// PROCITY Lane B — discovery.js  [v9 §Layer-2 THE FOG, round 39]
//
// WHAT YOU HAVE WALKED PAST. The map used to hand over every shop in the plan on the first M press
// (minimap.js:52-63, ungated) — 493 shops on the synthetic, and 5,330 m / 9,622 m / 5,797 m of walking
// (4.8 / 8.7 / 5.3 game-days at WALK 4.6 m/s against lighting.js's 240 s day) is what earning that
// legitimately costs. This module is the ledger of what has actually been earned.
//
// THREE LAWS, all load-bearing:
//
//  1. DISCOVERY IS A PROXIMITY PROBE, NOT A STREAMING EVENT. `chunks.onChunkBuilt` looks like the
//     seam and is not: every real town is BIG_CITY (index.html:151) ⇒ RADIUS 2, so the outermost live
//     chunk centre is 128 m away and its far corner 181 m. Chunk-built discovery would hand you shops
//     three blocks away through a wall. We probe by DISTANCE (FOG_RADIUS_M) and, so that a walk down
//     the back lane does not reveal the shopfronts on the far side of the buildings, by SIDE: you must
//     be in front of the shopfront plane. (At R=2 anything within 25 m is always in a live chunk, so
//     the probe never disagrees with what is streamed — it just doesn't depend on it.)
//
//  2. DISCOVERY IS PLAYER STATE (THE DELTA LAW). It is saved — in the save, next to cash and the
//     collection — and NEVER on the plan. The world still regenerates from seed with nothing
//     remembered about it; what is remembered is what the player saw. save.js owns the storage and the
//     bound (§39, `game.knownStore(fogKey)`); this module owns the geometry of "walked past".
//
//  3. IT IS KEYED BY TOWN, NOT BY townKey. Measured across all 23 shipped caches at seeds 20261990 / 7
//     / 424242: shop ids, edge ids, and every lot's geometry+frontEdge are IDENTICAL across seeds
//     (only `storeys`/`hours` re-jitter). A re-seed is the same Katoomba with different secrets, so the
//     map you learned survives it. The synthetic is the stated exception — its shop count itself moves
//     with the seed (493 / 479 / 465) — so it keys `default@<seed>`.
//
// Pure except for the store it is handed: no THREE, no DOM, no fetch, no plan mutation. It is
// constructed ONLY when the game layer is on, so ?classic=1 / ?game=0 never build it at all.

export const FOG_RADIUS_M = 25;      // "walked past a shopfront" — the probe radius
export const FOG_FRONT_M = 0;        // ...and on the street side of it (dot with the facade normal)
export const FOG_STREET_PAD_M = 4;   // "walked this street" — kerb (width/2) + footpath tolerance
export const PROBE_EVERY = 6;        // frames — the cadence hud.js:337 already raycasts doors on
const CELL = 32;                     // spatial-hash cell (m). > FOG_RADIUS_M so 3×3 cells always cover it.

// The fog key. `plansrc`/`town`/`seed` are exactly what the shell already computed for TOWNKEY; the
// difference is deliberate and is law 3 above: the real towns drop the seed, the synthetic keeps it.
export function fogKeyFor(plansrc, town, seed) {
  return plansrc === 'osm' ? `osm/${town || 'melbourne'}` : `synthetic/default@${seed >>> 0}`;
}

// Every shopfront as a point + an outward normal.
//
// THE SIGN IS buildings.js's, NOT THE SHELL'S, AND THEY DISAGREE. `buildShopfront` puts the facade,
// the door and the doorRect at local +Z — `toWorld(lot,0,0,d/2)` = `lot + (sin ry, cos ry)·d/2`
// (buildings.js:410-416, :583-597) — and minimap.js's own front-edge tick has always been drawn at
// local +Z too. The shell's patronage door points (index.html:384) and cluster spawn (:450) use
// `(-sin ry, -cos ry)`, i.e. the BACK of the building. Measured, taking each lot's own front and back
// point and asking which is nearer the kerb: the back point wins on **471 of 493** synthetic shops and
// **70 of 72** on katoomba_real. My first cut copied the shell's sign and the walk read 4 shops known
// / 1,231 in-radius rejections on the synthetic — the fog was hiding the whole town from a player
// standing in front of it. Filed for the shell; this module follows the geometry that actually renders.
export function shopFronts(plan) {
  const lots = new Map((plan.lots || []).map((l) => [l.id, l]));
  const out = [];
  for (const s of plan.shops || []) {
    const l = lots.get(s.lot);
    if (!l) continue;
    const ry = l.ry || 0, nx = Math.sin(ry), nz = Math.cos(ry);
    out.push({ id: s.id, x: l.x + nx * (l.d / 2), z: l.z + nz * (l.d / 2), nx, nz });
  }
  return out;
}

function segDist2(px, pz, ax, az, bx, bz) {
  const vx = bx - ax, vz = bz - az, wx = px - ax, wz = pz - az;
  const vv = vx * vx + vz * vz;
  let t = vv > 0 ? (wx * vx + wz * vz) / vv : 0;
  t = t < 0 ? 0 : t > 1 ? 1 : t;
  const dx = px - (ax + vx * t), dz = pz - (az + vz * t);
  return dx * dx + dz * dz;
}

// createDiscovery({ plan, known, radius? }) → the probe.
//   known — the KNOWN STORE (save.js `game.knownStore(fogKey)`): addShop/addEdge/hasShop/hasEdge/
//           counts/version. Anything with that shape works (the headless gates pass a plain object).
export function createDiscovery({ plan, known, radius = FOG_RADIUS_M, streetPad = FOG_STREET_PAD_M } = {}) {
  const R2 = radius * radius;
  const fronts = shopFronts(plan);
  const nodes = new Map((plan.streets?.nodes || []).map((n) => [n.id, n]));
  const edges = [];
  for (const e of plan.streets?.edges || []) {
    const a = nodes.get(e.a), b = nodes.get(e.b);
    if (!a || !b) continue;
    const pad = (e.width || 0) / 2 + streetPad;
    edges.push({ id: e.id, ax: a.x, az: a.z, bx: b.x, bz: b.z, pad2: pad * pad, pad });
  }

  // spatial hash — shops by their front point, edges by every cell their padded bbox touches
  const cells = new Map();
  const key = (cx, cz) => cx + ',' + cz;
  const cellOf = (cx, cz) => { const k = key(cx, cz); let c = cells.get(k); if (!c) cells.set(k, c = { s: [], e: [] }); return c; };
  for (const f of fronts) cellOf(Math.floor(f.x / CELL), Math.floor(f.z / CELL)).s.push(f);
  for (const e of edges) {
    const x0 = Math.floor((Math.min(e.ax, e.bx) - e.pad) / CELL), x1 = Math.floor((Math.max(e.ax, e.bx) + e.pad) / CELL);
    const z0 = Math.floor((Math.min(e.az, e.bz) - e.pad) / CELL), z1 = Math.floor((Math.max(e.az, e.bz) + e.pad) / CELL);
    for (let cx = x0; cx <= x1; cx++) for (let cz = z0; cz <= z1; cz++) cellOf(cx, cz).e.push(e);
  }

  let frame = 0, probes = 0, rejectedBehind = 0, lastNew = 0;
  // the front test's falsifiability control: WHICH shops came inside the radius and were refused for
  // being behind their own facade. `behind.size − (those later learned from the front)` is the count
  // of shops a radius-only probe would have handed over through a wall.
  const behind = new Set();

  // probe(pos) → number of NEW things learned. Called directly by the gates; the shell goes through
  // update(), which owns the cadence.
  function probe(pos) {
    probes++;
    let n = 0;
    const cx = Math.floor(pos.x / CELL), cz = Math.floor(pos.z / CELL);
    for (let ix = cx - 1; ix <= cx + 1; ix++) for (let iz = cz - 1; iz <= cz + 1; iz++) {
      const c = cells.get(key(ix, iz));
      if (!c) continue;
      for (const f of c.s) {
        if (known.hasShop(f.id)) continue;
        const dx = pos.x - f.x, dz = pos.z - f.z;
        if (dx * dx + dz * dz > R2) continue;
        // ...and you must be in FRONT of it. A shopfront seen through its own back wall is not seen.
        if (dx * f.nx + dz * f.nz <= FOG_FRONT_M) { rejectedBehind++; behind.add(f.id); continue; }
        if (known.addShop(f.id)) n++;
      }
      for (const e of c.e) {
        if (known.hasEdge(e.id)) continue;
        if (segDist2(pos.x, pos.z, e.ax, e.az, e.bx, e.bz) > e.pad2) continue;
        if (known.addEdge(e.id)) n++;
      }
    }
    if (n) lastNew = probes;
    return n;
  }

  return {
    probe,
    // the shell's per-street-frame call — same throttle class as hud.js's door raycast
    update(pos) { frame++; return (frame % PROBE_EVERY === 0) ? probe(pos) : 0; },
    // you walked in the door: you know the shop, whatever the geometry says
    discoverShop(id) { return known.addShop(id) ? 1 : 0; },
    get store() { return known; },
    get stats() {
      const c = known.counts();
      let behindOnly = 0;
      for (const id of behind) if (!known.hasShop(id)) behindOnly++;
      return { ...c, shopsTotal: fronts.length, edgesTotal: edges.length, probes, rejectedBehind,
               behindShops: behind.size, behindOnly, lastNew, radius, streetPad };
    },
  };
}