/**
 * Enhancement cards (implications.md §7).
 *
 * These are the 18 cards that make up the largest block of the "third of the deck that does
 * nothing". Several change core loops — Small Yard makes the facing-point switching puzzle
 * solvable at all, and ABS Signals amends Gap 2's unconditional collisions.
 */

import { describe, it } from 'node:test';
import assert from 'node:assert/strict';

import { advance } from '../src/engine/advance.ts';
import { applyIntent, areaOf, check, hasDistrictEnhancement, isProtectedFromDerail } from '../src/engine/apply.ts';
import { ENHANCEMENT_RULES, enhancementRule, trainProfile } from '../src/engine/content.ts';
import { createGame } from '../src/engine/setup.ts';
import type { GameConfig, GameState, GridCoord, TrackCard } from '../src/engine/state.ts';
import { coordKey, subdivisions, turnOf } from '../src/engine/state.ts';

const config: GameConfig = {
  mode: 'solitaire',
  victory: 'highestAfterDays',
  length: 'standard',
  optionalRules: { reducedVisibility: false, sisterTrains: false, employeeRotation: false, emergencyToolbox: false },
};
const game = (seed = 5): GameState => createGame({ id: 'g', seed, config, playerNames: ['p'] });
const at = (row: number, col: number): GridCoord => ({ row, col });

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

function addCard(s: GameState, coord: GridCoord, card: TrackCard): void {
  areaOf(s, 0).grid.set(coordKey(coord), card);
}

/**
 * An Enhancement in hand — minting one if the deck does not deal it.
 *
 * Facing Point Locks, the Water Column and the Overpass answer opponent-directed cards, which are
 * held out of every deck until they are implemented, so those three are no longer dealt either
 * (v0.4.7). Their RULES are still live and still worth testing: they fire the moment their attacker
 * returns, and a rule nobody exercises is a rule that rots. So the card is put in hand directly
 * rather than fished out of a deck that deliberately no longer contains it.
 */
function handEnhancement(s: GameState, key: string): string {
  for (const [id, card] of s.cards) {
    if (card.kind.kind === 'enhancement' && card.kind.key === key) {
      s.decks.hands.set(0, [id]);
      return id;
    }
  }
  const id = `mint-${key}-${s.cards.size}`;
  s.cards.set(id, { id, kind: { kind: 'enhancement', key } } as never);
  s.decks.hands.set(0, [id]);
  return id;
}

/** Puts a specific track card in hand and returns its id. */
function trackInHand(s: GameState, geometry: string, hand: string): string {
  for (const [id, card] of s.cards) {
    const k = card.kind as { kind: string; geometry?: string; hand?: string };
    if (k.kind === 'track' && k.geometry === geometry && k.hand === hand) {
      s.decks.hands.set(0, [id]);
      return id;
    }
  }
  throw new Error(`no track card: ${geometry}/${hand}`);
}

function placeTray(s: GameState, coord: GridCoord, consist: TrackCard['standing'] = []): string {
  const id = s.freeTrays.pop()!;
  s.trays.set(id, {
    id, trainNumber: 9, trainIsExtra: false, engineAt: 0,
    consist, direction: 'east', position: { at: 'grid', seat: 0, coord }, movesUsed: 0,
  });
  return id;
}

// ---------------------------------------------------------------------------

describe('enhancement placement', () => {
  it('defines a rule for every enhancement card', () => {
    assert.equal(ENHANCEMENT_RULES.length, 10);
    for (const r of ENHANCEMENT_RULES) assert.ok(enhancementRule(r.key), r.key);
  });

  it('puts Interlocking on a Running Track straight, not a Secondary one', () => {
    const s = game();
    addCard(s, at(0, 2), straight());
    addCard(s, at(-1, 0), straight());
    const id = handEnhancement(s, 'interlocking');
    applyIntent(s, 0, { type: 'localOps.choose', option: 'draw' });
    assert.equal(check(s, 0, { type: 'card.play', cardId: id, placement: at(0, 2) }), null);
    assert.equal(check(s, 0, { type: 'card.play', cardId: id, placement: at(-1, 0) }), 'NOT_CONNECTED');
  });

  it('puts Small Yard on a Secondary Track straight, not the Running Track', () => {
    const s = game();
    addCard(s, at(0, 2), straight());
    addCard(s, at(-1, 0), straight());
    const id = handEnhancement(s, 'smallYard');
    applyIntent(s, 0, { type: 'localOps.choose', option: 'draw' });
    assert.equal(check(s, 0, { type: 'card.play', cardId: id, placement: at(-1, 0) }), null);
    assert.equal(check(s, 0, { type: 'card.play', cardId: id, placement: at(0, 2) }), 'NOT_CONNECTED');
  });

  it('stacks Telephone on Telegraph and Radio on Telephone, never bare', () => {
    const s = game();
    addCard(s, at(0, 2), straight());
    applyIntent(s, 0, { type: 'localOps.choose', option: 'draw' });

    const phone = handEnhancement(s, 'telephone');
    assert.equal(check(s, 0, { type: 'card.play', cardId: phone, placement: at(0, 2) }), 'NOT_CONNECTED');

    const tel = handEnhancement(s, 'telegraph');
    assert.ok(applyIntent(s, 0, { type: 'card.play', cardId: tel, placement: at(0, 2) }).ok);

    const phone2 = handEnhancement(s, 'telephone');
    assert.equal(check(s, 0, { type: 'card.play', cardId: phone2, placement: at(0, 2) }), null);
  });

  it('will not stack two straight-placed enhancements on one card', () => {
    // A straight-placed Enhancement REPLACES the straight — its printed placement is "any Running
    // Track Straight", so the card goes down in place of it and what stands there afterwards is an
    // Interlocking, not a straight carrying one. A second such card has no straight left to take.
    // This was unchecked, because an enhancement only pushes a string onto `enhancements[]` and
    // leaves the geometry alone: one straight could hold Interlocking, Telegraph and a Water Column
    // at once.
    const s = game();
    addCard(s, at(0, 2), straight());
    addCard(s, at(0, 3), straight());
    applyIntent(s, 0, { type: 'localOps.choose', option: 'draw' });

    const lock = handEnhancement(s, 'interlocking');
    assert.ok(applyIntent(s, 0, { type: 'card.play', cardId: lock, placement: at(0, 2) }).ok);

    for (const key of ['telegraph', 'waterColumn'] as const) {
      const id = handEnhancement(s, key);
      assert.equal(
        check(s, 0, { type: 'card.play', cardId: id, placement: at(0, 2) }),
        'NOT_CONNECTED',
        `${key} was stacked on top of an Interlocking`,
      );
      // The bare straight next door is still a legal home for it.
      assert.equal(
        check(s, 0, { type: 'card.play', cardId: id, placement: at(0, 3) }), null,
        `${key} should still be playable on a straight that carries nothing`,
      );
    }

    // And a turnout cannot upgrade it either — the straight it would replace is no longer there.
    assert.equal(
      check(s, 0, { type: 'card.play', cardId: trackInHand(s, 'turnout', 'right'), placement: at(0, 2), variant: 0 }),
      'UPGRADE_ENHANCED',
      'a turnout was laid over a built Interlocking',
    );
  });

  it('requires an Interlocking in the district before Facing Point Locks', () => {
    const s = game();
    addCard(s, at(0, 2), straight());
    applyIntent(s, 0, { type: 'localOps.choose', option: 'draw' });
    const fpl = handEnhancement(s, 'facingPointLocks');
    assert.equal(check(s, 0, { type: 'card.play', cardId: fpl, placement: at(0, 2) }), 'NOT_CONNECTED');

    const lock = handEnhancement(s, 'interlocking');
    applyIntent(s, 0, { type: 'card.play', cardId: lock, placement: at(0, 2) });
    const fpl2 = handEnhancement(s, 'facingPointLocks');
    assert.equal(check(s, 0, { type: 'card.play', cardId: fpl2, placement: at(0, 2) }), null);
    assert.ok(isProtectedFromDerail(areaOf(s, 0)) === false, 'not protected until actually played');
  });
});

// ---------------------------------------------------------------------------

describe('Small Yard — the card that makes switching solvable', () => {
  function yardGame() {
    const s = game();
    const yard = at(-1, 0);
    const card = straight();
    card.enhancements.push('smallYard');
    addCard(s, yard, card);
    const tray = placeTray(s, yard, [
      { type: 'boxcar', loaded: false },
      { type: 'hopper', loaded: true },
      { type: 'coach', loaded: false },
    ]);
    applyIntent(s, 0, { type: 'localOps.choose', option: 'switch' });
    return { s, tray, yard };
  }

  it('re-orders a consist, including bringing a buried car to the end', () => {
    // §A.3 forces cars off in seated order, so without this the middle car can never be spotted.
    const { s, tray } = yardGame();
    const r = applyIntent(s, 0, { type: 'switch.sortConsist', trayId: tray, order: [0, 2, 1] });
    assert.ok(r.ok);
    assert.deepEqual(
      s.trays.get(tray)!.consist.map((c) => c.type),
      ['boxcar', 'coach', 'hopper'],
      'the hopper is now on the droppable end',
    );
  });

  it('costs one Move — "spends one move in the yard"', () => {
    const { s, tray } = yardGame();
    const before = turnOf(s, 0).movesRemaining;
    applyIntent(s, 0, { type: 'switch.sortConsist', trayId: tray, order: [2, 1, 0] });
    assert.equal(turnOf(s, 0).movesRemaining, before - 1);
  });

  it('is refused anywhere without a Small Yard', () => {
    const s = game();
    addCard(s, at(-1, 0), straight());
    const tray = placeTray(s, at(-1, 0), [
      { type: 'boxcar', loaded: false },
      { type: 'hopper', loaded: true },
    ]);
    applyIntent(s, 0, { type: 'localOps.choose', option: 'switch' });
    assert.equal(
      check(s, 0, { type: 'switch.sortConsist', trayId: tray, order: [1, 0] }),
      'NOT_CONNECTED',
    );
  });

  it('refuses an order that is not a permutation of the consist', () => {
    const { s, tray } = yardGame();
    for (const bad of [[0, 1], [0, 1, 1], [0, 1, 5]]) {
      assert.equal(
        check(s, 0, { type: 'switch.sortConsist', trayId: tray, order: bad }),
        'CONSIST_ORDER',
        `accepted ${JSON.stringify(bad)}`,
      );
    }
  });
});

// ---------------------------------------------------------------------------

describe('Interlocking and Yard Office relieve the Office', () => {
  function inbound(s: GameState, consist: TrackCard['standing']) {
    const id = 'inbound';
    s.trays.set(id, {
      id, trainNumber: 9, trainIsExtra: false, engineAt: 0,
      consist, direction: 'east', position: { at: 'mainline', index: 1 }, movesUsed: 0,
    });
    const ml = s.division.nodes[1];
    if (ml?.kind === 'mainline') {
      // Pin the terrain. Mainline types are drawn from the SHUFFLED deck, so deck composition
      // would otherwise decide this test's outcome — and Double Track / Uncontrolled Siding set
      // `trainsMayPass`, which legitimately removes the §8.1 bar being asserted here.
      ml.card = 'plains';
      ml.transits.push({ tray: id, stagesRemaining: 1, stagesTotal: 1, direction: 'east' });
    }
    s.clock.phase = 'mainline';
    s.movedThisPhase = new Set();
    return id;
  }

  it('holds a train at the Limits instead of colliding when the Office is full', () => {
    // Gap 2d made a full Office an automatic collision. Interlocking is the designed answer.
    const s = game();
    const card = straight();
    card.enhancements.push('interlocking');
    addCard(s, at(0, 2), card);
    areaOf(s, 0).adOccupancy = ['blocker'];
    const id = inbound(s, [{ type: 'hopper', loaded: true }]);

    advance(s);
    assert.equal(s.players[0]!.revenue, 0, 'no collision penalty');
    assert.ok(areaOf(s, 0).heldAtLimits.includes(id), 'train is held at the Limits');
  });

  it('still collides without an Interlocking', () => {
    const s = game();
    areaOf(s, 0).adOccupancy = ['blocker'];
    inbound(s, [{ type: 'hopper', loaded: true }]);
    advance(s);
    assert.equal(s.players[0]!.revenue, -5);
  });

  it('diverts a coachless train to the Yard Office', () => {
    const s = game();
    const card = straight();
    card.enhancements.push('yardOffice');
    addCard(s, at(-1, 0), card);
    const id = inbound(s, [{ type: 'hopper', loaded: true }]);

    advance(s);
    const pos = s.trays.get(id)!.position;
    assert.ok(pos.at === 'grid' && pos.coord.row === -1, 'arrived at the Yard Office');
    assert.ok(!areaOf(s, 0).adOccupancy.includes(id), 'did not take an A/D track');
  });

  it('does not divert a train carrying coaches', () => {
    // "An inbound train with NO COACHES" — passengers must reach the Train Order Office.
    const s = game();
    const card = straight();
    card.enhancements.push('yardOffice');
    addCard(s, at(-1, 0), card);
    const id = inbound(s, [{ type: 'coach', loaded: true }]);

    advance(s);
    assert.ok(areaOf(s, 0).adOccupancy.includes(id), 'a coach train must use the Office');
  });
});

// ---------------------------------------------------------------------------

describe('ABS Signals amend the collision rule', () => {
  it('turns a following-train judgment into a plain hold', () => {
    // "Trains on this card will not rear-end each other. They will stop short of a collision."
    const s = game();
    const ml = s.division.nodes[1];
    if (ml?.kind === 'mainline') {
      // Pin the terrain — see the meet tests below. Double Track and Uncontrolled Siding let trains
      // pass, so the following train would never be held and there would be nothing for ABS to do.
      ml.card = 'plains';
      ml.absSignals = true;
      ml.transits.push({ tray: 'ahead', stagesRemaining: 2, stagesTotal: 2, direction: 'east' });
    }
    s.trays.set('ahead', {
      id: 'ahead', trainNumber: 4, trainIsExtra: false, engineAt: 0,
      consist: [], direction: 'east', position: { at: 'mainline', index: 1 }, movesUsed: 0,
    });
    s.trays.set('behind', {
      id: 'behind', trainNumber: 2, trainIsExtra: false, engineAt: 0,
      consist: [], direction: 'east', position: { at: 'divisionPoint', side: 'west' }, movesUsed: 0,
    });
    s.clock.phase = 'mainline';
    s.movedThisPhase = new Set();

    const r = advance(s);
    assert.equal(r.needsInput, false, 'no clearance decision is needed with signals');
    assert.equal(s.clock.pendingDecision, null);
    assert.deepEqual(s.trays.get('behind')!.position, { at: 'divisionPoint', side: 'west' });
  });
});

// ---------------------------------------------------------------------------

describe('train revenue per transit — paid to EVERY player when a train completes its run', () => {
  /**
   * `trainPerTransit` is a dial now, and it defaults to ZERO: at 1 it was worth ~5.4 Revenue against
   * a bot mean of 7.0, drowning out the freight and passenger economies the game is about. These
   * tests are about the rule, so they set the rate; the last one is about the default.
   */
  const paying = (rate = 1, seed = 5): GameState =>
    createGame({
      id: 'g',
      seed,
      config: { ...config, houseRules: { revenue: { trainPerTransit: rate } } },
      playerNames: ['p'],
    });

  /** A train sitting on the A/D track, made up and ready to highball. */
  const readyToLeave = (s: GameState, direction: 'east' | 'west' = 'east'): string => {
    const id = 'leaving';
    s.trays.set(id, {
      id, trainNumber: 2, trainIsExtra: false, engineAt: 0,
      consist: [], direction, position: { at: 'grid', seat: 0, coord: areaOf(s, 0).officeCoord },
      movesUsed: 0,
    });
    areaOf(s, 0).adOccupancy.push(id);
    for (const n of s.division.nodes) if (n.kind === 'mainline') n.card = 'plains';
    s.clock.phase = 'mainline';
    s.movedThisPhase = new Set();
    return id;
  };

  it('pays nothing for merely leaving the Office', () => {
    /**
     * THE RULE CHANGED IN v0.4.2. It used to pay 1 to the Office a train departed, which meant a
     * five-Office railroad paid five times for one train and paid most to whoever it happened to
     * pass first. Departing is now worth nothing on its own.
     */
    const s = game();
    const before = s.players[0]!.revenue;
    readyToLeave(s, 'east');

    advance(s);

    assert.equal(s.players[0]!.revenue, before, 'departing the Office still paid');
  });

  it('pays every player once the train runs off the end of the Division', () => {
    const s = paying();
    const before = s.players.map((p) => p.revenue);
    readyToLeave(s, 'east');

    // Run the Mainline Phase until the train has crossed the Division and left it.
    const seen: typeof s.players[number]['revenue'][] = [];
    let completed: { type: string; side?: string } | undefined;
    for (let i = 0; i < 20 && !completed; i++) {
      s.movedThisPhase = new Set();
      s.clock.phase = 'mainline';
      const r = advance(s);
      completed = r.events.find((e) => e.type === 'trainCompleted');
      if (completed) {
        assert.equal(completed.side, 'east', 'an eastbound train left by the wrong Division Point');
        assert.ok(
          r.events.some((e) => e.type === 'revenueChanged' && e.reason === 'a train completed its run'),
          'no revenue event was emitted for the completed run',
        );
      }
      seen.push(s.players[0]!.revenue);
    }
    assert.ok(completed, 'the train never left the Division');
    assert.deepEqual(s.players.map((p) => p.revenue), before.map((r) => r + 1), 'not every player was paid');

    // Paid ONCE — the train is gone, so there is nothing left to pay again.
    const after = s.players.map((p) => p.revenue);
    for (let i = 0; i < 8; i++) { s.movedThisPhase = new Set(); s.clock.phase = 'mainline'; advance(s); }
    assert.deepEqual(s.players.map((p) => p.revenue), after, 'the same run was paid twice');
  });

  it('pays nothing for a local crew, which is switching rather than running', () => {
    const s = paying();
    const before = s.players[0]!.revenue;
    const id = readyToLeave(s, 'east');
    s.trays.get(id)!.trainNumber = null;

    for (let i = 0; i < 20; i++) { s.movedThisPhase = new Set(); s.clock.phase = 'mainline'; advance(s); }

    assert.equal(s.players[0]!.revenue, before, 'a switching crew was paid as though it had completed a run');
  });

  it('pays at the rate the game was dealt with, and nothing at the default of zero', () => {
    // Zero is not "one, suppressed": no revenue event is emitted at all, so the history does not
    // fill with "+0 Revenue" for work that did not pay.
    const run = (rate: number): { revenue: number; events: number } => {
      const s = rate === 0 ? game() : paying(rate);
      readyToLeave(s, 'east');
      let events = 0;
      let done = false;
      for (let i = 0; i < 20 && !done; i++) {
        s.movedThisPhase = new Set();
        s.clock.phase = 'mainline';
        const r = advance(s);
        events += r.events.filter(
          (e) => e.type === 'revenueChanged' && e.reason === 'a train completed its run',
        ).length;
        done = r.events.some((e) => e.type === 'trainCompleted');
      }
      assert.ok(done, `the train never left the Division at rate ${rate}`);
      return { revenue: s.players[0]!.revenue, events };
    };

    assert.deepEqual(run(0), { revenue: 0, events: 0 }, 'the default paid for a transit');
    assert.deepEqual(run(1), { revenue: 1, events: 1 });
    assert.deepEqual(run(5), { revenue: 5, events: 1 }, 'the top of the range pays 5 in one event');
  });
});

// ---------------------------------------------------------------------------

describe('§8.1 — a train that just arrived from the mainline stops for the Stage', () => {
  /**
   * "The train did not just initially arrive from a mainline card at the Office this Stage."
   *
   * This holds today, but only as a SIDE EFFECT: the Mainline Phase visits each train once per Stage
   * in numeric order, so a train that spends its visit arriving has no visit left to depart with.
   * Nothing states the rule, which makes it exactly the kind of property a later change to the loop
   * would break in silence. These pin it.
   *
   * It is also what gives the printed **Expedite** rule something to do — an Expedited train departs
   * at the END of the Stage it arrived, precisely because the general rule forbids it departing at
   * all. It stands through Load/Unload first, which is what makes its coaches workable.
   */
  const arriving = (s: GameState, trainNumber: number, isExtra = false): string => {
    const id = 'arriving';
    s.trays.set(id, {
      id, trainNumber, trainIsExtra: isExtra, engineAt: 0,
      consist: [], direction: 'east', position: { at: 'mainline', index: 1 }, movesUsed: 0,
    });
    const ml = s.division.nodes[1];
    if (ml?.kind === 'mainline') {
      ml.card = 'plains';
      // One Stage left to run, so this Stage it rolls off the card and into the Office.
      ml.transits.push({ tray: id, stagesRemaining: 1, stagesTotal: 1, direction: 'east' });
    }
    s.clock.phase = 'mainline';
    s.movedThisPhase = new Set();
    return id;
  };

  it('does not depart the Stage it rolls in', () => {
    const s = game();
    const id = arriving(s, 9);
    assert.notEqual(trainProfile(9, false)?.rules.expedite, true, 'train 9 must NOT be an Expedite train');

    advance(s);

    assert.ok(areaOf(s, 0).adOccupancy.includes(id), 'the train did not arrive at the Office at all');
    assert.equal(
      s.trays.get(id)!.position.at, 'grid',
      'the train departed again in the same Stage it arrived from a mainline card',
    );
  });

  it('unless its card prints Expedite — but it still stands through Load/Unload first', () => {
    /**
     * Q3, as revised in v0.4.2. An Expedite train leaves the Stage it arrives, but at the END of that
     * Stage rather than inside the Mainline Phase. It used to be gone before Load/Unload ran, which
     * made the coaches on every coach-carrying express (1/2, 5/6, 19) permanently unworkable —
     * measured, Train 2 arrived 32 times in 60 games and stood for Load/Unload in none of them.
     */
    const s = game();
    assert.equal(trainProfile(3, false)?.rules.expedite, true, 'train 3 should be an Expedite train');
    const id = arriving(s, 3);

    advance(s);

    assert.equal(
      s.trays.get(id)!.position.at, 'grid',
      'an Expedite train left inside the Mainline Phase, before Load/Unload could reach it',
    );
    assert.equal(s.trays.get(id)!.departsThisStage, true, 'it is not flagged to leave at the end of the Stage');
    assert.ok(areaOf(s, 0).adOccupancy.includes(id), 'it is not standing on an A/D track');

    // Run the end of the Stage directly. Load/Unload waits on the player, and the thing under test
    // is the departure pass that follows it — not that phase's own input handling.
    s.clock.phase = 'shiftChange';
    advance(s);
    assert.notEqual(
      s.trays.get(id)?.position.at, 'grid',
      'an Expedite train should be gone by the end of the Stage it arrived',
    );
  });
});

// ---------------------------------------------------------------------------

describe('§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." This used to inspect only the card being entered, so a train ran headlong
   * into a Subdivision an opposing train was two cards deep in and was stopped only when they met.
   *
   * At game start every Office is a Whistle Post — not a Control Point — so the whole railroad is ONE
   * Subdivision: nodes [1, 2, 3] between the two Division Points. That is what makes early traffic so
   * constrained, and each upgrade to a Control Point splits it and buys capacity back.
   */
  const facingTrainOn = (s: GameState, index: number): void => {
    // EVERY Mainline card is pinned, not just the one the facing train stands on: Double Track and
    // Uncontrolled Siding print "trains may pass", so terrain anywhere in the Subdivision can clear
    // the departure. Terrain is dealt from the same RNG stream as the cards, so leaving any of it to
    // the seed makes this luck — which is exactly how it broke when the deck composition changed.
    for (const n of s.division.nodes) if (n.kind === 'mainline') n.card = 'plains';
    const ml = s.division.nodes[index];
    if (ml?.kind === 'mainline') {
      ml.transits.push({ tray: 'facing', stagesRemaining: 2, stagesTotal: 2, direction: 'west' });
    }
    s.trays.set('facing', {
      id: 'facing', trainNumber: 4, trainIsExtra: false, engineAt: 0,
      consist: [], direction: 'west', position: { at: 'mainline', index }, movesUsed: 0,
    });
    s.trays.set('considered', {
      id: 'considered', trainNumber: 2, trainIsExtra: false, engineAt: 0,
      consist: [], direction: 'east', position: { at: 'divisionPoint', side: 'west' }, movesUsed: 0,
    });
    s.clock.phase = 'mainline';
    s.movedThisPhase = new Set();
  };

  it('holds a train out of a Subdivision an opposing train is deep inside', () => {
    const s = game();
    assert.deepEqual(subdivisions(s), [[1, 2, 3]], 'the fixture assumes one Subdivision of three nodes');

    // The facing train is on node 3 — NOT the card being entered, which is node 1.
    facingTrainOn(s, 3);
    const r = advance(s);

    assert.equal(r.needsInput, false, 'an opposing train is an absolute bar, never a judgment call');
    assert.equal(s.clock.pendingDecision, null);
    assert.deepEqual(
      s.trays.get('considered')!.position, { at: 'divisionPoint', side: 'west' },
      'the train departed into a Subdivision already occupied by a train coming the other way',
    );
  });

  it('ignores a train standing clear on Secondary Track in a Whistle Post district', () => {
    // The last §8.1 condition: "if the Subdivision contains a Whistle Post yet a train is occupying
    // Secondary Track there (i.e. clear of the Running Track), the Superintendent MUST Highball the
    // train." The Office node sits inside this Subdivision, so a scan that counted everything in the
    // group would have blocked on it. Only Mainline occupancy counts.
    const s = game();
    assert.deepEqual(subdivisions(s), [[1, 2, 3]], 'node 2 is the Office, inside the Subdivision');

    addCard(s, at(-1, 0), straight());
    placeTray(s, at(-1, 0));

    s.trays.set('considered', {
      id: 'considered', trainNumber: 2, trainIsExtra: false, engineAt: 0,
      consist: [], direction: 'east', position: { at: 'divisionPoint', side: 'west' }, movesUsed: 0,
    });
    const ml = s.division.nodes[1];
    if (ml?.kind === 'mainline') ml.card = 'plains';
    s.clock.phase = 'mainline';
    s.movedThisPhase = new Set();

    advance(s);

    assert.deepEqual(
      s.trays.get('considered')!.position, { at: 'mainline', index: 1 },
      'a train standing clear on Secondary Track held up the whole Subdivision',
    );
  });

  it('still lets it go once a Control Point splits that Subdivision away', () => {
    // The same position, with the Office upgraded to a Depot: node 2 becomes a boundary, so the
    // facing train on node 3 is in a DIFFERENT Subdivision and no longer bars the departure.
    const s = game();
    areaOf(s, 0).tier = 'depot';
    assert.deepEqual(subdivisions(s), [[1], [3]], 'a Control Point should split the Division in two');

    facingTrainOn(s, 3);
    advance(s);

    assert.deepEqual(
      s.trays.get('considered')!.position, { at: 'mainline', index: 1 },
      'a train in another Subdivision must not hold this one at the Division Point',
    );
  });
});

// ---------------------------------------------------------------------------

describe('Telegraph, Telephone and Radio dispatch meets', () => {
  function meet(s: GameState, device?: string) {
    if (device) {
      const card = straight();
      card.enhancements.push(device);
      addCard(s, at(0, 2), card);
    }
    // An oncoming senior train — §8.1 makes this an absolute bar without a device.
    s.trays.set('oncoming', {
      id: 'oncoming', trainNumber: 3, trainIsExtra: false, engineAt: 0,
      consist: [], direction: 'west', position: { at: 'mainline', index: 1 }, movesUsed: 0,
    });
    const ml = s.division.nodes[1];
    if (ml?.kind === 'mainline') {
      // Pin the terrain. Mainline types are drawn from the shuffled deck, so deck composition would
      // otherwise decide this test's outcome — and Double Track / Uncontrolled Siding set
      // `trainsMayPass`, which legitimately removes the §8.1 bar this test is about.
      ml.card = 'plains';
      ml.transits.push({ tray: 'oncoming', stagesRemaining: 2, stagesTotal: 2, direction: 'west' });
    }
    s.trays.set('mine', {
      id: 'mine', trainNumber: 9, trainIsExtra: false, engineAt: 0,
      consist: [], direction: 'east', position: { at: 'divisionPoint', side: 'west' }, movesUsed: 0,
    });
    s.clock.phase = 'mainline';
    s.movedThisPhase = new Set();
  }

  it('holds a facing train with no device — §8.1 stands', () => {
    const s = game();
    meet(s);
    advance(s);
    assert.deepEqual(s.trays.get('mine')!.position, { at: 'divisionPoint', side: 'west' });
  });

  it('lets a junior train win the meet with a Telegraph', () => {
    // Train 9 against Train 3: +4 makes the other count as 7 — still senior. Radio's +12 wins.
    const s = game();
    meet(s, 'radio');
    advance(s);
    assert.equal(s.trays.get('mine')!.position.at, 'mainline', 'the meet was dispatched');
    assert.ok(areaOf(s, 0).dispatchUsedToday.includes('radio'));
  });

  it('spends each device only once a Day', () => {
    const s = game();
    meet(s, 'radio');
    advance(s);
    assert.deepEqual(areaOf(s, 0).dispatchUsedToday, ['radio']);
    // Reset happens at the Day boundary.
    s.clock.stage = 12;
    s.clock.phase = 'shiftChange';
    advance(s);
    assert.deepEqual(areaOf(s, 0).dispatchUsedToday, [], 'devices reset each Day');
  });

  it('gives Radio the largest bonus and Telegraph the smallest', () => {
    assert.equal(enhancementRule('telegraph')!.dispatchBonus, 4);
    assert.equal(enhancementRule('telephone')!.dispatchBonus, 8);
    assert.equal(enhancementRule('radio')!.dispatchBonus, 12);
  });
});

// ---------------------------------------------------------------------------

describe('defensive enhancements', () => {
  it('reports district protection only once actually built', () => {
    // These guard against opponent-directed cards, which a solitaire deck omits entirely (Q6).
    const s = game();
    assert.equal(isProtectedFromDerail(areaOf(s, 0)), false);
    const card = straight();
    card.enhancements.push('facingPointLocks');
    addCard(s, at(0, 2), card);
    assert.equal(isProtectedFromDerail(areaOf(s, 0)), true);
    assert.equal(hasDistrictEnhancement(areaOf(s, 0), 'waterColumn'), false);
  });
});