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

export const CHO: string;
export const JUNG: string;
export const JONG: string;

/** [initialIndex, medialIndex, finalIndex], or null if not a syllable block. */
export function decompose(ch: string): [number, number, number] | null;
export function compose(i: number, m: number, f?: number): string;

export const isJamo: {
  initial(c: string): boolean;
  medial(c: string): boolean;
  final(c: string): boolean;
};

/**
 * A 두벌식 IME. Hold one per input: feed jamo with key(), literal text with
 * text(), Backspace with back(). Each call returns the full new value.
 */
export class Composer {
  cho: string | null;
  jung: string | null;
  jong: string | null;
  reset(): void;
  readonly empty: boolean;
  /** The syllable currently being assembled, as text. */
  render(): string;
  key(value: string, jamo: string): string;
  back(value: string): string;
  /** Commit the buffer and append literal text (space, punctuation). */
  text(value: string, t: string): string;
}

export const KEYBOARD: {
  rows: string[][];
  shift: Record<string, string>;
};

/* ── letter-level marking ───────────────────────────────────────────── */

/** Two-consonant batchim clusters, unpacked: "ㄼ" → "ㄹ+ㅂ". */
export const CLUSTER: Record<string, string>;

/** ["first consonant", "vowel", "batchim"] — the three slots of a syllable. */
export const SLOT: string[];

/** "짧다" → "짧=ㅉ+ㅏ+ㄼ(ㄹ+ㅂ) · 다=ㄷ+ㅏ" */
export function spellOut(word: string): string;

/** The exact jamo difference, naming what was correct as well as what was
    wrong. "" when either side is empty; "identical" when they match. */
export function letterDiff(expected: string, written: string): string;

export interface LetterRow {
  /** The item as the student saw it — for a recall task, the English. */
  prompt: string;
  expected: string;
  written: string;
}

/** The LETTER-LEVEL CHECK block for a marking message; "" when nothing differs. */
export function letterCheck(rows: LetterRow[]): string;