Files
station-master/src/engine/advance.ts
T
Jesse.MarkowitzandClaude Fable 5.1 04ca74c365 v0.8.5 — housekeeping from the audit, and the playtest line retired
The third release from the audit; nothing a player sees changes. CHANGELOG has the detail.

The 0.4.9 playtest line is no longer maintained (Jesse, 2026-09-29): the deploy rule that
existed for it is gone and #85 is moot. The table test (#39 #35 #42a #40) is closed — every
line of the checklist was met at a table. #46 is done and cannot regrow: the 36 unused
declarations are removed and `noUnusedLocals`/`noUnusedParameters` are on; two of them were
dead bot functions from rejected candidates the round said it had deleted. The documents no
longer teach `trainCapSlack` (a knob that throws), point at `as-built.md` (deleted in 0.8.2),
model `officeType` (the engine says `tier`) or describe `collisionOccurred` (never emitted);
the README's account of bot flags now matches the bot's. Five playtest saves committed in
`docs/` against the repository's own rule are in the ignored `playtests/`.

What the audit found and did not fix is written down as TODO #112-#117, each with its reason.
#112 is `docs/plans/structure.md`, the proposal for `http.ts`, `main.ts` and `check`. #117 —
`/api/save` hands a seat the seed mid-game — waits on a conversation.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FrCWubm9GAftYCm2hWdKwK
2026-09-29 17:02:33 -04:00

2008 lines
91 KiB
TypeScript

/**
* Component 5 — The phase driver.
*
* `advance(state) -> { events, needsInput }`. Everything the game does WITHOUT a player acting:
* Mainline movement, highball evaluation, collisions, train make-up, the Stage and Day clock,
* Superintendent rotation, and victory checks.
*
* See architecture/components.md §2 A.5. This lives inside the engine rather than the session
* layer so that all rules knowledge stays in one pure deterministic place — which is also what
* makes the balance harness a plain loop over `advance` and `applyIntent`, with no server.
*
* USAGE:
* while (true) {
* const r = advance(state);
* if (r.needsInput || state.status === 'finished') break;
* }
*/
import {
COLLISION_PENALTY,
EXPEDITE_FAULT_PENALTY,
MAINLINE_PROFILES,
enhancementRule,
crossingStages,
trainProfile,
startRegion,
MOVES_PER_LOCAL_OPS,
MOVES_PER_LOCAL_OPS_NIGHT,
STAGES_PER_DAY,
STAGES_PER_SHIFT,
houseRules,
officeProfile,
mainlineProfile,
consistSize,
} from './content.ts';
import type { CarType, Direction, MainlineEntry, MainlineKind } from './content.ts';
import type { GameEvent } from './events.ts';
// `trainNeedingCars` lives in apply.ts beside `check`'s copy of the same question, so the phase and
// the legality test cannot disagree about which train is being assembled.
import { acceptsCar, areaAtSeat, areaOf, isBeingMadeUp, occupancyFor, trainNeedingCars } from './apply.ts';
import { legalActions } from './legal.ts';
import type { CrewTray, DivisionNode, GameState, GridCoord, Outcome, PlayerIndex, RollingStock, SeatIndex, TrayId } from './state.ts';
import { cloneTally, coordKey, freshTurns, isExtendable, playerAtSeat, playerLeftOf, pooled, railFacingOf, subdivisions, totalRevenue, turnOf } from './state.ts';
import { reachableDestinations } from './track.ts';
import { tallyEvent } from './tally.ts';
export type AdvanceResult = {
events: GameEvent[];
/** True when the game is waiting on a player. The caller should stop pumping. */
needsInput: boolean;
};
const NIGHT_STAGES = new Set([1, 2, 3, 11, 12]);
/**
* IS EVERY CAR ON THIS TRAIN LOADED? (Gitea#13)
*
* "You only get credit for a circus or campaign train (one point per stop) if you have it fully
* loaded. Not much of a circus if all the cars are empty."
*
* A COACH COUNTS AS LOADED WHEN IT IS OCCUPIED, which is what makes this the right test for the
* Campaign Train: X17 carries one coach and no freight, so "fully loaded" is precisely "the
* candidate is aboard" (Jesse's ruling, 2026-08-29). The engine already models an occupied coach
* as `loaded`, so no second notion is introduced here.
*
* A CABOOSE IS EXEMPT, and it costs nothing to say so: every caboose in `ROLLING_STOCK_SUPPLY` is
* minted `loaded: true` — there is no empty one — so including it would change no outcome today.
* It is excluded anyway because a caboose is crew space rather than payload, and a supply table
* that grew an empty caboose should not silently start voiding circus points.
*
* AN EMPTY TRAIN IS NOT FULLY LOADED. A Circus that departed short and carries nothing at all earns
* nothing: `every` on an empty list is vacuously true, which would pay the emptiest train of the
* lot, so the length is tested first.
*/
function fullyLoaded(tray: CrewTray): boolean {
const payload = tray.consist.filter((c) => c.type !== 'caboose');
return payload.length > 0 && payload.every((c) => c.loaded);
}
function movesForStage(s: GameState): number {
return s.config.optionalRules.reducedVisibility && NIGHT_STAGES.has(s.clock.stage)
? MOVES_PER_LOCAL_OPS_NIGHT
: MOVES_PER_LOCAL_OPS;
}
// ---------------------------------------------------------------------------
// Division navigation
// ---------------------------------------------------------------------------
function nodeIndexOfOffice(s: GameState, seat: SeatIndex): number {
return s.division.nodes.findIndex((n) => n.kind === 'office' && n.seat === seat);
}
const step = (d: Direction): number => (d === 'east' ? 1 : -1);
/** The Division node a train is standing on — its Office, its Mainline card, or its Division Point. */
function nodeIndexOfTray(s: GameState, tray: CrewTray): number | null {
const at = tray.position;
if (at.at === 'grid') return nodeIndexOfOffice(s, at.seat);
if (at.at === 'mainline') return at.index;
if (at.at === 'divisionPoint') {
const side = at.side;
return s.division.nodes.findIndex((n) => n.kind === 'divisionPoint' && n.side === side);
}
return null;
}
// ---------------------------------------------------------------------------
// advance
// ---------------------------------------------------------------------------
/**
* The phase driver, plus the two things that have to happen around EVERY batch of events it
* produces. `advanceInner` below is the driver itself, unchanged.
*
* ORDER IS THE WHOLE POINT of this wrapper, and it is the one subtle thing in Gitea#16.
* `checkVictory` runs deep inside the driver, so if the official result froze a copy of the Tally
* from in there it would freeze it BEFORE this batch's events had been counted — and the batch that
* ends a game is exactly the one carrying the last Day's work. So the Tally is folded first and the
* result frozen second, both out here where the whole batch is in hand.
*
* Safe because both endings `return` the moment they fire: no scoring event is emitted after a game
* has ended within a single batch, so "everything in this batch" and "everything up to the ending"
* are the same set of events. `test/tally.test.ts` pins that.
*/
export function advance(s: GameState): AdvanceResult {
const r = advanceInner(s);
for (const e of r.events) tallyEvent(s, e);
freezeOfficial(s);
return r;
}
/**
* THE OFFICIAL RESULT, written once (Gitea#11).
*
* "The winner is based upon the original game length" — so the first ending is the real one and
* every later evaluation is informational. Idempotent by construction: it does nothing once
* `official` is set, which is what stops an extended Day, or a §3.4 breach during one, from
* rewriting a recorded win.
*/
function freezeOfficial(s: GameState): void {
if (s.official !== null || s.outcome === null) return;
s.official = {
day: s.config.days,
outcome: { ...s.outcome },
revenues: s.players.map((p) => p.revenue),
collisionsTotal: s.collisionsTotal,
tally: cloneTally(s.tally),
};
}
function advanceInner(s: GameState): AdvanceResult {
const events: GameEvent[] = [];
if (s.status === 'finished') return { events, needsInput: false };
/**
* §3.3 (Gitea#11) — the timetable has run out and the table is being asked whether to play one
* more Day. Nothing runs itself while that question is open, so this is `needsInput` rather than
* an ending: `pump` stops here, the server keeps the game in memory, and the only intent the
* rules will take is `game.extend`.
*/
if (s.status === 'awaitingExtension') return { events, needsInput: true };
// The Superintendent's clearance ruling interrupts the Mainline Phase (§8.1).
if (s.clock.pendingDecision !== null) return { events, needsInput: true };
switch (s.clock.phase) {
case 'localOps':
return playerPhase(s, events, 'localOps');
case 'newTrain':
return newTrainPhase(s, events);
case 'mainline':
return mainlinePhase(s, events);
case 'loadUnload':
return playerPhase(s, events, 'loadUnload');
case 'shiftChange':
return shiftChange(s, events);
}
}
// ---------------------------------------------------------------------------
// Player-driven phases (Local Ops, Load/Unload)
// ---------------------------------------------------------------------------
function playerPhase(
s: GameState,
events: GameEvent[],
phase: 'localOps' | 'loadUnload',
): AdvanceResult {
/**
* THE CURSOR STILL WALKS ONE PLAYER AT A TIME.
*
* Turn state is now per-player, but only the player at `actorOffset` is ever asked to act, so this
* behaves exactly as it did when there was a single `TurnState` — which is the point: the model
* change is neutral, and letting local work happen off-cursor is a later change to `isActor`
* alone (`docs/architecture/multiplayer.md` D19).
*/
const actor = actorAt(s, s.clock.actorOffset);
const turn = turnOf(s, actor);
// A Freight Agent operation is a whole action in itself, so the turn ends with it (§6.3).
if (phase === 'localOps' && turn.option === 'freightAgent' && turn.freightAgentUsed) {
turn.done = true;
}
// Spending the last Move ends a switching turn without needing an explicit end (§6.1).
if (phase === 'localOps' && turn.option === 'switch' && turn.movesRemaining === 0) {
turn.done = true;
}
if (!turn.done) {
s.clock.currentActor = actor;
// SAFETY NET. If the actor has no legal action at all, the turn ends rather than deadlocking.
// This should never fire — an option with no follow-up is already unavailable (§6, apply.ts) —
// but a rules gap that stranded a player would otherwise hang the game rather than fail
// visibly, and a hung game is far harder to diagnose than a forfeited turn.
if (legalActions(s, s.clock.currentActor).length === 0) {
turn.done = true;
} else {
return { events, needsInput: true };
}
}
s.clock.actorOffset += 1;
if (s.clock.actorOffset >= s.players.length) {
return { events: [...events, ...enterPhase(s, nextPhase(phase))], needsInput: false };
}
s.clock.currentActor = actorAt(s, s.clock.actorOffset);
events.push({ type: 'actorChanged', player: s.clock.currentActor });
return { events, needsInput: false };
}
function actorAt(s: GameState, offset: number): PlayerIndex {
return playerLeftOf(s, s.clock.superintendent, offset);
}
function nextPhase(p: GameState['clock']['phase']): GameState['clock']['phase'] {
switch (p) {
case 'localOps':
return 'newTrain';
case 'newTrain':
return 'mainline';
case 'mainline':
return 'loadUnload';
case 'loadUnload':
return 'shiftChange';
default:
return 'localOps';
}
}
function enterPhase(s: GameState, phase: GameState['clock']['phase']): GameEvent[] {
s.clock.phase = phase;
s.clock.actorOffset = 0;
// Every player gets a turn at phase entry, not one at a time as the cursor reaches them. With the
// cursor still walking sequentially this is indistinguishable from the old behaviour.
s.turns = freshTurns(s.players.length, movesForStage(s));
s.clock.currentActor = phase === 'mainline' ? null : actorAt(s, 0);
return [
{ type: 'phaseBegan', phase },
{ type: 'actorChanged', player: s.clock.currentActor },
];
}
// ---------------------------------------------------------------------------
// New Train Phase (§7)
// ---------------------------------------------------------------------------
function newTrainPhase(s: GameState, events: GameEvent[]): AdvanceResult {
// Make up any Timetabled Train due this Stage, if a Crew Tray is free (§7).
const due = s.timetable[s.clock.stage - 1];
if (due !== null && due !== undefined && !trainRunning(s, due, false)) {
if (s.freeTrays.length === 0) {
// "Held train" — no crew available. It waits; the Stage moves on (§7).
events.push({ type: 'trainHeld', trainNumber: due, reason: 'no free Crew Tray' });
return { events: [...events, ...enterPhase(s, 'mainline')], needsInput: false };
}
const profile = trainProfile(due, false);
if (profile) {
const trayId = s.freeTrays.pop()!;
const direction: Direction = profile.direction === 'east' ? 'east' : 'west';
// An eastbound train starts at the Western Division Point and runs east.
const side: Direction = direction === 'east' ? 'west' : 'east';
const tray: CrewTray = {
id: trayId,
trainNumber: due,
trainIsExtra: false,
engineAt: 0,
consist: [],
direction,
position: { at: 'divisionPoint', side },
movesUsed: 0,
};
s.trays.set(trayId, tray);
const dp = s.division.nodes.find((n) => n.kind === 'divisionPoint' && n.side === side);
if (dp && dp.kind === 'divisionPoint') dp.holding.push(trayId);
events.push({
type: 'trainMadeUp',
trainNumber: due,
isExtra: false,
at: side === 'west' ? 'West Division Point' : 'East Division Point',
direction,
});
}
}
// Q9 — a second section runs immediately behind its first, with the same number, rules and
// consist. It needs its own Crew Tray, and because it follows a train of the same number into
// the same Subdivision it will usually force the §8.1 clearance decision.
if (s.pendingSecondSections.length > 0 && s.freeTrays.length > 0) {
const number = s.pendingSecondSections.shift()!;
const profile = trainProfile(number, false);
if (profile) {
const trayId = s.freeTrays.pop()!;
const direction: Direction = profile.direction === 'east' ? 'east' : 'west';
const side: Direction = direction === 'east' ? 'west' : 'east';
s.trays.set(trayId, {
id: trayId,
trainNumber: number,
trainIsExtra: false,
engineAt: 0,
consist: [],
direction,
position: { at: 'divisionPoint', side },
movesUsed: 0,
});
const dp = s.division.nodes.find((n) => n.kind === 'divisionPoint' && n.side === side);
if (dp?.kind === 'divisionPoint') dp.holding.push(trayId);
events.push({
type: 'trainMadeUp',
trainNumber: number,
isExtra: false,
at: side === 'west' ? 'West Division Point' : 'East Division Point',
direction,
});
}
}
/**
* §7 — "if there is a played Extra Train card and an available Crew Tray, the player who played
* the card may place the Crew Tray in either division point for immediate departure."
*
* THIS USED TO LAUNCH EVERY EXTRA EASTBOUND FROM THE WEST DIVISION POINT, with the simplification
* flagged in a comment. Jesse's rule: an Extra runs the way its NUMBER says, exactly as a
* timetabled train does — odd runs west, even runs east (§2.3) — so it starts at the Division
* Point it runs FROM. It may instead start at any Control Point, which is any Office above a
* Whistle Post, at the player's choice.
*
* That is a decision, so the phase stops for it the same way it stops to have cars placed. The
* chooser is the acting player; §7 says the player who PLAYED the card, which is the same person
* in solitaire and needs `pendingExtras` to carry a player before it is not.
*/
const extra = s.pendingExtras[0];
if (extra !== undefined && s.freeTrays.length > 0) {
// §7 — the player who PLAYED the card places it. `pendingExtras` carries them (2026-08-23);
// before that it was a bare train number and this asked whoever the acting order was on, which
// is the same person in solitaire and the wrong one at every table. Reported by Jesse from a
// two-player game.
if (s.clock.currentActor !== extra.player) events.push({ type: 'actorChanged', player: extra.player });
s.clock.currentActor = extra.player;
return { events, needsInput: true };
}
/**
* Gap 9 — the car-placement round REPEATS until the consist is full or no suitable car remains,
* cycling Superintendent-then-left one car at a time (§7).
*
* `tray.consist.length` IS the round position: a freshly made-up tray always starts with
* `consist: []`, and each `newTrain.placeCar` appends exactly one car to it (`apply.ts`'s
* `carPlacedOnTrain` reducer), so it counts placements toward THIS tray without any new state —
* and resets to 0 naturally for the next train made up, which a phase-wide `actorOffset` cannot
* do. Reproduces the rulebook's worked example exactly: 2 players, 4-coach Limited → seats
* 0, 1, 0, 1.
*/
const filling = trainNeedingCars(s);
if (filling) {
const tray = s.trays.get(filling)!;
/**
* TWO DIFFERENT RULES, and §7 states them a paragraph apart. A TIMETABLED train's consist is
* built by the table — "starting with the Superintendent and working left, each player may place
* ONE car" — while an EXTRA is loaded by the player who played it, "as he chooses". So an Extra
* does not enter the round at all; it belongs to `builtBy` until it is full.
*/
const nextActor =
tray.trainIsExtra && tray.builtBy !== undefined
? tray.builtBy
: actorAt(s, tray.consist.length % s.players.length);
if (s.clock.currentActor !== nextActor) events.push({ type: 'actorChanged', player: nextActor });
s.clock.currentActor = nextActor;
return { events, needsInput: true };
}
/**
* SAY SO WHEN A TRAIN GOT NOTHING, before the round is over and the train runs (playtest,
* 2026-09-16: "train 5, the sparrow, has no coaches, which seems strange").
*
* `trainNeedingCars` returns null both when every consist is full and when the Division Yard holds
* nothing a short train will take — the same answer for "done" and for "cannot be done" — so the
* phase moved on in silence and the only trace was a MADE UP line promising "now taking cars". The
* Sparrow calls for three coaches and left empty twice in one game.
*
* REPORTED HERE RATHER THAN AT THE MADE-UP MOMENT, because a train made up early in the round can
* still be filled by a later placement; only once the round has nothing left to offer is the
* shortfall a fact. This is reached exactly once per Stage — the next line enters the Mainline
* Phase — so the report cannot repeat.
*/
for (const tray of s.trays.values()) {
if (!isBeingMadeUp(tray) || tray.trainNumber === null) continue;
const profile = trainProfile(tray.trainNumber, tray.trainIsExtra);
if (!profile) continue;
const category = (t: CarType): 'freight' | 'coach' | 'caboose' =>
t === 'coach' ? 'coach' : t === 'caboose' ? 'caboose' : 'freight';
// What the card still wants: asked of `acceptsCar` per category, so a full category and a
// category barred by the card's own rules answer the same way here as they do to a player.
const missing = (['freight', 'coach', 'caboose'] as const).filter((cat) => {
const sample: CarType = cat === 'coach' ? 'coach' : cat === 'caboose' ? 'caboose' : 'boxcar';
return acceptsCar(tray, sample);
});
if (missing.length === 0) continue;
events.push({
type: 'makeUpShort',
trainNumber: tray.trainNumber,
isExtra: tray.trainIsExtra,
placed: tray.consist.length,
wanted: consistSize(profile.consist),
missing: [...missing],
waiting: s.yards.classificationYard.filter((c) => missing.includes(category(c.type))).length,
divisionYardHolds: s.yards.divisionYard.length,
});
}
return { events: [...events, ...enterPhase(s, 'mainline')], needsInput: false };
}
function trainRunning(s: GameState, number: number, isExtra: boolean): boolean {
for (const t of s.trays.values()) {
if (t.trainNumber === number && t.trainIsExtra === isExtra) return true;
}
return false;
}
// ---------------------------------------------------------------------------
// Mainline Phase (§8) — automatic, except the Superintendent's clearance ruling
// ---------------------------------------------------------------------------
function mainlinePhase(s: GameState, events: GameEvent[]): AdvanceResult {
s.clock.currentActor = null;
// §8 — trains move in numeric order, lowest first. Timetabled outranks an Extra of the same
// number (Gap 5): sort by (number, isExtra) ascending.
const order = [...s.trays.entries()]
// §8 — "Any train holding at a player's Office ... or a Division Point must attempt to move."
// Trains standing on an A/D track are included: they are exactly the ones due to highball.
.filter(([, t]) => t.trainNumber !== null)
.sort(([, a], [, b]) => {
const d = (a.trainNumber ?? 0) - (b.trainNumber ?? 0);
return d !== 0 ? d : Number(a.trainIsExtra) - Number(b.trainIsExtra);
});
/**
* Q3 — A STATION MASTER FAULT: an expedited train not at the station when a Mainline Phase begins
* was not kept ready to highball, wherever in the district it has been left — switched onto
* Secondary Track to clear a move, say. Checked against positions as they stand BEFORE this phase
* moves anything, and charged every Phase it is still caught away: the fault is in leaving it
* there, not a one-time slip. A train the ordinary §8.1 rules are holding at the Office itself is
* unaffected — this only bites when the train is not even in the queue to leave.
*/
/**
* ONCE PER PHASE, NOT ONCE PER QUESTION (v0.8.3). This function is re-entered from the top after
* every clearance, Yard Office and Red Flag ruling, and the loop below ran unguarded — so a train
* left on a siding was fined once per interruption. A pending answer is the mark of a resumption:
* it is set by the ruling and consumed further down, inside the move it belongs to.
*/
for (const [, tray] of s.clock.decisionAnswer === null ? order : []) {
if (!isExpedited(tray) || tray.position.at !== 'grid') continue;
const area = areaAtSeat(s, tray.position.seat);
const { coord } = tray.position;
if (coord.row === area.officeCoord.row && coord.col === area.officeCoord.col) continue;
const owner = playerAtSeat(s, tray.position.seat);
const p = s.players[owner];
if (!p) continue;
p.revenue -= EXPEDITE_FAULT_PENALTY;
events.push({
type: 'expediteFault',
player: owner,
trainNumber: tray.trainNumber ?? 0,
where: `(${coord.col},${coord.row})`,
});
events.push({
type: 'revenueChanged',
player: owner,
delta: -EXPEDITE_FAULT_PENALTY,
total: p.revenue,
reason: 'expedited train left off the station',
});
}
for (const [id, tray] of order) {
if (s.movedThisPhase.has(id)) continue;
const where = tray.position;
const moved = moveTrain(s, id, tray, events);
/**
* X18 CIRCUS / X17 CAMPAIGN — a Stage spent set up in somebody's Office Area earns a point.
*
* The flag was declared on the profile and read NOWHERE, so the one card in the deck that paid
* for standing still paid nothing: reported from a playtest where TX18 sat on a siding for a
* full Stage and no point arrived.
*
* ONCE PER OFFICE AREA (Gitea#13, Jesse 2026-08-29): "once per stop in an office area. In a
* multiplayer game, each player could score if the circus stops in their area." So a Circus
* touring three districts is paid three times and one parked in the same district all game is
* paid once, which `stopPointSeats` records per seat.
*
* ONLY IN AN OFFICE AREA. It used to pay for standing on the Mainline or at a Division Point
* too, and misattributed both: `playerAtSeat` needs a seat, and off the grid there is none, so
* the fallback handed the point to PLAYER 0 wherever the train happened to be. Scoping the rule
* to Office Areas is what Jesse's ruling says and it removes that bug rather than patching it.
*
* FULLY LOADED, or nothing. "Not much of a circus if all the cars are empty" — see
* `fullyLoaded` below for what that means for a train whose only car is a coach.
*
* "Stopped" is measured against the Mainline Phase: the train attempted to move and stayed where
* it was. A train that is still in the district when the phase runs has not moved either, which
* is the circus setting up on a siding rather than crossing the Division.
*/
if (trainProfile(tray.trainNumber ?? 0, tray.trainIsExtra)?.rules.stopEarnsPoint) {
const stillThere =
tray.position.at === where.at &&
(tray.position.at !== 'mainline' || where.at !== 'mainline' || tray.position.index === where.index) &&
(tray.position.at !== 'grid' ||
where.at !== 'grid' ||
(tray.position.coord.row === where.coord.row && tray.position.coord.col === where.coord.col));
// Bound as one value so the grid case narrows: `tray.position` is a union, and testing a
// `seat` extracted from it does not tell the compiler which member it came from.
const at = tray.position.at === 'grid' ? tray.position : null;
const alreadyPaidHere = at !== null && (tray.stopPointSeats ?? []).includes(at.seat);
if (stillThere && at !== null && !alreadyPaidHere && fullyLoaded(tray)) {
tray.stopPointSeats = [...(tray.stopPointSeats ?? []), at.seat];
// The point goes to whoever is SITTING in the district it stopped in.
const owner = playerAtSeat(s, at.seat);
const label = `(${at.coord.col},${at.coord.row})`;
events.push({ type: 'trainStoodStill', trainNumber: tray.trainNumber ?? 0, where: label });
const p = s.players[owner];
if (p) {
p.revenue += 1;
events.push({
type: 'revenueChanged',
player: owner,
delta: 1,
total: p.revenue,
reason: 'set up in the district — a Stage spent standing still, fully loaded',
});
}
}
}
if (moved === 'needsClearance') return { events, needsInput: true };
s.movedThisPhase.add(id);
}
releaseHeldAtLimits(s, events);
s.movedThisPhase = new Set();
return { events: [...events, ...enterPhase(s, 'loadUnload')], needsInput: false };
}
/**
* A TRAIN HELD AT THE LIMITS TAKES A TRACK THAT FREES — whoever freed it (v0.8.3).
*
* `arriveAtOffice` promises "held at the Limits until an A/D track frees up", and until now the
* only release was inside `arriveAtOffice` itself, for a DIFFERENT train arriving. An Office that
* emptied by departures alone kept its held train at the Limits for the rest of the game — with no
* transit, no place in `adOccupancy` and no part in the clearance check, so nothing on the board or
* in the rules could see it. Every train has now attempted its move for this Phase, so any track
* still free is genuinely free, and the held trains take them in the order they were held.
*/
function releaseHeldAtLimits(s: GameState, events: GameEvent[]): void {
for (const area of s.officeAreas.values()) {
const capacity = officeProfile(area.tier).adTracks;
while (area.heldAtLimits.length > 0 && area.adOccupancy.length < capacity) {
const id = area.heldAtLimits.shift()!;
const held = s.trays.get(id);
if (!held) continue;
area.adOccupancy.push(id);
held.position = { at: 'grid', seat: area.seat, coord: area.officeCoord };
events.push({
type: 'trainReleasedFromLimits',
trainNumber: held.trainNumber ?? 0,
office: officeProfile(area.tier).name,
owner: playerAtSeat(s, area.seat),
freedBy: null,
});
}
}
}
type MoveOutcome = 'moved' | 'held' | 'needsClearance';
/**
* §8.2 — why this train is not fit to run, or null if it is.
*
* "The engine in front, cars behind, and if there is a caboose, the caboose at the rear."
*
* DIRECTION-FREE, deliberately. The engine may be at either end of the tray — pulling or pushing —
* and which of those counts as "in front" depends on which way the train is pointed, which the tray
* does not reliably record for a crew that has been shunting round a siding. What a train may NOT be
* is broken-backed: the engine buried among its own cars, with some ahead of it and some behind. The
* caboose then has to ride at the far end from the engine, which is the rear whichever way it runs.
*
* This is reachable purely through switching. A train arrives made up, and only comes apart because
* the player took cars onto the nose or picked up a cut in a run-around.
*
* Exported for the switching planner (`sim/switch-planner.ts`), which has to know whether a plan
* leaves a train unable to run — and must ask this rule rather than keep a copy of it.
*/
export function badlyMadeUp(tray: CrewTray): string | null {
const n = tray.consist.length;
if (n === 0) return null;
const pulling = tray.engineAt === 0;
const pushing = tray.engineAt === n;
if (!pulling && !pushing) {
return `not made up — the engine is buried in the train, ${tray.engineAt} car${tray.engineAt === 1 ? '' : 's'} ahead of it`;
}
const caboose = tray.consist.findIndex((c) => c.type === 'caboose');
if (caboose === -1) return null;
// The rear is the end away from the engine.
const rear = pulling ? n - 1 : 0;
return caboose === rear ? null : 'not made up — the caboose must be at the rear of the train';
}
/**
* WHICH REGION OF A MAINLINE CARD A TRAIN IS STANDING IN (Gitea#3).
*
* A card is `regions` boxes wide and a train advances one per Stage, so what it has LEFT to run says
* where it is: enter with `regions` still to go and you are at the beginning; enter with one to go
* and you are in the last box.
*
* This used to be derived from a single global `REGIONS_PER_MAINLINE_CARD = 2`, with an entry term
* that put a one-Stage train in region 1 of a two-region card — a fast train did not traverse a fast
* card, it appeared at the far half of it. Cards carry their own region count now, so the position
* is simply the count minus what is left.
*/
export function regionOfTransit(card: MainlineKind, stagesRemaining: number): number {
const regions = mainlineProfile(card).regions;
return Math.min(regions - 1, Math.max(0, regions - stagesRemaining));
}
/** The entry a train would make onto this card, before occupancy is taken into account. */
function entryFor(
node: Extract<DivisionNode, { kind: 'mainline' }>,
tray: CrewTray,
startsAtBack = false,
): MainlineEntry {
const profile = trainProfile(tray.trainNumber ?? 0, tray.trainIsExtra);
return {
trainSpeed: profile?.speed ?? 'slow',
direction: tray.direction,
gradeUp: node.gradeUp ?? 'east',
modifiers: node.modifiers ?? [],
...(startsAtBack ? { startsAtBack: true } : {}),
};
}
/**
* THE UNCONTROLLED SIDING RULE (Gitea#3): "if a train already exists when you arrive, you go in the
* second stage back — you are in the siding and are one behind the other train. This prevents a
* collision, since you are not in same exact location."
*
* So arriving at an occupied siding is not a collision and not a hold; it is a different, slower
* entry. Anywhere else this returns false and the ordinary start applies.
*/
function takesTheSiding(node: Extract<DivisionNode, { kind: 'mainline' }>): boolean {
return node.card === 'uncontrolledSiding' && node.transits.length > 0;
}
/**
* IS MOVING ONTO THIS CARD A COLLISION? (Gitea#3)
*
* A card can be ONE region wide — Plains, Double Track and Trestle all are — so a following train
* granted clearance arrives in the same region as the train ahead the moment it enters. There was no
* test for that at all: the catch-up check lives inside `stagesRemaining > 1`, which a one-Stage
* crossing never reaches, so entering behind another train on a Plains was silently free.
*
* ABS is the card that answers it, in RAR's words: "This is played on a mainline card to prevent
* collisions. If a collision would normally occur, the train moving onto the card is instead held
* back." Held, not waved through — it tries again next Stage.
*
* The Uncontrolled Siding never conflicts on entry, because `takesTheSiding` has already moved this
* train a region back; that is the whole point of the card.
*/
function entryConflict(
s: GameState,
node: Extract<DivisionNode, { kind: 'mainline' }>,
id: TrayId,
tray: CrewTray,
events: GameEvent[],
startsAtBack = false,
): 'collided' | 'held' | null {
if (mainlineProfile(node.card).trainsMayPass) return null;
const start = startRegion(node.card, entryFor(node, tray, startsAtBack || takesTheSiding(node)));
const ahead = node.transits.find(
(t) =>
t.tray !== id &&
t.direction === tray.direction &&
regionOfTransit(node.card, t.stagesRemaining) === start,
);
if (!ahead) return null;
/**
* A BACKSTOP, not the main path. `evaluateClearance` already refuses to clear a train onto a card
* carrying ABS, so in the ordinary run of things nothing reaches here with signals up. It stays
* because the two rules answer to different questions — clearance looks at the whole Subdivision,
* this looks at one region — and a card that promises no rear-enders should not depend on the
* wider check happening to fire first.
*/
if (node.absSignals) {
events.push({
type: 'trainHeld',
trainNumber: tray.trainNumber ?? 0,
reason: 'ABS Signals — held short of the train ahead',
});
return 'held';
}
// §10 — the Superintendent cleared it into an occupied region, so it is the Superintendent's fault.
collide(s, s.clock.superintendent, [id, ahead.tray], events, 'ran into the train ahead', 'the Mainline');
return 'collided';
}
/** Puts a train onto a Mainline card with its crossing time already computed. */
function enterMainline(
node: Extract<DivisionNode, { kind: 'mainline' }>,
id: TrayId,
tray: CrewTray,
index: number,
startsAtBack = false,
): void {
const stages = crossingStages(node.card, entryFor(node, tray, startsAtBack || takesTheSiding(node)));
node.transits.push({ tray: id, stagesRemaining: stages, stagesTotal: stages, direction: tray.direction });
tray.position = { at: 'mainline', index };
// It is running now, so it is no longer being assembled (state.ts). A train at a Division Point
// needs no equivalent: leaving one changes its position, which is what that case reads.
delete tray.beingMadeUp;
/**
* OUT OF THE DISTRICT, AND THE SPUR PORT GOES WITH IT.
*
* `facing` is a port on the card the train is standing on, and switching round a district leaves
* it holding a real compass port — 'n' or 's' off a curve. Nothing cleared it when the train
* departed, so it carried that port out onto a Division that runs east and west, and then into
* the next Office, whose card has no north or south edge at all.
*
* That is not cosmetic. `movesFor` explores from `facing` and from its opposite, and a card with
* neither port yields no destinations either way — so a train that had been shunted onto a spur
* arrived at the next Office **unable to make a single Move**. It also drew a ▲ on the Division
* map, where there is no north to point at.
*
* A train out here is running one way along an east-west railroad with its engine at one end, so
* this is what `facing` means on the Division; there is nothing else it could be. `railFacing`
* follows for the same reason — this IS the east-west sense, freshly known.
*/
tray.facing = tray.direction === 'west' ? 'w' : 'e';
tray.railFacing = tray.facing;
}
/**
* Telegraph / Telephone / Radio — "once a day, when dispatching facing trains, add +N to the other
* train's number". Spends the best available device the owning player has, once per Day each.
*
* Returns the bonus applied to the opposing train's number (0 if none was available or needed).
*/
function spendDispatchBonus(
s: GameState,
tray: CrewTray,
other: CrewTray,
events: GameEvent[],
): number {
const mine = tray.trainNumber ?? 99;
const theirs = other.trainNumber ?? 99;
/**
* The Fedora is held by a PLAYER; the devices are installed in an Office Area, which is keyed by
* SEAT. `areaOf` is what reconciles the two — it resolves through `seatOf` — so this is correct
* under Employee Rotation and not only while seating happens to be the identity map.
*
* This comment used to say the opposite, warning that indexing one with the other was safe only
* while seating was identity. It read as a live bug and was not one: `areaOf(s, player)` IS
* `areaAtSeat(s, seatOf(s, player))`. Pinned by test rather than asserted here — see #101's
* "spends the Superintendent's own devices under non-identity seating".
*/
const area = areaOf(s, s.clock.superintendent);
// Best device first — Radio (+12) beats Telephone (+8) beats Telegraph (+4).
for (const key of ['radio', 'telephone', 'telegraph'] as const) {
if (area.dispatchUsedToday.includes(key)) continue;
const present = [...area.grid.values()].some((c) => c.enhancements.includes(key));
if (!present) continue;
const bonus = enhancementRule(key)?.dispatchBonus ?? 0;
// Spend it only if it actually wins the meet — the device makes the OTHER train count as
// junior, so ours may proceed.
if (mine >= theirs + bonus) continue;
area.dispatchUsedToday.push(key);
events.push({
type: 'dispatchBonusUsed',
key,
bonus,
trainNumber: tray.trainNumber ?? 0,
againstTrain: other.trainNumber ?? 0,
});
return bonus;
}
return 0;
}
/**
* Q3 — is this train subject to the "kept ready" fault (§7)?
*
* Expedite does not change WHEN a train leaves — it is released by the ordinary §8.1 rules like any
* other train, and may be switched normally while it stands. What it means is that it must not be
* held anywhere but the station: a train the player parks on Secondary Track to clear a switching
* move faults if it is not back on the Office square by the next Mainline Phase (`mainlinePhase`).
*
* Two ways to earn it. `expedite` is printed and permanent. `stopThenExpedite` is the X17 Campaign
* Train — "one turn at station (speeches) then expedite": its FIRST arrival is an ordinary stop while
* the speeches are made, and every arrival after that is expedited. `speechMade` is set on that first
* stop, so the train is exempt once and subject to the fault thereafter.
*/
export function isExpedited(tray: {
trainNumber: number | null;
trainIsExtra: boolean;
speechMade?: boolean;
}): boolean {
const rules = trainProfile(tray.trainNumber ?? 0, tray.trainIsExtra)?.rules;
if (!rules) return false;
if (rules.expedite) return true;
return rules.stopThenExpedite === true && tray.speechMade === true;
}
function moveTrain(s: GameState, id: TrayId, tray: CrewTray, events: GameEvent[]): MoveOutcome {
const dir = step(tray.direction);
if (tray.position.at === 'divisionPoint') {
// Read BEFORE `enterMainline` overwrites `tray.position`: the departure line named the side the
// train was leaving FROM, and taking it afterwards read the mainline position instead — so every
// train reported leaving the Eastern Division Point, including the eastbound ones that had just
// been made up at the Western one.
const fromSide = (tray.position as { side: Direction }).side;
const dpIndex = s.division.nodes.findIndex(
(n) => n.kind === 'divisionPoint' && n.side === fromSide,
);
const target = dpIndex + dir;
const node = s.division.nodes[target];
if (!node || node.kind !== 'mainline') return 'held';
const clearance = evaluateClearance(s, id, tray, target, events);
if (clearance === 'blocked') return 'held';
if (clearance === 'ask') return 'needsClearance';
const conflict = entryConflict(s, node, id, tray, events);
if (conflict === 'held') return 'held';
if (conflict === 'collided') return 'moved';
enterMainline(node, id, tray, target);
const dp = s.division.nodes[dpIndex];
if (dp?.kind === 'divisionPoint') dp.holding = dp.holding.filter((t) => t !== id);
events.push({
type: 'trainHighballed',
trainNumber: tray.trainNumber ?? 0,
from: `the ${fromSide === 'west' ? 'Western' : 'Eastern'} Division Point`,
to: 'the Mainline',
// Narrated as a phase marker until now — "▸ train 8 highballed phase" — which is not a phase
// and told the player nothing about why the train had started its run.
why: 'it was made up and the Subdivision ahead was clear, so its run begins',
});
return 'moved';
}
// §8.1 — a train standing on an A/D track attempts to highball onto the next Mainline card.
// Without this a train that arrives at an Office never leaves, holding an A/D track forever and
// colliding with every train that follows it.
if (tray.position.at === 'grid') {
const seat = tray.position.seat;
const area = areaAtSeat(s, seat);
// Only a train at the Office itself is eligible; one on Secondary Track is not (§8.1, Gap 2b).
if (
tray.position.coord.row !== area.officeCoord.row ||
tray.position.coord.col !== area.officeCoord.col
) {
return 'held';
}
/**
* §8.2 — A TRAIN MUST BE MADE UP BEFORE IT MAY LEAVE.
*
* The engine leads, the cars follow, and a caboose rides at the rear. A train that has been
* shunting can easily be in none of those states: taking cars on the nose puts them AHEAD of the
* engine ("pushing them into the Facility"), and cars picked up in a run-around land wherever the
* approach put them. Nothing checked, so a crew could shove a cut into a siding and then highball
* onto the Mainline engine-last with the caboose in the middle.
*
* The remedy is in the player's hands and is the reason both exist: run around the train, or
* spend a Move in a Small Yard, which re-makes it (`consistSorted` puts the engine back on the
* nose). Held rather than rejected — a train that cannot leave stays where it is, which is what
* makes an A/D track fill up and eventually bite.
*/
const badOrder = badlyMadeUp(tray);
if (badOrder !== null) {
events.push({ type: 'trainHeld', trainNumber: tray.trainNumber ?? 0, reason: badOrder });
return 'held';
}
const officeIndex = nodeIndexOfOffice(s, seat);
const target = officeIndex + dir;
const node = s.division.nodes[target];
if (!node) return 'held';
if (node.kind === 'mainline') {
const clearance = evaluateClearance(s, id, tray, target, events);
if (clearance === 'blocked') return 'held';
if (clearance === 'ask') return 'needsClearance';
const conflict = entryConflict(s, node, id, tray, events);
if (conflict === 'held') return 'held';
// The wreck's A/D track is released by `collide` itself, which is why it has to be.
if (conflict === 'collided') return 'moved';
enterMainline(node, id, tray, target);
area.adOccupancy = area.adOccupancy.filter((t) => t !== id);
events.push({
type: 'trainHighballed',
trainNumber: tray.trainNumber ?? 0,
from: 'the Office',
to: 'the Mainline',
why: 'it stood a full Stage at the Office, so §8.1 released it this Mainline Phase',
});
return 'moved';
}
/**
* CURRENTLY UNREACHABLE, and kept correct rather than deleted.
*
* `buildDivision` always lays `DP · Mainline · Office · Mainline · … · DP`, so an Office is never
* adjacent to a Division Point and this branch cannot be entered at any player count. It is left
* in — with the departure paid, so it would behave — because the layout is a setup decision that
* could reasonably change, and a branch that silently failed to score would be hard to spot.
* `setup.test.ts` asserts the flanking invariant that makes this dead.
*/
if (node.kind === 'divisionPoint') {
area.adOccupancy = area.adOccupancy.filter((t) => t !== id);
retireTrain(s, id, tray, node.side, events);
return 'moved';
}
return 'held';
}
if (tray.position.at === 'mainline') {
const { index } = tray.position;
const node = s.division.nodes[index];
if (!node || node.kind !== 'mainline') return 'held';
/**
* §7/§8.1 — AN EXTRA HIGHBALLING OUT OF THE INTERCHANGE'S YARD.
*
* Standing in `holding` rather than crossing in `transits` (state.ts), which is the position an
* Extra started at an Interchange begins in. It leaves exactly the way a train at a Division
* Point does — clearance first, then onto the running line — except that the card it enters is
* the one it is already standing beside rather than the next one along.
*
* That reuse is the whole point of modelling the yard separately: Jesse's rule is "a guaranteed
* collision holds it at the Interchange for another Stage and it tries again; a potential one is
* the Superintendent's to hold", and those are precisely `evaluateClearance`'s `blocked` and
* `ask`. Nothing new decides collisions here.
*/
if (node.holding?.includes(id)) {
const clearance = evaluateClearance(s, id, tray, index, events);
if (clearance === 'blocked') {
events.push({
type: 'trainHeld',
trainNumber: tray.trainNumber ?? 0,
reason: 'held in the Interchange — the Subdivision ahead is occupied',
});
return 'held';
}
if (clearance === 'ask') return 'needsClearance';
/**
* AN EXTRA PULLING OUT OF THE INTERCHANGE STARTS IN THE BACK REGION (Gitea#3) — "interchange
* has new extras show up in second region (like uncontrolled siding)", and earlier, "Plains is
* 1 stage for ALL trains. So are interlockings, with a second stage for incoming extras to hold
* at." A train running THROUGH the Interchange starts past that region and crosses in one
* Stage; one that began its run here has the holding region to clear first.
*/
const conflict = entryConflict(s, node, id, tray, events, true);
if (conflict === 'held') return 'held';
if (conflict === 'collided') return 'moved';
node.holding = node.holding.filter((t) => t !== id);
enterMainline(node, id, tray, index, true);
events.push({
type: 'trainHighballed',
trainNumber: tray.trainNumber ?? 0,
from: 'the Interchange',
to: 'the Mainline',
why: 'it was made up in the yard and the Subdivision was clear, so its run begins',
});
return 'moved';
}
const transit = node.transits.find((t) => t.tray === id);
if (!transit) return 'held';
// Q1/Q2 — crossing takes a whole number of Stages set by the card's speed and the train's
// Fast/Slow class. Count it down rather than stepping through printed cells.
if (transit.stagesRemaining > 1) {
/**
* Q13 — REAR-END COLLISIONS, answered: a train collides when it CATCHES UP.
*
* §10 makes a Mainline collision the Superintendent's fault and removes both trains, and ABS
* Signals exists to stop trains rear-ending each other — but §8.3's trigger list never named
* one and none was implemented, so granting clearance was free: both trains survived, no
* penalty, and ABS Signals protected against nothing.
*
* Colliding on CATCHING UP is the version that rewards judging the gap. A following train
* that closes on the one ahead runs into it; a following train that never closes is fine, so
* clearance becomes a bet on relative speed rather than a formality. §2.1 divides the card
* into two regions, and sharing one is what "caught up" means.
*
* ABS Signals does what it says instead: the follower stops SHORT of the collision and holds.
*/
// NOT on a card that prints "trains may pass" — Double Track holds two trains because it HAS
// two roads, so a train catching another there goes past it. That is what the card is for.
//
// The Uncontrolled Siding used to be in that set and no longer is: it keeps two trains apart
// by putting the second one in the siding a region back (`takesTheSiding`), not by letting
// them share a place. Marking it "may pass" skipped this test entirely and made the siding do
// nothing at all.
const mayPass = mainlineProfile(node.card).trainsMayPass;
const next = regionOfTransit(node.card, transit.stagesRemaining - 1);
const ahead = mayPass
? undefined
: node.transits.find(
(t) =>
t.tray !== id &&
t.direction === transit.direction &&
regionOfTransit(node.card, t.stagesRemaining) === next,
);
if (ahead) {
if (node.absSignals) {
// "Trains on this card will not rear-end each other; they stop short of a collision."
events.push({
type: 'trainHeld',
trainNumber: tray.trainNumber ?? 0,
reason: 'ABS Signals — held short of the train ahead',
});
return 'held';
}
// §10 — the Superintendent let it in behind the other, so it is the Superintendent's fault.
collide(s, s.clock.superintendent, [id, ahead.tray], events, 'ran into the train ahead', 'the Mainline');
return 'moved';
}
transit.stagesRemaining -= 1;
return 'moved';
}
// Off the end of the card: into the adjoining Limit, then straight to the Office (§8.2).
const target = index + dir;
const dest = s.division.nodes[target];
/**
* §11 (Gitea#5) — the Yard Office offer is put BEFORE the train leaves the Mainline card, for
* the same reason §8.1's clearance is: `needsClearance` unwinds the whole phase and the driver
* re-enters here from the top, so anything already mutated is mutated twice or, worse, left
* half-applied. Asking after the `transits` filter below cost the train its place on the card
* and it was never seen again — the question was asked and the answer had nowhere to land.
*/
if (dest?.kind === 'office') {
/**
* §Q, RED FLAGS (Gitea#19) — asked and answered before the train leaves the card, for exactly
* the reason the Yard Office offer is (see below): `needsClearance` unwinds the phase.
*
* Order matters. A flag stops the train OUTSIDE the Limits, so it never reaches the point
* where the Yard Office would be offered — flagging is about keeping a train out altogether.
*/
const flagged = redFlagStop(s, id, tray, dest, events);
if (flagged === 'ask') return 'needsClearance';
if (flagged === 'held') return 'held';
if (yardOfficeQuestion(s, id, tray, dest.seat, events) === 'ask') return 'needsClearance';
}
node.transits = node.transits.filter((t) => t.tray !== id);
if (!dest) return 'held';
if (dest.kind === 'divisionPoint') {
// The train has run the length of the Division and leaves the game (§2.3).
dest.holding.push(id);
tray.position = { at: 'divisionPoint', side: dest.side };
retireTrain(s, id, tray, dest.side, events);
return 'moved';
}
if (dest.kind === 'office') {
return arriveAtOffice(s, id, tray, dest.seat, events);
}
}
return 'held';
}
/**
* §8.1 — the highball conditions that involve the next Subdivision.
*
* A train moving TOWARDS the considered train is an absolute bar. A train moving the SAME
* direction is the Superintendent's judgment call — and Gap 2 made the consequences automatic
* precisely so that this decision carries full weight.
*/
function evaluateClearance(
s: GameState,
id: TrayId,
tray: CrewTray,
targetIndex: number,
events: GameEvent[] = [],
): 'clear' | 'blocked' | 'ask' {
// A ruling already given for this train is consumed here — this is what stops the driver from
// re-asking the same question every time it re-evaluates the train.
const answer = s.clock.decisionAnswer;
if (answer && answer.kind === 'clearance' && answer.train === id) {
s.clock.decisionAnswer = null;
return answer.allow ? 'clear' : 'blocked';
}
const node = s.division.nodes[targetIndex];
if (!node || node.kind !== 'mainline') return 'clear';
/**
* "TRAINS MAY PASS" IS A PROPERTY OF ONE CARD, NOT OF THE SUBDIVISION (Jesse, 2026-09-23).
*
* This returned `clear` outright, before the subdivision was looked at — so a train entering a
* Double Track was released however busy the rest of the Subdivision was, including against a
* train coming the other way three cards deeper in. Reported from a table: Train 8 highballed
* from the Western Division Point with no ruling asked, and the reason was this line rather than
* anything about Control Points.
*
* What the card actually prints is that TWO TRAINS MAY SHARE IT. So it excuses occupants ON THIS
* CARD and nothing else, which is what `passesHere` below is for.
*/
const profile = MAINLINE_PROFILES.find((m) => m.kind === node.card);
const passesHere = profile?.trainsMayPass === true;
/**
* §8.1 asks about the next SUBDIVISION, not the next card.
*
* "If there is a train in the next Subdivision moving towards the considered train, the considered
* train will not depart" — and the same for a following train. This used to inspect only
* `node.transits`, the one card being entered, so a train ran headlong into a Subdivision an
* opposing train was two cards deep in and was stopped only on the Stage they met. `subdivisions()`
* had existed for this the whole time and was called by nothing outside a test.
*
* It bites hardest early: every Office starts as a Whistle Post, so the entire railroad is ONE
* Subdivision until someone upgrades, which is exactly why §8 describes early traffic as
* constrained. Each Office upgrade to a Control Point splits one in two and buys capacity.
*/
const subdivision = subdivisions(s).find((group) => group.includes(targetIndex)) ?? [targetIndex];
/**
* ONLY WHAT IS AHEAD (Gitea#26). §8.1 asks about a train the considered train would FOLLOW, and one
* moving TOWARDS it — both of which are ahead of it. A Subdivision runs the length of every Whistle
* Post between two Control Points, so it can hold a train BEHIND the one departing: in the reported
* game X15 highballed west from an Office while X18, also westbound, was still crossing the card to its
* east. Counting X18 put a meaningless ruling to the Superintendent; holding X15 kept the Whistle Post's
* one A/D track full, and X18 arrived into it and was destroyed. A train behind and moving away is no
* threat at all.
*
* "Behind" is strictly behind the card the departing train stands on. A train on that same card is still
* counted, exactly as before: which of two trains sharing a card is in front is `entryConflict`'s region
* question, and this is not the place to answer it.
*/
const from = nodeIndexOfTray(s, tray);
const behind = (onCard: number): boolean =>
from !== null && from >= 0 && (tray.direction === 'east' ? onCard < from : onCard > from);
const occupants: { tray: TrayId; onCard: number }[] = [];
for (const i of subdivision) {
const n = s.division.nodes[i];
if (behind(i)) continue;
if (n?.kind === 'mainline') {
// A card that lets trains pass is not an obstruction on its own account.
if (i === targetIndex && passesHere) continue;
for (const t of n.transits) if (t.tray) occupants.push({ tray: t.tray, onCard: i });
continue;
}
/**
* A TRAIN STANDING AT AN OFFICE WITH NOWHERE TO PUT IT OCCUPIES THE SUBDIVISION TOO.
*
* Jesse's ruling, 2026-09-23, from a table where Train 19 was released from the Eastern
* Division Point towards Train 14 and nobody was asked: at the moment of the decision Train 14
* was not in `transits` at all, it was standing in a district. §8.1 was only ever reading
* trains in transit, so a train about to re-enter the very Subdivision being entered counted
* for nothing.
*
* CAPACITY IS THE TEST, not the mere presence of a train — his reasoning exactly. At a Whistle
* Post, one A/D track and a train on it means there is nowhere for the two to pass and no
* choice to be made. At a Depot or a Terminal with a track still free there is somewhere to go,
* and the train at the Office is not in the way.
*/
if (n?.kind === 'office') {
const area = areaAtSeat(s, n.seat);
if (area.adOccupancy.length < officeProfile(area.tier).adTracks) continue;
for (const held of area.adOccupancy) occupants.push({ tray: held, onCard: i });
}
}
/**
* TWO PASSES, NOT ONE — an opposite-direction occupant is an absolute bar and has to be checked
* against EVERY occupant before any same-direction judgment call is offered.
*
* A single pass returned on whichever occupant it examined first, in `node.transits` insertion
* order — which is fine while a Subdivision holds at most one train, but the dispatch exception
* below means it now legitimately can hold two: a Telegraph-cleared facing train sits on the same
* card as whatever it was cleared past. Found from a playtest report where the Superintendent was
* asked to rule on a same-direction train instead of being auto-held against an uncleared
* opposite-direction one also on the card — the loop had reached the same-direction occupant
* first simply because it entered the transit list first, and returned before ever looking at
* the other.
*/
for (const { tray: other } of occupants) {
if (other === id) continue;
const otherTray = s.trays.get(other);
if (!otherTray || otherTray.direction === tray.direction) continue;
// §8.1 — a train moving TOWARDS the considered train is an absolute bar. That stands.
//
// The exception is dispatching technology. Telegraph/Telephone/Radio exist precisely so the
// Superintendent can arrange a meet with a facing train: "once a day, when dispatching
// facing trains, add +4/+8/+12 to the other train's number". Without a device there is no
// way to pass the order, so the train simply holds.
if (spendDispatchBonus(s, tray, otherTray, events) > 0) continue;
/**
* SAY SO (Jesse, 2026-09-23: "does it make sense to have something listed in history or
* somewhere else when the train is not allowed to pass?").
*
* A facing train is an absolute bar and this returned silently — the train simply did not
* depart, Stage after Stage, with nothing on screen saying why. Only the ABS Signals case
* below announced itself, and it was given a line for exactly this reason.
*
* NAMES WHAT IS IN THE WAY, because the answer to "why is nothing happening" is a specific
* train somewhere specific, not a rule number.
*/
events.push({
type: 'trainHeld',
trainNumber: tray.trainNumber ?? 0,
reason:
`Train ${otherTray.trainNumber ?? '?'} is coming the other way in the same Subdivision — ` +
'§8.1 holds a train against a facing one, and there is no Control Point between them to pass at',
});
return 'blocked';
}
for (const { tray: other, onCard } of occupants) {
if (other === id) continue;
const otherTray = s.trays.get(other);
if (!otherTray || otherTray.direction !== tray.direction) continue;
const onNode = s.division.nodes[onCard];
// Red Flags — "a stopped train is prevented from being hit; the approaching train is prevented
// from moving". Flagging is per-train rather than per-card, so it protects one specific train
// where ABS Signals protects everything on the card.
//
// Red Flags used to protect a stopped train here as well. Gitea#19 replaced that rule outright
// (Jesse, 2026-08-29): a flag is now planted on a district's Limits and holds trains coming from
// one direction, so it never applies out on the Mainline. ABS Signals is what protects a train
// standing on a Mainline card now, and it always did the job better.
/**
* ABS Signals — "this is played on a mainline card to prevent collisions. If a collision would
* normally occur, the train moving onto the card is instead held back" (RAR, Gitea#3).
*
* With signals in place a following train simply holds and the Superintendent has no judgment
* call to make, which is the amendment to Gap 2's unconditional collisions. It is caught HERE
* rather than at the entry itself, so the train never gets as far as the card.
*
* IT USED TO HOLD SILENTLY. A blocked clearance emits nothing on the Office and Division Point
* paths, so the one card whose entire purpose is to stop a wreck did its job invisibly: the
* train simply did not move, Stage after Stage, with nothing on screen saying why. The card is
* unplayable to reason about without this line.
*/
if (onNode?.kind === 'mainline' && onNode.absSignals) {
events.push({
type: 'trainHeld',
trainNumber: tray.trainNumber ?? 0,
reason: 'ABS Signals — held short of the train ahead',
});
return 'blocked';
}
// Same direction — the Superintendent must rule (§8.1, fourth condition).
s.clock.pendingDecision = { kind: 'clearance', train: id, occupiedBy: other };
events.push({ type: 'clearanceRequested', trainId: id, occupiedBy: other });
return 'ask';
}
return 'clear';
}
/**
* CAN THIS TRAIN REACH THE YARD OFFICE, AND IS THE LEAD CLEAR? (Gitea#5)
*
* Three answers, because Jesse's ruling (2026-08-29) splits two failures his issue describes
* separately: "if the Yard Office is not accessible in one move, you should not get the option"
* and "cars on the tracks you use to get in result in a crash".
*
* - `clear` — a route exists and nothing is standing on it. Offer it; taking it is safe.
* - `fouled` — a route exists and there are cars on it. Offer it; taking it collides.
* - `none` — no route in one move. Do not offer it, and say why in the history.
*
* WALKED WITH THE ENGINE'S OWN MOVE RULES rather than a bespoke adjacency test. `exploreMoves`
* already means exactly what the card's "in one move" means — any distance without changing
* direction, finishing on Operational Rail (§2.4, §A.1) — so using it is what makes the code and
* the card agree, which was the whole complaint.
*
* THE FOULING SIGNAL IS `couples`. The walk does not treat standing cars as obstructions: it
* COUPLES them, because that is what a switching move does (§A.4). An arriving train is not
* switching, so anything it would have coupled is instead something it is about to hit — the same
* reading §8.3 already applies to the Running Track.
*
* The walk starts at the Office square, where a standard arrival puts the train, and leaves by the
* way the train is already facing. Reversing is a separate Move (§A.5), so a Yard Office that can
* only be reached by backing up is correctly "not in one move".
*/
/**
* The flag comes down as it stops the train — one card, one train (Gitea#19).
*
* MUTATES RATHER THAN EMITTING A REDUCED EVENT, because this is the phase driver: `advance.ts`
* changes state directly and then describes what it did, and roughly a third of the event types are
* never reduced at all (`README.md`, and `tally.ts` on the same asymmetry). A `redFlagSpent`
* reducer case looked right and never fired — the flag stayed up and held every train that came.
*/
function spendFlag(
office: Extract<DivisionNode, { kind: 'office' }>,
tray: CrewTray,
side: Direction,
events: GameEvent[],
): 'held' {
delete office.redFlag;
events.push({ type: 'redFlagSpent', seat: office.seat, side, trainNumber: tray.trainNumber ?? 0 });
events.push({
type: 'trainHeld',
trainNumber: tray.trainNumber ?? 0,
reason: 'Red Flags — held short of the Limits',
});
return 'held';
}
/**
* §Q, RED FLAGS (Gitea#19) — does a flag stop this train, and should its owner be offered one?
*
* Two jobs, because they are the same moment seen twice: a flag already planted stops the train
* outright, and a train about to run into trouble is the cue to offer a flag to somebody holding
* the card. "You can play the card normally or out of phase, but only if you need it."
*
* - `held` — a flag was up on the side this train is coming from. It loses this Mainline
* Phase and the flag comes down with it: one card, one train (Jesse, 2026-08-29).
* - `ask` — entering would collide and the district's owner holds a Red Flags card.
* - `proceed` — neither.
*
* WHICH SIDE. A train running WEST arrives from the east, so `FLAG EAST` is what holds it — which
* is the example the issue gives, and the reason the flag names a side rather than a heading.
*/
function redFlagStop(
s: GameState,
id: TrayId,
tray: CrewTray,
dest: Extract<DivisionNode, { kind: 'office' }>,
events: GameEvent[],
): 'held' | 'ask' | 'proceed' {
const from: Direction = tray.direction === 'east' ? 'west' : 'east';
// The answer to a prompt already put. Consumed here so the driver cannot ask twice.
const answer = s.clock.decisionAnswer;
if (answer && answer.kind === 'redFlag' && answer.train === id) {
s.clock.decisionAnswer = null;
if (!answer.flag) return 'proceed';
// The card was spent planting the flag; it stops this train and comes down again at once.
return spendFlag(dest, tray, from, events);
}
if (dest.redFlag === from) return spendFlag(dest, tray, from, events);
/**
* "In actual cases of danger… if there is a train or cars on the track and there will be a
* collision, then you break in with a dialog." The two ways an arrival collides are §8.3's own:
* no free A/D track, and cars fouling the Running Track. Asked only of a player who can actually
* answer — offering a flag to somebody holding no card is a prompt with one button.
*/
const owner = playerAtSeat(s, dest.seat);
const holdsFlag = (s.decks.hands.get(owner) ?? []).some((cid) => {
const c = s.cards.get(cid);
return c?.kind.kind === 'maneuver' && c.kind.key === 'redFlags';
});
if (!holdsFlag) return 'proceed';
if (!arrivalWouldCollide(s, dest.seat)) return 'proceed';
s.clock.pendingDecision = { kind: 'redFlag', train: id, seat: dest.seat, from };
return 'ask';
}
/**
* Would this arrival collide? §8.3's two triggers, asked before the train commits.
*
* Deliberately a READ of the same conditions `arriveAtOffice` enforces rather than a second rule:
* if these two ever diverge, the prompt offers a flag against a collision that will not happen, or
* stays silent before one that will.
*/
function arrivalWouldCollide(s: GameState, seat: SeatIndex): boolean {
const area = areaAtSeat(s, seat);
const hasInterlocking = [...area.grid.values()].some((c) => c.enhancements.includes('interlocking'));
const full = area.adOccupancy.length >= officeProfile(area.tier).adTracks;
// Interlocking turns a full Office into a hold rather than a collision, so it is not danger.
if (full && !hasInterlocking) return true;
// A coach may legally stand at the Office while its engine switches (§A.4's carve-out), so it is
// not a hazard to the next arrival. Anything else on the Running Track is.
const officeCard = area.grid.get(coordKey(area.officeCoord));
return officeCard !== undefined && officeCard.standing.some((c) => c.type !== 'coach');
}
/**
* §11 (Gitea#5) — should the district's owner be asked about the Yard Office, and is there
* anything to ask about?
*
* Returns `ask` only when the offer is real: a coachless train, a Yard Office card in the district,
* and a route to it in one move. Everything else is `proceed`, which means the ordinary arrival.
*
* ALSO THE PLACE THE HISTORY LEARNS WHY NOT. Jesse, 2026-08-29: "make sure this is logged in
* history — why can't move so user knows why they can't get to yard." A qualifying train that is
* simply never offered the choice looks exactly like the feature being broken, which is how the
* missing reachability check went unnoticed for so long.
*/
function yardOfficeQuestion(
s: GameState,
id: TrayId,
tray: CrewTray,
seat: SeatIndex,
events: GameEvent[],
): 'ask' | 'proceed' {
// Already answered: `arriveAtOffice` consumes it. Asking again would loop the phase for ever.
const answer = s.clock.decisionAnswer;
if (answer && answer.kind === 'yardOffice' && answer.train === id) return 'proceed';
if (tray.consist.some((c) => c.type === 'coach')) return 'proceed';
const area = areaAtSeat(s, seat);
if (![...area.grid.values()].some((c) => c.enhancements.includes('yardOffice'))) return 'proceed';
const route = yardOfficeRoute(s, seat, id, tray);
if (route.kind === 'none') {
events.push({
type: 'trainDiverted',
trainNumber: tray.trainNumber ?? 0,
to: 'the Office',
reason: `the Yard Office could not be offered — ${route.why}`,
});
return 'proceed';
}
s.clock.pendingDecision = { kind: 'yardOffice', train: id, seat };
return 'ask';
}
type YardOfficeRoute =
| { kind: 'clear' | 'fouled'; coord: GridCoord }
| { kind: 'none'; why: string };
function yardOfficeRoute(s: GameState, seat: SeatIndex, id: TrayId, tray: CrewTray): YardOfficeRoute {
const area = areaAtSeat(s, seat);
const target = [...area.grid.entries()].find(([, card]) => card.enhancements.includes('yardOffice'));
if (!target) return { kind: 'none', why: 'there is no Yard Office in this district' };
const [key] = target;
const [row, col] = key.split(',').map(Number);
const coord = { row: row!, col: col! };
const player = playerAtSeat(s, seat);
const facing = railFacingOf(tray);
const found = reachableDestinations(
{
area,
occupancy: occupancyFor(s, player, id),
consistSize: tray.consist.length,
self: id,
},
area.officeCoord,
facing,
).find((d) => d.coord.row === coord.row && d.coord.col === coord.col);
if (!found) {
return {
kind: 'none',
why: 'it cannot be reached from the Office in one move, running the way this train is facing',
};
}
return { kind: found.couples.length > 0 ? 'fouled' : 'clear', coord };
}
/**
* §8.3 — arriving at an Office. Collisions here are AUTOMATIC (Gap 2a): if the trigger holds,
* the collision happens, with no die roll and no judgment.
*/
function arriveAtOffice(
s: GameState,
id: TrayId,
tray: CrewTray,
seat: SeatIndex,
events: GameEvent[],
): MoveOutcome {
const area = areaAtSeat(s, seat);
const capacity = officeProfile(area.tier).adTracks;
const hasEnhancement = (key: string): boolean =>
[...area.grid.values()].some((c) => c.enhancements.includes(key));
/**
* §11, THE YARD OFFICE (Gitea#5) — offered, not imposed.
*
* "Trains that are only freight (cabooses ok, no coaches allowed) that arrive in a player's area
* who has the yard office card get an extra ability. On the turn (mainline phase) that the train
* arrives the game will offer that player the option to have that train go directly to the yard
* office card instead of the standard office. They can of course still choose to have the train
* go to the standard office."
*
* WHAT THIS USED TO DO, and why all three of the rule's conditions were missing: a qualifying
* train was TELEPORTED onto the Yard Office card. The player was never asked, no route was ever
* computed — so the card's own printed text, "that can reach the yard office in one move", was
* unenforced — and because nothing was walked, nothing was ever met on the way in.
*
* The answer comes back through `pendingDecision`, so this returns `needsClearance` and is
* re-entered once the player has answered. `yardOfficeOffer` below is where the route is walked.
*/
/**
* The answer to the offer `yardOfficeQuestion` put before the train left the Mainline card.
* Absent — because the train has no Yard Office, or no route to it, or carries coaches — this
* falls straight through to the ordinary arrival below.
*/
const answer = s.clock.decisionAnswer;
if (answer && answer.kind === 'yardOffice' && answer.train === id) {
s.clock.decisionAnswer = null;
const route = answer.take ? yardOfficeRoute(s, seat, id, tray) : { kind: 'none' as const };
if (route.kind !== 'none') {
tray.position = { at: 'grid', seat, coord: route.coord };
events.push({
type: 'trainDiverted',
trainNumber: tray.trainNumber ?? 0,
to: 'the Yard Office',
reason: 'no coaches, so it need not occupy the Train Order Office',
});
/**
* Cars on the lead are a COLLISION, not a coupling — the same §8.3 rule that governs the
* Running Track, and the third of the three things this implementation was missing. An
* arriving train is at speed and is not expecting them (§A.4).
*/
if (route.kind === 'fouled') {
collide(s, playerAtSeat(s, seat), [id], events, 'cars fouling the lead into the Yard Office', 'the Yard Office');
}
return 'moved';
}
// Declined: fall through to the standard Office, with its own capacity and collision rules.
}
// Gap 2d — no room at the station is a collision, and it is the local player's fault (§10).
if (area.adOccupancy.length >= capacity) {
// Interlocking — "may stop an inbound train on the Limit Track". Instead of an automatic
// collision, the train is held at the Limits until an A/D track frees up. This is the designed
// answer to the A/D overflow that Gap 2d made fatal.
if (hasEnhancement('interlocking')) {
area.heldAtLimits.push(id);
events.push({
type: 'trainDiverted',
trainNumber: tray.trainNumber ?? 0,
to: 'the Limits',
reason: 'Interlocking held it clear of a full Office instead of a collision',
});
return 'moved';
}
collide(s, playerAtSeat(s, seat), [id], events, 'no free A/D track', 'the Office');
return 'moved';
}
/**
* A TRAIN HELD AT THE LIMITS TAKES THE FIRST FREE A/D TRACK BEFORE ANY NEWCOMER — and taking it
* FILLS IT, which is what this used to forget.
*
* Reported from a table, 2026-09-23: a Whistle Post with one A/D track held Trains 8 and 19 at
* once. The capacity test above had passed (nothing standing), this block then moved the held
* train in, and the arriving train was pushed in after it without anyone asking again whether
* there was room. So the Office ended up over capacity and the collision §8.3 calls for never
* happened.
*
* The held train has priority — it has been waiting — so the NEWCOMER takes the consequence, and
* it is the same consequence it would have met had the held train got there first: held at its
* own Limits where there is an Interlocking, and a collision where there is not.
*
* IT IS ALSO ANNOUNCED. The release used to be a silent side effect of somebody else's arrival:
* the train simply appeared at the Office, and the report was "wasn't clear what changed and why
* train 8 was suddenly released".
*/
if (area.heldAtLimits.length > 0 && area.heldAtLimits[0] !== id) {
const first = area.heldAtLimits.shift()!;
area.adOccupancy.push(first);
const held = s.trays.get(first);
if (held) held.position = { at: 'grid', seat, coord: area.officeCoord };
events.push({
type: 'trainReleasedFromLimits',
trainNumber: held?.trainNumber ?? 0,
office: officeProfile(area.tier).name,
owner: playerAtSeat(s, seat),
freedBy: tray.trainNumber ?? 0,
});
// The slot it just took is gone. Ask again for the train that is arriving now.
if (area.adOccupancy.length >= capacity) {
if (hasEnhancement('interlocking')) {
area.heldAtLimits.push(id);
events.push({
type: 'trainDiverted',
trainNumber: tray.trainNumber ?? 0,
to: 'the Limits',
reason: 'Interlocking held it clear of a full Office instead of a collision',
});
return 'moved';
}
collide(s, playerAtSeat(s, seat), [id], events, 'no free A/D track', 'the Office');
return 'moved';
}
}
area.heldAtLimits = area.heldAtLimits.filter((t) => t !== id);
// §8.3 — cars standing on the Running Track between the Limits and the Office. A train at speed
// is not expecting them (§A.4), so this is a collision too, not a coupling.
//
// A coach is the one exception (v0.5.0, §A.4's Office carve-out): it may be legally, deliberately
// parked at the Office while its engine switches, so it must not become a hazard to the next
// arrival. Anything else standing there is still illegal to have dropped in the first place —
// `canDropCarsAt` already refuses it — so this filter only ever excludes a coach in practice.
const officeCard = area.grid.get(coordKey(area.officeCoord));
if (officeCard && officeCard.standing.some((c) => c.type !== 'coach')) {
collide(s, playerAtSeat(s, seat), [id], events, 'cars fouling the Running Track', 'the Running Track');
return 'moved';
}
area.adOccupancy.push(id);
tray.position = { at: 'grid', seat, coord: area.officeCoord };
events.push({
type: 'trainArrived',
trainNumber: tray.trainNumber ?? 0,
consist: tray.consist.map((c) => ({ ...c })),
office: officeProfile(area.tier).name,
owner: playerAtSeat(s, seat),
expedited: isExpedited(tray),
});
/**
* X17 Campaign Train — the speeches happen at the first Office it reaches, and every arrival after
* that runs expedited (`isExpedited` reads `speechMade`). Setting it here is idempotent on every
* later arrival, so it needs no guard against re-firing.
*/
if (trainProfile(tray.trainNumber ?? 0, tray.trainIsExtra)?.rules.stopThenExpedite) {
tray.speechMade = true;
}
return 'moved';
}
function collide(
s: GameState,
faultPlayer: PlayerIndex,
trains: TrayId[],
events: GameEvent[],
reason: string,
where = 'the Office',
): void {
// Record WHAT was lost before removing it. The log said only "COLLISION: NO FREE A/D TRACK", so a
// player could see the 5 points go without learning which train had just been written off, or
// what it was carrying.
const lost: { label: string; consist: RollingStock[] }[] = [];
for (const id of trains) {
const tray = s.trays.get(id);
if (!tray) continue;
lost.push({
label:
tray.trainNumber === null
? 'the local crew'
: `Train ${tray.trainIsExtra ? 'X' : ''}${tray.trainNumber}`,
consist: [...tray.consist],
});
// Gap 2c — engines and cabooses return to the Division Yard, everything else to Classification.
// `pooled` because a car reaching a yard is back in the common supply: the load's origin stamp
// (state.ts) belongs to the load, not to the car that happened to be carrying it.
for (const car of tray.consist) {
if (car.type === 'caboose') s.yards.divisionYard.push(pooled(car));
else s.yards.classificationYard.push(pooled(car));
}
s.trays.delete(id);
s.freeTrays.push(id);
/**
* TAKE THE WRECK OFF THE CARD.
*
* Nothing did. `s.trays.delete` removed the train and left its `Transit` sitting on the Mainline
* card it died on, and `evaluateClearance` counts every transit as an occupant — so a rear-end
* collision (the caller at "ran into the train ahead") permanently poisoned that card: every
* later train was either held against a ghost or put to the Superintendent about one. The only
* other place a transit is removed is a train rolling off the far end, which a destroyed train
* never does.
*
* Found while adding the Interchange start, which clears onto the running line through that
* same occupant list.
*/
for (const n of s.division.nodes) {
if (n.kind !== 'mainline') continue;
n.transits = n.transits.filter((t) => t.tray !== id);
if (n.holding) n.holding = n.holding.filter((t) => t !== id);
}
/**
* AND OFF THE A/D TRACK, for exactly the same reason as the transit above.
*
* It never mattered while every collision happened to a train already out on the road. Gitea#3
* adds one that can happen as a train LEAVES — a following train entering an occupied region —
* and that train is still standing at the Office when it dies. Without this its A/D track stays
* marked forever: the Office reads as permanently full, and every later arrival collides against
* a train that no longer exists.
*/
for (const [, area] of s.officeAreas) {
area.adOccupancy = area.adOccupancy.filter((t) => t !== id);
}
}
if (lost.length > 0) {
events.push({ type: 'trainsDestroyed', player: faultPlayer, trains: lost, reason, where });
}
s.collisionsToday += 1;
s.collisionsTotal += 1;
const player = s.players[faultPlayer];
if (player) {
player.revenue -= COLLISION_PENALTY;
events.push({
type: 'revenueChanged',
player: faultPlayer,
delta: -COLLISION_PENALTY,
total: player.revenue,
reason: `collision: ${reason}`,
});
}
}
/**
* ONE REVENUE TO EVERY PLAYER WHEN A TRAIN COMPLETES ITS RUN.
*
* Jesse's rule, revised. It used to pay 1 to the Office a train departed — "it left YOUR section" —
* which meant a five-Office railroad paid five times for one train and paid the most to whoever the
* train happened to pass first. It pays once now, when the train runs off the end of the Division,
* and it pays EVERYBODY: getting a train the whole length of the railroad is the shared achievement,
* and every Office it crossed had to clear it.
*
* Unlike freight and passengers it pays for traffic no one has to work, which is the point: keeping
* the line moving is the Superintendent's job, and nothing else paid for doing it well. It rewards
* splitting a Subdivision with a Control Point, holding a following train rather than gambling on
* it, and building the A/D capacity to turn arrivals around.
*
* A crew with no train number is a local switching move, not a run, so it earns nothing.
*
* NOW A DIAL, AND OFF BY DEFAULT. At 1 it was worth ~5.4 Revenue against a bot mean of 7.0 — the
* railroad was making most of its money from the one thing no one has to work, and the freight and
* passenger economies it exists to reward could not be read through it. `trainPerTransit` sets the
* rate per player, and 0 (the default) means no event at all rather than a run of "+0" entries.
*/
function awardCompletedRun(s: GameState, tray: CrewTray, events: GameEvent[]): void {
if (tray.trainNumber === null) return;
const rate = houseRules(s.config).revenue.trainPerTransit;
if (rate <= 0) return;
for (const p of s.players) {
p.revenue += rate;
events.push({
type: 'revenueChanged',
player: p.index,
delta: rate,
total: p.revenue,
reason: 'a train completed its run',
});
}
}
/** A completed run frees the crew; Extras go to the Salvage Yard (§2.3, Gap 2c). */
function retireTrain(
s: GameState,
id: TrayId,
tray: CrewTray,
side: Direction,
events: GameEvent[],
): void {
// `pooled` — see `trainsDestroyed` above; a load's origin stamp does not survive the yard.
for (const car of tray.consist) {
if (car.type === 'caboose') s.yards.divisionYard.push(pooled(car));
else s.yards.classificationYard.push(pooled(car));
}
s.trays.delete(id);
s.freeTrays.push(id);
const dp = s.division.nodes.find(
(n) => n.kind === 'divisionPoint' && n.holding.includes(id),
);
if (dp?.kind === 'divisionPoint') dp.holding = dp.holding.filter((t) => t !== id);
events.push({
type: 'trainCompleted',
trainNumber: tray.trainNumber ?? 0,
isExtra: tray.trainIsExtra,
side,
consist: tray.consist.map((c) => ({ ...c })),
});
awardCompletedRun(s, tray, events);
}
// ---------------------------------------------------------------------------
// Shift change, Stage and Day advance
// ---------------------------------------------------------------------------
function shiftChange(s: GameState, events: GameEvent[]): AdvanceResult {
// §5 — the Fedora passes every three Stages: shift changes at Stages 3, 6, 9 and 12.
if (s.clock.stage % STAGES_PER_SHIFT === 0) {
s.clock.superintendent = playerLeftOf(s, s.clock.superintendent);
events.push({ type: 'actorChanged', player: s.clock.superintendent });
/**
* SAID OUT LOUD, as well as recorded. `actorChanged` is turn bookkeeping and the log discards it,
* so this — the one time in three Stages that it means the Fedora moved — had no line anywhere
* (playtest, 2026-09-16). Emitted alongside rather than instead: `actorChanged` still carries the
* cursor, and anything reading it keeps working.
*/
events.push({ type: 'superintendentChanged', player: s.clock.superintendent, stage: s.clock.stage });
}
// §9.1 — Laborers and Porters reset at the start of each Stage, not each Phase.
for (const area of s.officeAreas.values()) {
for (const card of area.grid.values()) {
if (card.facility) card.facility.usedThisStage = { laborers: 0, porters: 0 };
}
}
/**
* §3.4 — EVERY MODE, SOLITAIRE INCLUDED: a Day's collisions against `maxCollisionsPerDay` and the
* game's running total against `maxCollisionsTotal`. `0` disables either check. Flat, not scaled
* by player count — Jesse's call, 2026-08-20: more players is more independent chances to collide,
* not a bigger shared budget.
*
* JUDGED BEFORE THE DAY ROLLS OVER (v0.8.3). This block sat below the rollover, which resets
* `collisionsToday` — so a breach reached in Stage 12 was read as zero and the last Stage of every
* Day was the one Stage the floor could not fire in. Pinned in `advance.test.ts`.
*
* SOLITAIRE WAS EXCLUDED UNTIL 2026-08-30 and nothing said so. The gate here read `mode ===
* 'competitive' || mode === 'coop'`, while `SOLO_CONFIG` carried both limits and the New Game
* dialog offered them as live settings — so a solitaire player could set a collision limit, read
* "the game ends in a loss" beside it, and crash as often as they liked. Found reviewing that
* screen's wording (Jesse, 2026-08-30); his ruling is that the settings should do what they say,
* so the gate is gone rather than the controls.
*
* A SOLITAIRE GAME CAN THEREFORE NOW END EARLY, which no measurement in `TODO.md` was taken
* under. At the shipped defaults (3 a Day, 5 total) it is a rare ending rather than a common one —
* the bot averages 0.06 collisions a game — but any figure quoted from a full-length run predates
* it.
*/
{
const perDayBreach =
s.config.maxCollisionsPerDay > 0 && s.collisionsToday >= s.config.maxCollisionsPerDay;
const totalBreach =
s.config.maxCollisionsTotal > 0 && s.collisionsTotal >= s.config.maxCollisionsTotal;
if (perDayBreach || totalBreach) {
s.status = 'finished';
/**
* NOT EXTENDABLE, AND IT DOES NOT REWRITE A RECORDED RESULT (Gitea#11).
*
* A breach during an EXTENDED Day ends play at once, exactly as it would during the regular
* game — but by then the official result already exists, and a railroad declared unsafe on
* Day 9 does not retract who won on Day 5. `freezeOfficial` is what keeps that true: it
* writes only when `official` is still null, so assigning `outcome` here is safe.
*/
s.outcome = { result: 'loss', winner: null, reason: 'collisionFloor' };
return { events, needsInput: false };
}
}
if (s.clock.stage >= STAGES_PER_DAY) {
// Telegraph/Telephone/Radio are each usable once a Day.
for (const area of s.officeAreas.values()) area.dispatchUsedToday = [];
s.clock.day += 1;
s.clock.stage = 1;
// Captured BEFORE the reset: the Day-end dialog reports the Day that just finished, and it is
// drawn from the frame this rollover produces. See `collisionsPrevDay` in `state.ts`.
s.collisionsPrevDay = s.collisionsToday;
s.collisionsToday = 0;
events.push({ type: 'stageBegan', day: s.clock.day, stage: 1 });
rotateSeats(s, events);
const finished = checkVictory(s, events);
if (finished) return { events, needsInput: false };
} else {
s.clock.stage += 1;
events.push({ type: 'stageBegan', day: s.clock.day, stage: s.clock.stage });
}
return { events: [...events, ...enterPhase(s, 'localOps')], needsInput: false };
}
/**
* §3.3 — evaluated at the end of a Day.
*
* Unified 2026-08-20 across all three modes: play `config.days`, then whoever has the most Revenue
* wins — unless the table's combined Revenue missed `config.minCombinedRevenue`, in which case
* everyone loses. Solitaire is "everyone" with one player, so this is the same win/lose shape it
* always had, just against a configured floor instead of a `length`-preset `target`. Coop keeps its
* "the table's score is everyone's Revenue summed" model — winner stays null, the achievement is
* shared — now against the same configurable floor.
*/
/**
* EMPLOYEE ROTATION (Appendix B) — "at the end of the day, all players move one chair to the left
* and take over the next station up the line. Take your points (and the Fedora) with you."
*
* This is the rule the whole seat/player split exists for (D9, and `state.ts`'s note on
* `SeatIndex`), which is why it is four lines: `seating` is the only thing that moves. Everything
* keyed by PLAYER — Revenue, hands, the Superintendent, whose turn it is — travels with them for
* free, and everything keyed by SEAT — the Office, the district, the grid, trains standing in it —
* stays exactly where it is. Inheriting the state of the district you move into is the point of the
* rule, not a side effect of it.
*
* "Left" is `seatOf + 1`, matching `playerLeftOf`, which is the convention the rest of the engine
* already turns the table by.
*/
function rotateSeats(s: GameState, events: GameEvent[]): void {
if (!s.config.optionalRules.employeeRotation || s.seating.length < 2) return;
const n = s.seating.length;
const next: PlayerIndex[] = new Array<PlayerIndex>(n);
for (let seat = 0; seat < n; seat++) next[(seat + 1) % n] = s.seating[seat]!;
s.seating = next;
events.push({ type: 'seatsRotated', day: s.clock.day, seating: [...next] });
}
function checkVictory(s: GameState, _events: GameEvent[]): boolean {
const daysElapsed = s.clock.day - 1;
/**
* `extraDays` is Gitea#11. `config.days` is never touched by an extension — it is what the
* OFFICIAL result is decided at — so the Day the timetable currently runs to is the sum of the
* two. On the first ending they are equal, which is why `freezeOfficial` can record `config.days`
* as the official Day without asking anything further.
*/
if (daysElapsed < s.config.days + s.extraDays) return false;
s.outcome = decideOutcome(s);
/**
* §3.3, EXTENDED PLAY — an ending the table may play past PAUSES rather than finishing.
*
* `freezeOfficial` (the `advance` wrapper) records the first of these as the official result, so
* by the time a second one is reached the winner is already settled and everything here is
* informational. The votes are cleared each time because the question is asked again at the end
* of every extended Day: agreeing once does not agree to the rest of the game.
*/
if (isExtendable(s.outcome.reason)) {
s.status = 'awaitingExtension';
s.extensionVotes = s.players.map(() => null);
} else {
s.status = 'finished';
}
return true;
}
/**
* WHO WON, on the evidence as it stands right now.
*
* Split out of `checkVictory` for Gitea#11: it is asked once per ending, and an extended game has
* more than one. Unchanged in substance — the revenue floor, then co-op's shared achievement, then
* the highest Revenue — it simply no longer writes to the state it is reasoning about.
*/
function decideOutcome(s: GameState): Outcome {
const combined = totalRevenue(s);
if (s.config.minCombinedRevenue > 0 && combined < s.config.minCombinedRevenue) {
return { result: 'loss', winner: null, reason: 'revenueFloor' };
}
if (s.config.mode === 'coop') {
return { result: 'win', winner: null, reason: 'daysElapsed' };
}
const best = Math.max(...s.players.map((p) => p.revenue));
return {
result: 'win',
winner: s.players.findIndex((p) => p.revenue === best),
reason: 'daysElapsed',
};
}
// ---------------------------------------------------------------------------
// Pump helper
// ---------------------------------------------------------------------------
/** Runs automatic work until a player must act or the game ends. */
export function pump(s: GameState, maxSteps = 10_000): GameEvent[] {
const all: GameEvent[] = [];
for (let i = 0; i < maxSteps; i++) {
const r = advance(s);
all.push(...r.events);
if (r.needsInput || s.status === 'finished') return all;
}
throw new Error('phase driver failed to settle — probable infinite loop');
}
export { nodeIndexOfOffice };