joke-app/packages/engine/src/betting.ts

/**
 * Shared betting engine for poker modes and seotda (docs/games/poker.md §5.2, §5.3, §5.5;
 * docs/games/seotda.md §5.4). Pure functions over a JSON state.
 *
 * Chips here are room-only play points (no money value, docs/04 §6).
 *
 * Styles:
 *  - korean:   check / 삥(ping) / call / 따당(double) / quarter / half / full / die.
 *              One raise-type action (ping included) per player per round, and only as that
 *              player's first action in the round (no check-raise, no call-raise).
 *  - noLimit:  fold / check / call / bet-raise (raiseTo between min and stack) / all-in.
 *  - potLimit: same, max raiseTo = currentBet + (pot + toCall).
 */

export type BetStyle = 'korean' | 'noLimit' | 'potLimit';
export type KoreanMax = 'half' | 'full';
export type BetterStatus = 'active' | 'folded' | 'allIn' | 'out';

export interface Better {
  id: string;
  stack: number;
  /** Chips put in during the current round (blinds included, antes excluded). */
  round: number;
  /** Chips put in during the whole hand (antes included). */
  total: number;
  status: BetterStatus;
  /** Has taken a voluntary action this round (posting a blind does not count). */
  acted: boolean;
  /** korean: already used the one raise-type action this round. */
  raised: boolean;
  /** noLimit/potLimit: may raise when next to act (false after an incomplete all-in raise). */
  mayRaise: boolean;
}

export interface BettingState {
  style: BetStyle;
  baseUnit: number;
  koreanMax: KoreanMax;
  /** Seat order (index = seat in this hand). */
  players: Better[];
  currentBet: number;
  /** korean: someone has put chips in this round. */
  opened: boolean;
  /** noLimit/potLimit: size of the last full raise (starts at baseUnit). */
  lastRaise: number;
  /** Index of the player to act, or null when the round is complete. */
  turn: number | null;
}

export type KoreanKind = 'check' | 'ping' | 'call' | 'double' | 'quarter' | 'half' | 'full' | 'die';
export type BetAction =
  | { kind: KoreanKind }
  | { kind: 'fold' }
  | { kind: 'check' }
  | { kind: 'call' }
  | { kind: 'raise'; to: number }
  | { kind: 'allIn' };

export interface LegalBet {
  kind: BetAction['kind'];
  /** Chips that leave the stack for this action (capped at the stack → all-in). */
  amount: number;
  /** True when the amount is the whole stack. */
  allIn: boolean;
  /** noLimit/potLimit raise range (raiseTo totals for this round). */
  minTo?: number;
  maxTo?: number;
}

export interface BetEvent {
  type: 'bet';
  player: string;
  kind: BetAction['kind'];
  amount: number;
  allIn: boolean;
}

// ---------------------------------------------------------------- setup

export function newBetting(
  ids: { id: string; stack: number }[],
  opts: { style: BetStyle; baseUnit: number; koreanMax?: KoreanMax },
): BettingState {
  return {
    style: opts.style,
    baseUnit: opts.baseUnit,
    koreanMax: opts.koreanMax ?? 'half',
    players: ids.map((p) => ({
      id: p.id,
      stack: p.stack,
      round: 0,
      total: 0,
      status: p.stack > 0 ? 'active' : 'out',
      acted: false,
      raised: false,
      mayRaise: true,
    })),
    currentBet: 0,
    opened: false,
    lastRaise: opts.baseUnit,
    turn: null,
  };
}

const clone = (s: BettingState): BettingState => structuredClone(s);

export const potTotal = (s: BettingState): number => s.players.reduce((a, p) => a + p.total, 0);
export const chipsInPlay = (s: BettingState): number => s.players.reduce((a, p) => a + p.total + p.stack, 0);
export const contenders = (s: BettingState): Better[] => s.players.filter((p) => p.status === 'active' || p.status === 'allIn');
export const canAct = (p: Better): boolean => p.status === 'active';

function put(p: Better, want: number, toRound: boolean): number {
  const amt = Math.max(0, Math.min(want, p.stack));
  p.stack -= amt;
  p.total += amt;
  if (toRound) p.round += amt;
  if (p.stack === 0 && p.status === 'active') p.status = 'allIn';
  return amt;
}

/** Ante: goes to the pot, not to the round (korean 학교 / 7포커 기본 판돈). */
export function postAnte(state: BettingState, amount: number): BettingState {
  const s = clone(state);
  for (const p of s.players) if (p.status === 'active') put(p, amount, false);
  return s;
}

/** Blind: counts towards the round but is not a voluntary action. */
export function postBlind(state: BettingState, idx: number, amount: number): BettingState {
  const s = clone(state);
  const p = s.players[idx]!;
  if (p.status !== 'active') return s;
  put(p, amount, true);
  s.currentBet = Math.max(s.currentBet, p.round);
  s.opened = s.currentBet > 0;
  return s;
}

/** Starts a betting round. Blinds (if any) must be posted after this call. */
export function startRound(state: BettingState, firstIdx: number): BettingState {
  const s = clone(state);
  for (const p of s.players) {
    p.round = 0;
    p.acted = false;
    p.raised = false;
    p.mayRaise = true;
  }
  s.currentBet = 0;
  s.opened = false;
  s.lastRaise = s.baseUnit;
  s.turn = null;
  s.turn = findNext(s, firstIdx - 1);
  if (roundComplete(s)) s.turn = null;
  return s;
}

/** After posting blinds, (re)select who acts first. */
export function setFirstToAct(state: BettingState, firstIdx: number): BettingState {
  const s = clone(state);
  s.turn = findNext(s, firstIdx - 1);
  if (roundComplete(s)) s.turn = null;
  return s;
}

// ---------------------------------------------------------------- queries

export const toCallOf = (s: BettingState, p: Better): number => Math.max(0, s.currentBet - p.round);

function needsAction(s: BettingState, p: Better): boolean {
  return p.status === 'active' && (!p.acted || p.round < s.currentBet);
}

/** True when nobody needs to act any more in this round. */
export function roundComplete(s: BettingState): boolean {
  if (contenders(s).length <= 1) return true;
  const actives = s.players.filter(canAct);
  if (actives.length === 0) return true;
  if (actives.length === 1 && actives[0]!.round >= s.currentBet) {
    // Lone player facing only all-ins and nothing to call: nothing to decide.
    const others = contenders(s).filter((p) => p !== actives[0]);
    if (others.every((p) => p.status === 'allIn')) return true;
  }
  return actives.every((p) => !needsAction(s, p));
}

/** Only one player left who has not folded → hand is decided without showdown. */
export const handDecided = (s: BettingState): boolean => contenders(s).length <= 1;

/** No more betting possible for the rest of the hand (≤1 player can still act and nothing is owed). */
export function bettingClosed(s: BettingState): boolean {
  const actives = s.players.filter(canAct);
  return handDecided(s) || (actives.length <= 1 && roundComplete(s));
}

function findNext(s: BettingState, from: number): number | null {
  const n = s.players.length;
  for (let k = 1; k <= n; k++) {
    const i = (((from + k) % n) + n) % n;
    if (needsAction(s, s.players[i]!)) return i;
  }
  return null;
}

function koreanAmount(s: BettingState, p: Better, kind: KoreanKind): number {
  const toCall = toCallOf(s, p);
  const pot = potTotal(s);
  const bump = (extra: number) => toCall + Math.max(extra, s.baseUnit);
  switch (kind) {
    case 'check':
    case 'die':
      return 0;
    case 'ping':
      return s.baseUnit;
    case 'call':
      return toCall;
    case 'double':
      return 2 * toCall;
    case 'quarter':
      return bump(Math.floor((pot + toCall) / 4));
    case 'half':
      return bump(Math.floor((pot + toCall) / 2));
    case 'full':
      return bump(pot + toCall);
  }
}

/** All legal betting actions for player `idx` (empty if it is not their turn). */
export function legalBets(s: BettingState, idx: number): LegalBet[] {
  if (s.turn !== idx) return [];
  const p = s.players[idx]!;
  const toCall = toCallOf(s, p);
  const mk = (kind: BetAction['kind'], want: number, extra: Partial<LegalBet> = {}): LegalBet => ({
    kind,
    amount: Math.min(want, p.stack),
    allIn: want >= p.stack && want > 0,
    ...extra,
  });
  if (s.style === 'korean') {
    const out: LegalBet[] = [];
    const mayRaise = !p.acted && !p.raised;
    if (!s.opened) {
      out.push(mk('check', 0));
      if (mayRaise) out.push(mk('ping', s.baseUnit));
    } else if (toCall > 0) out.push(mk('call', toCall));
    else out.push(mk('check', 0));
    if (mayRaise) {
      const raises: KoreanKind[] = toCall > 0 ? ['double', 'quarter', 'half'] : ['quarter', 'half'];
      if (s.koreanMax === 'full') raises.push('full');
      for (const k of raises) {
        const amt = koreanAmount(s, p, k);
        // A raise must put in more than the call; if the stack can't, the call/all-in covers it.
        if (amt > toCall && p.stack > toCall) out.push(mk(k, amt));
      }
    }
    out.push(mk('die', 0));
    return dedupeAllIn(out);
  }
  // noLimit / potLimit
  const out: LegalBet[] = [mk('fold', 0)];
  if (toCall === 0) out.push(mk('check', 0));
  else out.push(mk('call', toCall));
  if (p.mayRaise && p.stack > toCall) {
    const minTo = s.currentBet === 0 ? s.baseUnit : s.currentBet + s.lastRaise;
    const stackTo = p.round + p.stack;
    let maxTo = stackTo;
    if (s.style === 'potLimit') maxTo = Math.min(stackTo, s.currentBet + potTotal(s) + toCall);
    if (stackTo > s.currentBet) {
      if (minTo <= maxTo) out.push({ kind: 'raise', amount: minTo - p.round, allIn: minTo >= stackTo, minTo, maxTo });
      if (s.style === 'noLimit' || stackTo <= maxTo) out.push(mk('allIn', p.stack));
    }
  }
  return out;
}

function dedupeAllIn(list: LegalBet[]): LegalBet[] {
  // Several korean raises may all cap at the stack; keep the smallest-named one plus call/die.
  const seen = new Set<number>();
  return list.filter((b) => {
    if (!b.allIn || b.kind === 'call' || b.kind === 'die') return true;
    if (seen.has(b.amount)) return false;
    seen.add(b.amount);
    return true;
  });
}

/** Returns a Korean error message if the action is illegal, else null. */
export function validateBet(s: BettingState, idx: number, a: BetAction): string | null {
  if (s.turn !== idx) return '지금은 내 차례가 아니에요.';
  const legal = legalBets(s, idx);
  if (a.kind === 'raise') {
    const r = legal.find((l) => l.kind === 'raise');
    if (!r) return '지금은 올릴 수 없어요.';
    const p = s.players[idx]!;
    const stackTo = p.round + p.stack;
    if (!Number.isInteger(a.to) || a.to < r.minTo! || a.to > r.maxTo!) {
      if (a.to === stackTo && legal.some((l) => l.kind === 'allIn')) return null;
      return `${r.minTo}~${r.maxTo} 칩 사이로 올려 주세요.`;
    }
    return null;
  }
  if (!legal.some((l) => l.kind === a.kind)) {
    const names: Record<string, string> = {
      check: '체크', ping: '삥', call: '콜', double: '따당', quarter: '쿼터', half: '하프', full: '풀', die: '다이', fold: '폴드', allIn: '올인',
    };
    return `지금은 ${names[a.kind] ?? a.kind}을(를) 할 수 없어요.`;
  }
  return null;
}

// ---------------------------------------------------------------- apply

/** Applies a validated action. Advances the turn; `turn === null` means the round is over. */
export function applyBet(state: BettingState, idx: number, a: BetAction): { state: BettingState; event: BetEvent } {
  const err = validateBet(state, idx, a);
  if (err) throw new Error(`illegal bet: ${err}`);
  const s = clone(state);
  const p = s.players[idx]!;
  const before = p.round;
  let paid = 0;
  const raiseTo = (to: number) => {
    paid = put(p, to - p.round, true);
    const size = p.round - s.currentBet;
    const full = size >= s.lastRaise;
    if (p.round > s.currentBet) {
      if (full || s.style === 'korean') {
        if (s.style !== 'korean') s.lastRaise = size;
        // A full raise reopens the action for everyone else.
        for (const o of s.players) if (o !== p && o.status === 'active') o.mayRaise = true;
      } else {
        // Incomplete all-in raise: players who already acted may only call or fold.
        for (const o of s.players) if (o !== p && o.status === 'active' && o.acted) o.mayRaise = false;
      }
      s.currentBet = p.round;
    }
  };
  switch (a.kind) {
    case 'check':
      break;
    case 'die':
    case 'fold':
      p.status = 'folded';
      break;
    case 'call':
      paid = put(p, toCallOf(s, p), true);
      break;
    case 'ping':
    case 'double':
    case 'quarter':
    case 'half':
    case 'full': {
      const amt = koreanAmount(s, p, a.kind);
      raiseTo(p.round + amt);
      p.raised = true;
      s.opened = true;
      break;
    }
    case 'raise':
      raiseTo(Math.min(a.to, p.round + p.stack));
      break;
    case 'allIn':
      if (p.round + p.stack > s.currentBet) raiseTo(p.round + p.stack);
      else paid = put(p, p.stack, true);
      break;
  }
  if (s.style === 'korean' && p.round > 0) s.opened = true;
  p.acted = true;
  if (p.stack === 0 && p.status === 'active') p.status = 'allIn';
  s.turn = roundComplete(s) ? null : findNext(s, idx);
  return {
    state: s,
    event: { type: 'bet', player: p.id, kind: a.kind, amount: p.round - before || paid, allIn: p.status === 'allIn' && paid > 0 },
  };
}

/**
 * Auto action on timeout / disconnect (docs: korean → check if possible else die;
 * noLimit → check if possible else fold).
 */
export function timeoutBet(s: BettingState, idx: number): BetAction {
  const legal = legalBets(s, idx);
  if (legal.some((l) => l.kind === 'check')) return { kind: 'check' };
  return s.style === 'korean' ? { kind: 'die' } : { kind: 'fold' };
}

// ---------------------------------------------------------------- pots

export interface Pot {
  amount: number;
  /** Player ids eligible to win this pot (not folded). */
  eligible: string[];
}

/**
 * Returns the uncalled part of the biggest contribution to its owner
 * (the amount above the second-largest total). Call when a round ends or the hand is decided.
 */
export function returnUncalled(state: BettingState): { state: BettingState; refunded: { id: string; amount: number } | null } {
  const s = clone(state);
  const sorted = [...s.players].sort((a, b) => b.total - a.total);
  const top = sorted[0];
  const second = sorted[1]?.total ?? 0;
  if (!top || top.total <= second) return { state: s, refunded: null };
  const extra = top.total - second;
  top.total -= extra;
  top.round = Math.max(0, top.round - extra);
  top.stack += extra;
  if (top.status === 'allIn' && top.stack > 0) top.status = 'active';
  s.currentBet = Math.max(...s.players.map((p) => p.round));
  return { state: s, refunded: { id: top.id, amount: extra } };
}

/**
 * Splits everything put in this hand into main/side pots (poker.md §5.5).
 * Levels are the totals of non-folded all-in players; folded chips stay in the pots they reached.
 * Side pots come last; callers usually award them first.
 */
export function buildPots(players: Pick<Better, 'id' | 'total' | 'status'>[]): Pot[] {
  const live = players.filter((p) => p.status === 'active' || p.status === 'allIn');
  const levels = [...new Set(live.filter((p) => p.status === 'allIn').map((p) => p.total))].sort((a, b) => a - b);
  const maxLive = Math.max(0, ...live.map((p) => p.total));
  if (!levels.includes(maxLive)) levels.push(maxLive);
  const pots: Pot[] = [];
  let prev = 0;
  for (const level of levels) {
    if (level <= prev) continue;
    let amount = 0;
    for (const p of players) amount += Math.max(0, Math.min(p.total, level) - prev);
    // Active players can still call up to any level, so they stay eligible mid-round.
    const eligible = live.filter((p) => p.status === 'active' || p.total >= level).map((p) => p.id);
    if (amount > 0) pots.push({ amount, eligible });
    prev = level;
  }
  // Chips from folded players above the top live level (only possible if a folder over-contributed).
  const leftover = players.reduce((a, p) => a + Math.max(0, p.total - prev), 0);
  if (leftover > 0) {
    if (pots.length) pots[pots.length - 1]!.amount += leftover;
    else pots.push({ amount: leftover, eligible: live.map((p) => p.id) });
  }
  // Merge consecutive pots with identical eligibility.
  const merged: Pot[] = [];
  for (const pot of pots) {
    const last = merged[merged.length - 1];
    if (last && last.eligible.join() === pot.eligible.join()) last.amount += pot.amount;
    else merged.push({ ...pot, eligible: [...pot.eligible] });
  }
  return merged;
}

/**
 * Splits `amount` among `winners` (already ordered by priority for odd chips,
 * e.g. seat order starting left of the dealer). Returns id → chips.
 */
export function splitAmount(amount: number, winners: string[]): Record<string, number> {
  const out: Record<string, number> = {};
  if (winners.length === 0) return out;
  const share = Math.floor(amount / winners.length);
  let rest = amount - share * winners.length;
  for (const w of winners) {
    out[w] = (out[w] ?? 0) + share + (rest > 0 ? 1 : 0);
    if (rest > 0) rest--;
  }
  return out;
}

/**
 * Awards every pot to the best eligible hand(s). `compare(a, b)` > 0 when a beats b.
 * `order` gives odd-chip priority (seat order from left of dealer).
 */
export function awardPots(pots: Pot[], compare: (a: string, b: string) => number, order: string[]): Record<string, number> {
  const won: Record<string, number> = {};
  for (const pot of pots) {
    let best: string[] = [];
    for (const id of pot.eligible) {
      if (best.length === 0) best = [id];
      else {
        const c = compare(id, best[0]!);
        if (c > 0) best = [id];
        else if (c === 0) best.push(id);
      }
    }
    best.sort((x, y) => order.indexOf(x) - order.indexOf(y));
    for (const [id, amt] of Object.entries(splitAmount(pot.amount, best))) won[id] = (won[id] ?? 0) + amt;
  }
  return won;
}

/** Display helper shared by UIs: never a currency (docs/04 §6). */
export function formatChips(n: number): string {
  return `${n.toLocaleString('ko-KR')} 칩`;
}