// 在页面里注入一个悬浮"下载视频"按钮，贴在当前视频播放器右下角。
// 点击后通过 postMessage 通知宿主程序开始下载流程。
(function () {
  var BTN_ID = "qz-video-download-btn";

  function post(msg) {
    try {
      if (
        window.chrome &&
        window.chrome.webview &&
        window.chrome.webview.postMessage
      ) {
        window.chrome.webview.postMessage(JSON.stringify(msg));
      }
    } catch (e) {}
  }

  function bigVideo() {
    var vids = document.querySelectorAll("video");
    var best = null,
      bestArea = 0;
    for (var i = 0; i < vids.length; i++) {
      var r = vids[i].getBoundingClientRect();
      var area = r.width * r.height;
      if (r.width > 120 && r.height > 60 && area > bestArea) {
        best = vids[i];
        bestArea = area;
      }
    }
    return best;
  }

  function ensureButton() {
    var btn = document.getElementById(BTN_ID);
    var v = bigVideo();

    if (!btn && v) {
      btn = document.createElement("button");
      btn.id = BTN_ID;
      btn.type = "button";
      btn.innerText = "下载视频";
      btn.style.cssText =
        "position:fixed;z-index:2147483647;padding:5px 12px;border:0;border-radius:16px;" +
        "background:#ff2d55;color:#fff;font-size:13px;line-height:1.4;cursor:pointer;" +
        'box-shadow:0 2px 8px rgba(0,0,0,.35);font-family:system-ui,"Microsoft YaHei",sans-serif;';
      btn.addEventListener(
        "click",
        function (e) {
          e.preventDefault();
          e.stopPropagation();
          post({ type: "downloadClick", pageUrl: location.href });
        },
        true,
      );
      document.documentElement.appendChild(btn);
    }

    if (btn) {
      if (!v) {
        btn.style.display = "none";
        return;
      }
      var r = v.getBoundingClientRect();
      btn.style.display = "block";
      btn.style.left = Math.max(8, r.right - btn.offsetWidth - 12) + "px";
      btn.style.top = Math.max(8, r.bottom - btn.offsetHeight - 12) + "px";
    }
  }

  // 播放进度变化时（抖音翻页、切换清晰度）重新定位
  document.addEventListener("timeupdate", ensureButton, true);
  window.addEventListener("resize", ensureButton, true);
  window.addEventListener("scroll", ensureButton, true);
  document.addEventListener("mouseover", ensureButton, true);

  if (!window.__downloadBtnTimer) {
    window.__downloadBtnTimer = setInterval(ensureButton, 800);
  }
  ensureButton();
})();