Add a new Calendar advanced service example.

Author: Ryan Roth

advanced/calendar.gs

@@ -129,3 +129,72 @@ function parseDate(string) {
   return new Date(parts.join(' '));
 }
 // [END listNext10Events]
+
+// [START logSyncedEvents]
+
+/**
+ * Retrieve and log events from the given calendar that have been modified
+ * since the last sync. If the sync token is missing or invalid, log all
+ * events from up to a month ago (a full sync).
+ *
+ * @param calendarId The ID of the calender to retrieve events from.
+ * @param fullSync If true, throw out any existing sync token and perform a full sync;
+ *        if false, use the existing sync token if possible.
+ */
+function logSyncedEvents(calendarId, fullSync) {
+  var properties = PropertiesService.getUserProperties();
+  var pageToken;
+  var options = {
+    maxResults: 100
+  };
+  var syncToken = properties.getProperty('syncToken');
+  if (syncToken && !fullSync) {
+    options['syncToken'] = syncToken;
+  } else {
+    // Sync events up to thirty days in the past.
+    options['timeMin'] = getRelativeDate(-30,0).toISOString();
+  }
+
+  // Retrieve events, one page at a time.
+  var events;
+  do {
+    try {
+      options['pageToken'] = pageToken;
+      events = Calendar.Events.list(calendarId, options);
+    } catch (e) {
+      // Check to see if the sync token was invalidated by the server;
+      // if so, perform a full sync instead.
+      if (e.message === "Sync token is no longer valid, a full sync is required." ) {
+        properties.deleteProperty('syncToken');
+        logSyncedEvents(calendarId, true);
+        return;
+      } else {
+        throw e.message;
+      }
+    }
+    
+    if (events.items && events.items.length > 0) {
+      for(var i = 0; i < events.items.length; i++) {
+         var event = events.items[i];
+         if (event.status === 'cancelled') {
+           console.log('Event id %s was cancelled.', event.id);
+         } else if (event.start.date) {
+           // All-day event.
+           var start = parseDate(event.start.date);
+           console.log('%s (%s)', event.summary, start.toLocaleDateString());
+         } else {
+           var start = parseDate(event.start.dateTime);
+           console.log('%s (%s)', event.summary, start.toLocaleString());
+         }
+      }
+    } else {
+      console.log('No events found.');
+    }
+
+    pageToken = events.nextPageToken;
+  } while (pageToken);
+  
+  properties.setProperty('syncToken', events.nextSyncToken);
+}
+
+// [END logSyncedEvents]