async function save(event) {
  event.preventDefault();
  event.stopImmediatePropagation();
  let content = "";
  // iterate ghrough all windows and all tabs
  // windows are separated by a blank line
  // tabs are separated by newline
  const _windows = await chrome.windows.getAll({ populate: true });
  _windows.forEach((_window, _windowIndex) => {
    _window.tabs.forEach((_tab, _tabIndex) => {
      content += _tab.url + "\n";
    });
    content += "\n";
  });
  
  const fileHandle = await showSaveFilePicker();
  const writable = await fileHandle.createWritable();
  await writable.write(content);
  await writable.close();
  window.close();
}

async function restore(event) {
  event.preventDefault();
  event.stopImmediatePropagation();
  let tabs = [];
  const [fileHandle] = await window.showOpenFilePicker();
  const file = await fileHandle.getFile();
  const contents = await file.text();

  // get tabs from text file (each line is a tab, an empty line indicates we can open a window with previous tabs)
  contents.split("\n").forEach(async (line) => {
    if (line == "" && tabs.length) {
      // create new window with tabs in array
      chrome.windows.create({
        state: "maximized",
        url: tabs,
      });
      tabs = []; // reset tabs array
    } else {
      // add tab to array
      tabs.push(line);
    }
  });
}

document.querySelector("a.save").onclick = save;
document.querySelector("a.restore").onclick = restore;