(() => {
  'use strict';

  // 浏览器插件在 document_start 阶段写入这个属性（见 extension/*/detect.js）。
  const EXT_ATTR = 'data-navi-ext';
  const INSTALL_SELECTOR = 'a[href*="/extension/install"]';

  function extensionInstalled() {
    return document.documentElement.hasAttribute(EXT_ATTR);
  }

  // 已装插件的浏览器不需要安装入口：连外层网格单元一起隐藏，
  // 否则 .item-wrapper 会留下一个空位。
  function hideInstallEntry() {
    if (!extensionInstalled()) return;
    document.querySelectorAll(INSTALL_SELECTOR).forEach((link) => {
      const cell = link.closest('.item-wrapper') || link.parentElement || link;
      if (cell.style.display !== 'none') cell.style.display = 'none';
    });
  }

  function mountSearch() {
    if (document.querySelector('.navi-search-bar')) return;
    const form = document.createElement('form');
    form.className = 'navi-search-bar';
    form.method = 'GET';
    form.action = '/search';
    form.target = '_blank';
    form.setAttribute('role', 'search');

    const icon = document.createElement('span');
    icon.innerHTML = '<svg width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2.5" stroke-linecap="round" stroke-linejoin="round"><circle cx="11" cy="11" r="8"/><line x1="21" y1="21" x2="16.65" y2="16.65"/></svg>';
    icon.setAttribute('aria-hidden', 'true');

    const input = document.createElement('input');
    input.type = 'search';
    input.name = 'q';
    input.placeholder = '搜索…';
    input.autocomplete = 'off';
    input.setAttribute('aria-label', '搜索');

    const button = document.createElement('button');
    button.type = 'submit';
    button.textContent = '→';
    button.title = '搜索';

    form.append(icon, input, button);
    document.body.appendChild(form);
  }

  function run() {
    mountSearch();
    hideInstallEntry();
  }

  if (document.readyState === 'loading') {
    document.addEventListener('DOMContentLoaded', run, { once: true });
  } else {
    run();
  }
  new MutationObserver(run).observe(document.documentElement, { childList: true, subtree: true });
})();