/* Declarations for lib/srs.js — the module itself ships unchanged. */

export const AGAIN: 0;
export const HARD: 1;
export const GOOD: 2;
export const EASY: 3;
export type Grade = 0 | 1 | 2 | 3;

export const NEW: 0;
export const LEARNING: 1;
export const REVIEW: 2;
export type CardState = 0 | 1 | 2;

/** Days at which a card counts as known. */
export const SECURE_INTERVAL: number;

export interface Card {
  state: CardState;
  interval: number;
  ease: number;
  /** Day number, not a timestamp — see dayNumber(). */
  due: number;
  reps: number;
  lapses: number;
}

export function newCard(): Card;
export function grade(card: Card, g: Grade, today: number): Card;
export function markKnown(today: number): Card;

export type CardStatus = "new" | "learning" | "review" | "secure";
export function statusOf(card: Card | null | undefined): CardStatus;

/** Label for the interval a grade would produce — shown on the buttons. */
export function preview(card: Card | null | undefined, g: Grade, today: number): string;

/** Local day number, DST-safe. */
export function dayNumber(d?: Date): number;

/* ── recall evidence, kept separate from the schedule ──────────────── */

export const LEARNED_OK: number;
export const LEARNED_STREAK: number;
export const LEARNED_SPAN: number;

export interface Evidence {
  ok: number;
  wrong: number;
  lookups: number;
  streak: number;
  /** Round of the first outcome of any kind. */
  firstRound: number;
  /** Round of the latest outcome of any kind. */
  lastRound: number;
  lastSeen: number;
  /** Distinct rounds with an outcome. */
  rounds: number;
}

export function newEvidence(): Evidence;

/** Pure: returns a new record. A lookup is never a recall and resets the streak. */
export function noteOutcome(
  ev: Evidence,
  outcome: "ok" | "wrong",
  round: number,
  lookedUp?: boolean,
): Evidence;

export function isLearned(ev: Evidence): boolean;

/** Whether a tutor's ::confirmed for this word may be stored. */
export function acceptConfirmation(ev: Evidence): boolean;