(function () {
  'use strict';

  const root = window.PixelIslandModules ||= {};
  let worker = null;
  let nextId = 1;
  const pending = new Map();

  function canUseWorkers() {
    return typeof Worker === 'function';
  }

  function getWorker() {
    if (!canUseWorkers()) return null;
    if (worker) return worker;
    worker = new Worker('./js/pixel-worker.js');
    worker.onmessage = (event) => {
      const { id, ok, result, error } = event.data || {};
      const entry = pending.get(id);
      if (!entry) return;
      pending.delete(id);
      if (ok) entry.resolve(result);
      else entry.reject(new Error(error || 'worker_error'));
    };
    worker.onerror = (event) => {
      const error = new Error(event.message || 'worker_error');
      for (const entry of pending.values()) entry.reject(error);
      pending.clear();
      worker?.terminate();
      worker = null;
    };
    return worker;
  }

  function request(type, payload) {
    const target = getWorker();
    if (!target) return Promise.reject(new Error('workers_unavailable'));
    const id = nextId++;
    const promise = new Promise((resolve, reject) => pending.set(id, { resolve, reject }));
    target.postMessage({ id, type, payload });
    return promise;
  }

  function buildPixelBlobs(assets) {
    return request('buildPixelBlobs', {
      assets,
      palette: root.Palette?.PALETTE || [],
      defaultColorCode: root.Palette?.DEFAULT_SELECTED_COLOR_CODE || 'a'
    });
  }

  root.WorkerClient = { canUseWorkers, buildPixelBlobs };
})();