Fixed world clock: no player time controls (ISS-117)

The world always runs at WORLD_TIME_SCALE = 24 (lib/worldClock.ts). A server
background tick (instrumentation.ts -> startBackgroundTick, 1 s interval)
advances the sim with no open browser; idle-pause freezes the clock exactly
while no plane is flying or in repair. Fresh worlds start year 2000
(STARTING_CLOCK_MS in seed.ts).

- Removed: POST /api/sim + OpenAPI entry, applyTimeControls/clampTimeScale,
  lib/timeScale.ts, LeftPane pause button + scale slider machinery,
  ISS-057 slow-on-landing/resume in flyPlane.
- Snapshot simState is now { clockMs } only; client extrapolates at the fixed
  rate between polls and freezes while idle (useSimClock).
- New test-only hook POST /api/test/set-timescale behind FLIGHT_TEST_HOOKS=1
  (sibling of set-health); all e2e setScale helpers call it, afterEach restores
  the world rate. E2E pause tests replaced by idle-pause assertions; sim.spec.ts
  activates the world via set-health + /repair for advance/expiry tests.

lib/sim/engine.ts

@@ -18,20 +18,20 @@ import {
 } from '@/lib/game/seed';
 import { arrivalTimeFor, fuelAtWeighted, requiredFuelFor, windBurnFactor } from './movement';
 
-// Server-authoritative sim engine (v0.7.0) — tick-on-read: there is NO background
-// timer. Every read/action endpoint calls tickNow() first; the clock advances by
-// (real ms since last tick) × timeScale, clamped per tick so long absences never
-// fast-forward the game.
+// Server-authoritative sim engine (v0.7.0). ISS-117 (v0.52.0): the clock advances on a background
+// tick (~1 s, started at boot from instrumentation.ts) AND on every read/action — both through the
+// same locked tickOnce path. Each tick advances by (real ms since last tick) × timeScale, clamped
+// per tick so long absences never fast-forward the game; while no plane is flying or in repair the
+// clock stays frozen (idle-pause) but lastRealTickMs keeps tracking real time.
 
-// Clamp constant: max real-time gap counted by a single tick. Chosen at 2000 ms —
-// comfortably above a normal client poll interval (~1 s), so active play advances
-// ~real time × scale; small enough that one stale read after an absence moves game
-// time by at most 2 s × scale (≈ 33 min even at max scale 1000). The sim therefore
-// only meaningfully progresses while actively polled.
+// Clamp constant: max real-time gap counted by a single tick. Chosen at 2000 ms — comfortably above
+// both the client poll interval (~1 s) and the background-tick interval, so active play advances
+// ~real time × scale; small enough that one stale read after an absence moves game time by at most
+// 2 s × scale.
 export const MAX_TICK_ELAPSED_MS = 2_000;
 
-export const MIN_TIME_SCALE = 1;
-export const MAX_TIME_SCALE = 1000; // top of the slider ladder (v0.14.0)
+// ISS-117: the fixed world rate — re-exported here so server code and tests have one familiar home.
+export { WORLD_TIME_SCALE } from '@/lib/worldClock';
 
 // Reputation gain per delivered package: BASE + PER_KM × great-circle km, rounded
 // to 2 decimals (reputation is REAL). A short hop (~300 km) earns ~1.15 rep, a
@@ -43,11 +43,6 @@ export function reputationGainFor(km: number): number {
   return Math.round((REP_BASE + REP_PER_KM * km) * 100) / 100;
 }
 
-export interface SimControlsInput {
-  timeScale?: number;
-  paused?: boolean;
-}
-
 // Serialize ticks across concurrent requests (Next.js route handlers run in the
 // same process): each tick re-reads sim_state after the previous one wrote it, so
 // no advance is ever applied twice.
@@ -63,23 +58,36 @@ function withLock<T>(fn: () => Promise<T>): Promise<T> {
 
 // --- Tick core (takes a GameDb so unit tests can inject their own instance) ---
 
+// ISS-117: idle-pause decision — pure, so unit tests feed it synthetic fleets. The world clock
+// advances only while something is happening: at least one plane flying OR in repair. A fully
+// grounded fleet freezes the clock (and with it expiries/spawns) until a dispatch or repair starts.
+export function shouldAdvanceTime(planes: Array<{ status: string }>): { advance: boolean; flying: number; repairing: number } {
+  let flying = 0;
+  let repairing = 0;
+  for (const p of planes) {
+    if (p.status === 'flying') flying++;
+    else if (p.status === 'repairing') repairing++;
+  }
+  return { advance: flying > 0 || repairing > 0, flying, repairing };
+}
+
 export async function tickOnce(inst: GameDb): Promise<schema.SimStateRow> {
   const rows = await inst.db.select().from(schema.simState);
   const sim = rows[0];
   if (!sim) throw new Error('sim_state row missing');
 
   const nowMs = Date.now();
+  // ISS-117: frozen while nothing is happening (see shouldAdvanceTime). lastRealTickMs still
+  // tracks real time, so a takeoff resumes cleanly with no catch-up jump for the idle duration.
+  const planeRows = await inst.db.select().from(schema.planes);
+  const { advance } = shouldAdvanceTime(planeRows.map((p) => ({ status: p.status })));
   const elapsed = Math.max(0, nowMs - sim.lastRealTickMs);
-  // While paused the clock is frozen; lastRealTickMs still tracks real time so
-  // unpausing resumes cleanly with no catch-up jump for the pause duration.
-  const advanceMs = sim.paused ? 0 : Math.min(elapsed, MAX_TICK_ELAPSED_MS) * sim.timeScale;
+  const advanceMs = advance ? Math.min(elapsed, MAX_TICK_ELAPSED_MS) * sim.timeScale : 0;
   const clockMs = Math.round(sim.clockMs + advanceMs);
 
-  let landedThisTick = 0;
   if (advanceMs > 0) {
     await expirePackages(inst, clockMs);
-    // ISS-057: remember the landings so the tick can slow down when a plane is left on ground.
-    landedThisTick = await deliverPackages(inst, clockMs);
+    await deliverPackages(inst, clockMs);
     // v0.39.0 (ISS-069): repairs whose gate has passed flip back to 'available' — runs even when
     // nothing landed this tick; BEFORE the spawns so a just-repaired plane gets coverage work too.
     await finishRepairs(inst, clockMs);
@@ -89,25 +97,8 @@ export async function tickOnce(inst: GameDb): Promise<schema.SimStateRow> {
     await spawnCoveragePackages(inst, clockMs);
   }
 
-  const sets: Partial<Pick<schema.SimStateRow, 'clockMs' | 'lastRealTickMs' | 'timeScale'>> = {
-    clockMs,
-    lastRealTickMs: nowMs,
-  };
-  // Slow on landing (ISS-057): when ≥1 plane landed this tick and ANY plane is grounded
-  // ('available') afterwards, drop the sim to MIN_TIME_SCALE — a just-landed plane counts, so
-  // any real landing slows. A chained plane stays 'flying' via deliverPackages' auto-chain
-  // branch, so a pure-chain tick with nothing grounded does NOT slow. Pause is manual-only now;
-  // flyPlane restores lastSelectedTimeScale when the last grounded plane takes off. Arrival-
-  // triggered by design: a grounded fleet at high scale is left alone (no idle-enforcement), and
-  // a paused tick never processes landings (advanceMs === 0), so the trigger only fires on an
-  // advancing tick — a manual speed change while planes sit grounded survives until the next landing.
-  if (landedThisTick > 0) {
-    const available = await inst.db.select().from(schema.planes).where(eq(schema.planes.status, 'available'));
-    if (available.length >= 1) sets.timeScale = MIN_TIME_SCALE;
-  }
-
   // Persist lastRealTickMs even when nothing advanced — it is the tick anchor.
-  await inst.db.update(schema.simState).set(sets);
+  await inst.db.update(schema.simState).set({ clockMs, lastRealTickMs: nowMs });
   await persist(inst);
   const updated = (await inst.db.select().from(schema.simState))[0];
   if (!updated) throw new Error('sim_state row missing after tick');
@@ -174,8 +165,7 @@ export async function finishRepairs(inst: GameDb, clockMs: number): Promise<numb
 // remaining fuel and the queue kept intact for a later dispatch.
 // Idempotent — a finalized plane either leaves the 'flying' state or starts a NEW
 // leg whose own arrival is in the future, so it can never be awarded twice.
-// Returns planes landed. NOTE: runs BEFORE tickOnce's slow-down check on purpose —
-// a chained plane is already 'flying' again here, so a pure-chain landing never slows the sim.
+// Returns planes landed.
 export async function deliverPackages(inst: GameDb, clockMs: number): Promise<number> {
   const [planeRows, packageRows] = await Promise.all([
     inst.db.select().from(schema.planes),
@@ -423,6 +413,17 @@ export function tickNow(): Promise<schema.SimStateRow> {
   return withLock(async () => tickOnce(await getGameDb()));
 }
 
+// ISS-117: the world clock runs even with nobody polling — a ~1 s interval drives the same locked
+// tick path as reads/actions. Started once at server boot from instrumentation.ts (Next ≥15); the
+// guard makes double-starts harmless (dev HMR reloads).
+let backgroundTimer: ReturnType<typeof setInterval> | null = null;
+export function startBackgroundTick(intervalMs = 1_000): void {
+  if (backgroundTimer !== null) return;
+  backgroundTimer = setInterval(() => {
+    tickNow().catch((err) => console.error('flight: background tick failed', err));
+  }, intervalMs);
+}
+
 // Run a game action atomically with respect to ticks (v0.8.0): the clock is
 // advanced FIRST so validation and mutation see current game time, then fn runs —
 // all under the same promise lock as tickNow(), so no concurrent request can
@@ -436,31 +437,17 @@ export function runAction<T>(fn: (inst: GameDb) => Promise<T>): Promise<T> {
   });
 }
 
-// Tick first so the returned state reflects current time, then apply the new
-// controls. timeScale is clamped to [1, 1000]; validation of raw input happens in
-// the route handler (400 on non-number / non-boolean). ISS-057: posting a timeScale
-// ALSO records it as lastSelectedTimeScale — the resume target flyPlane restores when
-// the last grounded plane takes off. A {paused}-only post never touches it, so the
-// last manual intent wins without an extra flag.
-export function applyTimeControls(input: SimControlsInput): Promise<schema.SimStateRow> {
+// Test-hook backing (FLIGHT_TEST_HOOKS=1 only — see app/api/test/set-timescale/route.ts): set the
+// effective time scale under the same lock as ticks so a background tick can never interleave
+// between read and write. Input validation happens in the route; this trusts its number.
+export function setTestTimeScale(scale: number): Promise<schema.SimStateRow> {
   return withLock(async () => {
     const inst = await getGameDb();
     await tickOnce(inst);
-    const sets: Partial<Pick<schema.SimStateRow, 'timeScale' | 'lastSelectedTimeScale' | 'paused'>> = {};
-    if (input.timeScale !== undefined) {
-      const scale = clampTimeScale(input.timeScale);
-      sets.timeScale = scale;
-      sets.lastSelectedTimeScale = scale;
-    }
-    if (input.paused !== undefined) sets.paused = input.paused;
-    if (Object.keys(sets).length > 0) await inst.db.update(schema.simState).set(sets);
+    await inst.db.update(schema.simState).set({ timeScale: scale });
     await persist(inst);
     const updated = (await inst.db.select().from(schema.simState))[0];
     if (!updated) throw new Error('sim_state row missing');
     return updated;
   });
 }
-
-export function clampTimeScale(v: number): number {
-  return Math.min(MAX_TIME_SCALE, Math.max(MIN_TIME_SCALE, v));
-}