Add sample for public Xero apps.

Author: Eric Koleda

samples/XeroPublic.gs

@@ -0,0 +1,109 @@
+/*
+ * Xero public applications guide:
+ * https://developer.xero.com/documentation/auth-and-limits/public-applications
+ *
+ * This script must be published as a web app (Publish > Deploy as web app) in
+ * order to function. The web app URL is used instead of the normal callback
+ * URL to work around a limitation in the Xero API's OAuth implementation
+ * (callback URLs are limited to 250 characters). Make sure to republish the
+ * web app after updating the code.
+ */
+
+var CONSUMER_KEY = '...';
+var CONSUMER_SECRET = '...';
+
+/**
+ * Authorizes and makes a request to the Xero API.
+ */
+function run() {
+  var service = getService();
+  if (service.hasAccess()) {
+    var url = 'https://api.xero.com/api.xro/2.0/Organisations';
+    var response = service.fetch(url, {
+      headers: {
+        Accept: 'application/json'
+      }
+    });
+    var result = JSON.parse(response.getContentText());
+    Logger.log(JSON.stringify(result, null, 2));
+  } else {
+    var authorizationUrl = service.authorize();
+    Logger.log('Open the following URL and re-run the script: %s',
+        authorizationUrl);
+  }
+}
+
+/**
+ * Reset the authorization state, so that it can be re-tested.
+ */
+function reset() {
+  var service = getService();
+  service.reset();
+}
+
+/**
+ * Configures the service.
+ */
+function getService() {
+  var service = OAuth1.createService('Xero')
+      // Set the endpoint URLs.
+      .setRequestTokenUrl('https://api.xero.com/oauth/RequestToken')
+      .setAuthorizationUrl('https://api.xero.com/oauth/Authorize')
+      .setAccessTokenUrl('https://api.xero.com/oauth/AccessToken')
+
+      // Set the consumer key and secret.
+      .setConsumerKey(CONSUMER_KEY)
+      .setConsumerSecret(CONSUMER_SECRET)
+
+      // Set the name of the callback function in the script referenced
+      // above that should be invoked to complete the OAuth flow.
+      .setCallbackFunction('authCallback')
+
+      // Set the property store where authorized tokens should be persisted.
+      .setPropertyStore(PropertiesService.getUserProperties());
+
+  // Override the callback URL method to use the web app URL instead.
+  service.getCallbackUrl = function() {
+    return ScriptApp.getService().getUrl();
+  };
+  
+  // Override the parseToken_ method to record the time granted.
+  var originalParseToken = service.parseToken_;
+  service.parseToken_ = function(content) {
+    var token = originalParseToken.apply(this, [content]);
+    token.granted_time = Math.floor((new Date()).getTime() / 1000);
+    return token;
+  }
+  
+  // Override the hasAccess method to handle token expiration.
+  var orginalHasAccess = service.hasAccess;
+  service.hasAccess = function() {
+    // First do the normal check.
+    if (!orginalHasAccess.apply(this)) return false;
+    
+    // Check to see if the access token has expired
+    // (or will expire in the next 60 seconds).
+    var token = this.getToken_();
+    var expiresTime = token.granted_time + Number(token.oauth_expires_in);
+    var now = Math.floor((new Date()).getTime() / 1000);
+    return (expiresTime - now) > 60;
+  }
+
+  return service;
+}
+
+/**
+ * Handles GET requests to the web app.
+ */
+function doGet(request) {
+  // Determine if the request is part of an OAuth callback.
+  if (request.parameter.oauth_token) {
+    var service = getService();
+    var authorized = service.handleCallback(request);
+    if (authorized) {
+      return HtmlService.createHtmlOutput('Success!');
+    } else {
+      return HtmlService.createHtmlOutput('Denied');
+    }
+  }
+}