// Worker thread running 7-Zip (compiled to WASM) for ZIP/7Z/RAR archives.
// 7-Zip calls are synchronous, so they run here to keep the server responsive.

const { parentPort } = require('worker_threads');
const SevenZip = require('7z-wasm');

let sevenZip = null;
const output = [];

// The host filesystem is mounted at /host inside the WASM filesystem.
const host = (p) => `/host${p}`;

async function instance() {
  if (!sevenZip) {
    sevenZip = await SevenZip({ print: (l) => output.push(l), printErr: (l) => output.push(l) });
    sevenZip.FS.mkdir('/host');
    sevenZip.FS.mount(sevenZip.NODEFS, { root: '/' }, '/host');
  }
  return sevenZip;
}

async function run(args) {
  const sz = await instance();
  output.length = 0;
  let code;
  try {
    code = sz.callMain(args);
  } catch (err) {
    code = err && typeof err.status === 'number' ? err.status : 2;
  }
  return { code, lines: output.slice() };
}

function errorText(lines) {
  const line = lines.find((l) => /error|wrong password|can ?not open|unsupported|headers/i.test(l));
  return line ? line.trim() : null;
}

// Parses `7zz l -slt` into [{ path, size }] for files (folders are dropped).
function parseListing(lines) {
  const start = lines.findIndex((l) => l.startsWith('----------'));
  if (start === -1) return null;
  const entries = [];
  let cur = {};
  const flush = () => {
    const isFolder = cur.Folder === '+' || (cur.Attributes || '').startsWith('D');
    if (cur.Path !== undefined && !isFolder) entries.push({ path: cur.Path, size: Number(cur.Size) || 0 });
    cur = {};
  };
  for (const line of lines.slice(start + 1)) {
    if (!line.trim()) { flush(); continue; }
    const i = line.indexOf(' = ');
    if (i > 0) cur[line.slice(0, i)] = line.slice(i + 3);
  }
  flush();
  return entries;
}

async function list(archive) {
  // A dummy password makes encrypted archives fail fast instead of prompting.
  const { code, lines } = await run(['l', '-slt', '-pprinthive', host(archive)]);
  const entries = parseListing(lines);
  if (code !== 0 || !entries) throw new Error(errorText(lines) || `7-Zip could not read the archive (exit ${code})`);
  return entries;
}

// Extracts the named entries (keeping their folders) under destDir. Callers
// check which files actually arrived.
async function extract(archive, entries, destDir) {
  const { code, lines } = await run(
    ['x', host(archive), `-o${host(destDir)}`, '-y', '-spd', '-bsp0', '-pprinthive', '--', ...entries]);
  return { code, error: code === 0 ? null : errorText(lines) };
}

parentPort.on('message', async ({ id, op, archive, entries, destDir }) => {
  try {
    const result = op === 'list' ? await list(archive) : await extract(archive, entries, destDir);
    parentPort.postMessage({ id, result });
  } catch (err) {
    parentPort.postMessage({ id, error: err.message });
  }
});