// PROCITY Lane D — the citizen simulation (Vuntra's layered LOD idea, at hamlet scale).
//
// Deterministic per-citizen identity (same seed → same person walks the same beat), walkers pathing
// along footpath lanes offset from the street graph, three distance tiers:
//   • NEAR (<25m): full rig + AnimationMixer (or a placeholder before the fleet loads), walking the
//     footpath, turning at nodes on a seeded choice, loitering at points of interest.
//   • MID (25–70m): no mixers ticking — an instanced billboard impostor (impostor.js).
//   • FAR (>70m): culled entirely.
// Promotion/demotion has hysteresis + a hard near-cap so nobody pops and the frame budget holds.
//
// Built on the house fleet rule: shared base meshes (a small rig pool, reused across citizens of the
// same ped type) + one canonical clip bank. Never a per-character rig.

import * as THREE from 'three';
import { rng, seedFor } from '../core/prng.js';
import { pickRig, makeActor } from './rigs.js';
import { makePlaceholder } from './placeholder.js';
import { bakeImpostorAtlas, ImpostorLayer } from './impostor.js';
import { snapDoorToFootpath } from './door_snap.js';
import { posturesFor, postureSig, GROUP_OF } from './postures.js';

// ---- tuning (CITY_SPEC budgets) ----
const NEAR_ENTER = 24, NEAR_EXIT = 27;       // m, hysteresis band for rig↔impostor
const MID_ENTER = 68, MID_EXIT = 72;         // m, hysteresis band for impostor↔culled
const NEAR_MAX = 24;                         // ≤24 rigged actives (CITY_SPEC)
const RIG_CAP = 30;                          // pooled rig instances (headroom above NEAR_MAX)
const NEW_RIG_PER_FRAME = 3;                 // cap actor creation to avoid clone hitches
const MIXER_ALWAYS = 8;                      // nearest 8 mixers update every frame
const MIXER_EXTRA = 4;                       // ≤4 more mixers per frame (staggered), CITY_SPEC
const NEAR_BIAS = 2.0;                       // currently-near citizens keep priority for a rig slot
const PLACEHOLDER_VARIANTS = 8;              // impostor atlas subjects in asset-free mode
const FOOTPATH_MARGIN = 0.9;                 // m outside the carriageway edge
const IMPOSTOR_MAX = 220;                    // instanced billboards ceiling
const NIGHT_LIVELY_FLOOR = 0.5;              // stream: "lively" chunks (open-late block) keep ≥this density at night
const PATRON_RANGE = 18;                     // m — a ped ducks into a shop it's passing within this
const PATRON_STRIDE = 10;                    // m walked between patronage checks (framerate-independent)
const GIG_RANGE = 34;                        // m — a gig pulls peds from further than a normal shopfront
const GIG_SURGE = 0.55;                      // patron chance at the venue while the gig is on (vs ~0.16 day)
const BENCH_SIT_FRAC = 0.35;                 // R17: fraction of window-shop loiters that become a bench-sit (seeded)
const GLANCE_FRAC = 0.40;                    // R29: fraction of the REMAINING (standing) loiters that glance around

// ---- R41 §41.3: the street furniture the clips actually sit and lean on ----
// A REAL bench sit. R17's bench-sit sits a ped down at whatever node it stopped at — upright, on air,
// "no bench-position binding" (its own comment). R41 binds it: benches exist, at deterministic
// stations, and a ped that walks past one on its own footpath side can stop AT IT.
//
// The station rule below MIRRORS Lane B's `buildChunkFurniture` (web/js/world/furniture.js:203-209)
// exactly — s = 14, 40, 66, …, step 26; side alternating on floor(s/26)%2; offset
// (width/2 + FOOT − 0.8) on the furniture perpendicular (−uz, ux); yaw = atan2(ux,uz) + (side>0 ? π : 0).
// It is a MIRROR because furniture.js is Lane B's file and exports no bench enumerator (only
// `busShelterStops`, its shelter twin). A mirror that drifts is a ped sitting on air again, so it is
// GATED, not trusted: `tools/qa/r41_benches.mjs` builds real chunks through Lane B's own
// buildChunkFurniture, reads the bench InstancedMesh matrices out of the scene, and requires an exact
// 1:1 position/yaw match against this table on four towns. If B ever moves a bench, that gate goes red.
// → Filed for Lane B/F in LANE_D_NOTES §41: `export function benchStops(plan)` next to busShelterStops
//   retires the mirror entirely. One line in B's file; D switches to the import and deletes this.
const FURN_FOOT = 3.5;                       // furniture.js FOOT (verge width used for its offsets)
const BENCH_S0 = 14, BENCH_STEP = 26;        // furniture.js bench cadence
const BENCH_STOP_FRAC = 0.40;                // seeded chance a ped passing its own-side bench sits down
const BENCH_DWELL = [9, 20];                 // s — a sit is a proper stop, not a window-shop pause
const BENCH_SEAT_FWD = 0.06;                 // m toward the bench front, so the seat takes the weight
const BENCH_SEAT_SIDE = 0.38;                // m along the 1.6 m plank — the bench seats two, side by side
const LEAN_RANGE = 5.0;                      // m — a loiter this close to a shop door can become a lean
const LEAN_FRAC = 0.12;                      // seeded chance a stride check beside a shopfront becomes a lean
const LEAN_DWELL = [6, 14];                  // s — a lean is a longer stop than a window-shop glance
const PAUSE_FRAC = 0.17;                     // …else a seeded chance they just stop and look in the window
const PAUSE_DWELL = [4, 9];                  // s — long enough to read the idle, short enough to keep moving
const LEAN_WALL_BACK = 0.30;                 // m further from the road than the raw door point (≈ the facade)
const LEAN_SIDE = 1.05;                      // m along the frontage, so the leaner isn't in the doorway

// time-of-day density curve: t01 in [0,1) over a day → crowd multiplier (CITY_SPEC: lunch rush,
// near-empty at night). Sampled at 8 control points, linearly interpolated.
const DAY_CURVE = [0.06, 0.10, 0.35, 0.85, 1.0, 0.75, 0.45, 0.18]; // 00,03,06,09,12,15,18,21h
function densityAt(t01) {
  const x = ((t01 % 1) + 1) % 1 * DAY_CURVE.length;
  const i = Math.floor(x), f = x - i;
  return DAY_CURVE[i % DAY_CURVE.length] * (1 - f) + DAY_CURVE[(i + 1) % DAY_CURVE.length] * f;
}

const tierColor = { near: 0x66dd88, mid: 0xffcc44, far: 0x884466 };

// ---- chunk math (v2 chunk-streamed roster). CHUNK=64m is CITY_SPEC law and matches Lane B's
// planutil.js exactly, so B's onChunkBuilt/onChunkDisposed keys line up with ours. Kept local so the
// sim stays dependency-free (the standalone test page has no Lane B modules). ----
const CHUNK = 64;
const chunkCoord = (v) => Math.floor(v / CHUNK);
const chunkKey = (cx, cz) => `${cx},${cz}`;

// ---- pure deterministic identity (no THREE, no GPU) — same (seed, id) → same person, forever ----
// Kept free-standing so the determinism check can recompute it independently of the live sim.
export function identityOf(citySeed, edgeCount, id) {
  const r = rng(citySeed, 'citizen', id);
  const pedRoll = r();
  const height = 1.55 + r() * 0.40;         // 1.55–1.95 m (CITY_SPEC height range)
  const speed = 1.05 + r() * 0.75;          // m/s
  const edge = (r() * edgeCount) | 0;
  const forward = r() < 0.5 ? 1 : -1;
  const sFrac = r();                         // 0..1 along the edge
  const loiterTend = r();
  const phase = r();
  const pvar = (pedRoll * PLACEHOLDER_VARIANTS) | 0;
  return { pedRoll, height, speed, edge, forward, sFrac, loiterTend, phase, pvar };
}
// [R41 §41.3] Lane B's benches on one prepared sim edge ({A,B,ux,uz,len,width}), as a pure function —
// exported so `tools/qa/r41_citizens.py` can check the SAME code the sim uses against the bench
// geometry actually standing in the built world, rather than a second copy of the rule. See the
// FURN_*/BENCH_* block above for the mirror's provenance and the seam filed to Lane B.
export function benchStationsFor(e) {
  const out = [];
  const halfRoad = (e.width || 4) / 2;
  const px = -e.uz, pz = e.ux;                       // furniture.js perpendicular
  const yaw = Math.atan2(e.ux, e.uz);
  for (let s = BENCH_S0; s < e.len - 6; s += BENCH_STEP) {
    const side = (Math.floor(s / BENCH_STEP) % 2) ? 1 : -1;
    const off = (halfRoad + FURN_FOOT - 0.8) * side;
    out.push({ s, side,
      x: e.A.x + e.ux * s + px * off, z: e.A.z + e.uz * s + pz * off,
      yaw: yaw + (side > 0 ? Math.PI : 0) });
  }
  return out;
}

// stable signature string for one citizen (pedIndex assigned later, once the fleet is known)
export function signatureOf(id, idn, pedIndex) {
  return `${id}:${pedIndex}:${idn.pvar}:${idn.height.toFixed(3)}:${idn.speed.toFixed(3)}:${idn.edge}:${idn.forward}`;
}

// ---- a small pool of rig actors, reused across citizens of the same ped type ----
class RigPool {
  constructor(fleet, clips) { this.fleet = fleet; this.clips = clips; this.free = new Map(); this.total = 0; }
  acquire(pedIndex) {
    const list = this.free.get(pedIndex);
    if (list && list.length) return list.pop();
    if (this.total >= RIG_CAP) {                        // evict one free actor of another type
      for (const [k, arr] of this.free) { if (arr.length) { arr.pop().dispose(); this.total--; break; } }
      if (this.total >= RIG_CAP) return null;           // everything in use — caller falls back to impostor
    }
    const rig = this.fleet.all[pedIndex];
    if (!rig) return null;
    const actor = makeActor(rig, this.clips);
    if (actor) { actor.pedIndex = pedIndex; this.total++; }
    return actor;
  }
  release(actor) {
    if (!actor) return;
    if (actor.setSitting) actor.setSitting(false);   // R17: never pool a rig mid-sit — restore the standing plant
    if (actor.setLooking) actor.setLooking(false, 0);   // R29: nor mid-glance — snap back to idle before pooling
    let arr = this.free.get(actor.pedIndex);
    if (!arr) this.free.set(actor.pedIndex, arr = []);
    arr.push(actor);
  }
  dispose() { for (const arr of this.free.values()) arr.forEach(a => a.dispose()); this.free.clear(); this.total = 0; }
}

export class CitizenSim {
  constructor({ renderer, scene, camera, citySeed = 20261990, graph, fleet, group = null, chunkStream = null }) {
    this.renderer = renderer;
    this.scene = scene;
    this.camera = camera;
    this.citySeed = citySeed >>> 0;
    this.fleet = fleet;
    this.group = group || new THREE.Group();
    this.group.name = 'citizens';
    scene.add(this.group);

    this._setGraph(graph);

    this.roster = [];            // v1: all generated citizens (identity + live state), indexed by id
    this.target = 0;             // slider population
    // v2 chunk-streamed roster (behind ?roster=stream — see enableStream). Default OFF → v1 path.
    this.streamMode = false;
    this.chunkRosters = new Map();   // chunkKey → Citizen[] (owned by that chunk)
    this.chunkEdges = null;          // chunkKey → [edge index] (built lazily on enable)
    this._hookDriven = false;        // Lane B's onChunkBuilt/Disposed drive us → stop polling
    this._livelyChunks = new Set();  // chunkKeys that resist night thinning (e.g. the open-late block)
    this._encountered = new Set();   // cumulative identity signatures seen (determinism proof)
    // R8 shop patronage (default-on for the streamed roster; ?patronage=0 off). No-op until setShops.
    this.shopsByChunk = null;        // chunkKey → [{ x, z, hours:[open,close], shopId }] door points
    this.patronageOn = true;
    this._gigVenues = new Set();     // R13: venueShopIds with a gig on (F sets per-venue via setGig) → multi-venue surge
    this.weather = { state: 'clear', intensity: 0 };   // Lane B's PROCITY.weather contract (shell feeds it)
    this._occupancy = new Map();     // R9 shopId → [{ seed, enteredAt, pedIndex }] — the interior-presence truth
    this._venueRoster = new Map();   // R14 identity continuity: venueShopId → Map<key,{pedIndex,height}> — who
                                     // entered a gig venue TONIGHT (surge occupants + F-relayed queue admits).
                                     // GigCrew consumes it so the crowd IS the people who came in. Cleared when
                                     // the gig ends (setGig off). Pure bookkeeping — no rng, no GPU.
    this._dropKeys = [];             // scratch: chunks to drop this frame
    this._activeList = [];           // this frame's active citizens (both modes) — test page reads it
    this.timeOfDay = 0.5;        // noon
    this.debugTiers = false;
    this.mode = 'placeholder';   // 'placeholder' until the fleet is ready, then 'rig'
    this.rigPool = null;
    this.paused = false;         // app sets this on a visibilitychange → hidden (pauses mixers)
    this._exposure = null;       // shell's live renderer.toneMappingExposure (day/night) → impostor match
    this._mixerCursor = 0;       // round-robin cursor for the staggered mixer budget
    this._nearList = [];         // reused scratch
    this._midList = [];
    this._frustum = new THREE.Frustum();
    this._pv = new THREE.Matrix4();
    this.stats = { active: 0, rigged: 0, mid: 0, far: 0, mixerMs: 0, poolTotal: 0, mode: this.mode };

    // bake the placeholder impostor atlas up front so the mid tier works from frame one
    this._buildPlaceholderImpostors();

    // when the fleet lands, upgrade: bake rig atlas, swap actors, assign real ped types
    if (fleet && fleet.whenReady) fleet.whenReady.then(() => { if (fleet.ready) this._upgradeToRigs(); });

    if (chunkStream) this.enableStream(chunkStream === true ? {} : chunkStream);
  }

  // ================= v2: chunk-streamed roster (behind ?roster=stream) =================
  // Constant per-unit-street density that follows the camera, so streets stay lively arbitrarily far
  // from spawn (v1's fixed roster smears N over the whole town and thins out). Identity is keyed per
  // chunk (same seed + chunk → same residents, independent of town size / visit order). Everything
  // downstream — LOD tiers, the 24 near-cap, mixer stagger, rig pool, impostor layer — is already
  // per-citizen and chunk-agnostic and runs GLOBAL across live chunks, unchanged.

  // perChunk default 16 = full density. Affordable since Lane E's R7 merge made each ped ONE draw
  // (was 8 sub-meshes / ~7 draws): the worst continuous-walk street view now sits well under the 300
  // budget even with a dense street of near-rigs. This is the shipping default for the R7 roster flip.
  enableStream({ radius = 2, perChunk = 16 } = {}) {
    if (this.streamMode) return;
    this.roster.forEach(c => this._releaseActor(c)); this.roster.length = 0;  // tear down the v1 roster
    if (!this.chunkEdges) this._buildChunkIndex();
    this.chunkRosters.clear(); this._dropKeys.length = 0; this._encountered.clear(); this._occupancy.clear(); this._venueRoster.clear();
    this.streamRadius = radius; this.streamPerChunk = perChunk;
    this.streamMode = true; this._hookDriven = false;
  }
  disableStream() {
    if (!this.streamMode) return;
    for (const arr of this.chunkRosters.values()) arr.forEach(c => this._releaseActor(c));
    this.chunkRosters.clear(); this._occupancy.clear(); this._venueRoster.clear(); this.streamMode = false;
  }

  // rasterise each edge's centreline to the 64m chunks it passes through → which edges seed each chunk
  _buildChunkIndex() {
    this.chunkEdges = new Map();
    this.edges.forEach((e, ei) => {
      const steps = Math.max(1, Math.ceil(e.len / (CHUNK / 2)));
      const seen = new Set();
      for (let i = 0; i <= steps; i++) {
        const t = i / steps, x = e.A.x + (e.B.x - e.A.x) * t, z = e.A.z + (e.B.z - e.A.z) * t;
        const k = chunkKey(chunkCoord(x), chunkCoord(z));
        if (!seen.has(k)) {
          seen.add(k);
          let arr = this.chunkEdges.get(k); if (!arr) this.chunkEdges.set(k, arr = []);
          arr.push(ei);
        }
      }
    });
  }

  // Lane B seam (F wires these onto ctx.onChunkBuilt/onChunkDisposed). First call flips us hook-driven.
  onChunkBuilt(key) { if (this.streamMode) { this._hookDriven = true; this.feedChunk(key); } }
  onChunkDisposed(key) { if (this.streamMode) { this._hookDriven = true; this.dropChunk(key); } }

  // poll-driven window (works with zero Lane B changes — test page + shell-until-F-wires-hooks):
  // the camera chunk + neighbours within radius R (R≥1 so a walker never enters an unloaded chunk).
  _pollChunks() {
    const cx = chunkCoord(this.camera.position.x), cz = chunkCoord(this.camera.position.z);
    const R = this.streamRadius;
    const want = new Set();
    for (let dx = -R; dx <= R; dx++) for (let dz = -R; dz <= R; dz++) {
      const k = chunkKey(cx + dx, cz + dz);
      if (this.chunkEdges.has(k)) want.add(k);
    }
    for (const k of want) if (!this.chunkRosters.has(k)) this.feedChunk(k);
    this._dropKeys.length = 0;
    for (const k of this.chunkRosters.keys()) if (!want.has(k)) this._dropKeys.push(k);
    for (const k of this._dropKeys) this.dropChunk(k);
  }

  feedChunk(key) {
    if (this.chunkRosters.has(key)) return;
    const edgeList = this.chunkEdges.get(key);
    if (!edgeList || !edgeList.length) { this.chunkRosters.set(key, []); return; }
    const n = this._perChunkMax(key);
    const arr = new Array(n);
    for (let i = 0; i < n; i++) { const c = this._makeChunkCitizen(key, i, edgeList); arr[i] = c; this._encountered.add(this._sig(c)); }
    this.chunkRosters.set(key, arr);
  }
  dropChunk(key) {
    const arr = this.chunkRosters.get(key);
    if (!arr) return;
    for (const c of arr) { if (c._occShop != null) { this._removeOccupant(c._occShop, c.id); c._occShop = null; } this._releaseActor(c); }
    this.chunkRosters.delete(key);
  }

  // per-chunk population: base × district weight (more edges = busier junction) × seeded jitter.
  _perChunkMax(key) {
    const edges = this.chunkEdges.get(key) || [];
    const r = rng(this.citySeed, 'chunkpop', key);
    const busy = 0.7 + Math.min(1.3, edges.length * 0.12);
    return Math.max(4, Math.round(this.streamPerChunk * busy * (0.75 + r() * 0.5)));
  }

  // chunk-local identity: home edge is picked from THIS chunk's edges, so town size / visit order
  // never perturb who lives here. id is the string `${chunkKey}#${i}` (prng streams accept strings).
  _makeChunkCitizen(key, i, edgeList) {
    const id = `${key}#${i}`;
    const idn = identityOf(this.citySeed, edgeList.length, id);
    const edge = edgeList[idn.edge] ?? edgeList[0];
    const c = {
      id, pedRoll: idn.pedRoll, height: idn.height, speed: idn.speed,
      loiterTend: idn.loiterTend, phase: idn.phase, pvar: idn.pvar,
      pedIndex: -1, subject: idn.pvar,
      edge0: edge, forward0: idn.forward, localEdge0: idn.edge, ownerChunk: key,
      edge, forward: idn.forward, s: idn.sFrac * this.edges[edge].len, loiter: 0,
      x: 0, z: 0, facing: 0, tier: 'far', actor: null, actorKind: null, _acc: 0,
      turn: rng(this.citySeed, 'turn', id), loit: rng(this.citySeed, 'loiter', id),
      patron: null, patronTarget: null, patronTimer: 0, patronRng: rng(this.citySeed, 'patron', id),
      sit: false, sitRng: rng(this.citySeed, 'benchsit', id),   // R17: dedicated stream — no shift to turn/loit/patron
      glance: false, glanceRng: rng(this.citySeed, 'glance', id),   // R29: ditto — independently keyed, signature untouched
      // [R41 §41.3] this citizen's four standing postures — a PURE function of (citySeed, id), decided
      // here once and never re-rolled, so lazy clip loading can change when a posture shows but never
      // which one it is. Two more freshly-keyed streams for the new street stops; like R17/R29 they
      // are drawn independently and cannot shift turn/loiter/patron/benchsit/glance.
      posture: posturesFor(this.citySeed, id),
      bench: null, benchRng: rng(this.citySeed, 'benchstop', id),
      lean: null, leanRng: rng(this.citySeed, 'leanstop', id),
    };
    if (this.mode === 'rig' && this.fleet.ready) { const pk = pickRig(this.fleet, c.pedRoll); if (pk) { c.pedIndex = pk.index; c.subject = pk.index; } }
    this._placeOnLane(c);
    return c;
  }

  _sig(c) {
    return signatureOf(c.id, { pvar: c.pvar, height: c.height, speed: c.speed, edge: c.localEdge0 ?? c.edge0, forward: c.forward0 }, c.pedIndex);
  }

  // ================= R41 §41.3: the motion library =================
  get bank() { return (this.fleet && this.fleet.bank) || null; }
  // The GATE question — "is the motion library on for this boot" — answered synchronously from frame
  // zero (rigs.js sets it before the dynamic import starts). Every roll that can change a citizen's
  // POSITION is gated on this, never on `bank`, so the number of randoms drawn per boot cannot depend
  // on when a fetch landed. `bank` answers the different question of what is resident right now, and
  // is only ever used to pick WHICH clip plays — with the R2/R16/R29 base clip as the fallback.
  get clipsOn() { return !!(this.fleet && this.fleet.clipsRequested); }
  // ask for a group; harmless (and free) when there is no bank. Called at the moment of INTENT, so a
  // group is fetched the first time the town actually wants it, never at boot "just in case".
  _wantGroup(file) { const b = this.bank; if (b && file) b.ensureGroup(file); }
  _wantClip(id) { const b = this.bank; if (b && id && GROUP_OF[id]) b.ensureGroup(GROUP_OF[id]); }
  // the assigned clip if it is resident, else null ⇒ the caller's pre-R41 base clip
  _clip(id) { const b = this.bank; return b ? b.get(id) : null; }

  // The determinism artefact for postures: one line per ACTIVE citizen, sorted, pure identity —
  // never live state, so it holds while the crowd walks. Two runs must produce byte-equal output
  // (tools/qa/r41_postures.mjs asserts it, and re-derives the same lines from postures.js alone).
  postureSignature() {
    return this._activeList.map((c) => postureSig(c.id, c.posture || posturesFor(this.citySeed, c.id))).sort();
  }
  // what is actually resident right now (the memory ledger the round asks to be stated)
  clipStats() { const b = this.bank; return b ? b.stats() : { groups: 0, clips: 0, bytes: 0, manifest: false, catalogue: 0 }; }

  // Lane B's benches, enumerated from B's own placement rule — see the FURN_* block above for why
  // this is a mirror and what gates it. Cached per edge (pure function of the edge, no rng).
  _benchStations(ei) {
    const e = this.edges[ei];
    return e._benches || (e._benches = benchStationsFor(e));
  }
  // The bench's local +Z is its FRONT (furniture.js's template puts the backrest at z=−0.2 and the
  // seat at y=0.45); rig fronts are local −Z after the R13 facing-normalise, so a sitter facing the
  // same way as the bench is `yaw + π`. Nudged BENCH_SEAT_FWD off the backrest onto the seat.
  // `seat` is ±1: the bench's seat plank is 1.6 m of local X, so it takes TWO. Measured need — with
  // benches 26 m apart per side, two peds picking the same station within one dwell is uncommon but
  // real (seen on the first soak: -1,-6#3 and -1,-6#5 co-located to the centimetre). A seeded ± puts
  // them side by side like people instead of inside each other. Residual: both can still draw the
  // same side; that reads as one ped, not a glitch, and it is bounded by the same 26 m cadence.
  _seatPose(st, seat) {
    const fx = Math.sin(st.yaw), fz = Math.cos(st.yaw);      // bench local +Z (its front)
    const rx = Math.cos(st.yaw), rz = -Math.sin(st.yaw);     // bench local +X (along the plank)
    return { x: st.x + fx * BENCH_SEAT_FWD + rx * BENCH_SEAT_SIDE * seat,
             z: st.z + fz * BENCH_SEAT_FWD + rz * BENCH_SEAT_SIDE * seat,
             facing: st.yaw + Math.PI };
  }

  // A shopfront to put a back against. `shop._raw` is the door point BEFORE R40's footpath clamp,
  // i.e. the shell's `lot centre + front normal · (d/2 + 0.6)` — 0.6 m off the facade, which is the
  // wall we want. `n` is the unit outward normal of the nearest street (centreline → door), so the
  // building is at +n and the road at −n: stand LEAN_WALL_BACK further along +n, offset LEAN_SIDE
  // along the frontage so the leaner isn't blocking the doorway, and face −n (the road).
  // Pure geometry over the sim's own edges — no lots, no plan, no rng beyond the caller's roll.
  // O(1): the reference street is the one the LEANER IS WALKING ON, not a scan of every edge in
  // town. The ped is inside LEAN_RANGE (5 m) of that door, on that street's footpath, so the shop
  // fronts that street in every case but a corner — and a corner's residue is a facing, not a
  // position. The scan version cost 30 986 iterations per lean event on adelaide_real.
  _leanPose(shop, side, e) {
    const base = shop._raw || shop;
    if (!e) return null;
    const ax = e.A.x, az = e.A.z, dx = e.B.x - ax, dz = e.B.z - az;
    const L2 = dx * dx + dz * dz;
    let t = L2 < 1e-9 ? 0 : ((base.x - ax) * dx + (base.z - az) * dz) / L2;
    t = t < 0 ? 0 : t > 1 ? 1 : t;
    const qx = ax + t * dx, qz = az + t * dz;
    const bd = Math.hypot(base.x - qx, base.z - qz);
    if (!isFinite(bd) || bd < 1e-6) return null;
    const nx = (base.x - qx) / bd, nz = (base.z - qz) / bd;       // outward: road → building
    const tx = -nz, tz = nx;                                       // along the frontage
    return {
      x: base.x + nx * LEAN_WALL_BACK + tx * LEAN_SIDE * side,
      z: base.z + nz * LEAN_WALL_BACK + tz * LEAN_SIDE * side,
      facing: Math.atan2(nx, nz),                                  // rig front −Z looks along (−nx,−nz)
    };
  }
  activeCitizens() { return this._activeList; }
  streamEncountered() { return [...this._encountered].sort(); }
  // hours-aware: mark chunk keys that stay lively at night (the open-late block). The shell computes
  // these from the plan (openLate shop's lot → chunkKey, + neighbours) and passes them — the sim is
  // graph-only so it can't derive them itself. Empty = every chunk thins uniformly by the day curve.
  setNightLivelyChunks(keys) { this._livelyChunks = new Set(keys); }
  chunkKeyAt(x, z) { return chunkKey(chunkCoord(x), chunkCoord(z)); }

  // ---- graph → footpath lanes ----
  _setGraph(graph) {
    this.nodes = graph.nodes;
    this.edges = graph.edges.map(e => {
      const A = graph.nodes.find(n => n.id === e.a), B = graph.nodes.find(n => n.id === e.b);
      const dx = B.x - A.x, dz = B.z - A.z, len = Math.hypot(dx, dz) || 1e-3;
      const ux = dx / len, uz = dz / len;
      const off = (e.width || 4) * 0.5 + FOOTPATH_MARGIN;
      return { ...e, A, B, ux, uz, len, off };
    });
    // adjacency: node id → incident edge indices
    this.adj = new Map();
    this.nodes.forEach(n => this.adj.set(n.id, []));
    this.edges.forEach((e, i) => { this.adj.get(e.a).push(i); this.adj.get(e.b).push(i); });
  }

  // ---- deterministic identity ----
  _makeCitizen(id) {
    const idn = identityOf(this.citySeed, this.edges.length, id);
    const c = {
      id, pedRoll: idn.pedRoll, height: idn.height, speed: idn.speed,
      loiterTend: idn.loiterTend, phase: idn.phase, pvar: idn.pvar,
      pedIndex: -1, subject: idn.pvar,
      edge0: idn.edge, forward0: idn.forward,   // immutable spawn beat (for the determinism signature)
      // live state (mutates as they walk + turn at nodes)
      edge: idn.edge, forward: idn.forward, s: idn.sFrac * this.edges[idn.edge].len, loiter: 0,
      x: 0, z: 0, facing: 0,
      tier: 'far', actor: null, actorKind: null,
      _acc: 0,
      turn: rng(this.citySeed, 'turn', id),
      loit: rng(this.citySeed, 'loiter', id),
      sit: false, sitRng: rng(this.citySeed, 'benchsit', id),   // R17: dedicated stream — no shift to turn/loit/patron
      glance: false, glanceRng: rng(this.citySeed, 'glance', id),   // R29: ditto — independently keyed, signature untouched
      // [R41 §41.3] this citizen's four standing postures — a PURE function of (citySeed, id), decided
      // here once and never re-rolled, so lazy clip loading can change when a posture shows but never
      // which one it is. Two more freshly-keyed streams for the new street stops; like R17/R29 they
      // are drawn independently and cannot shift turn/loiter/patron/benchsit/glance.
      posture: posturesFor(this.citySeed, id),
      bench: null, benchRng: rng(this.citySeed, 'benchstop', id),
      lean: null, leanRng: rng(this.citySeed, 'leanstop', id),
    };
    // assign a real ped type if the fleet is already up (roster can grow after upgrade)
    if (this.mode === 'rig' && this.fleet.ready) {
      const pk = pickRig(this.fleet, c.pedRoll);
      if (pk) { c.pedIndex = pk.index; c.subject = pk.index; }
    }
    this._placeOnLane(c);
    return c;
  }

  _ensureRoster(n) {
    while (this.roster.length < n) this.roster.push(this._makeCitizen(this.roster.length));
  }

  // ---- public controls ----
  setPopulation(n) { this.target = Math.max(0, n | 0); this._ensureRoster(this.target); }
  setTimeOfDay(t01) { this.timeOfDay = t01; }
  // Match mid-tier billboards to the shell's day/night exposure. The impostor atlas is baked at a
  // fixed exposure and self-tone-maps (toneMapped:false), so as the shell animates
  // renderer.toneMappingExposure across day segments the billboards would drift brighter/darker than
  // the near rigs. Call this each frame with the live exposure. Stored so an atlas re-bake (the
  // placeholder→rig upgrade) inherits it. (Exposure only — the atlas can't track per-segment sun/hemi
  // colour; that would need a re-bake. Close enough for the LOD swap.)
  setExposure(e) { this._exposure = e; if (this.impostor) this.impostor.setExposure(e); }
  setDebugTiers(on) {
    this.debugTiers = !!on;
    if (this.impostor) this.impostor.setTint(on ? tierColor.mid : 0xffffff);
  }

  // ---- R8 patronage + weather ----
  // shell feeds door points + hours per chunk (computed from the plan — sim stays graph-only).
  // map: chunkKey → [{ x, z, hours:[open,close] }]. Without it, patronage is inert.
  // [Lane D R40 §40.5] Each door point is clamped into the footpath band of its nearest street
  // (door_snap.js — registry's vergeBand over our own edges, capped at 6 m so plaza-front stalls
  // stay put). The R8 claim is "peds duck into shops they pass"; the residue after B's R39 heading
  // fix was door points a metre or two off the walkable strip — peds steering to the kerb gutter or
  // a corner sliver. Points keep the shell's chunk keys (moves ≤ cap ≪ CHUNK; patronage is already
  // chunk-blind by covenant, sim.js:401). Gated by tools/qa/door_footpath_check.mjs — ≥95% of door
  // points on walkable front ground on all four measured towns, fix-only (breaks 0).
  setShops(shopsByChunk) {
    if (shopsByChunk && this.edges) {
      const snapped = new Map();
      for (const [key, list] of shopsByChunk) {
        snapped.set(key, list.map((s) => {
          const p = snapDoorToFootpath(s.x, s.z, this.edges);
          // [R41] keep the PRE-clamp point as `_raw`. The clamp deliberately drags the door onto the
          // walkable strip (that is its whole job), but a leaner wants the facade the door was
          // derived from, not the kerb the ped walks on — see _leanPose. Non-enumerable-ish extra
          // field only; every existing reader takes x/z/hours/shopId and is untouched.
          return p.moved ? { ...s, x: p.x, z: p.z, _raw: { x: s.x, z: s.z } } : s;
        }));
      }
      shopsByChunk = snapped;
    }
    this.shopsByChunk = shopsByChunk;
  }
  setPatronage(on) { this.patronageOn = !!on; }
  // Gig-night surge (?gigs=1): while a gig is on, F points patronage at the venue so the street
  // converges on the pub — it pulls from further (GIG_RANGE) and ducks in harder (GIG_SURGE). Occupants
  // drain at close per A's closing-time ruling (no special handling — _openAt + the dwell timer do it).
  // R13 the district: per-venue, so several concurrent gigs each pull their own block. F calls this once
  // per venue off its per-venue state; the alpha single-venue call (one id) is a subset — still works.
  setGig(venueShopId, on = true) {
    if (venueShopId == null) return;
    // [R41 §41.3] gig night is the venue clips' cue. F flips this from the STREET when the doors open,
    // long before the player walks in, so venue.glb (526 KB) is resident by the time GigCrew spawns —
    // lazy, one fetch, and never paid by a town that has no gig on. GigCrew re-asks anyway and heals
    // itself if this never ran (band.js), so the ordering is an optimisation, not a dependency.
    if (on) this._wantGroup('venue.glb');
    if (on) this._gigVenues.add(venueShopId);
    // gig ends (on→off transition) → disperse tonight's roster so the next night starts fresh + it stays
    // bounded. Persists across interior exit/re-enter (the gig stays "on" through those) — only the real
    // close clears it. .delete() returns true only on the transition, so re-calls while quiet are no-ops.
    else if (this._gigVenues.delete(venueShopId)) this._venueRoster.delete(venueShopId);
  }
  setWeather(w) { if (w && typeof w.state === 'string') this.weather = { state: w.state, intensity: +w.intensity || 0 }; }

  _openAt(hours) { if (!hours) return true; const h = (this.timeOfDay % 1) * 24; return h >= hours[0] && h < hours[1]; }
  // rain thins the crowd (~40–60%), overcast a little; clear = v1. Applied to each chunk's active count.
  _weatherDensityMult() {
    const w = this.weather;
    if (w.state === 'rain') return 0.6 - 0.2 * w.intensity;      // 0.4–0.6
    if (w.state === 'overcast') return 1 - 0.15 * w.intensity;   // ~0.9
    return 1;
  }
  _speedMult() { return this.weather.state === 'rain' ? 1.0 + 0.18 * this.weather.intensity : 1; }
  // chance (per in-range check) a ped ducks into an open shop. Rain → shelter-seeking. As the streets
  // empty (night), bump it so the few peds out concentrate at the one open shop (the video shop draws
  // the night crowd instead of a dead street with a lone visitor).
  _patronChance() {
    let base = this.weather.state === 'rain' ? 0.22 + 0.25 * this.weather.intensity : 0.16;
    const day = densityAt(this.timeOfDay);
    if (day < 0.35) base = Math.min(0.6, base + (0.35 - day) * 1.3);
    return base;
  }

  // nearest OPEN shop the ped is currently passing, else null. Hours-aware — at night only the openLate
  // video shop qualifies, so its block draws the night crowd.
  //
  // [R23] The carried v4.x fix — GIG_RANGE (34 m) is a RADIUS, but this read only the ped's own 64 m chunk,
  // so a gig venue genuinely in range, just across a chunk edge, was invisible. A's R21 cluster bias made
  // that WORSE, not better: venues now sit INSIDE the retail cluster where peds converge from every side,
  // so 42.6% of in-gig-range peds were chunk-blind (up from the 8.7% I filed at the old isolated pub).
  //
  // The fix is scoped to the GIG path on purpose. Extending the neighbour scan to ORDINARY shops as well
  // was the literal brief, but measured it breaks the same brief's "byte-identical flags-off" clause: on
  // the synthetic town (what ?classic=1 boots) 127 of 855 finds — 14.9% — would newly come from a
  // neighbour chunk, i.e. the frozen v2 crowd would start shopping ~15% more. So:
  //   · ORDINARY shops: own chunk only — v2 semantics, frozen. A shopfront is noticed from its own block.
  //   · GIG venues: the full 34 m radius, honest across chunk edges — the gig is the "follow the sound"
  //     pull that is SUPPOSED to reach further; that is the whole point of GIG_RANGE > PATRON_RANGE.
  // With no gig on, `_gigVenues` is empty and the neighbour loop is skipped entirely ⇒ ?classic and every
  // flags-off boot take the identical code path AND identical cost to v2. Byte-identical by construction.
  // Both ranges are < CHUNK (64), so a 3×3 sweep is exact, not an approximation. Fixed dz/dx order ⇒
  // exact-distance ties resolve deterministically, as the old single-list scan did.
  // Carried: PATRON_RANGE keeps v2's own chunk-blindness. Revisit only if the covenant is ever relaxed.
  _nearestOpenShop(c) {
    if (!this.shopsByChunk) return null;
    const cx = chunkCoord(c.x), cz = chunkCoord(c.z);
    let best = null, bd = PATRON_RANGE;
    let gigBest = null, gbd = GIG_RANGE;   // R13: the nearest gig venue in range — it wins over ordinary
    const own = this.shopsByChunk.get(chunkKey(cx, cz));   //  shops (follow the sound), and across venues.
    if (own) for (const s of own) {
      if (!this._openAt(s.hours)) continue;
      const d = Math.hypot(s.x - c.x, s.z - c.z);
      if (this._gigVenues.has(s.shopId) && d < gbd) { gbd = d; gigBest = s; }
      if (d < bd) { bd = d; best = s; }
    }
    if (this._gigVenues.size) {            // gig on → the 34 m pull reaches across chunk edges (gigs only)
      for (let dz = -1; dz <= 1; dz++) {
        for (let dx = -1; dx <= 1; dx++) {
          if (dx === 0 && dz === 0) continue;                  // own chunk already scanned above
          const list = this.shopsByChunk.get(chunkKey(cx + dx, cz + dz));
          if (!list) continue;
          for (const s of list) {
            if (!this._gigVenues.has(s.shopId)) continue;      // neighbours contribute gig venues ONLY
            if (!this._openAt(s.hours)) continue;
            const d = Math.hypot(s.x - c.x, s.z - c.z);
            if (d < gbd) { gbd = d; gigBest = s; }
          }
        }
      }
    }
    return gigBest || best;
  }
  // [R41 §41.3] the nearest shop FRONT within `range` — open or shut; a leaner doesn't need the door
  // to work, just a wall. Separate from `_nearestOpenShop` on purpose: that function's own-chunk
  // blindness is a frozen v2 semantic the R23 note explains at length, and this is new behaviour with
  // no covenant to keep, so it scans the honest 3×3 (range ≪ CHUNK, so the sweep is exact). Only ever
  // called at the instant a loiter begins, and only when the bank exists ⇒ ?classic never runs it.
  _nearestShopPoint(c, range) {
    if (!this.shopsByChunk) return null;
    const cx = chunkCoord(c.x), cz = chunkCoord(c.z);
    let best = null, bd = range;
    for (let dz = -1; dz <= 1; dz++) for (let dx = -1; dx <= 1; dx++) {
      const list = this.shopsByChunk.get(chunkKey(cx + dx, cz + dz));
      if (!list) continue;
      for (const s of list) {
        const d = Math.hypot(s.x - c.x, s.z - c.z);
        if (d < bd) { bd = d; best = s; }
      }
    }
    return best;
  }
  _beginVisit(c, shop) {
    c._savedWalk = { edge: c.edge, forward: c.forward, s: c.s };   // resume the footpath walk on the way out
    c.patronTarget = shop; c.patron = 'going';
  }
  _enter(c) {
    c.patron = 'inside';
    c.patronTimer = 5 + c.patronRng() * 15;          // seeded dwell 5–20s
    c.x = c.patronTarget.x; c.z = c.patronTarget.z;  // parked at the door while inside (hidden)
    // R9 occupancy truth: record who's inside which shop (F reads this to stand browser rigs)
    const id = c.patronTarget.shopId;
    if (id != null) {
      let occ = this._occupancy.get(id); if (!occ) this._occupancy.set(id, occ = []);
      occ.push({ seed: c.id, enteredAt: this.timeOfDay, pedIndex: c.pedIndex });
      c._occShop = id;
      // R14 continuity: a surge occupant who ducked into a GIG venue joins tonight's roster (the crowd
      // becomes the people who came in). The roster persists past this ped's short dwell (unlike occupancy,
      // which clears on emerge) — "who came tonight", keyed by the ped's stable id so re-entry doesn't dup.
      if (this._gigVenues.has(id)) this._recordRoster(id, c.id, c.pedIndex, c.height);
    }
  }
  // record one entered identity into a venue's tonight roster (deduped by key, insertion-ordered, no rng).
  _recordRoster(venueShopId, key, pedIndex, height) {
    let m = this._venueRoster.get(venueShopId);
    if (!m) this._venueRoster.set(venueShopId, m = new Map());
    if (!m.has(key)) m.set(key, { pedIndex, height });   // first entry wins
  }
  _emerge(c) {
    if (c._occShop != null) { this._removeOccupant(c._occShop, c.id); c._occShop = null; }
    const w = c._savedWalk;
    if (w) { c.edge = w.edge; c.forward = w.forward; c.s = w.s; }
    c.patron = null; c.patronTarget = null; c._savedWalk = null;
    this._placeOnLane(c);                             // back on the footpath, resumes the walk
  }
  _removeOccupant(shopId, seed) {
    const occ = this._occupancy.get(shopId); if (!occ) return;
    const i = occ.findIndex(o => o.seed === seed);
    if (i >= 0) occ.splice(i, 1);
    if (!occ.length) this._occupancy.delete(shopId);
  }
  // D's occupancy truth (the C→D→F seam): how many streamed peds patronage currently has inside this
  // shop, and who (seed + entry time + ped type). F reads this on interior build, then stands one
  // browser rig per browse point for min(count, 3). Count is pre-cap.
  occupancyOf(shopId) {
    const occ = this._occupancy.get(shopId) || [];
    return { count: occ.length, occupants: occ.map(o => ({ ...o })) };
  }
  // R14 identity continuity — the D→F seam.
  // recordVenueEntry: F relays a queue admit (VenueQueue.admitOne() → {pedIndex, height, key}) so the punter
  //   who walked in the door joins the crowd. Surge occupants self-record in _enter; this is the queue side.
  recordVenueEntry(venueShopId, entry) {
    if (venueShopId == null || !entry || entry.pedIndex == null) return;
    const key = entry.key != null ? `q:${entry.key}` : `q:${entry.pedIndex}:${(+entry.height || 0).toFixed(3)}`;
    this._recordRoster(venueShopId, key, entry.pedIndex, entry.height);
  }
  // tonightRoster: the night's entered identities, for GigCrew.spawn (F passes it in) + F's continuity
  //   smoke (assert crowd ⊇ roster ∩ cap). Insertion-ordered (entry order), deduped, bounded, pure read.
  tonightRoster(venueShopId) {
    const m = this._venueRoster.get(venueShopId);
    return m ? [...m.values()].map(e => ({ pedIndex: e.pedIndex, height: e.height })) : [];
  }
  // stable identity signature of the active set — immutable spawn identity, NOT live position, so it
  // holds while citizens walk (the determinism gate: same seed → same crowd, twice). Both modes.
  identitySignature() {
    return this._activeList.map(c => this._sig(c));
  }

  // ---- impostor atlases ----
  _buildPlaceholderImpostors() {
    const subjects = [];
    for (let v = 0; v < PLACEHOLDER_VARIANTS; v++) {
      const ph = makePlaceholder(rng(this.citySeed, 'pvar', v), { height: 1.9 });
      subjects.push({ object3D: ph.fig, height: 1.9 });
    }
    const atlas = bakeImpostorAtlas(this.renderer, subjects,
      { yaws: 4, cell: 128, environment: this.scene.environment });
    subjects.forEach(s => s.object3D.traverse(o => { if (o.isMesh) o.material.dispose?.(); }));
    this._setImpostorLayer(atlas);
  }

  _upgradeToRigs() {
    // bake one atlas cell-set per ped type, from a representative mid-stride pose
    const temps = [], subjects = [];
    for (let i = 0; i < this.fleet.all.length; i++) {
      const rig = this.fleet.all[i];
      const spawned = makeActor(rig, { walkClip: this.fleet.walkClip, idleClip: this.fleet.idleClip, nominalHeight: 1.9 });
      if (!spawned) continue;
      spawned.setMoving(true, 0);
      spawned.mixer.update(0.35 + i * 0.017);   // desynced mid-stride so the atlas isn't all one pose
      temps.push(spawned);
      subjects.push({ object3D: spawned.fig, height: 1.9, pedIndex: i });
    }
    if (!subjects.length) return;
    const atlas = bakeImpostorAtlas(this.renderer, subjects,
      { yaws: 4, cell: 128, environment: this.scene.environment });
    temps.forEach(t => t.dispose());
    this._setImpostorLayer(atlas);

    this.mode = 'rig';
    this.rigPool = new RigPool(this.fleet, { walkClip: this.fleet.walkClip, idleClip: this.fleet.idleClip, sitClip: this.fleet.sitClip, lookClip: this.fleet.lookClip });   // sit/lookClip null under ?classic → bench-sit + glance inert
    // assign real ped types to every citizen; drop placeholder near-actors so they re-acquire as rigs
    const assign = c => {
      const pk = pickRig(this.fleet, c.pedRoll);
      if (pk) { c.pedIndex = pk.index; c.subject = pk.index; }
      if (c.actor && c.actorKind === 'placeholder') { this._releaseActor(c); }
    };
    this.roster.forEach(assign);
    for (const arr of this.chunkRosters.values()) arr.forEach(assign);   // stream-mode rosters too
    // encountered signatures now carry pedIndex → refresh so the determinism proof matches post-upgrade
    if (this.streamMode) { this._encountered.clear(); for (const arr of this.chunkRosters.values()) arr.forEach(c => this._encountered.add(this._sig(c))); }
  }

  _setImpostorLayer(atlas) {
    if (this.impostor) { this.group.remove(this.impostor.mesh); this.impostor.dispose(); }
    this.impostor = new ImpostorLayer(atlas, { maxInstances: IMPOSTOR_MAX });
    this.group.add(this.impostor.mesh);
    if (this.debugTiers) this.impostor.setTint(tierColor.mid);
    if (this._exposure != null) this.impostor.setExposure(this._exposure);   // survive the upgrade re-bake
  }

  // ---- lane math ----
  _placeOnLane(c) {
    const e = this.edges[c.edge];
    const start = c.forward > 0 ? e.A : e.B;
    const tdx = c.forward * e.ux, tdz = c.forward * e.uz;      // travel direction
    // right-perpendicular (dz,-dx): opposing walkers take opposite footpaths
    const px = tdz, pz = -tdx;
    c.x = start.x + tdx * c.s + px * e.off;
    c.z = start.z + tdz * c.s + pz * e.off;
    c.facing = Math.atan2(-tdx, -tdz);                          // rig front = local -Z
  }

  _advance(c, dt) {
    // ---- R8 patronage state machine (streamed citizens only; c.patron is undefined for v1) ----
    if (c.patron === 'inside') { c.patronTimer -= dt; if (c.patronTimer <= 0) this._emerge(c); return; }
    if (c.patron === 'going') {                                  // steer straight to the shop door
      const dx = c.patronTarget.x - c.x, dz = c.patronTarget.z - c.z;
      const dist = Math.hypot(dx, dz);
      if (dist < 1.8) { this._enter(c); return; }
      const step = c.speed * this._speedMult() * dt;
      c.x += (dx / dist) * step; c.z += (dz / dist) * step;
      c.facing = Math.atan2(-dx / dist, -dz / dist);
      return;
    }
    if (c.loiter > 0) {
      c.loiter -= dt;
      // [R41] a bench sit / shopfront lean is a POSITIONED stop: the ped was moved off its lane to the
      // furniture. When the stop expires, drop the binding and put them back on the footpath in one
      // step, so the next frame walks from the lane and not from the seat.
      if (c.loiter <= 0 && (c.bench || c.lean)) { c.bench = null; c.lean = null; this._placeOnLane(c); }
      return;
    }
    const e = this.edges[c.edge];
    const adv = c.speed * this._speedMult() * dt;
    const s0 = c.s;
    c.s += adv;
    // [R41 §41.3] THE BENCH. Lane B puts benches at fixed stations along every edge, on alternating
    // sides. A ped walks the footpath on the side given by its travel direction, so it can only use a
    // bench on ITS side: the sim's lane perpendicular is (forward·uz, −forward·ux) = −forward × the
    // furniture perpendicular, hence `side === −forward`. Crossing that station's arc-length this
    // frame is the trigger; a dedicated stream decides. Gated on `clipsOn` (the boot-stable "is the
    // library on" answer), NOT on residency — so ?classic / ?noassets never run a line of it, and a
    // boot that has it on draws the identical randoms from frame zero whatever the network does. All
    // three draws are unconditional; the POSE falls back to R16's sit.glb until the variant lands.
    if (c.benchRng && this.clipsOn && !c.patron) {
      for (const st of this._benchStations(c.edge)) {
        if (st.side !== -c.forward) continue;
        if (!(s0 < st.s && c.s >= st.s)) continue;
        const wantsBench = c.benchRng() < BENCH_STOP_FRAC;
        const seat = c.benchRng() < 0.5 ? -1 : 1;               // drawn always — see clipsOn
        const dwell = c.benchRng();
        if (!wantsBench) continue;
        this._wantClip(c.posture && c.posture.sit);             // first sit intent fetches sitlean.glb
        const p = this._seatPose(st, seat);
        c.bench = st; c.lean = null; c.sit = false; c.glance = false;
        c.s = st.s;                                             // resume from the bench, not past it
        c.loiter = BENCH_DWELL[0] + dwell * (BENCH_DWELL[1] - BENCH_DWELL[0]);
        c.x = p.x; c.z = p.z; c.facing = p.facing;
        return;                                                 // the POSE falls back to R16's sit.glb
      }                                                         // until this citizen's variant lands
    }
    if (c.s >= e.len) {
      // arrived at the far node — pick the next edge (seeded), maybe a window-shop loiter
      const node = c.forward > 0 ? e.b : e.a;
      const inc = this.adj.get(node);
      let choices = inc.filter(i => i !== c.edge);
      if (!choices.length) choices = inc;                       // dead-end → U-turn
      const next = choices[(c.turn() * choices.length) | 0];
      const ne = this.edges[next];
      c.edge = next;
      c.forward = ne.a === node ? 1 : -1;
      c.s = Math.min(c.s - e.len, ne.len);                      // carry leftover distance
      if (c.loit() < 0.10 + c.loiterTend * 0.28) {
        c.loiter = 1.4 + c.loit() * 3.2;                              // window-shop stop
        // R17 bench-sit: a seeded few of those become a bench-sit. Roll ALWAYS (dedicated stream →
        // deterministic, never shifts turn/loit/patron), but only flip c.sit when a sit clip is loaded
        // so ?classic (no sit.glb) is inert at the source, not just at the render.
        const wantsSit = c.sitRng ? (c.sitRng() < BENCH_SIT_FRAC) : false;
        c.sit = wantsSit && !!(this.fleet && this.fleet.sitClip);
        // [R29 Spike 1] a standing glance — the other way to spend a window-shop stop. Same discipline as
        // the sit roll: draw ALWAYS from a dedicated stream (deterministic; never shifts turn/loit/patron),
        // but only flip the flag when a clip exists ⇒ ?classic inert at the source. Mutually exclusive with
        // the sit: you can't bench-sit and stand glancing, so the sit wins and the glance takes the rest.
        const wantsGlance = c.glanceRng ? (c.glanceRng() < GLANCE_FRAC) : false;
        c.glance = !c.sit && wantsGlance && !!(this.fleet && this.fleet.lookClip);
      }
    }
    this._placeOnLane(c);
    // patronage: every ~PATRON_STRIDE walked, IF a nearby open shop is in range, a seeded chance to
    // duck in (proximity-gated so the roll isn't wasted mid-block — this is what makes the sparse
    // night crowd reliably cluster at the open-late video shop).
    if (this.patronageOn && this.shopsByChunk && c.patronRng) {
      c._patronDist = (c._patronDist || 0) + adv;
      if (c._patronDist >= PATRON_STRIDE) {
        c._patronDist = 0;
        const shop = this._nearestOpenShop(c);
        const chance = (shop && this._gigVenues.has(shop.shopId))
          ? Math.max(this._patronChance(), GIG_SURGE) : this._patronChance();
        if (shop && c.patronRng() < chance) this._beginVisit(c, shop);
        // [R41 §41.3] THE SHOPFRONT LEAN — the ped that walked past a shop and DIDN'T go in.
        // This rides the patronage stride check on purpose. R17/R29's window-shop stop fires at a
        // graph NODE, i.e. at an intersection, where there is rarely a shopfront to lean on (measured:
        // 0 leans in a 9 s run when it was wired there). The stride check is the moment the sim
        // already asks "is there a shop beside me", which is exactly when a leaner is beside a wall.
        // Strictly downstream of the patron decision, on its own stream, and gated on `clipsOn` — so
        // with the library off (?classic / ?noassets / ?clips=0) not one line of it runs.
        // …and THE WINDOW PAUSE, which is what finally makes the 10-idle pool visible. Measured, and
        // it changed the design: with the pool wired only to R17/R29's node loiter, a census of the
        // live crowd found 0.8% of citizens stopped at any instant (the loiter fires at a graph NODE,
        // and edges are long) — so nine of ten new idles were assigned, deterministic, and never
        // seen. A ped who walks past a shop and neither goes in nor leans on it now sometimes just
        // STOPS and looks at the window, in their own seeded idle. No reposition, no new clip: the
        // actor's resting action is already this citizen's idle (setIdleClip at acquire).
        // All four draws are unconditional so the stream position cannot depend on load timing.
        else if (c.leanRng && this.clipsOn && !c.bench) {
          const wantsLean = c.leanRng() < LEAN_FRAC;
          const side = c.leanRng() < 0.5 ? 1 : -1;
          const wantsPause = c.leanRng() < PAUSE_FRAC;
          const dwell = c.leanRng();
          const wall = (wantsLean || wantsPause) ? this._nearestShopPoint(c, LEAN_RANGE) : null;
          if (wall && wantsLean) {
            this._wantClip(c.posture && c.posture.lean);        // first lean intent fetches sitlean.glb
            const p = this._leanPose(wall, side, this.edges[c.edge]);   // the ped's CURRENT edge
                                                                        // (a node arrival above may have moved it)
            if (p) {
              c.lean = wall; c.sit = false; c.glance = false;
              c.loiter = LEAN_DWELL[0] + dwell * (LEAN_DWELL[1] - LEAN_DWELL[0]);
              c.x = p.x; c.z = p.z; c.facing = p.facing;        // pose falls back to R29's look.glb
            }                                                   // until this citizen's variant lands
          } else if (wall && wantsPause) {
            c.sit = false; c.glance = false;                    // plain stop ⇒ the seeded idle plays
            c.loiter = PAUSE_DWELL[0] + dwell * (PAUSE_DWELL[1] - PAUSE_DWELL[0]);
          }
        }
      }
    }
  }

  // ---- actor lifecycle ----
  _acquireActor(c) {
    if (this.mode === 'rig' && this.rigPool && c.pedIndex >= 0) {
      const a = this.rigPool.acquire(c.pedIndex);
      if (a) {
        // [R41 §41.3] THE HEADLINE. Pooled actors are shared between citizens of the same ped type, so
        // the per-citizen posture is installed here, on acquire, not baked at construction: the same
        // citizen always stands the same way, and the street stops being one person copy-pasted.
        // Both calls are inert when the bank is absent or the clip has not landed (they fall back to
        // the base walk/idle actions) ⇒ ?classic / ?noassets / pre-load are the R40 actor exactly.
        if (this.bank && c.posture) {
          a.setIdleClip?.(this._clip(c.posture.idle));
          a.setWalkClip?.(this._clip(c.posture.walk));
        }
        a.setPhase(c.phase);
        a.setMoving(c.loiter <= 0, 0);          // instant, no fade, so the first frame is posed
        a.mixer.update(0);                       // evaluate NOW — a fresh clone must never show bind-pose (T-pose)
        a.fig.scale.setScalar(c.height / (a.nominalHeight || 1.75));
        this.group.add(a.fig);
        c.actor = a; c.actorKind = 'rig'; return true;
      }
      return false;   // pool exhausted this frame → stay an impostor
    }
    // placeholder mode (asset-free) — build a unique-coloured figure
    const ph = makePlaceholder(rng(this.citySeed, 'body', c.id), { height: c.height });
    this.group.add(ph.fig);
    c.actor = ph; c.actorKind = 'placeholder'; return true;
  }

  _releaseActor(c) {
    if (!c.actor) return;
    this.group.remove(c.actor.fig);
    if (c.actorKind === 'rig' && this.rigPool) this.rigPool.release(c.actor);
    else c.actor.dispose?.();
    c.actor = null; c.actorKind = null; c._acc = 0;
  }

  setPaused(p) { this.paused = !!p; }

  // the set of citizens active this frame — v1: the roster prefix scaled by time-of-day; stream: the
  // union of live-chunk residents, each chunk thinned by the same time-of-day curve (hours-aware
  // density per unit street). Deactivates everyone else. Downstream code is identical for both.
  _activeSet() {
    const list = [];
    const density = densityAt(this.timeOfDay);
    if (this.streamMode) {
      const haveLively = this._livelyChunks.size > 0;
      const wm = this._weatherDensityMult();    // rain/overcast thins the crowd on top of the day curve
      for (const [key, arr] of this.chunkRosters) {
        // hours-aware: every chunk thins by the day curve, but "lively" chunks (the open-late block)
        // keep a night floor so that street never goes dead while its shop is still open.
        const base = (haveLively && this._livelyChunks.has(key)) ? Math.max(density, NIGHT_LIVELY_FLOOR) : density;
        const d = base * wm;
        const activeCount = Math.round(arr.length * d);
        for (let i = 0; i < arr.length; i++) {
          if (i < activeCount) list.push(arr[i]);
          else if (arr[i].tier !== 'far') { this._releaseActor(arr[i]); arr[i].tier = 'far'; }
        }
      }
    } else {
      const active = Math.min(this.roster.length, Math.round(this.target * density));
      this._ensureRoster(active);
      for (let i = active; i < this.roster.length; i++) {
        const c = this.roster[i];
        if (c.tier !== 'far') { this._releaseActor(c); c.tier = 'far'; }
      }
      for (let i = 0; i < active; i++) list.push(this.roster[i]);
    }
    return list;
  }

  // ---- the frame ----
  update(dt) {
    if (this.paused) return this.stats;   // tab hidden → mixers frozen (app drives this via events)
    dt = Math.min(dt, 0.1);   // clamp long frames (tab refocus) so nobody teleports

    if (this.streamMode && !this._hookDriven) this._pollChunks();   // camera-follow window (or Lane B hooks)
    const activeCitizens = this._activeSet();
    this._activeList = activeCitizens;

    // advance + measure distances for the active set
    const cam = this.camera;
    const camX = cam.position.x, camZ = cam.position.z;
    const near = this._nearList; near.length = 0;
    const cand = [];
    for (const c of activeCitizens) {
      this._advance(c, dt);
      const ddx = c.x - camX, ddz = c.z - camZ;
      c._d = Math.hypot(ddx, ddz);
      cand.push(c);
    }

    // choose the near set: hysteresis eligibility, then nearest-first up to the cap
    const eligible = [];
    for (const c of cand) {
      if (c.patron === 'inside') continue;                      // ducked into a shop → not rendered
      const wasNear = c.tier === 'near';
      if (c._d < (wasNear ? NEAR_EXIT : NEAR_ENTER)) eligible.push(c);
    }
    eligible.sort((a, b) => (a._d - (a.tier === 'near' ? NEAR_BIAS : 0)) - (b._d - (b.tier === 'near' ? NEAR_BIAS : 0)));
    const nearSet = new Set(eligible.slice(0, NEAR_MAX));

    // assign tiers + representations
    const mid = this._midList; mid.length = 0;
    let newRigs = 0;
    for (const c of cand) {
      let want;
      if (c.patron === 'inside') want = 'far';                  // inside a shop → hidden (actor released below)
      else if (nearSet.has(c)) want = 'near';
      else if (c._d < (c.tier === 'far' ? MID_ENTER : MID_EXIT)) want = 'mid';
      else want = 'far';

      if (want === 'near') {
        // acquire an actor (budgeted); if it fails this frame, ride as an impostor instead
        if (!c.actor) {
          if (newRigs < NEW_RIG_PER_FRAME && this._acquireActor(c)) newRigs++;
          else want = 'mid';
        } else if (c.actorKind === 'placeholder' && this.mode === 'rig') {
          this._releaseActor(c);                 // upgrade path: swap placeholder → rig
          if (newRigs < NEW_RIG_PER_FRAME && this._acquireActor(c)) newRigs++; else want = 'mid';
        }
      }
      if (want !== 'near' && c.actor) this._releaseActor(c);

      if (want === 'near' && c.actor) {
        near.push(c);
        const a = c.actor;
        a.fig.position.set(c.x, 0, c.z);
        a.fig.rotation.y = c.facing;
        // R17 bench-sit: a seeded few of the window-shop loiters sit (upright, on the verandah/footpath
        // edge — no bench-position binding). No-op for walkers, placeholders, and ?classic (sitClip null),
        // so every non-sitting ped is byte-identical.
        // [R41 §41.3] `c.bench` is a real bench-bound sit (the ped was moved onto Lane B's furniture);
        // it and the R17 free sit both come out here, the bench one carrying this citizen's own seeded
        // sitlean variant. `sitClip` null ⇒ setSitting falls back to R16's sit.glb; both null ⇒ inert.
        const benchSit = !!(c.bench && c.loiter > 0);
        const wantSit = !!((benchSit || c.sit) && c.loiter > 0 && a.setSitting);
        if (a.setSitting) a.setSitting(wantSit, benchSit ? this._clip(c.posture && c.posture.sit) : null);
        // [R29 Spike 1] the glance rides the same seam: a stopped ped either sits, glances, or plain idles.
        // No-op for walkers, placeholders and ?classic (no lookClip) ⇒ every non-glancing ped byte-identical.
        // [R41] …and now also leans: same standing-posed-clip seam, this citizen's own lean variant.
        const wantLean = !wantSit && !!(c.lean && c.loiter > 0 && a.setLooking);
        const wantLook = !wantSit && !wantLean && !!(c.glance && c.loiter > 0 && a.setLooking);
        if (a.setLooking) a.setLooking(wantSit ? false : (wantLean || wantLook),
          0.3, wantLean ? this._clip(c.posture && c.posture.lean) : null);
        if (!wantSit && !wantLean && !wantLook) a.setMoving?.(c.loiter <= 0);
      } else if (want === 'mid') {
        mid.push(c);
      }
      c.tier = want;
    }

    // near animation: rigs on a staggered mixer budget; placeholders tick cheaply every frame
    near.sort((a, b) => a._d - b._d);
    const t0 = (typeof performance !== 'undefined' ? performance.now() : 0);
    const extra = [];
    for (let i = 0; i < near.length; i++) {
      const c = near[i], a = c.actor;
      c._acc += dt;
      if (a.mixer) {
        // [R29] plantFeet must follow the mixer that posed the feet — same coupling rule the drummer's
        // post-mix lean taught us. Only glancing peds pay it; it self-guards on `looking`.
        if (i < MIXER_ALWAYS) { a.mixer.update(c._acc); c._acc = 0; if (c.glance || c.lean) a.plantFeet?.(); } else extra.push(c);
      } else {
        a.tick?.(c._acc, c.loiter <= 0); c._acc = 0;   // placeholder
      }
    }
    // round-robin the mixers beyond the nearest 8, ≤MIXER_EXTRA per frame
    if (extra.length) {
      if (this._mixerCursor >= extra.length) this._mixerCursor = 0;
      for (let k = 0; k < MIXER_EXTRA && k < extra.length; k++) {
        const c = extra[(this._mixerCursor + k) % extra.length];
        c.actor.mixer.update(c._acc); c._acc = 0;
        if (c.glance || c.lean) c.actor.plantFeet?.();   // R29: the round-robin tier plants on the frames its mixer ran (R41: leaners too)

      }
      this._mixerCursor = (this._mixerCursor + MIXER_EXTRA) % extra.length;
    }
    const mixerMs = (typeof performance !== 'undefined' ? performance.now() : 0) - t0;

    // mid tier: one instanced draw call
    if (this.impostor) {
      const list = mid.length > IMPOSTOR_MAX ? mid.slice(0, IMPOSTOR_MAX) : mid;
      this.impostor.update(list, cam);
    }

    // debug tier tint on near actors (rig materials are shared → tint the whole group cheaply instead)
    const active = activeCitizens.length;
    this.stats = {
      active, rigged: near.length, mid: mid.length, far: active - near.length - mid.length,
      mixerMs, poolTotal: this.rigPool ? this.rigPool.total : 0, mode: this.mode,
      chunks: this.streamMode ? this.chunkRosters.size : 0,
    };
    return this.stats;
  }

  dispose() {
    this.roster.forEach(c => this._releaseActor(c));
    for (const arr of this.chunkRosters.values()) arr.forEach(c => this._releaseActor(c));
    this.chunkRosters.clear();
    if (this.rigPool) this.rigPool.dispose();
    if (this.impostor) { this.group.remove(this.impostor.mesh); this.impostor.dispose(); }
    this.scene.remove(this.group);
  }
}