/* uploads.js — model/texture asset handling for the character manager.
 * Files land in LIVE_DIR/assets (Docker volume) and are served at /assets/...
 * so uploads survive image rebuilds without being baked into the repo.
 */
const fs = require('fs');
const path = require('path');
const crypto = require('crypto');

const ALLOWED = {
  '.obj': 'model/obj', '.mtl': 'model/mtl',
  '.png': 'image/png', '.jpg': 'image/jpeg', '.jpeg': 'image/jpeg', '.webp': 'image/webp',
};
const MAX_BYTES = 12 * 1024 * 1024;

function safeName(name) {
  const base = path.basename(String(name || 'file')).replace(/[^a-zA-Z0-9._-]/g, '_');
  return base.slice(-80) || 'file';
}

class Assets {
  constructor(liveDir) {
    this.dir = path.join(liveDir, 'assets');
    this.indexPath = path.join(liveDir, 'assets.json');
    fs.mkdirSync(this.dir, { recursive: true });
    this.index = this.read();
  }
  read() {
    try { return JSON.parse(fs.readFileSync(this.indexPath, 'utf8')); } catch { return { assets: [] }; }
  }
  write() { fs.writeFileSync(this.indexPath, JSON.stringify(this.index, null, 2)); }
  list() { return this.index; }

  /* body: { name, kind: 'model'|'texture', dataBase64 } */
  save({ name, kind, dataBase64 }) {
    const clean = safeName(name);
    const ext = path.extname(clean).toLowerCase();
    if (!ALLOWED[ext]) throw new Error(`unsupported file type ${ext || '(none)'} — allowed: ${Object.keys(ALLOWED).join(', ')}`);
    const buf = Buffer.from(String(dataBase64 || ''), 'base64');
    if (!buf.length) throw new Error('empty file');
    if (buf.length > MAX_BYTES) throw new Error(`file too large (${(buf.length / 1048576).toFixed(1)} MB, max 12 MB)`);

    const id = crypto.randomBytes(6).toString('hex');
    const stored = `${id}${ext}`;
    fs.writeFileSync(path.join(this.dir, stored), buf);
    const rec = {
      id, name: clean, kind: kind === 'texture' ? 'texture' : 'model',
      url: `/assets/${stored}`, bytes: buf.length, uploadedAt: Date.now(),
    };
    this.index.assets.push(rec);
    this.write();
    return rec;
  }

  remove(id) {
    const i = this.index.assets.findIndex(a => a.id === id);
    if (i < 0) throw new Error('asset not found');
    const [rec] = this.index.assets.splice(i, 1);
    try { fs.unlinkSync(path.join(this.dir, path.basename(rec.url))); } catch {}
    this.write();
    return rec;
  }
}

module.exports = { Assets, ALLOWED, MAX_BYTES };