/*
 * 新闻静态页软导航：点击站内 /news/ 链接时，用 fetch 拉取目标页并仅替换 #news-app 区域，
 * 配合 history.pushState / popstate 实现无整页刷新跳转，CSS/JS 走浏览器缓存，避免每次从 OSS 重新下载整页。
 */
(function () {
  var APP_ID = 'news-app';

  function isInternal(href) {
    if (!href) return false;
    var a = document.createElement('a');
    a.href = href;
    if (a.origin !== location.origin) return false;
    return a.pathname.indexOf('/news/') === 0;
  }

  function swap(url) {
    fetch(url, { credentials: 'omit' })
      .then(function (r) {
        if (!r.ok) throw new Error('http ' + r.status);
        return r.text();
      })
      .then(function (html) {
        var doc = new DOMParser().parseFromString(html, 'text/html');
        var incoming = doc.getElementById(APP_ID);
        var current = document.getElementById(APP_ID);
        if (!incoming || !current) {
          location.href = url;
          return;
        }
        current.innerHTML = incoming.innerHTML;
        var t = doc.querySelector('title');
        if (t) document.title = t.textContent;
        ['canonical', 'alternate'].forEach(function (rel) {
          var neo = doc.querySelector('link[rel="' + rel + '"]');
          var old = document.querySelector('link[rel="' + rel + '"]');
          if (neo && old) old.outerHTML = neo.outerHTML;
        });
        window.scrollTo(0, 0);
      })
      .catch(function () {
        // 兜底：fetch 失败（如跨域/网络异常）则退回普通跳转
        location.href = url;
      });
  }

  document.addEventListener('click', function (e) {
    if (e.defaultPrevented || e.button !== 0 || e.metaKey || e.ctrlKey || e.shiftKey || e.altKey) return;
    var a = e.target.closest('a');
    if (!a) return;
    var href = a.getAttribute('href');
    if (!isInternal(href)) return;
    var target = new URL(href, location.href);
    if (target.pathname + target.search === location.pathname + location.search) return;
    e.preventDefault();
    history.pushState({ url: href }, '', href);
    swap(href);
  });

  window.addEventListener('popstate', function (e) {
    if (e.state && e.state.url) swap(e.state.url);
  });
})();