// PROCITY Lane B — ground.js
// Roads, footpaths, kerbs, the market plaza, and a base ground plane, built ONCE as merged strips
// per material (not per-chunk streamed). Rationale: the street graph is a handful of edges; merged
// flat quads are a few draw calls total and — unlike per-chunk road clipping — can never seam.
// UV tiling is baked into the geometry so one shared ground material serves strips of any length.
// (If Lane A ships a many-hundred-edge city, Lane F revisits streaming the ground.)

import * as THREE from 'three';
import { mergeGeometries } from 'three/addons/utils/BufferGeometryUtils.js';
import { resolveEdges } from './planutil.js';
import { vergeBand } from '../core/registry.js';
import { townCharacter } from './character.js';   // [R38 §1.2] the per-town ground palette

const FOOT = 3.5;        // footpath width OUTBOARD of the corridor (unchanged since v1)
const TILE = 5;          // metres per texture tile
const OVERLAP = 1.5;     // road segments overrun their nodes so intersections fill

// ── THE KERB IS FOOTPATH (v8 ruling 1, ROUND37 §0.1) ───────────────────────────────
// `edge.width` is the whole CORRIDOR — carriageway + verge — and this file painted all of it as
// bitumen from v1 to v7, which put the band registry.js calls "verandah'd footpath" (and that
// buildings.js already builds an awning over) under road texture: 14 gig posters, every bench and
// every ped lane stood in the road on the boot every player gets. Lane A's published corridor law
// (core/registry.js) is now the single source of truth for where the bitumen stops: the road quad
// narrows to the carriageway and the EXISTING merged `footGeos` class extends inward to meet it.
// Same merged meshes, same quad count ⇒ measured +0 draws (identical at all 102 steps of the walked
// spine) and tris that go DOWN, not up: −8 on the synthetic town, −288 on katoomba_real, because the
// only quads this adds are the ones the arcade case removes. The charter's "~2 k tris" was an
// estimate against a class that already existed; the honest number is a re-parameterisation.
//
// We consume `vergeBand(e)[0]`, NOT `roadWidth(e)/2`. Both `roadWidth` and `edge.width` are full
// widths — one of the carriageway, one of the corridor — and A names that collision as the reason
// this bug existed at all; `vergeBand`'s inner bound is the number A's own corrected gate reads, so
// the gate and the geometry cannot drift apart (Lane A, R37, verified over 31,039 corpus edges).
// The band is NOT one number: 9 m is synthetic-only (main @28 m). A real main is 24 m ⇒ 7 m, and the
// corpus's dominant edge is `side` @12 m — 22,415 of 31,039 edges (72%) — ⇒ 3 m. Never branch on a
// literal band; branch on the degenerate test (`outer <= inner`), which is exactly the class of bug
// this whole item exists to retire.
//
// `?verge=0` reverts to the pre-ruling geometry, permanently — it is Lane F's falsifiability
// control for the poster-clearance gate (the pre-change failure is known and counted at exactly 14).
// `?classic=1` forces it off (the R31 dig-flip pattern): the covenanted town's render does not move
// on a render-side ruling without an amendment ruling from Fable.
const VERGE = (() => {
  try {
    const p = new URLSearchParams(location.search);
    const classic = p.has('classic') && p.get('classic') !== '0';
    return !classic && p.get('verge') !== '0';
  } catch (e) { return false; }        // unparseable search ⇒ pre-ruling geometry, never a throw
})();

// Edges that keep a GRASS VERGE instead of pavement: the nature strip is period-correct in front of
// houses and nowhere else. An edge is residential if a house/yard lot fronts it, or if its fronting
// lots sit in a `residential` district. Real towns are 100% shop/mainstreet today ⇒ empty set ⇒ they
// pave, which is the intent.
function residentialEdges(plan) {
  const set = new Set();
  const districtOfBlock = new Map((plan.blocks || []).map((b) => [b.id, b.district]));
  const kindOfDistrict = new Map((plan.districts || []).map((d) => [d.id, d.kind]));
  for (const l of plan.lots || []) {
    if (l.frontEdge == null) continue;
    if (l.use === 'house' || l.use === 'yard' || kindOfDistrict.get(districtOfBlock.get(l.block)) === 'residential') {
      set.add(l.frontEdge);
    }
  }
  return set;
}

// Horizontal quad in XZ centred at (cx,cz), aligned to unit dir/perp, size len×wid, at height y.
// UVs baked to tile every TILE metres.
function hQuad(cx, cz, dir, perp, len, wid, y) {
  const hl = len / 2, hw = wid / 2;
  const ax = dir.x * hl, az = dir.z * hl;   // along
  const bx = perp.x * hw, bz = perp.z * hw;  // across
  const P = (sa, sb) => [cx + sa * ax + sb * bx, y, cz + sa * az + sb * bz];
  const c0 = P(-1, -1), c1 = P(1, -1), c2 = P(1, 1), c3 = P(-1, 1);
  const repU = Math.max(1, len / TILE), repV = Math.max(1, wid / TILE);
  const g = new THREE.BufferGeometry();
  // winding c0,c2,c1 / c0,c3,c2 so the geometric normal points +Y (up) — FrontSide stays visible.
  g.setAttribute('position', new THREE.BufferAttribute(new Float32Array([
    ...c0, ...c2, ...c1, ...c0, ...c3, ...c2]), 3));
  g.setAttribute('uv', new THREE.BufferAttribute(new Float32Array([
    0, 0, repU, repV, repU, 0, 0, 0, 0, repV, repU, repV]), 2));
  g.setAttribute('normal', new THREE.BufferAttribute(new Float32Array([
    0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0]), 3));
  return g;
}

// Axis-aligned rectangle helper (plaza, base plane).
function rectGeo(cx, cz, w, d, y, tile = TILE) {
  return hQuad(cx, cz, new THREE.Vector3(1, 0, 0), new THREE.Vector3(0, 0, 1), w, d, y);
}

// [R38 §1.2 — THE PER-TOWN CHARACTER VECTOR] `townKey` is the ?town= key the shell resolved; the
// plan deliberately does NOT carry it (plan_osm.js:515 — "town key stays OFF the plan (keeps the
// Melbourne golden frozen)"), so it arrives as an option. `townCharacter(null)` returns the frozen
// v1 literals, which is what the synthetic default and ?classic=1 both get — so this whole item is
// +0 draws / +0 tris AND byte-identical on the covenanted boot BY CONSTRUCTION, with no flag test
// anywhere in this file. `add()` merges each surface class into ONE town-wide mesh regardless of
// town size (measured: exactly 5 meshes, synthetic AND katoomba_real), so swapping which skin/tint
// that one shared material carries cannot cost a draw at any N.
export function buildGround(plan, skins, { townKey = null } = {}) {
  const group = new THREE.Group();
  group.name = 'ground';
  const edges = resolveEdges(plan);
  const character = townCharacter(townKey);

  const roadGeos = [], footGeos = [], kerbGeos = [];
  const dir = new THREE.Vector3(), perp = new THREE.Vector3();

  const grassy = VERGE ? residentialEdges(plan) : null;
  // Surface heights are a painter's order, not elevations — the whole stack is 9 cm thick and every
  // class is a flat quad, so what these numbers decide is who wins where two strips CROSS.
  // Pre-ruling the footpath (0.02) sat above the road (0.0) and that was invisible: a 3.5 m path
  // outboard of the corridor only ever crossed the far corner of a junction. At 12.5 m it crosses
  // the whole of the perpendicular CARRIAGEWAY, and the first cut of this change painted every
  // intersection shut — four roads arriving at a pedestrian plaza, screenshotted and rejected.
  // So under the ruling the carriageway goes on top: roads run through junctions, footpaths stop at
  // the kerb they meet, which is what an intersection actually looks like. Road-on-road overlap in
  // the junction box is unchanged and still invisible (one skin, one y, uniform asphalt — R20).
  const ROAD_Y = VERGE ? 0.04 : 0.0;

  for (const e of edges) {
    const dx = e.bx - e.ax, dz = e.bz - e.az;
    const len = Math.hypot(dx, dz) || 1;
    dir.set(dx / len, 0, dz / len);
    perp.set(-dir.z, 0, dir.x);
    const cx = (e.ax + e.bx) / 2, cz = (e.az + e.bz) / 2;
    const roadLen = len + OVERLAP * 2;
    const half = e.width / 2;                                   // corridor half-width (the v1 kerb line)
    // A's law, as A publishes it: [kerb, corridor edge] measured from the centreline.
    const [bandInner, bandOuter] = vergeBand(e);
    // Where the kerb goes. `min(…, half)` is the inversion guard: no edge in the 31,039-edge corpus
    // has a carriageway wider than its corridor, but a `side` under 6 m would, and an inverted band
    // would flip a footpath quad inside out. A DEGENERATE band (`bandOuter <= bandInner` — all
    // carriageway, no verge: 56 real `lane` edges, 2 synthetic ones, and NOT the [2,2] literal the
    // brief carried) then lands on `bandInner === half`, i.e. the pre-ruling geometry, by arithmetic
    // rather than by a special case.
    const kerbHalf = VERGE ? Math.min(bandInner, half) : half;

    // ARCADE (1,102 corpus edges): a covered pedestrian lane has no carriageway at all, so a road
    // quad here is zero-area and the two kerbs land on top of each other at the centreline. Emit
    // neither, and pave the whole corridor as ONE footpath quad (no centreline seam).
    if (VERGE && kerbHalf <= 0) {
      footGeos.push(hQuad(cx, cz, dir, perp, roadLen, e.width + FOOT * 2, 0.02));
      continue;
    }

    roadGeos.push(hQuad(cx, cz, dir, perp, roadLen, kerbHalf * 2, ROAD_Y));
    // Footpaths flank the road: from the kerb line out to the corridor edge + FOOT. Two bands keep
    // their v1 outboard-only pavement — a DEGENERATE band (no verge exists to pave: the laneway
    // case, tested, never assumed from a width) and a RESIDENTIAL edge, where the verge stays grass
    // because a nature strip is what is period-correct in front of a house.
    const inner = (bandOuter <= bandInner || (grassy && grassy.has(e.id))) ? half : kerbHalf;
    const fw = half + FOOT - inner;
    const off = inner + fw / 2;
    footGeos.push(hQuad(cx + perp.x * off, cz + perp.z * off, dir, perp, roadLen, fw, 0.02));
    footGeos.push(hQuad(cx - perp.x * off, cz - perp.z * off, dir, perp, roadLen, fw, 0.02));
    // low kerbs between road and footpath
    const koff = kerbHalf + 0.12;
    kerbGeos.push(hQuad(cx + perp.x * koff, cz + perp.z * koff, dir, perp, roadLen, 0.24, 0.06));
    kerbGeos.push(hQuad(cx - perp.x * koff, cz - perp.z * koff, dir, perp, roadLen, 0.24, 0.06));
  }

  // market plaza (brickpave) over the central square
  const sq = (plan.districts || []).find((d) => d.kind === 'market');
  const plazaGeos = [];
  if (sq) plazaGeos.push(rectGeo(0, 0, 46, 46, 0.015));

  // base ground plane under the whole town (grass/dirt), sized to the plan extent
  let minX = -60, maxX = 60, minZ = -60, maxZ = 60;
  for (const n of plan.streets.nodes) { minX = Math.min(minX, n.x); maxX = Math.max(maxX, n.x); minZ = Math.min(minZ, n.z); maxZ = Math.max(maxZ, n.z); }
  for (const l of plan.lots) { minX = Math.min(minX, l.x); maxX = Math.max(maxX, l.x); minZ = Math.min(minZ, l.z); maxZ = Math.max(maxZ, l.z); }
  const bw = (maxX - minX) + 120, bd = (maxZ - minZ) + 120;
  const bcx = (minX + maxX) / 2, bcz = (minZ + maxZ) / 2;
  const baseGeo = rectGeo(bcx, bcz, bw, bd, -0.03);

  const meshes = [];
  const add = (geos, material, receive = true) => {
    if (!geos.length) return;
    const merged = mergeGeometries(geos, false);
    geos.forEach((g) => g.dispose());
    const m = new THREE.Mesh(merged, material);
    m.receiveShadow = receive; m.castShadow = false;
    group.add(m); meshes.push(m);
  };

  // [R38 §1.2] Five classes, five town-wide meshes, five shared materials — exactly as before. The
  // only thing the character vector changes is WHICH skin name and WHICH tint each of those five
  // asks for. An unmatched town key returns the same literals a null key does (and says so in
  // `character.matched`), so a new town cache appearing in E's index before this table knows about
  // it degrades to today's palette instead of to a default branch nobody printed.
  const g = character.ground, tint = character.tint;
  add([baseGeo], skins.groundMat(g.base, tint.base));
  add(roadGeos, skins.groundMat(g.road, tint.road));
  add(footGeos, skins.groundMat(g.foot, tint.foot));
  add(plazaGeos, skins.groundMat(g.plaza, tint.plaza));
  const kerbMat = new THREE.MeshStandardMaterial({ color: character.kerb, roughness: 0.9 });
  add(kerbGeos, kerbMat);

  function dispose() {
    for (const m of meshes) m.geometry.dispose();
    kerbMat.dispose();
    group.clear();
  }
  return { group, dispose, verge: VERGE, character, get meshCount() { return meshes.length; } };
}