Flight-Ops/lib/sim/engine.ts

import { randomInt, randomUUID } from 'node:crypto';
import { eq, inArray } from 'drizzle-orm';
import { getGameDb, persist, type GameDb } from '@/lib/db/client';
import * as schema from '@/lib/db/schema';
import { loadAirportsGeoJson } from '@/lib/airports';
import { haversineKm, initialBearingDeg } from '@/lib/geo';
import { weatherFor } from '@/lib/weather';
import { FUEL_DISCOUNT_PER_REP, FUEL_PRICE_PER_L, MAX_FUEL_DISCOUNT, PLANE_TYPES, REPAIR_DURATION_MS, repRate, WEAR_PER_KM } from '@/lib/game/catalog';
import { SPECIALS } from '@/lib/game/specials';
import { getStateSnapshot, parseIcaoQueue, sseFrame } from '@/lib/game/state';
import { broadcast } from '@/lib/sse';

import {
  generatePackage,
  MARKET_TARGET_OPEN_PACKAGES,
  mulberry32,
  pickDestWithinCap,
  type Rng,
  type SeedAirport,
} from '@/lib/game/seed';
import { arrivalTimeFor, fuelAtWeighted, requiredFuelFor, windBurnFactor } from './movement';

// 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
// world clock stays FROZEN (#135 v0.62.0 — final ISS-117 semantics), and lastRealTickMs always
// keeps tracking real time, so resuming activity never fast-forwards the frozen span.

// 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;

// 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
// cross-Europe leg (~3000 km) ~2.5 — slow growth from the starting 10.
export const REP_BASE = 1;
export const REP_PER_KM = 0.0005;

export function reputationGainFor(km: number): number {
  return Math.round((REP_BASE + REP_PER_KM * km) * 100) / 100;
}

// 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.
// ISS-129 (v0.57.0): the chain lives on globalThis — instrumentation.ts and route handlers get
// separate module instances from Next.js, so a plain `let` would give each layer its own lock and let
// their ticks interleave against the shared DB below.
const g = globalThis as unknown as { __flightTickChain?: Promise<unknown> };
function withLock<T>(fn: () => Promise<T>): Promise<T> {
  const run = (g.__flightTickChain ??= Promise.resolve()).then(fn);
  g.__flightTickChain = run.then(
    () => undefined,
    () => undefined,
  );
  return run;
}

// --- Tick core (takes a GameDb so unit tests can inject their own instance) ---

// #135: advance decision — pure, so unit tests feed it synthetic fleets. The world clock runs at
// full scale only while something is happening (at least one plane flying OR in repair); a fully
// grounded fleet freezes it entirely — no expiry/spawn/repair progress until a dispatch or repair
// starts again.
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();
  // #135: a fully grounded fleet freezes the world — no advance, no expiry/spawn/repair progress.
  // An active fleet keeps its full scale, including any FLIGHT_TEST_HOOKS override in sim.timeScale.
  // lastRealTickMs always tracks real time, so resuming activity never fast-forwards the frozen span.
  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);
  const advanceMs = advance ? Math.min(elapsed, MAX_TICK_ELAPSED_MS) * sim.timeScale : 0;
  const clockMs = Math.round(sim.clockMs + advanceMs);

  if (advanceMs > 0) {
    await expirePackages(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);
    await spawnOpenPackages(inst, clockMs);
    // AFTER delivery on purpose: a plane that just landed gets work spawned
    // at its new location within the same tick.
    await spawnCoveragePackages(inst, clockMs);
  }

  // Persist lastRealTickMs even when nothing advanced — it is the tick anchor.
  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');
  return updated;
}

// Packages whose deadline has passed become 'expired' — both OPEN ones (they leave
// the market so spawn can top it back up) and LOADED ones (v0.12.0: they keep
// occupying their slot, deliver no reward on arrival, and abandon for free).
// Delivered/abandoned packages are terminal and never flip. Returns the count.
export async function expirePackages(inst: GameDb, clockMs: number): Promise<number> {
  const rows = await inst.db.select().from(schema.packages).where(inArray(schema.packages.status, ['open', 'loaded']));
  let n = 0;
  for (const p of rows) {
    if (p.deadlineSimTime <= clockMs) {
      await inst.db.update(schema.packages).set({ status: 'expired' }).where(eq(schema.packages.id, p.id));
      n++;
    }
  }
  return n;
}

// Repairs heal gradually (v0.45.0, ISS-089): while a plane is 'repairing', its health climbs along
// round(f × 100), where f is the fraction of REPAIR_DURATION_MS elapsed since the repair started —
// derived from the stored gate alone (start = gate − duration), so no schema change. The plane flips
// back to 'available' exactly when it reaches full health, i.e. at the gate. Same shape as
// expirePackages: one guarded pass over the rows. Returns the count flipped.
export async function finishRepairs(inst: GameDb, clockMs: number): Promise<number> {
  const rows = await inst.db.select().from(schema.planes).where(eq(schema.planes.status, 'repairing'));
  let n = 0;
  for (const p of rows) {
    if (p.repairUntilSimTime === null) continue; // defensive — repairing always carries a gate
    // ponytail: constant duration regardless of starting health — the curve is absolute (f × 100), so a
    // plane at 90 heals in the same sim time as one at 5. Proportional duration would need storing the
    // start health; add a column if balance wants it. The flip stays strictly at the gate (`<=` inclusive,
    // as before) — round(f × 100) can hit 100 a hair early (f ≥ 0.995), which is cosmetic only: the plane
    // is still 'repairing' and grounded until the gate passes.
    const f = Math.min(1, Math.max(0, (clockMs - (p.repairUntilSimTime - REPAIR_DURATION_MS)) / REPAIR_DURATION_MS));
    if (p.repairUntilSimTime <= clockMs) {
      await inst.db.update(schema.planes)
        .set({ status: 'available', health: 100, repairUntilSimTime: null })
        .where(eq(schema.planes.id, p.id));
      n++;
    } else {
      const newHealth = Math.min(100, Math.max(p.health, Math.round(f * 100)));
      if (newHealth !== p.health) {
        await inst.db.update(schema.planes).set({ health: newHealth }).where(eq(schema.planes.id, p.id));
      }
    }
  }
  return n;
}

// Finalize in-flight planes whose arrival time has passed (v0.12.0 delivery):
// for every package bound to the plane and destined for its dest_icao — 'loaded'
// ones still inside their deadline are delivered (cash += reward + reputation
// gain per package), 'expired' ones just unbind (no reward). Packages destined
// elsewhere stay loaded on the plane for a later leg. Then (v0.25.0, ISS-043)
// auto-chain: if the queue holds legs, fuel covers the first one and the plane is not
// broken by this landing's wear (v0.45.0, ISS-089), start it immediately from the arrival
// airport; with a short tank, ISS-082 (v0.42.0) tops
// up to 150% of the requirement (capped at tank capacity) when cash allows and
// chains anyway — only an unaffordable top-up grounds the plane there with its
// 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.
export async function deliverPackages(inst: GameDb, clockMs: number): Promise<number> {
  const [planeRows, packageRows] = await Promise.all([
    inst.db.select().from(schema.planes),
    inst.db.select().from(schema.packages),
  ]);

  const fc = await loadAirportsGeoJson();
  const byIcao = new Map(fc.features.map((f) => [f.properties.icao, f.properties]));

  let n = 0;
  for (const p of planeRows) {
    if (p.status !== 'flying' || p.departureSimTime == null || !p.destIcao) continue;
    const type = PLANE_TYPES[p.model];
    const from = byIcao.get(p.locationIcao);
    const to = byIcao.get(p.destIcao);
    if (!type || !from || !to) continue; // no route info — leave alone

    const distanceKm = haversineKm(from.lat, from.lon, to.lat, to.lon);
    if (clockMs < arrivalTimeFor(p.departureSimTime, distanceKm, type.speedKmh)) continue;

    // Arrived: progress is exactly 1 here, so remaining fuel is the full-leg weighted burn —
    // wind-adjusted (v0.36.0) by departure weather vs route heading, same factor flyPlane used.
    const w = weatherFor(p.locationIcao);
    const landedFuel = fuelAtWeighted(
      p.fuel,
      type.burnPerKm * windBurnFactor(w.windKt, w.windDirDeg, initialBearingDeg(from.lat, from.lon, to.lat, to.lon)),
      type.emptyWeightKg,
      type.maxFuel,
      distanceKm,
      1,
    );

    // Wear (v0.39.0, ISS-069): health drops by WEAR_PER_KM per km of this landed leg, clamped at 0.
    const newHealth = Math.max(0, p.health - WEAR_PER_KM * distanceKm);

    // Deliver every bound package whose destination is the airport just reached —
    // runs whether or not a queued leg chains next (ISS-043).
    const onBoard = packageRows.filter((pk) => pk.planeId === p.id && pk.destIcao === to.icao);
    for (const pk of onBoard) {
      if (pk.status === 'loaded' && clockMs <= pk.deadlineSimTime) {
        await inst.db.update(schema.packages).set({ status: 'delivered' }).where(eq(schema.packages.id, pk.id));
        // Fresh account read per award so multiple deliveries in one tick all count.
        const fresh = (await inst.db.select().from(schema.account))[0];
        if (!fresh) throw new Error('account row missing');
        // v0.37.0 (ISS-073): special packages add the registry's flat rep bonus on top of the
        // distance-based gain — same double-rounding convention as before (gain rounded to cents, total re-rounded).
        const repBonus = pk.special ? SPECIALS[pk.special]?.repBonus ?? 0 : 0;
        await inst.db.update(schema.account).set({
          cash: fresh.cash + pk.reward,
          reputation: Math.round((fresh.reputation + reputationGainFor(distanceKm) + repBonus) * 100) / 100,
        });
      } else if (pk.status === 'expired') {
        // Expired cargo keeps no value — just free the slot.
        await inst.db.update(schema.packages).set({ planeId: null }).where(eq(schema.packages.id, pk.id));
      }
    }

    // Auto-chain (ISS-043): with a non-empty queue and enough fuel for the first
    // queued leg, start it immediately from `to` — same feasibility rule as flyPlane
    // (requiredFuelFor is independent of current load). ISS-082 (v0.42.0): manual refuel is gone,
    // so a short tank no longer strands the chain — when cash allows, top up to 150% of the
    // requirement (capped at tank capacity) and chain anyway; unaffordable → ground here with the
    // queue kept intact. An unknown ICAO in the queue simply cannot chain either way. v0.45.0
    // (ISS-089): a plane that lands BROKEN (newHealth ≤ 0) never chains — it stays grounded with
    // the queue intact until repaired, exactly like flyPlane's broken guard.
    const queue = parseIcaoQueue(p.queue);
    let chainedTo: string | null = null;
    let topUpFuel: number | null = null; // post-top-up fuel for the chained departure, when a top-up happened
    if (queue.length > 0 && newHealth > 0) {
      const nextDest = queue[0];
      // ponytail: defensive guard for legacy rows — a queued leg to the airport we just landed at is a
      // zero-distance no-op hop; drop it and ground instead of flying. Normal play can't produce this
      // since v0.46.0 (flyPlane consumes queue[0] on dispatch, every chain shifts its own leg).
      if (nextDest === to.icao) {
        queue.shift();
      } else {
        const next = byIcao.get(nextDest); // unknown ICAO in the queue → cannot chain
        if (next) {
          // Wind-adjusted requirement for the NEXT leg — it departs from `to` (v0.36.0).
          const wNext = weatherFor(to.icao);
          const nextRequiredL = requiredFuelFor(
            type.burnPerKm * windBurnFactor(wNext.windKt, wNext.windDirDeg, initialBearingDeg(to.lat, to.lon, next.lat, next.lon)),
            type.emptyWeightKg,
            type.maxFuel,
            haversineKm(to.lat, to.lon, next.lat, next.lon),
          );
          // v0.46.0 backstop: a leg that doesn't fit even a full tank is unflyable — ground with the queue
          // intact, mirroring flyPlane's 409 without throwing in the engine.
          if (nextRequiredL > type.maxFuel) {
            // no chain — the grounded update below keeps the queue for a later dispatch
          } else if (nextRequiredL <= landedFuel) {
            queue.shift();
            chainedTo = nextDest;
          } else {
            // ISS-082: auto top-up — same target/price terms as flyPlane's dispatch refuel.
            const target = Math.min(type.maxFuel, Math.max(landedFuel, nextRequiredL * 1.5));
            const liters = Math.max(0, target - landedFuel);
            // Fresh account read (same pattern as the delivery awards above) so a top-up in this tick sees current cash.
            const fresh = (await inst.db.select().from(schema.account))[0];
            if (!fresh) throw new Error('account row missing');
            const cost = Math.round(liters * FUEL_PRICE_PER_L * (1 - repRate(fresh.reputation, FUEL_DISCOUNT_PER_REP, MAX_FUEL_DISCOUNT)) * 100) / 100;
            if (cost === 0 || fresh.cash >= cost) {
              queue.shift();
              chainedTo = nextDest;
              topUpFuel = target;
              if (cost > 0) await inst.db.update(schema.account).set({ cash: Math.round((fresh.cash - cost) * 100) / 100 });
            }
          }
        }
      }
    }
    await inst.db.update(schema.planes)
      .set(
        chainedTo
          ? {
              status: 'flying',
              locationIcao: to.icao,
              lat: to.lat,
              lon: to.lon,
              fuel: topUpFuel ?? landedFuel, // ISS-082: the post-top-up level when a top-up funded the chain
              health: newHealth, // v0.39.0 (ISS-069) — this leg's wear persists into the chained flight
              destIcao: chainedTo,
              departureSimTime: clockMs, // the arrival instant — position is exactly `to`
              queue: JSON.stringify(queue),
            }
          : {
              status: 'available',
              locationIcao: to.icao,
              lat: to.lat,
              lon: to.lon,
              fuel: landedFuel,
              health: newHealth, // v0.39.0 (ISS-069) — this leg's wear persists on the grounded plane
              departureSimTime: null,
              destIcao: null,
              queue: JSON.stringify(queue),
            },
      )
      .where(eq(schema.planes.id, p.id));
    n++;
  }
  return n;
}

// Top the market back up to MARKET_TARGET_OPEN_PACKAGES open packages using the
// SAME builder as the first-run seed (generatePackage), so spawned packages are
// indistinguishable from seeded ones. RNG is injectable for deterministic tests.
export async function spawnOpenPackages(
  inst: GameDb,
  clockMs: number,
  rng?: Rng,
): Promise<number> {
  const openCount = (
    await inst.db.select().from(schema.packages).where(eq(schema.packages.status, 'open'))
  ).length;
  const needed = MARKET_TARGET_OPEN_PACKAGES - openCount;
  if (needed <= 0) return 0;

  const fc = await loadAirportsGeoJson();
  const airports: SeedAirport[] = fc.features.map((f) => ({
    icao: f.properties.icao,
    name: f.properties.name,
    lat: f.properties.lat,
    lon: f.properties.lon,
  }));
  const rand = rng ?? mulberry32(randomInt(0, 2 ** 31));
  // v0.38.0 (ISS-072): spawned jobs carry the account's CURRENT reputation quality — read once per spawn batch.
  const account = (await inst.db.select().from(schema.account))[0];
  if (!account) throw new Error('account row missing');

  for (let i = 0; i < needed; i++) {
    await inst.db.insert(schema.packages).values(
      generatePackage({ id: randomUUID(), airports, rng: rand, nowMs: clockMs, reputation: account.reputation }),
    );
  }
  return needed;
}

// Spawn coverage rule (v0.8.0): in addition to topping the market up, every
// airport that currently has a grounded 'available' plane must have ≥1 OPEN
// package originating there — so work is always available where the fleet sits
// (including onboarding at EDDF). One package per uncovered airport, generated
// with generatePackage and origin forced to that airport. Runs after
// spawnOpenPackages in tickOnce, so randomly spawned packages count as coverage
// too; and after deliverPackages, so a plane that just landed gets work spawned
// at its new location within the same tick. Returns the number created.
export async function spawnCoveragePackages(
  inst: GameDb,
  clockMs: number,
  rng?: Rng,
): Promise<number> {
  const [planeRows, openRows] = await Promise.all([
    inst.db.select().from(schema.planes),
    inst.db.select().from(schema.packages).where(eq(schema.packages.status, 'open')),
  ]);

  // Distinct airports with at least one grounded plane (flying planes don't count —
  // they can't take new work until they land).
  const groundedIcas = [
    ...new Set(planeRows.filter((p) => p.status === 'available').map((p) => p.locationIcao)),
  ];
  if (groundedIcas.length === 0) return 0;

  const covered = new Set(openRows.map((c) => c.originIcao));
  const missing = groundedIcas.filter((icao) => !covered.has(icao));
  if (missing.length === 0) return 0;

  const fc = await loadAirportsGeoJson();
  const airports: SeedAirport[] = fc.features.map((f) => ({
    icao: f.properties.icao,
    name: f.properties.name,
    lat: f.properties.lat,
    lon: f.properties.lon,
  }));
  const rand = rng ?? mulberry32(randomInt(0, 2 ** 31));
  // v0.38.0 (ISS-072): same reputation quality as spawnOpenPackages — read once per batch.
  const account = (await inst.db.select().from(schema.account))[0];
  if (!account) throw new Error('account row missing');

  let n = 0;
  for (const icao of missing) {
    const oi = airports.findIndex((a) => a.icao === icao);
    if (oi < 0) continue; // defensive — the dataset is the source of all ICACs
    // v0.44.0 (ISS-079): cap the random dest at MAX_JOB_LEG_KM like generatePackage's unforced pairs —
    // one draw in the same stream position as the old uncapped pick, so downstream draws are unchanged.
    const di = pickDestWithinCap(airports, oi, rand);
    await inst.db.insert(schema.packages).values(
      generatePackage({
        id: randomUUID(),
        airports,
        rng: rand,
        nowMs: clockMs,
        originIcao: icao,
        ...(di >= 0 ? { destIcao: airports[di].icao } : {}), // di < 0 (no within-cap neighbour) → old uncapped behavior
        reputation: account.reputation,
      }),
    );
    n++;
  }
  return n;
}

// --- Public API (singleton DB + lock) — call from every read/action endpoint ---

// ISS-129 (v0.57.0): after each tick on the singleton path, push a fresh snapshot to all SSE
// subscribers (/api/events). ISS-133 (v0.59.0): frames carry the sseFrame projection — terminal
// package history is dropped, everything else matches GET /api/state exactly. Failures are logged,
// not fatal: polling still works either way. Background ticks (~1 s) cover action mutations for
// other clients too.
async function broadcastState(): Promise<void> {
  try {
    broadcast(JSON.stringify(sseFrame(await getStateSnapshot())));
  } catch (err) {
    console.error('flight: state broadcast failed', err);
  }
}

export function tickNow(): Promise<schema.SimStateRow> {
  return withLock(async () => {
    const row = await tickOnce(await getGameDb());
    await broadcastState();
    return row;
  });
}

// 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
// interleave between the tick and the mutation. Action functions in
// lib/game/actions.ts take an explicit GameDb so unit tests can inject their own.
export function runAction<T>(fn: (inst: GameDb) => Promise<T>): Promise<T> {
  return withLock(async () => {
    const inst = await getGameDb();
    await tickOnce(inst);
    return fn(inst);
  });
}

// 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);
    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;
  });
}