FEATURE: Allow selective dismissal of new and unread topics (#12976)

This PR improves the UI of bulk select so that its context is applied to the Dismiss Unread and Dismiss New buttons. Regular users (not just staff) are now able to use topic bulk selection on the /new and /unread routes to perform these dismiss actions more selectively.

For Dismiss Unread, there is a new count in the text of the button and in the modal when one or more topic is selected with the bulk select checkboxes.

For Dismiss New, there is a count in the button text, and we have added functionality to the server side to accept an array of topic ids to dismiss new for, instead of always having to dismiss all new, the same as the bulk dismiss unread functionality. To clean things up, the `DismissTopics` service has been rolled into the `TopicsBulkAction` service.

We now also show the top Dismiss/Dismiss New button based on whether the bottom one is in the viewport, not just based on the topic count.

lib/topics_bulk_action.rb

@@ -14,7 +14,7 @@ class TopicsBulkAction
     @operations ||= %w(change_category close archive change_notification_level
                        reset_read dismiss_posts delete unlist archive_messages
                        move_messages_to_inbox change_tags append_tags remove_tags
-                       relist)
+                       relist dismiss_topics)
   end
 
   def self.register_operation(name, &block)
@@ -26,7 +26,7 @@ class TopicsBulkAction
     raise Discourse::InvalidParameters.new(:operation) unless TopicsBulkAction.operations.include?(@operation[:type])
     # careful these are private methods, we need send
     send(@operation[:type])
-    @changed_ids
+    @changed_ids.sort
   end
 
   private
@@ -81,6 +81,24 @@ class TopicsBulkAction
     @changed_ids.concat @topic_ids
   end
 
+  def dismiss_topics
+    rows = Topic.where(id: @topic_ids)
+      .joins("LEFT JOIN topic_users ON topic_users.topic_id = topics.id AND topic_users.user_id = #{@user.id}")
+      .where("topics.created_at >= ?", dismiss_topics_since_date)
+      .where("topic_users.last_read_post_number IS NULL")
+      .where("topics.archetype <> ?", Archetype.private_message)
+      .order("topics.created_at DESC")
+      .limit(SiteSetting.max_new_topics).map do |topic|
+      {
+        topic_id: topic.id,
+        user_id: @user.id,
+        created_at: Time.zone.now
+      }
+    end
+    DismissedTopicUser.insert_all(rows) if rows.present?
+    @changed_ids = rows.map { |row| row[:topic_id] }
+  end
+
   def reset_read
     PostTiming.destroy_for(@user.id, @topic_ids)
   end
@@ -211,4 +229,18 @@ class TopicsBulkAction
     @topics ||= Topic.where(id: @topic_ids)
   end
 
+  def dismiss_topics_since_date
+    new_topic_duration_minutes = @user.user_option&.new_topic_duration_minutes || SiteSetting.default_other_new_topic_duration_minutes
+    setting_date =
+      case new_topic_duration_minutes
+      when User::NewTopicDuration::LAST_VISIT
+        @user.previous_visit_at || @user.created_at
+      when User::NewTopicDuration::ALWAYS
+        @user.created_at
+      else
+        new_topic_duration_minutes.minutes.ago
+      end
+    [setting_date, @user.created_at, Time.at(SiteSetting.min_new_topics_time).to_datetime].max
+  end
+
 end