// Pending source content exists only during the initial handshake. The dialog
// owns a structured clone after receipt, independent of the event page's life.
export async function showActionDialog(browser, payload) {
  const id = crypto.randomUUID();
  const url = browser.runtime.getURL('dialog/action.html') + '?request=' + id;
  let tabId;
  let port;
  let finished = false;
  let resolveOpened;
  const opened = new Promise(resolve => { resolveOpened = resolve; });
  let timer;
  let resolveDone, rejectDone;
  const done = new Promise((resolve, reject) => { resolveDone = resolve; rejectDone = reject; });
  // Attach rejection handling immediately, including when window creation stalls.
  void done.catch(() => {});
  function finish(error) {
    if (finished) return;
    finished = true;
    clearTimeout(timer);
    payload = null;
    browser.runtime.onConnect.removeListener(onConnect);
    browser.tabs.onRemoved.removeListener(onRemoved);
    if (port) {
      port.onMessage.removeListener(onMessage);
      port.onDisconnect.removeListener(onDisconnect);
      port.disconnect();
    }
    if (error) rejectDone(error); else resolveDone();
  }
  function onMessage(message) {
    if (message?.type === 'received') finish();
  }
  function onDisconnect() { finish(); }
  function onRemoved(removedId) { if (removedId === tabId) finish(); }
  async function onConnect(candidate) {
    if (candidate.name !== 'action-dialog:' + id) return;
    await opened;
    if (finished || port || candidate.sender?.id !== browser.runtime.id ||
        candidate.sender?.url !== url || candidate.sender?.tab?.id !== tabId) return;
    port = candidate;
    port.onMessage.addListener(onMessage);
    port.onDisconnect.addListener(onDisconnect);
    try { port.postMessage({ type: 'initialize', payload }); }
    catch { finish(new Error('Could not initialize action dialog')); }
  }
  browser.runtime.onConnect.addListener(onConnect);
  browser.tabs.onRemoved.addListener(onRemoved);
  timer = setTimeout(() => finish(new Error('Action dialog initialization timed out')), 15000);
  try {
    try {
      const win = await browser.windows.create({ url, type: 'popup', width: 480, height: 360 });
      tabId = win.tabs?.[0]?.id;
      if (typeof tabId !== 'number') throw new Error('Missing dialog tab');
    } catch {
      const tab = await browser.tabs.create({ url });
      tabId = tab.id;
    }
  } catch (error) { finish(error); }
  finally { resolveOpened(); }
  return done;
}