// PROCITY Lane B — planutil.js
// Pure plan/geometry helpers over a CityPlan (no THREE). Chunk math (CITY_SPEC: 64m cells),
// node/lot/shop indices, edge resolution, and the oriented-rectangle collider for a lot.
// If Lane A later ships an official chunkIndex(plan) we swap the import; the shapes match.

export const CHUNK = 64; // metres (CITY_SPEC law)

export const chunkCoord = (v) => Math.floor(v / CHUNK);
export const chunkKey = (cx, cz) => `${cx},${cz}`;
export const chunkOf = (x, z) => ({ cx: chunkCoord(x), cz: chunkCoord(z) });
export const parseKey = (k) => { const [cx, cz] = k.split(',').map(Number); return { cx, cz }; };

// Fast lookup maps built once per plan.
export function indexPlan(plan) {
  const nodes = new Map(plan.streets.nodes.map((n) => [n.id, n]));
  const lots = new Map(plan.lots.map((l) => [l.id, l]));
  const shopByLot = new Map(plan.shops.map((s) => [s.lot, s]));
  const shopsById = new Map(plan.shops.map((s) => [s.id, s]));
  return { nodes, lots, shopByLot, shopsById };
}

// Resolve street edges to world segments with widths.
export function resolveEdges(plan) {
  const nodes = new Map(plan.streets.nodes.map((n) => [n.id, n]));
  return plan.streets.edges.map((e) => {
    const a = nodes.get(e.a), b = nodes.get(e.b);
    return { id: e.id, kind: e.kind, width: e.width, ax: a.x, az: a.z, bx: b.x, bz: b.z };
  });
}

/**
 * chunkIndex(plan) → Map<chunkKey, { lots:[lot], shops:[shop], edges:[edgeId] }>
 * A lot belongs to the chunk containing its centre. An edge is registered to every chunk its
 * segment passes through (rasterised at CHUNK/4 steps) so the streamer can draw partial roads
 * if it ever needs to. Shops ride along with their lot.
 */
export function chunkIndex(plan) {
  const { shopByLot } = indexPlan(plan);
  const map = new Map();
  const cell = (cx, cz) => {
    const k = chunkKey(cx, cz);
    let c = map.get(k);
    if (!c) { c = { lots: [], shops: [], edges: [] }; map.set(k, c); }
    return c;
  };
  for (const lot of plan.lots) {
    const { cx, cz } = chunkOf(lot.x, lot.z);
    const c = cell(cx, cz);
    c.lots.push(lot);
    const s = shopByLot.get(lot.id);
    if (s) c.shops.push(s);
  }
  const nodes = new Map(plan.streets.nodes.map((n) => [n.id, n]));
  for (const e of plan.streets.edges) {
    const a = nodes.get(e.a), b = nodes.get(e.b);
    const dx = b.x - a.x, dz = b.z - a.z;
    const len = Math.hypot(dx, dz) || 1;
    const ux = dx / len, uz = dz / len, px = -uz, pz = ux;  // along + perpendicular units
    // Register every chunk the road BAND touches — not just the centreline — so furniture placed
    // at a perpendicular offset (footpath/verge) can never fall in an unbuilt chunk and vanish.
    const band = e.width / 2 + 10;
    const along = Math.max(1, Math.ceil(len / (CHUNK / 4)));
    const across = Math.max(1, Math.ceil((band * 2) / (CHUNK / 4)));
    const seen = new Set();
    for (let i = 0; i <= along; i++) {
      const sx = a.x + dx * (i / along), sz = a.z + dz * (i / along);
      for (let j = 0; j <= across; j++) {
        const o = -band + (2 * band) * (j / across);
        const { cx, cz } = chunkOf(sx + px * o, sz + pz * o);
        const k = chunkKey(cx, cz);
        if (!seen.has(k)) { seen.add(k); cell(cx, cz).edges.push(e.id); }
      }
    }
  }
  return map;
}

// Oriented-rectangle collider for a lot (local X = frontage w, local Z = depth d, rotated ry).
// Yards/houses get a fatter keep-out so you can't walk through private front gardens.
export function lotCollider(lot) {
  const yard = lot.use === 'house' || lot.use === 'yard';
  const pad = yard ? 2.5 : 0; // private-yard buffer in front of houses
  return {
    x: lot.x, z: lot.z, ry: lot.ry || 0,
    hw: lot.w / 2, hd: lot.d / 2 + pad / 2,
    use: lot.use,
  };
}

// Test/point-push a circle of radius r at (px,pz) out of an oriented rect collider.
// Returns [nx, nz] corrected position (or the same point if no overlap). Reused every frame —
// pass scratch out-array to avoid allocation.
export function pushOutRect(px, pz, r, col, out) {
  // Convention must match buildings.toWorld (local→world = RotY(ry)): dx = lx·cos + lz·sin,
  // dz = −lx·sin + lz·cos. So world→local is the inverse (RotY(−ry)) below, and the push-out
  // back-transform is RotY(ry). (Earlier this used the wrong sign and only happened to work for
  // axis-aligned ry ∈ {0,±π/2,π}; arbitrary ry from generatePlan needs the correct inverse.)
  const cos = Math.cos(col.ry), sin = Math.sin(col.ry);
  const dx = px - col.x, dz = pz - col.z;
  const lx = dx * cos - dz * sin;   // world→local (RotY(−ry))
  const lz = dx * sin + dz * cos;
  const ex = col.hw + r, ez = col.hd + r;
  if (lx > -ex && lx < ex && lz > -ez && lz < ez) {
    // overlapping — push along axis of least penetration
    const penX = ex - Math.abs(lx);
    const penZ = ez - Math.abs(lz);
    let nlx = lx, nlz = lz;
    if (penX < penZ) nlx = lx < 0 ? -ex : ex;
    else nlz = lz < 0 ? -ez : ez;
    out[0] = col.x + (nlx * cos + nlz * sin);   // local→world (RotY(ry)), inverse of the above
    out[1] = col.z + (-nlx * sin + nlz * cos);
    return true;
  }
  out[0] = px; out[1] = pz;
  return false;
}