FEATURE: warn about mailing list mode if it is checked

app/assets/javascripts/discourse/components/preference-checkbox.js.es6

@@ -3,5 +3,17 @@ export default Em.Component.extend({
 
   label: function() {
     return I18n.t(this.get('labelKey'));
-  }.property('labelKey')
+  }.property('labelKey'),
+
+  click() {
+    const warning = this.get('warning');
+
+    if (warning && !this.get('checked')) {
+      debugger;
+      this.sendAction('warning');
+      return false;
+    }
+
+    return true;
+  }
 });

app/assets/javascripts/discourse/controllers/preferences.js.es6

@@ -106,6 +106,22 @@ export default Ember.Controller.extend(CanCheckEmails, {
 
   actions: {
 
+    checkMailingList(){
+      Em.run.next(()=>{
+        const postsPerDay = this.get('model.mailing_list_posts_per_day');
+        if (!postsPerDay || postsPerDay < 2) {
+          this.set('model.user_option.mailing_list_mode', true);
+          return;
+        }
+
+        bootbox.confirm(I18n.t("user.enable_mailing_list", {count: postsPerDay}), I18n.t("no_value"), I18n.t("yes_value"), (success) => {
+          if (success) {
+            this.set('model.user_option.mailing_list_mode', true);
+          }
+        });
+      });
+    },
+
     save() {
       this.set('saved', false);
 

app/assets/javascripts/discourse/templates/user/preferences.hbs

@@ -186,7 +186,7 @@
       {{preference-checkbox labelKey="user.email_private_messages" checked=model.user_option.email_private_messages}}
       {{preference-checkbox labelKey="user.email_direct" checked=model.user_option.email_direct}}
       {{#unless siteSettings.disable_mailing_list_mode}}
-        {{preference-checkbox labelKey="user.mailing_list_mode" checked=model.user_option.mailing_list_mode}}
+        {{preference-checkbox warning="checkMailingList" labelKey="user.mailing_list_mode" checked=model.user_option.mailing_list_mode}}
       {{/unless}}
       {{preference-checkbox labelKey="user.email_always" checked=model.user_option.email_always}}
       {{#unless model.user_option.email_always}}

app/models/post.rb

@@ -451,6 +451,16 @@ class Post < ActiveRecord::Base
     PostCreator.before_create_tasks(self)
   end
 
+  def self.estimate_posts_per_day
+    val = $redis.get("estimated_posts_per_day")
+    return val.to_i if val
+
+    posts_per_day = Topic.listable_topics.secured.joins(:posts).merge(Post.created_since(30.days.ago)).count / 30
+    $redis.setex("estimated_posts_per_day", 1.day.to_i, posts_per_day.to_s)
+    posts_per_day
+
+  end
+
   # This calculates the geometric mean of the post timings and stores it along with
   # each post.
   def self.calculate_avg_time(min_topic_age=nil)

app/serializers/user_serializer.rb

@@ -95,7 +95,8 @@ class UserSerializer < BasicUserSerializer
                      :has_title_badges,
                      :card_image_badge,
                      :card_image_badge_id,
-                     :muted_usernames
+                     :muted_usernames,
+                     :mailing_list_posts_per_day
 
   untrusted_attributes :bio_raw,
                        :bio_cooked,
@@ -109,6 +110,11 @@ class UserSerializer < BasicUserSerializer
   ### ATTRIBUTES
   ###
 
+  def mailing_list_posts_per_day
+    val = Post.estimate_posts_per_day
+    [val,SiteSetting.max_emails_per_day_per_user].min
+  end
+
   def groups
     if scope.is_admin? || object.id == scope.user.try(:id)
       object.groups

config/locales/client.en.yml

@@ -661,6 +661,10 @@ en:
       other_settings: "Other"
       categories_settings: "Categories"
 
+      enable_mailing_list:
+        one: "Are you sure you want to be emailed for every new post?"
+        other: "Are you sure you want to be emailed for every new post?<br><br>This will result in approximately <b>{{count}} emails</b> per day."
+
       new_topic_duration:
         label: "Consider topics new when"
         not_viewed: "I haven't viewed them yet"