(function (global) {
  var definitions = {
    download: {
      endpoint: "/ui/dialog/download",
      elementId: "downloadAppDialog",
      css: "/static/css/downloadAppDialog.css?v=2",
      js: "/static/js/pages/downloadAppDialog.js?v=4",
      open: "openDownloadAppDialog",
    },
  };
  var pending = Object.create(null);
  var stubOpeners = Object.create(null);

  function hasRealOpener(name) {
    var definition = definitions[name];
    return (
      !!definition &&
      typeof global[definition.open] === "function" &&
      global[definition.open] !== stubOpeners[name]
    );
  }

  function loadStylesheet(href) {
    var existing = document.querySelector('link[rel="stylesheet"][href="' + href + '"]');
    if (existing) return Promise.resolve();
    return new Promise(function (resolve, reject) {
      var link = document.createElement("link");
      var settled = false;
      function finish(ok, err) {
        if (settled) return;
        settled = true;
        if (ok) resolve();
        else reject(err || new Error("dialog stylesheet failed"));
      }
      link.rel = "stylesheet";
      link.href = href;
      link.onload = function () {
        finish(true);
      };
      link.onerror = function () {
        finish(false, new Error("dialog stylesheet failed"));
      };
      document.head.appendChild(link);
      // 部分浏览器对缓存 CSS 不触发 onload，避免一直卡住弹窗
      requestAnimationFrame(function () {
        try {
          if (link.sheet) finish(true);
        } catch (e) {}
      });
      setTimeout(function () {
        finish(true);
      }, 1500);
    });
  }

  function loadScript(src) {
    var existing = document.querySelector('script[src="' + src + '"]');
    if (existing) {
      if (existing.getAttribute("data-loaded") === "1") return Promise.resolve();
      return new Promise(function (resolve, reject) {
        existing.addEventListener("load", resolve, { once: true });
        existing.addEventListener("error", function () {
          reject(new Error("dialog script failed"));
        }, { once: true });
      });
    }
    return new Promise(function (resolve, reject) {
      var script = document.createElement("script");
      script.src = src;
      script.async = true;
      script.onload = function () {
        script.setAttribute("data-loaded", "1");
        resolve();
      };
      script.onerror = function () {
        reject(new Error("dialog script failed"));
      };
      document.head.appendChild(script);
    });
  }

  function fetchFragment(definition) {
    if (document.getElementById(definition.elementId)) {
      return Promise.resolve();
    }
    return fetch(definition.endpoint, {
      credentials: "same-origin",
      headers: { "X-Requested-With": "XMLHttpRequest" },
    }).then(function (response) {
      if (!response.ok) throw new Error("dialog fragment failed");
      return response.text();
    }).then(function (html) {
      if (document.getElementById(definition.elementId)) return;
      var host = document.createElement("div");
      host.innerHTML = html;
      var dialog = host.querySelector("#" + definition.elementId);
      if (!dialog) throw new Error("dialog fragment is invalid");
      document.body.appendChild(dialog);
    });
  }

  function ensureDialog(name) {
    var definition = definitions[name];
    if (!definition) return Promise.reject(new Error("unknown dialog"));
    if (document.getElementById(definition.elementId) && hasRealOpener(name)) {
      return Promise.resolve();
    }
    if (pending[name]) return pending[name];

    pending[name] = loadStylesheet(definition.css)
      .then(function () {
        return fetchFragment(definition);
      })
      .then(function () {
        if (hasRealOpener(name)) return;
        return loadScript(definition.js);
      })
      .then(function () {
        if (!document.getElementById(definition.elementId) || !hasRealOpener(name)) {
          throw new Error("dialog opener is unavailable");
        }
      })
      .catch(function (error) {
        delete pending[name];
        throw error;
      });
    return pending[name];
  }

  function openDialog(name, value) {
    return ensureDialog(name)
      .then(function () {
        var opener = global[definitions[name].open];
        if (typeof opener !== "function" || opener === stubOpeners[name]) {
          throw new Error("dialog opener is unavailable");
        }
        return opener(value);
      })
      .catch(function (error) {
        throw error;
      });
  }

  Object.keys(definitions).forEach(function (name) {
    var apiName = definitions[name].open;
    var stub = function (value) {
      return openDialog(name, value);
    };
    stubOpeners[name] = stub;
    if (typeof global[apiName] !== "function") global[apiName] = stub;
  });

  function triggerName(target) {
    if (!target || !target.closest) return "";
    if (target.closest("[data-download-app-open]")) return "download";
    return "";
  }

  function isMobileViewport() {
    return typeof global.matchMedia === "function"
      ? global.matchMedia("(max-width: 767px)").matches
      : (global.innerWidth || 0) <= 767;
  }

  document.addEventListener("click", function (event) {
    var name = triggerName(event.target);
    if (!name) return;
    // 移动端下载入口保留原生链接行为，直接访问 appAddr，不加载下载弹窗。
    if (name === "download" && isMobileViewport()) return;
    event.preventDefault();
    event.stopPropagation();
    if (event.stopImmediatePropagation) event.stopImmediatePropagation();
    openDialog(name).catch(function () {});
  }, true);

  function appDownloadURL() {
    var el = document.querySelector("[data-app-download-url]");
    var url = el ? (el.getAttribute("data-app-download-url") || "").trim() : "";
    return url || "/download-app/";
  }

  // 付费内容统一入口：移动端直接跳下载地址，PC 弹下载二维码。
  function openDownloadApp() {
    if (isMobileViewport()) {
      global.location.href = appDownloadURL();
      return Promise.resolve();
    }
    return openDialog("download").catch(function () {
      global.location.href = appDownloadURL();
    });
  }

  global.ensureDialog = ensureDialog;
  global.openDownloadApp = openDownloadApp;
})(window);