Improve PR, adding more comments

server/notifications/email.js

@@ -1,6 +1,6 @@
-// cache the email text in a queue, and send them in a batch
+// buffer each user's email text in a queue, then flush them in single email
 Meteor.startup(() => {
-  Notifications.subscribe('cachedEmail', (user, title, description, params) => {
+  Notifications.subscribe('email', (user, title, description, params) => {
     // add quote to make titles easier to read in email text
     const quoteParams = _.clone(params);
     ['card', 'list', 'oldList', 'board', 'comment'].forEach((key) => {
@@ -8,28 +8,34 @@ Meteor.startup(() => {
     });
 
     const text = `${params.user} ${TAPi18n.__(description, quoteParams, user.getLanguage())}\n${params.url}`;
-    user.addEmailCache(text);
+    user.addEmailBuffer(text);
 
+    // unlike setTimeout(func, delay, args),
+    // Meteor.setTimeout(func, delay) does not accept args :-(
+    // so we pass userId with closure
     const userId = user._id;
     Meteor.setTimeout(() => {
       const user = Users.findOne(userId);
 
-      const emailCache = user.getEmailCache();
-      if (emailCache.length === 0) return;
+      // for each user, in the timed period, only the first call will get the cached content,
+      // other calls will get nothing
+      const texts = user.getEmailBuffer();
+      if (texts.length === 0) return;
 
-      const text = emailCache.join('\n\n');
-      user.clearEmailCache();
+      // merge the cached content into single email and flush
+      const text = texts.join('\n\n');
+      user.clearEmailBuffer();
 
       try {
         Email.send({
           to: user.emails[0].address,
           from: Accounts.emailTemplates.from,
-          subject : TAPi18n.__('act-activity-notify', {}, user.getLanguage()),
+          subject: TAPi18n.__('act-activity-notify', {}, user.getLanguage()),
           text,
         });
       } catch (e) {
         return;
       }
-    }, 30000, user._id);
+    }, 30000);
   });
 });