Open Source Monorail

appengine/monorail/static/js/framework/framework-ajax.js

+/* Copyright 2016 The Chromium Authors. All Rights Reserved.
+ *
+ * Use of this source code is governed by a BSD-style
+ * license that can be found in the LICENSE file or at
+ * https://developers.google.com/open-source/licenses/bsd
+ */
+
+
+/**
+ * @fileoverview AJAX-related helper functions.
+ */
+
+
+/**
+ * Builds a POST string from a parameter dictionary.
+ * @param {Object} args parameters to encode.
+ * @param {boolean} opt_includeToken whether to include an XSRF token.
+ *   If unspecified, defaults to true. Requires the user to be logged in.
+ * @return {string} encoded POST data.
+ */
+function CS_postData(args, opt_token) {
+  var params = [];
+  for (var key in args) {
+    params.push(key + "=" + encodeURIComponent(String(args[key])));
+  }
+  if (opt_token) {
+    params.push('token=' + encodeURIComponent(opt_token));
+  } else if (opt_token !== false) {
+    params.push('token=' + encodeURIComponent(CS_env.token));
+  }
+  return params.join('&');
+}
+
+/**
+ * Helper for an extremely common kind of XHR: a POST with an XHRF token
+ * where we silently ignore server or connectivity errors.  If the token
+ * has expired, get a new one and retry the original request with the new
+ * token.
+ * @param {string} url request destination.
+ * @param {function(event)} callback function to be called
+ *   upon successful completion of the request.
+ * @param {Object} args parameters to encode as POST data.
+ */
+function CS_doPost(url, callback, args, opt_token, opt_tokenPath) {
+  if (isTokenExpired()) {
+    var refreshXHR = XH_XmlHttpCreate();
+    var refreshURL = '/hosting/tokenRefresh.do';
+    var refreshArgs = {
+        form_token: opt_token || CS_env.token,
+        form_token_path: opt_tokenPath || 'xhr'
+    };
+    var refreshCallback = function(event) {
+        var xhr = event.target;
+        if (xhr.readyState != 4 || xhr.status != 200)
+            return;
+        var resp = CS_parseJSON(xhr);
+        if (opt_tokenPath)
+            CS_env[opt_tokenPath] = resp.form_token;
+        CS_env.tokenExpiresSec = Number(resp.token_expires_sec);
+        var retryXh = XH_XmlHttpCreate();
+        XH_XmlHttpPOST(
+            retryXh, url, CS_postData(args, resp.form_token), callback);
+    };
+    XH_XmlHttpPOST(
+        refreshXHR, refreshURL, CS_postData(refreshArgs), refreshCallback);
+  } else {
+    var xh = XH_XmlHttpCreate();
+    XH_XmlHttpPOST(
+        xh, url,
+        CS_postData(args, CS_env[opt_tokenPath] || opt_token),
+        callback);
+  }
+}
+
+
+/**
+ * Helper function to strip leading junk characters from a JSON response
+ * and then parse it into a JS constant.
+ *
+ * The reason that "}])'\n" is prepended to the response text is that
+ * it makes it impossible for a hacker to hit one of our JSON servlets
+ * via a <script src="..."> tag and do anything with the result.  Even
+ * though a JSON response is just a constant, it could be passed into
+ * hacker code by tricks such as overriding the array constructor.
+ */
+function CS_parseJSON(xhr) {
+  return JSON.parse(xhr.responseText.substr(5));
+}
+
+
+function isTokenExpired(opt_tokenExpiresSec) {
+  var expiresSec = opt_tokenExpiresSec || CS_env.tokenExpiresSec;
+  var tokenExpiresDate = new Date(expiresSec * 1000);
+  return tokenExpiresDate <= new Date();
+}
+
+/**
+ * After we refresh the form token, we need to actually submit the form.
+ * formToSubmit keeps track of which form the user was trying to submit.
+ */
+var formToSubmit = null;
+
+/**
+ * If the form token that was generated when the page was served has
+ * now expired, then request a refreshed token from the server, and
+ * don't submit the form until after it arrives.
+ */
+function refreshTokens(event, formToken, formTokenPath, tokenExpiresSec) {
+  if (!isTokenExpired(tokenExpiresSec))
+    return;
+
+  formToSubmit = event.target;
+  event.preventDefault();
+  CS_doPost("/hosting/tokenRefresh.do", gotXSRFToken,
+            {form_token: formToken,
+             form_token_path: formTokenPath});
+}
+
+/**
+ * If we got a new XSRF token from the server, use it to actually
+ * submit the form that the user wanted to submit.
+ */
+function gotXSRFToken(event) {
+  var xhr = event.target;
+  if (xhr.readyState != 4 || xhr.status != 200)
+    return;
+  var resp = CS_parseJSON(xhr);
+  var freshFormToken = resp["form_token"];
+  var tokenFields = document.querySelectorAll("input[name=token]");
+  for (var i = 0; i < tokenFields.length; ++i) {
+      tokenFields[i].value = freshFormToken;
+  }
+  if (formToSubmit) {
+    formToSubmit.submit();
+  }
+}