// PROCITY Lane C — real record sleeves for `?stock=real` (round 7). Feeds Lane E's GODVERSE stock pack
// (parody-transformed Discogs metadata + cover atlases) into the interior stock via the stockAdapter
// seam built in v1. Read-only, no economy (buying stays a stub — that's a later round).
//
// Pack contract (agreed in LANE_C_NOTES): stock_<type>_index.json →
//   { version, atlas_px, cell, atlases:["…webp"], items:[{ id,title,artist,price,price_band,atlas,uv }] }
//   uv = [u0,v0,u1,v1] cover rect, ORIGIN TOP-LEFT (image-natural) — this module flips V for WebGL.
//
// Batching: every sleeve samples ONE shared atlas material with a per-item UV baked into its geometry,
// so all real sleeves in a room merge (batch.js) to one draw per atlas — the ≤350 law holds.
// Leak-free: the atlas texture + material are shared/cached in the pack (NOT per-room), like depot GLBs;
// per-sleeve geometries are ctx-tracked and disposed with the room.
// Fail-soft: index/atlas missing → getStockPack returns null → callers fall back to parody canvas.

import * as THREE_NS from 'three';

const _texLoader = new THREE_NS.TextureLoader();
const _packs = new Map();      // type → Promise<pack|null>
const _resolved = new Map();   // type → pack|null (sync accessor for buildInterior)

// Preload a pack (fetch index + atlas textures). Cached. Call once before building with ?stock=real.
export function preloadStockPack(type, { base = 'assets/models/', THREE = THREE_NS } = {}) {
  if (_packs.has(type)) return _packs.get(type);
  const p = fetch(`${base}stock_${type}_index.json`)
    .then(r => (r.ok ? r.json() : null))
    .then(idx => (idx && idx.items && idx.items.length ? buildPack(type, idx, base, THREE) : null))
    .catch(() => null)
    .then(pack => { _resolved.set(type, pack); return pack; });
  _packs.set(type, p);
  return p;
}

// Synchronous accessor — the resolved pack if preloaded, else null (buildInterior uses this).
export function getStockPack(type) { return _resolved.get(type) || null; }

async function buildPack(type, idx, base, THREE) {
  const names = idx.atlases || [];
  const materials = {};
  await Promise.all(names.map(async (name) => {
    const url = /^depot:|^https?:/.test(name) ? name : base + name;
    let tex;
    try { tex = await _texLoader.loadAsync(url); } catch (e) { tex = null; }
    if (tex) { tex.colorSpace = THREE.SRGBColorSpace; tex.anisotropy = 4; }
    materials[name] = new THREE.MeshStandardMaterial({ color: 0xffffff, roughness: 0.72, map: tex || null });
  }));
  const first = names[0];
  return {
    type,
    items: idx.items,
    // shared material for an item's atlas (batching groups sleeves by this)
    material(item) { return materials[item.atlas] || materials[first]; },
    // WebGL-flipped cover rect [u0, v0, u1, v1] (origin bottom-left) for a plane's UV
    uvRect(item) { const u = item.uv; return [u[0], 1 - u[3], u[2], 1 - u[1]]; },
  };
}

// The stockAdapter for ?stock=real. Returns the pack POOL for a sleeve slot; consumers (stock.binFan /
// dig.js) pick a seeded subset per bin. Non-sleeve kinds → null (fall through to procedural).
export function makeStockAdapter(pack) {
  if (!pack || !pack.items || !pack.items.length) return null;
  return (shop, slotKind) => (slotKind === 'sleeve' ? { real: true, pack } : null);
}

// Build a leaning cover PLANE for one pack item, UV-remapped to its atlas rect, tagged isStock so
// batch.js merges it. Shared material (per atlas) → the whole bin batches to one draw.
export function realSleeveMesh(ctx, pack, item, w, h) {
  const THREE = ctx.THREE;
  const g = ctx.geom(new THREE.PlaneGeometry(w, h));
  const [u0, v0, u1, v1] = pack.uvRect(item);   // already WebGL-flipped
  const a = g.attributes.uv;
  a.setXY(0, u0, v1); a.setXY(1, u1, v1); a.setXY(2, u0, v0); a.setXY(3, u1, v0);   // TL,TR,BL,BR
  a.needsUpdate = true;
  const mesh = new THREE.Mesh(g, pack.material(item));
  mesh.userData.isStock = true;
  return mesh;
}