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

1 files changed, 49 insertions, 0 deletions

diff --git a/app/models/preview_card_provider_filter.rb b/app/models/preview_card_provider_filter.rb
new file mode 100644
index 000000000..1e90d3c9d
--- /dev/null
+++ b/app/models/preview_card_provider_filter.rb
@@ -0,0 +1,49 @@
+# frozen_string_literal: true
+
+class PreviewCardProviderFilter
+  KEYS = %i(
+    status
+  ).freeze
+
+  attr_reader :params
+
+  def initialize(params)
+    @params = params
+  end
+
+  def results
+    scope = PreviewCardProvider.unscoped
+
+    params.each do |key, value|
+      next if key.to_s == 'page'
+
+      scope.merge!(scope_for(key, value.to_s.strip)) if value.present?
+    end
+
+    scope.order(domain: :asc)
+  end
+
+  private
+
+  def scope_for(key, value)
+    case key.to_s
+    when 'status'
+      status_scope(value)
+    else
+      raise "Unknown filter: #{key}"
+    end
+  end
+
+  def status_scope(value)
+    case value.to_s
+    when 'approved'
+      PreviewCardProvider.trendable
+    when 'rejected'
+      PreviewCardProvider.not_trendable
+    when 'pending_review'
+      PreviewCardProvider.pending_review
+    else
+      raise "Unknown status: #{value}"
+    end
+  end
+end