import crypto from 'node:crypto';
import fs from 'node:fs/promises';
import path from 'node:path';

export class BlobStore {
  constructor(root) { this.root = root; }

  async hash(buf) {
    return crypto.createHash('sha256').update(buf).digest('hex');
  }

  path(sha) {
    return path.join(this.root, sha.slice(0, 2), sha);
  }

  async write(buf) {
    const sha = await this.hash(buf);
    const dest = this.path(sha);
    try {
      await fs.access(dest);
    } catch {
      await fs.mkdir(path.dirname(dest), { recursive: true });
      await fs.writeFile(dest, buf);
    }
    return { sha, path: dest };
  }
}

let _default = null;
export function defaultStore() {
  const root = process.env.BLOB_ROOT || '/var/lib/void/blobs';
  if (!_default || _default.root !== root) _default = new BlobStore(root);
  return _default;
}