/**
 * 마작패 (docs/games/mahjong.md §3, §8.1). Tile ids 0..135, kind = id >> 2 (0..33):
 * 0-8 1m-9m, 9-17 1p-9p, 18-26 1s-9s, 27-30 동남서북, 31-33 백발중.
 * Over the wire a tile is a short code "<kind><copy>[r]", e.g. "5m0r" (red five), "3p2", "7z1" (중) — unique per
 * tile so hidden-information leak checks stay meaningful.
 */
export type TileId = number;
export type Kind = number;

export const EAST = 27;
export const SOUTH = 28;
export const WEST = 29;
export const NORTH = 30;
export const HAKU = 31;
export const HATSU = 32;
export const CHUN = 33;

export const KIND_CODES: string[] = [
  ...['m', 'p', 's'].flatMap((s) => Array.from({ length: 9 }, (_, i) => `${i + 1}${s}`)),
  ...Array.from({ length: 7 }, (_, i) => `${i + 1}z`),
];
const KIND_BY_CODE: Record<string, Kind> = Object.fromEntries(KIND_CODES.map((c, i) => [c, i]));

export const kindOf = (id: TileId): Kind => id >> 2;
export const isHonor = (k: Kind): boolean => k >= 27;
export const isDragon = (k: Kind): boolean => k >= 31;
export const isWind = (k: Kind): boolean => k >= 27 && k <= 30;
export const isTerminal = (k: Kind): boolean => k < 27 && (k % 9 === 0 || k % 9 === 8);
export const isYaochu = (k: Kind): boolean => k >= 27 || k % 9 === 0 || k % 9 === 8;
export const suitOf = (k: Kind): number => (k < 27 ? Math.floor(k / 9) : 3);
export const numOf = (k: Kind): number => (k < 27 ? (k % 9) + 1 : 0);
export const YAOCHU: Kind[] = [0, 8, 9, 17, 18, 26, 27, 28, 29, 30, 31, 32, 33];
export const GREEN: Kind[] = [19, 20, 21, 23, 25, HATSU];

/** Kinds missing in 3-player (산마): 2m~8m. */
export const isSanmaRemoved = (k: Kind): boolean => k >= 1 && k <= 7;

export function allTiles(sanma: boolean): TileId[] {
  const out: TileId[] = [];
  for (let id = 0; id < 136; id++) if (!(sanma && isSanmaRemoved(kindOf(id)))) out.push(id);
  return out;
}

/** Red fives in use: 4인 3 → 5m·5p·5s, 2 → 5p·5s; 산마 → 5p·5s (or none). Copy 0 of each five is the red one. */
export function redTiles(akaDora: number, sanma: boolean): TileId[] {
  if (akaDora <= 0) return [];
  if (sanma || akaDora === 2) return [52, 88];
  return [16, 52, 88];
}

export function tileCode(id: TileId, red: readonly TileId[]): string {
  return `${KIND_CODES[kindOf(id)]}${id & 3}${red.includes(id) ? 'r' : ''}`;
}

/** Inverse of tileCode (the red marker is ignored); null when malformed. */
export function parseTileCode(code: string): TileId | null {
  const m = /^([1-9][mps]|[1-7]z)([0-3])r?$/.exec(code);
  if (!m) return null;
  return KIND_BY_CODE[m[1]!]! * 4 + Number(m[2]);
}

export const kindCode = (k: Kind): string => KIND_CODES[k]!;
export const kindFromCode = (code: string): Kind | null => KIND_BY_CODE[code] ?? null;

/** Dora shown by an indicator (§6.2, 산마: 1m ↔ 9m). */
export function doraFromIndicator(ind: Kind, sanma: boolean): Kind {
  if (ind < 27) {
    if (sanma && ind === 0) return 8;
    if (sanma && ind === 8) return 0;
    return ind - (ind % 9) + (((ind % 9) + 1) % 9);
  }
  if (ind <= 30) return ind === 30 ? 27 : ind + 1;
  return ind === 33 ? 31 : ind + 1;
}

const SUIT_KO = ['만수', '통수', '삭수'];
const HONOR_KO = ['동', '남', '서', '북', '백', '발', '중'];
/** Screen-reader / log name, e.g. "만수 5", "동", "중". */
export function kindNameKo(k: Kind): string {
  return k < 27 ? `${SUIT_KO[suitOf(k)]} ${numOf(k)}` : HONOR_KO[k - 27]!;
}
/** Short name, e.g. "5만", "3통", "7삭", "동". */
export function kindShortKo(k: Kind): string {
  return k < 27 ? `${numOf(k)}${['만', '통', '삭'][suitOf(k)]}` : HONOR_KO[k - 27]!;
}
export const WIND_KO = ['동', '남', '서', '북'];

/** Sort key: 만→통→삭→자, by number, red five before plain fives. */
export function compareTiles(a: TileId, b: TileId): number {
  return a - b;
}

export function counts34(kinds: Iterable<Kind>): number[] {
  const c = new Array<number>(34).fill(0);
  for (const k of kinds) c[k]!++;
  return c;
}