/**
 * Where the celilo monorepo is, if we are inside one.
 *
 * Its own module because two unrelated consumers need it and neither may
 * import the other: `cli/build.ts` uses it to find modules to package, and
 * `doctor.ts` uses it to fingerprint the source a baked image came from —
 * and `build.ts` already imports `doctor.ts`, so the reverse edge would be a
 * cycle. Re-exported from `cli/build.ts` so its existing callers and its
 * recurrence test are unchanged.
 */

import { existsSync } from 'node:fs';
import { join, resolve } from 'node:path';

/**
 * Walk up from `startDir` to the celilo checkout, or null.
 *
 * The marker is `apps/celilo/package.json` and must stay that specific
 * (ce-dbc): keying on a bare `modules/` directory made a stray empty
 * `node_modules/modules` from a botched `bun add -g` read as the monorepo
 * root, which skipped the published-staging path and crashed the packer for
 * every npm consumer.
 */
export function findMonorepoRoot(startDir: string): string | null {
  let dir = startDir;
  for (let i = 0; i < 10; i++) {
    if (existsSync(join(dir, 'apps', 'celilo', 'package.json'))) return dir;
    const parent = resolve(dir, '..');
    if (parent === dir) break;
    dir = parent;
  }
  return null;
}