * Schedules reviews at increasing intervals based on performance.
 *
 * @packageDocumentation
 */
import type { SkillId } from '../types/skill.js';
import type { MasteryState } from '../types/mastery.js';
import type { GraphStorage } from '../types/storage.js';
import type { ReviewSchedule, ReviewOptions } from '../types/query.js';
/**
 * Default options for review scheduling
 */
export declare const REVIEW_DEFAULTS: Required<ReviewOptions>;
/**
 * SM-2 algorithm constants
 */
export declare const SM2_CONSTANTS: {
    /** Minimum easiness factor */
    readonly MIN_EASINESS: 1.3;
    /** Default easiness factor */
    readonly DEFAULT_EASINESS: 2.5;
    /** Maximum easiness factor */
    readonly MAX_EASINESS: 3.5;
    /** Initial interval (days) after first review */
    readonly INITIAL_INTERVAL: 1;
    /** Second interval (days) after second review */
    readonly SECOND_INTERVAL: 6;
};
/**
 * Review quality rating (0-5 scale)
 */
export type ReviewQuality = 0 | 1 | 2 | 3 | 4 | 5;
/**
 * Learner review state
 */
export interface ReviewState {
    /** Mastery states for skills (keyed by skill ID) */
    masteryStates: Map<SkillId, MasteryState>;
}
/**
 * SM-2 update result
 */
export interface SM2Result {
    /** New easiness factor */
    easinessFactor: number;
    /** New interval in days */
    intervalDays: number;
    /** Next review date */
    nextReview: Date;
    /** Number of successful repetitions */
    repetitions: number;
}
/**
 * Spaced Repetition Scheduler
 *
 * Uses the SM-2 algorithm to schedule optimal review times.
 * The algorithm adjusts intervals based on recall quality:
 * - Quality 5: Perfect response
 * - Quality 4: Correct with hesitation
 * - Quality 3: Correct with difficulty
 * - Quality 2: Incorrect but easily recalled
 * - Quality 1: Incorrect, remembered when shown
 * - Quality 0: Complete blackout
 *
 * @example
 * ```typescript
 * const scheduler = new SpacedRepetitionScheduler(storage);
 *
 * // Get review schedule
 * const schedule = await scheduler.getSchedule(learnerState);
 * console.log(`${schedule.dueNow.length} reviews due now`);
 *
 * // Update after a review
 * const result = scheduler.calculateNextReview(masteryState, 4); // quality 4
 * console.log(`Next review in ${result.intervalDays} days`);
 * ```
 */
export declare class SpacedRepetitionScheduler {
    private readonly storage;
    constructor(storage: GraphStorage);
    /**
     * Get the review schedule for a learner
     *
     * @param learner - Current learner state
     * @param options - Schedule options
     * @returns Review schedule with due and upcoming items
     */
    getSchedule(learner: ReviewState, options?: ReviewOptions): Promise<ReviewSchedule>;
    /**
     * Calculate the next review interval using SM-2 algorithm
     *
     * @param currentState - Current mastery state
     * @param quality - Review quality (0-5)
     * @returns Updated SM-2 parameters
     */
    calculateNextReview(currentState: MasteryState, quality: ReviewQuality): SM2Result;
    /**
     * Convert review quality to mastery update
     *
     * @param quality - Review quality (0-5)
     * @returns Mastery level adjustment
     */
    qualityToMasteryAdjustment(quality: ReviewQuality): number;
    /**
     * Calculate next review date based on current mastery state
     */
    private calculateNextReviewDate;
    /**
     * Estimate previous interval from mastery state
     */
    private estimatePreviousInterval;
    /**
     * Calculate review priority
     * Higher priority = more urgent to review
     */
    private calculatePriority;
}
/**
 * Create a spaced repetition scheduler
 */
export declare function createSpacedRepetitionScheduler(storage: GraphStorage): SpacedRepetitionScheduler;
/**
 * Standalone SM-2 calculation (for use without storage)
 *
 * @param quality - Review quality (0-5)
 * @param previousEasiness - Previous easiness factor
 * @param previousInterval - Previous interval in days
 * @param repetitions - Number of previous successful repetitions
 * @returns Updated SM-2 parameters
 */
export declare function calculateSM2(quality: ReviewQuality, previousEasiness?: number, previousInterval?: number, repetitions?: number): SM2Result;
//# sourceMappingURL=spaced-repetition.d.ts.map