station-master/src/engine/setup.ts

/**
 * Game setup — rules §4.
 *
 * Builds the initial state deterministically from a seed. Part of component 2; the D12 rolls
 * come from component 7.
 */

import {
  ACTION_CARDS,
  ENHANCEMENT_CARDS,
  EXTRA_TRAINS,
  FREIGHT_PROFILES,
  MAINLINE_MODIFIER_CARDS,
  MANEUVER_CARDS,
  SPACE_USE_CARDS,
  MOVES_PER_LOCAL_OPS,
  MODIFIER_PROFILES,
  OFFICE_PROFILES,
  OPENING_DEALS,
  MAINLINE_DECK,
  houseRules,
  mainlineProfile,
  TRACK_CARDS,
  ROLLING_STOCK_SUPPLY,
  STAGES_PER_DAY,
  TIMETABLED_TRAINS,
  crewTrayCount,
  mainlineCardCount,
  officeProfile,
} from './content.ts';
import type { Rng } from './rng.ts';
import { createRng } from './rng.ts';
import type {
  Card,
  CardId,
  DivisionNode,
  SeatIndex,
  GameConfig,
  GameState,
  OfficeArea,
  PlayerIndex,
  RollingStock,
  TrackCard,
  TrayId,
} from './state.ts';
import { coordKey, emptyTally, freshTurns } from './state.ts';

export type SetupOptions = {
  id: string;
  seed: number;
  config: GameConfig;
  playerNames: string[];
};

/** Builds the 52-card Home Office deck (§12.1). Unshuffled; caller shuffles with the seeded RNG. */
export function buildDeck(mode: GameConfig['mode'] = 'competitive', pvpCardsAllowed = false): Card[] {
  /**
   * THE 22 OPPONENT-DIRECTED CARDS ARE OUT OF EVERY DECK REGARDLESS OF `pvpCardsAllowed`, for now.
   *
   * Q6 took them out of solitaire because they have no legal target in a one-player game. They are
   * out of the competitive deck too because `checkPlay` answers both categories `NOT_IMPLEMENTED`:
   * leaving them in would make ~9% of draws reject outright, which is worse than not dealing them.
   * `pvpCardsAllowed` (`GameConfig`, wired 2026-08-20) is the player-facing toggle, but ANDing it
   * with `cardsImplemented` keeps it inert until Phase 5 actually builds the cards — flipping
   * `pvpCardsAllowed` on today must not turn a working game into one where ~9% of draws reject.
   *
   * AND SO ARE THE SEVEN CARDS THAT ANSWER THEM — see below. They used to be dealt and sit dormant,
   * which is the same dead draw by another name. Recorded in TODO.md as multiplayer work.
   *
   * `mode` is still taken so the signature does not move when they return; it is deliberately unused
   * for these two categories today.
   */
  void mode;
  const cardsImplemented = false;
  const opponentCardsInDeck = pvpCardsAllowed && cardsImplemented;
  const cards: Card[] = [];
  let n = 0;
  const push = (kind: Card['kind']): void => {
    cards.push({ id: `c${n++}`, kind });
  };

  for (const t of TIMETABLED_TRAINS) push({ kind: 'timetabledTrain', number: t.number });
  for (const t of EXTRA_TRAINS) push({ kind: 'extraTrain', number: t.number });
  for (const o of OFFICE_PROFILES) {
    for (let i = 0; i < o.copiesInDeck; i++) push({ kind: 'office', tier: o.tier });
  }
  for (const f of FREIGHT_PROFILES) {
    for (let i = 0; i < f.copies; i++) push({ kind: 'freightFacility', facility: f.kind });
  }
  for (const m of MODIFIER_PROFILES) {
    for (let i = 0; i < m.copies; i++) push({ kind: 'modifier', modifier: m.kind });
  }
  if (opponentCardsInDeck) {
    for (const c of SPACE_USE_CARDS) {
      for (let i = 0; i < c.copies; i++) push({ kind: 'spaceUse', key: c.key });
    }
  }
  /**
   * A DEFENCE GOES OUT WITH THE ATTACK IT ANSWERS.
   *
   * Facing Point Locks (both kinds), the Water Column and the Overpass exist only to answer Derail,
   * a Watertower and a Railroad Crossing — all of which are among the 22 opponent-directed cards
   * held out above. Left in, they are dead draws for exactly the same reason the attacks would be,
   * and there are 7 of them. `SimpleCard.answers` names the pairing on the card itself, so they come
   * back together the moment `opponentCardsInDeck` does.
   */
  const dealt = (c: { answers?: string }): boolean => opponentCardsInDeck || !c.answers;
  for (const c of ENHANCEMENT_CARDS) {
    if (!dealt(c)) continue;
    for (let i = 0; i < c.copies; i++) push({ kind: 'enhancement', key: c.key });
  }
  for (const c of MAINLINE_MODIFIER_CARDS) {
    if (!dealt(c)) continue;
    for (let i = 0; i < c.copies; i++) push({ kind: 'mainlineModifier', key: c.key });
  }
  for (const c of MANEUVER_CARDS) {
    for (let i = 0; i < c.copies; i++) push({ kind: 'maneuver', key: c.key });
  }
  if (opponentCardsInDeck) {
    for (const c of ACTION_CARDS) {
      for (let i = 0; i < c.copies; i++) push({ kind: 'action', key: c.key });
    }
  }
  // Track is IN the deck, 96 cards of it — the single largest category, and the reason building a
  // district costs you the industry or train you did not draw instead.
  for (const t of TRACK_CARDS) {
    for (let i = 0; i < t.copiesInDeck; i++) push({ kind: 'track', geometry: t.geometry, hand: t.hand });
  }

  return cards;
}

/** The Division Yard starts with every rolling stock piece (§4.9). */
export function buildRollingStock(): RollingStock[] {
  const out: RollingStock[] = [];
  for (const s of ROLLING_STOCK_SUPPLY) {
    for (let i = 0; i < s.loaded; i++) out.push({ type: s.type, loaded: true });
    for (let i = 0; i < s.empty; i++) out.push({ type: s.type, loaded: false });
  }
  return out;
}

/**
 * A player's opening three cards: Limits, Whistle Post, Limits, in one horizontal row (§4.2).
 *
 * Gap 8 — the Office card carries a plain junction stub above and below, so Secondary Track can
 * branch from the opening Stage. The stubs are NOT turnouts: §A.1's directional rule governs
 * drawn turnout cards only.
 */
function buildOfficeArea(seat: SeatIndex): OfficeArea {
  const row = 0;
  const officeCoord = { row, col: 0 };
  const limitsWest = { row, col: -1 };
  const limitsEast = { row, col: 1 };

  const officeCard: TrackCard = {
    geometry: { kind: 'office' },
    baseOperationalRail: true,
    standing: [],
    standingWest: 0,
    facility: buildPassengerFacility('whistlePost'),
    modifiers: [],
    enhancements: [],
  };

  const limitsCard = (): TrackCard => ({
    geometry: { kind: 'limits' },
    baseOperationalRail: true,
    standing: [],
    standingWest: 0,
    facility: null,
    modifiers: [],
    enhancements: [],
  });

  const grid = new Map<string, TrackCard>();
  grid.set(coordKey(officeCoord), officeCard);
  grid.set(coordKey(limitsWest), limitsCard());
  grid.set(coordKey(limitsEast), limitsCard());

  return {
    seat,
    tier: 'whistlePost',
    grid,
    officeCoord,
    runningRow: row,
    limitsWest,
    limitsEast,
    adOccupancy: [],
    heldAtLimits: [],
    dispatchUsedToday: [],
  };
}

/**
 * A Whistle Post is not a Passenger Facility (§9), so it has no Porters and no slots — but the
 * Office card still carries a facility record so an upgrade is a property change rather than a
 * card swap (game-state.md constraint 9).
 */
function buildPassengerFacility(tier: Parameters<typeof officeProfile>[0]): NonNullable<TrackCard['facility']> {
  const p = officeProfile(tier);
  return {
    kind: 'passenger',
    subtype: 'office',
    allows: { outbound: p.isPassengerFacility, inbound: p.isPassengerFacility },
    outboundBox: [],
    inboundBox: [],
    capacity: { outbound: p.passengerOut, inbound: p.passengerIn },
    // No freight pipeline: a Depot, Station and Terminal work passengers only, and the MEN | AT |
    // WORK sign is printed "For Freight Facilities" (rules-v0.2.md:452). This was a three-slot array
    // of nulls, which read as "three empty boxes" to every renderer that looked.
    menAtWork: null,
    industryTrack: { cars: [] },
    laborers: 0,
    porters: p.porters,
    usedThisStage: { laborers: 0, porters: 0 },
  };
}

/**
 * §4.3-4.4 — the west-to-east chain, with a Division Point beyond each end.
 *
 * Each Mainline card is now a TYPE drawn at random (§4.2, "a Mainline card is drawn at random and
 * placed between each player"), which is what gives the Division its terrain and therefore its
 * crossing times.
 */
/**
 * THE MAINLINE CARDS ARE DEALT FROM A DECK, NOT ROLLED.
 *
 * `MAINLINE_PROFILES` is a list of card TYPES and this drew from it uniformly WITH replacement, so
 * a Division could be handed two Interchanges or two Tunnels, and Plains — printed twice in the
 * deck — carried the same weight as cards printed once. `MAINLINE_DECK` is the printed inventory
 * (`docs/StationMaster-Mainline-Deck-v0.4.5.md`, which flagged this as needing correction), and the
 * deal is now a deal: take cards out of it and do not put them back.
 *
 * The Extra-start rules are what forced the issue. "An Extra may start at the Interchange if one is
 * on the board" only reads as a rule if the board can hold at most one.
 *
 * A Division needs `players + 1` cards, so four players draw five from ten and the deck is never
 * close to exhausted; the throw is there because a silent short Division would be very hard to see.
 */
function buildDivision(players: number, rng: Rng): DivisionNode[] {
  const nodes: DivisionNode[] = [];
  const deck = [...MAINLINE_DECK];
  const mainline = (): DivisionNode => {
    if (deck.length === 0) throw new Error('the Mainline deck ran out — too many players for it');
    const card = deck.splice(rng.nextInt(deck.length), 1)[0]!;
    const node: DivisionNode = { kind: 'mainline', card, transits: [] };
    if (card === 'heavyGrade') {
      /**
       * SETTLED, not provisional (v0.5.0, Jesse's call) — this overrides the card's own printed
       * "Player sets orientation". A Heavy Grade sits on the shared west-to-east chain BETWEEN two
       * players (§4.2), or beyond an end Division Point next to one — never inside one player's own
       * district — so whichever direction climbs advantages one neighbour over the other, and there
       * is no single player who owns that call fairly. Orientation is rolled from the seed instead,
       * identically for solitaire and multiplayer, and this is not expected to change when setup
       * eventually gains an interactive phase for other decisions.
       *
       * RE-CONFIRMED 2026-08-23, when the question was raised again and giving the choice to the
       * Superintendent was considered and rejected — the office rotates every three Stages, the
       * advantage it would hand out does not. See implications.md §10 Q11.
       */
      node.gradeUp = rng.nextInt(2) === 0 ? 'east' : 'west';
    }
    return node;
  };

  nodes.push({ kind: 'divisionPoint', side: 'west', holding: [] });
  for (let p = 0; p < players; p++) {
    nodes.push(mainline());
    nodes.push({ kind: 'office', seat: p });
  }
  nodes.push(mainline());
  nodes.push({ kind: 'divisionPoint', side: 'east', holding: [] });

  return nodes;
}

export function createGame(opts: SetupOptions): GameState {
  const { id, seed, config, playerNames } = opts;
  if (playerNames.length < 1) throw new Error('a game needs at least one player');
  if (config.mode === 'solitaire' && playerNames.length !== 1) {
    throw new Error('solitaire is a one-player mode');
  }

  const rng = createRng(seed);
  const playerCount = playerNames.length;

  const players = playerNames.map((name, index) => ({ index, name, revenue: 0 }));

  // Offices are keyed by SEAT — a fixed position in the west-to-east chain. `seating` maps seats to
  // the players occupying them, and starts as the identity mapping, which is what makes the
  // seat/player split behaviour-neutral. Employee Rotation would rotate this array and nothing else.
  const officeAreas = new Map<SeatIndex, OfficeArea>();
  for (let seat = 0; seat < playerCount; seat++) officeAreas.set(seat, buildOfficeArea(seat));
  // §4.4 - highest D12 takes the Eastern Division Point; §4.5 - highest begins as Superintendent.
  // Both rolls are drawn even in solitaire so the RNG stream stays identical across player counts.
  const divisionRolls = players.map(() => rng.d12());
  const superRolls = players.map(() => rng.d12());
  const superintendent = argmax(superRolls);

  /**
   * §4.4 — THE OPENING D12 DECIDES WHO SITS WHERE.
   *
   * `seating[seat] = player`, and seat 0 is the WESTERN end of the chain (`buildDivision` lays the
   * Western Division Point, then office 0, and finishes at the Eastern one). So the highest roll
   * takes the last seat — "highest is the Eastern Division Point" — and the lowest ends up beside
   * the Western Division Point, which is the rule's other named position.
   *
   * The rule names only those two ends, because at a table the players are already sitting in a
   * chain and the roll only says which way round it is. There is no physical table here, so the
   * roll orders everybody: ascending by roll, west to east. It uses a number every player is
   * already told to roll, and it makes the roll matter to more than the winner.
   *
   * Ties break toward the LOWER player index sitting further east, which is the same convention
   * `argmax` uses for the Superintendent roll on the line above — first max wins.
   *
   * This was `void divisionRolls` until v0.4.1: the roll was drawn and discarded, and seating was
   * the identity mapping. Turning it on is what makes seat and player genuinely different at
   * runtime rather than only in the type names.
   */
  const seating: PlayerIndex[] = players
    .map((_, p) => p)
    .sort((a, b) => divisionRolls[a]! - divisionRolls[b]! || b - a);

  /**
   * §4.6-4.7 — THE OPENING DEAL, in whichever of the three shapes this game was dealt with.
   *
   * `threeRandom` and `sixRandom` deal off ONE shuffled deck; `threeTrackThreeOther` shuffles track
   * separately and deals three of each, then shuffles the remainder back together so the game runs
   * off one deck from the first draw onward either way. `content.ts` says what each option is for.
   *
   * A player dealt six holds six against a limit of three, on purpose: the first turn is spent
   * choosing what to keep — draw as usual, then play or discard down to three (§6.2, enforced on
   * `draw.end`, which needs no special case for this). A player dealt three is already at the limit.
   *
   * §4.7 — "starting from the Superintendent, deal each player…", which proceeds round the table and
   * is therefore SEAT order, not player order. That is the same in all three shapes.
   */
  const rules = houseRules(config);
  const deal = OPENING_DEALS[rules.startingHand];
  const deck = buildDeck(config.mode, config.pvpCardsAllowed);
  const cards = new Map<CardId, Card>();
  for (const c of deck) cards.set(c.id, c);

  const isTrack = (id: CardId): boolean => cards.get(id)?.kind.kind === 'track';
  const ids = deck.map((c) => c.id);
  const superSeat = seating.indexOf(superintendent);
  const hands = new Map<PlayerIndex, CardId[]>();
  const dealtTo = (i: number): PlayerIndex => seating[(superSeat + i) % playerCount]!;

  let shuffled: CardId[];
  if (deal.any > 0) {
    // One deck, one shuffle, the top cards off it — the prototype's own deal.
    const single = rng.shuffle(ids);
    let cut = 0;
    for (let i = 0; i < playerCount; i++) {
      hands.set(dealtTo(i), single.slice(cut, cut + deal.any));
      cut += deal.any;
    }
    shuffled = single.slice(cut);
  } else {
    // Shuffled in a fixed order — track first — so the RNG stream is deterministic for a given seed.
    const trackPile = rng.shuffle(ids.filter(isTrack));
    const otherPile = rng.shuffle(ids.filter((id) => !isTrack(id)));
    let trackCursor = 0;
    let otherCursor = 0;
    for (let i = 0; i < playerCount; i++) {
      hands.set(dealtTo(i), [
        ...trackPile.slice(trackCursor, trackCursor + deal.track),
        ...otherPile.slice(otherCursor, otherCursor + deal.other),
      ]);
      trackCursor += deal.track;
      otherCursor += deal.other;
    }
    // The remainder goes back into ONE deck for the rest of the game — the split is an opening-deal
    // device only, so track competes for the draw exactly as before from the first draw onward.
    shuffled = rng.shuffle([...trackPile.slice(trackCursor), ...otherPile.slice(otherCursor)]);
  }

  // §4.6-4.7 — three cards turned face up beside the deck. Each is the bottom of a Department pile
  // that grows as players discard onto it. Taken after the recombination, so a Department slot can
  // show track like any other card.
  let cursor = 0;
  const departments: CardId[][] = [[], [], []];
  for (const pile of departments) {
    const card = shuffled[cursor++];
    if (card) pile.push(card);
  }
  const homeOffice = shuffled.slice(cursor);

  const redFlags = new Map<PlayerIndex, boolean>();
  for (let p = 0; p < playerCount; p++) {
    redFlags.set(p, config.optionalRules.emergencyToolbox);
  }

  // §4.9 - Crew Trays near the turn sheet. Scarcity is an explicit mechanic (§7).
  const freeTrays: TrayId[] = [];
  for (let i = 0; i < crewTrayCount(playerCount); i++) freeTrays.push(`tray${i}`);

  const timetable: (number | null)[] = new Array(STAGES_PER_DAY).fill(null);

  return {
    id,
    config,
    seed,
    rngState: rng.getState(),
    players,
    seating,
    openingRolls: { division: divisionRolls, superintendent: superRolls },
    division: { nodes: buildDivision(playerCount, rng) },
    officeAreas,
    trays: new Map(),
    freeTrays,
    cards,
    decks: { homeOffice, departments, salvageYard: [], hands, redFlags },
    yards: { divisionYard: buildRollingStock(), classificationYard: [] },
    timetable,
    pendingExtras: [],
    pendingSecondSections: [],
    clock: {
      day: 1,
      stage: 1,
      phase: 'localOps',
      currentActor: superintendent,
      pendingDecision: null,
      decisionAnswer: null,
      superintendent,
      actorOffset: 0,
    },
    turns: freshTurns(playerCount, MOVES_PER_LOCAL_OPS),
    movedThisPhase: new Set(),
    collisionsToday: 0,
    collisionsPrevDay: 0,
    collisionsTotal: 0,
    status: 'active',
    outcome: null,
    extraDays: 0,
    extensionVotes: players.map(() => null),
    official: null,
    tally: emptyTally(playerCount),
  };
}

function argmax(values: number[]): number {
  let best = 0;
  for (let i = 1; i < values.length; i++) {
    if (values[i]! > values[best]!) best = i;
  }
  return best;
}

export { mainlineCardCount };