Add trending links (#16917)

* Add trending links

* Add overriding specific links trendability

* Add link type to preview cards and only trend articles

Change trends review notifications from being sent every 5 minutes to being sent every 2 hours

Change threshold from 5 unique accounts to 15 unique accounts

* Fix tests

7 files changed, 101 insertions, 105 deletions

diff --git a/spec/controllers/admin/tags_controller_spec.rb b/spec/controllers/admin/tags_controller_spec.rb
index 9145d887d..85c801a9c 100644
--- a/spec/controllers/admin/tags_controller_spec.rb
+++ b/spec/controllers/admin/tags_controller_spec.rb
@@ -9,18 +9,6 @@ RSpec.describe Admin::TagsController, type: :controller do
     sign_in Fabricate(:user, admin: true)
   end
 
-  describe 'GET #index' do
-    let!(:tag) { Fabricate(:tag) }
-
-    before do
-      get :index
-    end
-
-    it 'returns status 200' do
-      expect(response).to have_http_status(200)
-    end
-  end
-
   describe 'GET #show' do
     let!(:tag) { Fabricate(:tag) }
 
diff --git a/spec/controllers/api/v1/trends/tags_controller_spec.rb b/spec/controllers/api/v1/trends/tags_controller_spec.rb
new file mode 100644
index 000000000..e2e26dcab
--- /dev/null
+++ b/spec/controllers/api/v1/trends/tags_controller_spec.rb
@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe Api::V1::Trends::TagsController, type: :controller do
+  render_views
+
+  describe 'GET #index' do
+    before do
+      trending_tags = double()
+
+      allow(trending_tags).to receive(:get).and_return(Fabricate.times(10, :tag))
+      allow(Trends).to receive(:tags).and_return(trending_tags)
+
+      get :index
+    end
+
+    it 'returns http success' do
+      expect(response).to have_http_status(200)
+    end
+  end
+end
diff --git a/spec/controllers/api/v1/trends_controller_spec.rb b/spec/controllers/api/v1/trends_controller_spec.rb
deleted file mode 100644
index 91e0d18fe..000000000
--- a/spec/controllers/api/v1/trends_controller_spec.rb
+++ /dev/null
@@ -1,18 +0,0 @@
-# frozen_string_literal: true
-
-require 'rails_helper'
-
-RSpec.describe Api::V1::TrendsController, type: :controller do
-  render_views
-
-  describe 'GET #index' do
-    before do
-      allow(TrendingTags).to receive(:get).and_return(Fabricate.times(10, :tag))
-      get :index
-    end
-
-    it 'returns http success' do
-      expect(response).to have_http_status(200)
-    end
-  end
-end
diff --git a/spec/helpers/settings_helper_spec.rb b/spec/helpers/languages_helper_spec.rb
index 092c37583..6db617824 100644
--- a/spec/helpers/settings_helper_spec.rb
+++ b/spec/helpers/languages_helper_spec.rb
@@ -2,20 +2,15 @@
 
 require 'rails_helper'
 
-describe SettingsHelper do
+describe LanguagesHelper do
   describe 'the HUMAN_LOCALES constant' do
     it 'includes all I18n locales' do
-      options = I18n.available_locales
-
-      expect(described_class::HUMAN_LOCALES.keys).to include(*options)
+      expect(described_class::HUMAN_LOCALES.keys).to include(*I18n.available_locales)
     end
   end
 
   describe 'human_locale' do
     it 'finds the human readable local description from a key' do
-      # Ensure the value is as we expect
-      expect(described_class::HUMAN_LOCALES[:en]).to eq('English')
-
       expect(helper.human_locale(:en)).to eq('English')
     end
   end
diff --git a/spec/mailers/previews/admin_mailer_preview.rb b/spec/mailers/previews/admin_mailer_preview.rb
index 561a56b78..75ffbbf40 100644
--- a/spec/mailers/previews/admin_mailer_preview.rb
+++ b/spec/mailers/previews/admin_mailer_preview.rb
@@ -5,4 +5,14 @@ class AdminMailerPreview < ActionMailer::Preview
   def new_pending_account
     AdminMailer.new_pending_account(Account.first, User.pending.first)
   end
+
+  # Preview this email at http://localhost:3000/rails/mailers/admin_mailer/new_trending_tags
+  def new_trending_tags
+    AdminMailer.new_trending_tags(Account.first, Tag.limit(3))
+  end
+
+  # Preview this email at http://localhost:3000/rails/mailers/admin_mailer/new_trending_links
+  def new_trending_links
+    AdminMailer.new_trending_links(Account.first, PreviewCard.limit(3))
+  end
 end
diff --git a/spec/models/trending_tags_spec.rb b/spec/models/trending_tags_spec.rb
deleted file mode 100644
index dfbc7d6f8..000000000
--- a/spec/models/trending_tags_spec.rb
+++ /dev/null
@@ -1,68 +0,0 @@
-require 'rails_helper'
-
-RSpec.describe TrendingTags do
-  describe '.record_use!' do
-    pending
-  end
-
-  describe '.update!' do
-    let!(:at_time) { Time.now.utc }
-    let!(:tag1) { Fabricate(:tag, name: 'Catstodon', trendable: true) }
-    let!(:tag2) { Fabricate(:tag, name: 'DogsOfMastodon', trendable: true) }
-    let!(:tag3) { Fabricate(:tag, name: 'OCs', trendable: true) }
-
-    before do
-      allow(Redis.current).to receive(:pfcount) do |key|
-        case key
-        when "activity:tags:#{tag1.id}:#{(at_time - 1.day).beginning_of_day.to_i}:accounts"
-          2
-        when "activity:tags:#{tag1.id}:#{at_time.beginning_of_day.to_i}:accounts"
-          16
-        when "activity:tags:#{tag2.id}:#{(at_time - 1.day).beginning_of_day.to_i}:accounts"
-          0
-        when "activity:tags:#{tag2.id}:#{at_time.beginning_of_day.to_i}:accounts"
-          4
-        when "activity:tags:#{tag3.id}:#{(at_time - 1.day).beginning_of_day.to_i}:accounts"
-          13
-        end
-      end
-
-      Redis.current.zadd('trending_tags', 0.9, tag3.id)
-      Redis.current.sadd("trending_tags:used:#{at_time.beginning_of_day.to_i}", [tag1.id, tag2.id])
-
-      tag3.update(max_score: 0.9, max_score_at: (at_time - 1.day).beginning_of_day + 12.hours)
-
-      described_class.update!(at_time)
-    end
-
-    it 'calculates and re-calculates scores' do
-      expect(described_class.get(10, filtered: false)).to eq [tag1, tag3]
-    end
-
-    it 'omits hashtags below threshold' do
-      expect(described_class.get(10, filtered: false)).to_not include(tag2)
-    end
-
-    it 'decays scores' do
-      expect(Redis.current.zscore('trending_tags', tag3.id)).to be < 0.9
-    end
-  end
-
-  describe '.trending?' do
-    let(:tag) { Fabricate(:tag) }
-
-    before do
-      10.times { |i| Redis.current.zadd('trending_tags', i + 1, Fabricate(:tag).id) }
-    end
-
-    it 'returns true if the hashtag is within limit' do
-      Redis.current.zadd('trending_tags', 11, tag.id)
-      expect(described_class.trending?(tag)).to be true
-    end
-
-    it 'returns false if the hashtag is outside the limit' do
-      Redis.current.zadd('trending_tags', 0, tag.id)
-      expect(described_class.trending?(tag)).to be false
-    end
-  end
-end
diff --git a/spec/models/trends/tags_spec.rb b/spec/models/trends/tags_spec.rb
new file mode 100644
index 000000000..4f98c6aa4
--- /dev/null
+++ b/spec/models/trends/tags_spec.rb
@@ -0,0 +1,67 @@
+require 'rails_helper'
+
+RSpec.describe Trends::Tags do
+  subject { described_class.new(threshold: 5, review_threshold: 10) }
+
+  let!(:at_time) { DateTime.new(2021, 11, 14, 10, 15, 0) }
+
+  describe '#add' do
+    let(:tag) { Fabricate(:tag) }
+
+    before do
+      subject.add(tag, 1, at_time)
+    end
+
+    it 'records history' do
+      expect(tag.history.get(at_time).accounts).to eq 1
+    end
+
+    it 'records use' do
+      expect(subject.send(:recently_used_ids, at_time)).to eq [tag.id]
+    end
+  end
+
+  describe '#get' do
+    pending
+  end
+
+  describe '#refresh' do
+    let!(:today) { at_time }
+    let!(:yesterday) { today - 1.day }
+
+    let!(:tag1) { Fabricate(:tag, name: 'Catstodon', trendable: true) }
+    let!(:tag2) { Fabricate(:tag, name: 'DogsOfMastodon', trendable: true) }
+    let!(:tag3) { Fabricate(:tag, name: 'OCs', trendable: true) }
+
+    before do
+      2.times  { |i| subject.add(tag1, i, yesterday) }
+      13.times { |i| subject.add(tag3, i, yesterday) }
+      16.times { |i| subject.add(tag1, i, today) }
+      4.times  { |i| subject.add(tag2, i, today) }
+    end
+
+    context do
+      before do
+        subject.refresh(yesterday + 12.hours)
+        subject.refresh(at_time)
+      end
+
+      it 'calculates and re-calculates scores' do
+        expect(subject.get(false, 10)).to eq [tag1, tag3]
+      end
+
+      it 'omits hashtags below threshold' do
+        expect(subject.get(false, 10)).to_not include(tag2)
+      end
+    end
+
+    it 'decays scores' do
+      subject.refresh(yesterday + 12.hours)
+      original_score = subject.score(tag3.id)
+      expect(original_score).to eq 144.0
+      subject.refresh(yesterday + 12.hours + subject.options[:max_score_halflife])
+      decayed_score = subject.score(tag3.id)
+      expect(decayed_score).to be <= original_score / 2
+    end
+  end
+end