import fs from 'node:fs';
import fsp from 'node:fs/promises';
import path from 'node:path';
import { spawn } from 'node:child_process';
import { safeJoin } from './paths.mjs';

export async function createZipStream(ctx, items) {
  const existing = [];
  for (const rel of items) {
    const full = safeJoin(ctx.uploadDir, rel);
    if (fs.existsSync(full)) existing.push({ rel, full });
  }
  if (!existing.length) throw new Error('no files');

  const tmpZip = path.join(ctx.uploadDir, ctx.metaDirName, `download-${Date.now()}.zip`);
  await fsp.mkdir(path.dirname(tmpZip), { recursive: true });

  await new Promise((resolve, reject) => {
    const args = ['-r', tmpZip, ...existing.map((x) => x.full)];
    const proc = spawn('zip', args, { cwd: ctx.uploadDir });
    proc.on('error', reject);
    proc.on('close', (code) => (code === 0 ? resolve() : reject(new Error(`zip exit ${code}`))));
  });

  const stream = fs.createReadStream(tmpZip);
  stream.on('close', () => fsp.unlink(tmpZip).catch(() => {}));
  return stream;
}