FEATURE: new site setting suggested_topics_max_days_old

config/locales/server.en.yml

@@ -1036,6 +1036,7 @@ en:
 
     suggested_topics: "Number of suggested topics shown at the bottom of a topic."
     limit_suggested_to_category: "Only show topics from the current category in suggested topics."
+    suggested_topics_max_days_old: "Suggested topics should not be more than n days old."
 
     clean_up_uploads: "Remove orphan unreferenced uploads to prevent illegal hosting. WARNING: you may want to back up of your /uploads directory before enabling this setting."
     clean_orphan_uploads_grace_period_hours: "Grace period (in hours) before an orphan upload is removed."

config/site_settings.yml

@@ -77,6 +77,10 @@ basic:
     min: 0
   limit_suggested_to_category:
     default: false
+  suggested_topics_max_days_old:
+    default: 365
+    min: 7
+    max: 10000
   track_external_right_clicks:
     client: true
     default: false

lib/suggested_topics_builder.rb

@@ -26,6 +26,9 @@ class SuggestedTopicsBuilder
       results = results.where(category_id: @category_id)
     end
 
+    # Suggested topics should not be more than n days old
+    results = results.where("topics.created_at > ?", SiteSetting.suggested_topics_max_days_old.days.ago)
+
     results = results.to_a.reject { |topic| @category_topic_ids.include?(topic.id) }
 
     unless results.empty?

spec/components/suggested_topics_builder_spec.rb

@@ -95,6 +95,21 @@ describe SuggestedTopicsBuilder do
       end
     end
 
+    context "adding topics that are more than n days old" do
+      let!(:new_topic) { Fabricate(:topic, created_at: 2.days.ago) }
+      let!(:old_topic) { Fabricate(:topic, created_at: 3.years.ago) }
+
+      it "adds topics based on suggested_topics_max_days_old setting" do
+        SiteSetting.suggested_topics_max_days_old = 365
+
+        builder.add_results(Topic)
+        expect(builder.size).to eq(1)
+        expect(builder).not_to be_full
+        expect(builder.excluded_topic_ids.include?(old_topic.id)).to eq(false)
+        expect(builder.excluded_topic_ids.include?(new_topic.id)).to eq(true)
+      end
+    end
+
     context "category definition topics" do
       let!(:category) { Fabricate(:category) }