FEATURE: show watched first post in user page

app/assets/javascripts/discourse/models/user.js.es6

@@ -182,8 +182,9 @@ const User = RestModel.extend({
 
     var updatedState = {};
 
-    ['muted','watched','tracked'].forEach(s => {
-      let cats = this.get(s + 'Categories').map(c => c.get('id'));
+    ['muted','watched','tracked','watched_first_post'].forEach(s => {
+      let prop = s === "watched_first_post" ? "watchedFirstPostCategories" : s + "Categories";
+      let cats = this.get(prop).map(c => c.get('id'));
       updatedState[s + '_category_ids'] = cats;
 
       // HACK: denote lack of categories
@@ -360,14 +361,9 @@ const User = RestModel.extend({
     this.set("watchedCategories", Discourse.Category.findByIds(this.watched_category_ids));
   },
 
-  changedCategoryNotifications: function(type) {
-    const ids = this.get(type + "Categories").map(c => c.id);
-    const oldIds = this.get(type + "_category_ids");
-
-    return {
-      add: _.difference(ids, oldIds),
-      remove: _.difference(oldIds, ids),
-    };
+  @observes("watched_first_post_category_ids")
+  updateWatchedFirstPostCategories() {
+    this.set("watchedFirstPostCategories", Discourse.Category.findByIds(this.watched_first_post_category_ids));
   },
 
   @computed("can_delete_account", "reply_count", "topic_count")

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

@@ -264,6 +264,11 @@
         {{category-group categories=model.trackedCategories blacklist=selectedCategories}}
       </div>
       <div class="instructions">{{i18n 'user.tracked_categories_instructions'}}</div>
+      <div class="controls category-controls">
+        <label><span class="icon fa fa-dot-circle-o watching-first-post"></span> {{i18n 'user.watched_first_post_categories'}}</label>
+        {{category-group categories=model.watchedFirstPostCategories}}
+      </div>
+      <div class="instructions">{{i18n 'user.watched_first_post_categories_instructions'}}</div>
       <div class="controls category-controls">
         <label><span class="icon fa fa-times-circle muted"></span> {{i18n 'user.muted_categories'}}</label>
         {{category-group categories=model.mutedCategories blacklist=selectedCategories}}

app/assets/stylesheets/common/base/user.scss

@@ -288,3 +288,7 @@ and (max-width : 600px) {
     border: none;
   }
 }
+
+.user-preferences .watching-first-post.fa-dot-circle-o {
+  color: dark-light-choose(scale-color($primary, $lightness: 50%), scale-color($secondary, $lightness: 50%));
+}

app/serializers/user_serializer.rb

@@ -88,6 +88,7 @@ class UserSerializer < BasicUserSerializer
                      :muted_tags,
                      :tracked_category_ids,
                      :watched_category_ids,
+                     :watched_first_post_category_ids,
                      :private_messages_stats,
                      :system_avatar_upload_id,
                      :system_avatar_template,
@@ -273,6 +274,10 @@ class UserSerializer < BasicUserSerializer
     CategoryUser.lookup(object, :watching).pluck(:category_id)
   end
 
+  def watched_first_post_category_ids
+    CategoryUser.lookup(object, :watching_first_post).pluck(:category_id)
+  end
+
   def muted_usernames
     MutedUser.where(user_id: object.id).joins(:muted_user).pluck(:username)
   end

app/services/user_updater.rb

@@ -1,6 +1,7 @@
 class UserUpdater
 
   CATEGORY_IDS = {
+    watched_first_post_category_ids: :watching_first_post,
     watched_category_ids: :watching,
     tracked_category_ids: :tracking,
     muted_category_ids: :muted

config/locales/client.en.yml

@@ -550,6 +550,8 @@ en:
       watched_categories_instructions: "You will automatically watch all topics in these categories. You will be notified of all new posts and topics, and a count of new posts will also appear next to the topic."
       tracked_categories: "Tracked"
       tracked_categories_instructions: "You will automatically track all new topics in these categories. A count of new posts will appear next to the topic."
+      watched_first_post_categories: "Watching First Post Only"
+      watched_first_post_categories_instructions: "You will be notified of the first post in each new topic in these categories."
       muted_categories: "Muted"
       muted_categories_instructions: "You will not be notified of anything about new topics in these categories, and they will not appear in latest."
       delete_account: "Delete My Account"