// Splendor — pure state engine. No Phaser, no network, no rendering.
//
// State is immutable from the outside: every mutator deep-clones and returns a
// fresh state (the IslandLogic/BlokusLogic idiom). Randomness is seeded so games
// are reproducible and testable. A turn is exactly one action (take3 / take2 /
// reserve / buy); if it leaves the player over the 10-token limit the state
// parks in a 'discard' phase until tokens are returned, then the turn finalizes
// (noble visit + end-of-game check + advance).

import {
  GEMS, GOLD, CARDS_BY_TIER, NOBLES, tokenSupplyFor,
  WIN_POINTS, HAND_LIMIT, MAX_RESERVED, FACE_UP_PER_TIER, TAKE_SAME_MIN, NOBLE_POINTS,
} from './SplendorData.js';

const TIERS = [1, 2, 3];

// ── seeded RNG (mulberry32), matching IslandLogic ────────────────────────────
function rngFrom(seedState) {
  let a = seedState >>> 0;
  return () => {
    a |= 0; a = (a + 0x6D2B79F5) | 0;
    let t = Math.imul(a ^ (a >>> 15), 1 | a);
    t = (t + Math.imul(t ^ (t >>> 7), 61 | t)) ^ t;
    return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
  };
}
function shuffle(arr, rng) {
  const a = arr.slice();
  for (let i = a.length - 1; i > 0; i--) {
    const j = Math.floor(rng() * (i + 1));
    [a[i], a[j]] = [a[j], a[i]];
  }
  return a;
}

const clone = (s) => JSON.parse(JSON.stringify(s));
const emptyTokens = () => ({ white: 0, blue: 0, green: 0, red: 0, black: 0, gold: 0 });
const emptyBonuses = () => ({ white: 0, blue: 0, green: 0, red: 0, black: 0 });

// ── queries ──────────────────────────────────────────────────────────────────
export function currentPlayer(state) { return state.players[state.current]; }

export function tokenTotal(p) {
  return GEMS.reduce((n, g) => n + p.tokens[g], 0) + p.tokens[GOLD];
}

// How a player would pay for `card`: coloured tokens used per colour + gold to
// cover the shortfall after permanent bonuses.
export function purchaseCost(p, card) {
  const pay = {};
  let gold = 0;
  for (const color of GEMS) {
    const need = Math.max(0, (card.cost[color] ?? 0) - (p.bonuses[color] ?? 0));
    const use = Math.min(need, p.tokens[color]);
    pay[color] = use;
    gold += need - use;
  }
  return { pay, gold };
}

export function canAfford(p, card) {
  return purchaseCost(p, card).gold <= p.tokens[GOLD];
}

// Nobles the player currently qualifies for.
export function qualifyingNobles(state, p) {
  return state.nobles.filter((n) =>
    Object.entries(n.requires).every(([color, req]) => (p.bonuses[color] ?? 0) >= req));
}

export function cardById(state, id) {
  for (const t of TIERS) {
    const found = state.board[t].find((c) => c && c.id === id);
    if (found) return found;
  }
  for (const p of state.players) {
    const r = p.reserved.find((c) => c.id === id);
    if (r) return r;
  }
  return null;
}

// ── construction ─────────────────────────────────────────────────────────────
export function createInitialState({ playerCount = 4, names = [], seed } = {}) {
  const pc = Math.max(2, Math.min(4, playerCount));
  const s = {
    seed: (seed ?? Math.floor(Math.random() * 1e9)) >>> 0,
    rngCursor: 0,
    playerCount: pc,
    bank: tokenSupplyFor(pc),
    decks: {},
    board: {},
    nobles: [],
    players: [],
    current: 0,
    phase: 'turn',              // turn | discard | gameOver
    pendingDiscardSeat: null,
    triggeredEnd: false,
    lastVisit: null,            // { seat, nobleId } for the scene to animate
    log: [],
  };

  const rng = rngFrom((s.seed + 0x9e3779b9) >>> 0);
  for (const t of TIERS) {
    const deck = shuffle(CARDS_BY_TIER[t], rng);
    s.board[t] = deck.splice(0, FACE_UP_PER_TIER);
    while (s.board[t].length < FACE_UP_PER_TIER) s.board[t].push(null);
    s.decks[t] = deck;
  }
  s.nobles = shuffle(NOBLES, rng).slice(0, pc + 1);

  for (let seat = 0; seat < pc; seat++) {
    s.players.push({
      seat,
      name: names[seat] ?? (seat === 0 ? 'You' : `Player ${seat}`),
      tokens: emptyTokens(),
      bonuses: emptyBonuses(),
      reserved: [],
      nobles: [],
      points: 0,
      cardsCount: 0,
    });
  }
  return s;
}

// ── legal actions ────────────────────────────────────────────────────────────
function combinations(arr, k) {
  if (k === 0) return [[]];
  if (arr.length < k) return [];
  const [head, ...rest] = arr;
  return [
    ...combinations(rest, k - 1).map((c) => [head, ...c]),
    ...combinations(rest, k),
  ];
}

export function legalActions(state) {
  if (state.phase !== 'turn') return [];
  const p = currentPlayer(state);
  const actions = [];

  // take 3 different (or as many distinct colours as the bank can offer, up to 3)
  const avail = GEMS.filter((g) => state.bank[g] > 0);
  const k = Math.min(3, avail.length);
  if (k > 0) {
    for (const combo of combinations(avail, k)) {
      actions.push({ type: 'take3', colors: combo });
    }
  }

  // take 2 of one colour (pile must have ≥4)
  for (const g of GEMS) {
    if (state.bank[g] >= TAKE_SAME_MIN) actions.push({ type: 'take2', color: g });
  }

  // reserve (face-up card or top of a deck) — gains 1 gold if any left
  if (p.reserved.length < MAX_RESERVED) {
    for (const t of TIERS) {
      for (const c of state.board[t]) {
        if (c) actions.push({ type: 'reserve', cardId: c.id, tier: t });
      }
      if (state.decks[t].length > 0) actions.push({ type: 'reserveDeck', tier: t });
    }
  }

  // buy a face-up card or one of your reserved cards
  for (const t of TIERS) {
    for (const c of state.board[t]) {
      if (c && canAfford(p, c)) actions.push({ type: 'buy', cardId: c.id, source: 'board' });
    }
  }
  for (const c of p.reserved) {
    if (canAfford(p, c)) actions.push({ type: 'buy', cardId: c.id, source: 'reserve' });
  }

  return actions;
}

// ── helpers used by applyAction ──────────────────────────────────────────────
function drawTop(s, tier) {
  return s.decks[tier].length ? s.decks[tier].shift() : null;
}

function refillSlot(s, tier, cardId) {
  const row = s.board[tier];
  const idx = row.findIndex((c) => c && c.id === cardId);
  if (idx >= 0) row[idx] = drawTop(s, tier);
}

// After tokens change, either park for discard or finalize the turn.
function afterAction(s) {
  if (tokenTotal(currentPlayer(s)) > HAND_LIMIT) {
    s.phase = 'discard';
    s.pendingDiscardSeat = s.current;
    return s;
  }
  return finalizeTurn(s);
}

// Noble visit, win trigger, advance to next seat.
function finalizeTurn(s) {
  const p = currentPlayer(s);
  const eligible = qualifyingNobles(s, p);
  if (eligible.length) {
    // Award the highest-requirement noble (ties: first). One visit per turn.
    const noble = eligible[0];
    s.nobles = s.nobles.filter((n) => n.id !== noble.id);
    p.nobles.push(noble);
    p.points += NOBLE_POINTS;
    s.lastVisit = { seat: p.seat, nobleId: noble.id };
  } else {
    s.lastVisit = null;
  }

  if (p.points >= WIN_POINTS) s.triggeredEnd = true;

  s.current = (s.current + 1) % s.playerCount;
  s.phase = (s.triggeredEnd && s.current === 0) ? 'gameOver' : 'turn';
  s.pendingDiscardSeat = null;
  return s;
}

// ── apply a turn action ──────────────────────────────────────────────────────
export function applyAction(state, action) {
  const s = clone(state);
  if (s.phase !== 'turn') return s;
  const p = currentPlayer(s);

  switch (action.type) {
    case 'take3': {
      for (const g of action.colors) { s.bank[g]--; p.tokens[g]++; }
      s.log.push(`${p.name} takes ${action.colors.join(', ')}.`);
      return afterAction(s);
    }
    case 'take2': {
      s.bank[action.color] -= 2; p.tokens[action.color] += 2;
      s.log.push(`${p.name} takes 2 ${action.color}.`);
      return afterAction(s);
    }
    case 'reserve': {
      const card = cardById(s, action.cardId);
      if (!card) return s;
      refillSlot(s, action.tier, action.cardId);
      p.reserved.push(card);
      if (s.bank[GOLD] > 0) { s.bank[GOLD]--; p.tokens[GOLD]++; }
      s.log.push(`${p.name} reserves a tier-${action.tier} card.`);
      return afterAction(s);
    }
    case 'reserveDeck': {
      const card = drawTop(s, action.tier);
      if (!card) return s;
      p.reserved.push(card);
      if (s.bank[GOLD] > 0) { s.bank[GOLD]--; p.tokens[GOLD]++; }
      s.log.push(`${p.name} reserves the top tier-${action.tier} card.`);
      return afterAction(s);
    }
    case 'buy': {
      const card = cardById(s, action.cardId);
      if (!card || !canAfford(p, card)) return s;
      const { pay, gold } = purchaseCost(p, card);
      for (const color of GEMS) { p.tokens[color] -= pay[color]; s.bank[color] += pay[color]; }
      p.tokens[GOLD] -= gold; s.bank[GOLD] += gold;
      p.bonuses[card.bonus]++;
      p.points += card.points;
      p.cardsCount++;
      if (action.source === 'reserve') {
        p.reserved = p.reserved.filter((c) => c.id !== card.id);
      } else {
        refillSlot(s, card.tier, card.id);
      }
      s.log.push(`${p.name} buys a ${card.bonus} card${card.points ? ` (+${card.points})` : ''}.`);
      return afterAction(s);
    }
    case 'pass':
      // No legal action available (bank empty, nothing affordable, reserve full).
      s.log.push(`${p.name} cannot act and passes.`);
      return finalizeTurn(s);
    default:
      return s;
  }
}

// ── discard phase ────────────────────────────────────────────────────────────
// Default choice: return the most-abundant coloured tokens first, never gold.
export function defaultDiscards(state) {
  const p = currentPlayer(state);
  const excess = tokenTotal(p) - HAND_LIMIT;
  const map = {};
  let left = Math.max(0, excess);
  // Greedily shave from the largest non-gold piles.
  const pools = GEMS.map((g) => ({ g, n: p.tokens[g] }));
  while (left > 0) {
    pools.sort((a, b) => (b.n - (map[b.g] ?? 0)) - (a.n - (map[a.g] ?? 0)));
    const top = pools[0];
    if ((top.n - (map[top.g] ?? 0)) <= 0) break;
    map[top.g] = (map[top.g] ?? 0) + 1;
    left--;
  }
  return map;
}

export function applyDiscard(state, discardMap) {
  const s = clone(state);
  if (s.phase !== 'discard') return s;
  const p = currentPlayer(s);
  for (const [color, n] of Object.entries(discardMap)) {
    const take = Math.min(n, p.tokens[color] ?? 0);
    p.tokens[color] -= take;
    s.bank[color] += take;
  }
  if (tokenTotal(p) > HAND_LIMIT) {
    // Still over (incomplete discard) — stay parked.
    return s;
  }
  s.phase = 'turn';
  return finalizeTurn(s);
}

// ── end of game ──────────────────────────────────────────────────────────────
export function isGameOver(state) { return state.phase === 'gameOver'; }

// Ranking: most prestige, then fewest purchased cards (official tiebreak).
export function finalRanking(state) {
  return state.players
    .map((p) => ({ seat: p.seat, name: p.name, points: p.points, cards: p.cardsCount }))
    .sort((a, b) => (b.points - a.points) || (a.cards - b.cards));
}