FEATURE: Inline topic summary. Cached version accessible to everyone. (#22551)

* FEATURE:  Inline topic summary. Cached version accessible to everyone.

Anons and non-members of the `custom_summarization_allowed_groups_map` groups can see cached summaries for any accessible topic. After the first 12 hours and if the posts to summarize have changed, allowed users clicking on the button will automatically re-generate it.

* Ensure chat summaries work and prevent model hallucinations when there are no messages.

spec/lib/summarization/base_spec.rb

@@ -1,24 +1,67 @@
 # frozen_string_literal: true
 
 describe Summarization::Base do
-  subject(:summarization) { described_class.new }
-
   fab!(:user) { Fabricate(:user) }
   fab!(:group) { Fabricate(:group) }
+  fab!(:topic) { Fabricate(:topic) }
 
-  before { group.add(user) }
+  let(:plugin) { Plugin::Instance.new }
 
-  describe "#can_request_summaries?" do
-    it "returns true if the user group is present in the custom_summarization_allowed_groups_map setting" do
-      SiteSetting.custom_summarization_allowed_groups = group.id
+  before do
+    group.add(user)
 
-      expect(summarization.can_request_summaries?(user)).to eq(true)
+    strategy = DummyCustomSummarization.new("dummy")
+    plugin.register_summarization_strategy(strategy)
+    SiteSetting.summarization_strategy = strategy.model
+  end
+
+  describe "#can_see_summary?" do
+    context "when the user cannot generate a summary" do
+      before { SiteSetting.custom_summarization_allowed_groups = "" }
+
+      it "returns false" do
+        SiteSetting.custom_summarization_allowed_groups = ""
+
+        expect(described_class.can_see_summary?(topic, user)).to eq(false)
+      end
+
+      it "returns true if there is a cached summary" do
+        SummarySection.create!(
+          target: topic,
+          summarized_text: "test",
+          original_content_sha: "123",
+          algorithm: "test",
+          meta_section_id: nil,
+        )
+
+        expect(described_class.can_see_summary?(topic, user)).to eq(true)
+      end
     end
 
-    it "returns false if the user group is not present in the custom_summarization_allowed_groups_map setting" do
-      SiteSetting.custom_summarization_allowed_groups = ""
+    context "when the user can generate a summary" do
+      before { SiteSetting.custom_summarization_allowed_groups = group.id }
 
-      expect(summarization.can_request_summaries?(user)).to eq(false)
+      it "returns true if the user group is present in the custom_summarization_allowed_groups_map setting" do
+        expect(described_class.can_see_summary?(topic, user)).to eq(true)
+      end
+    end
+
+    context "when there is no user" do
+      it "returns false for anons" do
+        expect(described_class.can_see_summary?(topic, nil)).to eq(false)
+      end
+
+      it "returns true for anons when there is a cached summary" do
+        SummarySection.create!(
+          target: topic,
+          summarized_text: "test",
+          original_content_sha: "123",
+          algorithm: "test",
+          meta_section_id: nil,
+        )
+
+        expect(described_class.can_see_summary?(topic, nil)).to eq(true)
+      end
     end
   end
 end