let initialized = false;
let deferredInstallPrompt = null;
const listeners = new Set();

function notifyAvailability() {
  const canInstall = Boolean(deferredInstallPrompt);
  listeners.forEach((listener) => {
    try {
      listener(canInstall);
    } catch {
      // ignore listener errors
    }
  });
}

export function initPwaInstallPromptHandling() {
  if (initialized) return;
  initialized = true;

  window.addEventListener('beforeinstallprompt', (event) => {
    event.preventDefault();
    deferredInstallPrompt = event;
    notifyAvailability();
  });

  window.addEventListener('appinstalled', () => {
    deferredInstallPrompt = null;
    notifyAvailability();
  });
}

export function canInstallPwa() {
  return Boolean(deferredInstallPrompt);
}

export function isStandalonePwaMode() {
  return (
    window.matchMedia?.('(display-mode: standalone)')?.matches ||
    window.navigator?.standalone === true
  );
}

export async function promptPwaInstall() {
  if (!deferredInstallPrompt) {
    return { supported: false, outcome: '' };
  }

  const promptEvent = deferredInstallPrompt;
  deferredInstallPrompt = null;
  notifyAvailability();

  await promptEvent.prompt();
  const choice = await promptEvent.userChoice;
  return {
    supported: true,
    outcome: String(choice?.outcome || ''),
  };
}

export function onPwaInstallAvailabilityChange(handler) {
  if (typeof handler !== 'function') return () => {};
  listeners.add(handler);
  return () => {
    listeners.delete(handler);
  };
}