FIX: Sorting toggles on topic list (#24465)

- Correctly interpret string queryParams
- On first click of a new column, use "descending". Otherwise, toggle.
- Add system specs for behavior

spec/system/discovery_list_spec.rb

@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+describe "Topic list focus", type: :system do
+  fab!(:topics) { Fabricate.times(10, :post).map(&:topic) }
+  fab!(:reply) { Fabricate(:post, topic: topics.first) }
+
+  let(:discovery) { PageObjects::Pages::Discovery.new }
+
+  def nth_topic_id(n)
+    discovery.topic_list.find(".topic-list-item:nth-of-type(#{n})")["data-topic-id"]
+  end
+
+  it "can sort a topic list by activity" do
+    visit "/latest"
+    expect(discovery.topic_list).to have_topics(count: 10)
+    newest_topic_id = nth_topic_id(1)
+
+    find("th[data-sort-order='activity']").click
+
+    expect(page).to have_css("th[data-sort-order='activity'][aria-sort=ascending]")
+    expect(nth_topic_id(10)).to eq(newest_topic_id)
+
+    find("th[data-sort-order='activity']").click
+    expect(page).to have_css("th[data-sort-order='activity'][aria-sort=descending]")
+    expect(nth_topic_id(1)).to eq(newest_topic_id)
+  end
+
+  it "can sort a topic list by replies" do
+    visit "/latest"
+    expect(discovery.topic_list).to have_topics(count: 10)
+
+    find("th[data-sort-order='posts']").click
+
+    expect(page).to have_css("th[data-sort-order='posts'][aria-sort=descending]")
+    expect(nth_topic_id(1)).to eq(reply.topic_id.to_s)
+
+    find("th[data-sort-order='posts']").click
+    expect(page).to have_css("th[data-sort-order='posts'][aria-sort=ascending]")
+    expect(nth_topic_id(10)).to eq(reply.topic_id.to_s)
+  end
+end