1 files changed, 53 insertions, 0 deletions
diff --git a/app/models/preview_card_filter.rb b/app/models/preview_card_filter.rb
new file mode 100644
index 000000000..8dda9989c
--- /dev/null
+++ b/app/models/preview_card_filter.rb
@@ -0,0 +1,53 @@
+# frozen_string_literal: true
+
+class PreviewCardFilter
+  KEYS = %i(
+    trending
+  ).freeze
+
+  attr_reader :params
+
+  def initialize(params)
+    @params = params
+  end
+
+  def results
+    scope = PreviewCard.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
+  end
+
+  private
+
+  def scope_for(key, value)
+    case key.to_s
+    when 'trending'
+      trending_scope(value)
+    else
+      raise "Unknown filter: #{key}"
+    end
+  end
+
+  def trending_scope(value)
+    ids = begin
+      case value.to_s
+      when 'allowed'
+        Trends.links.currently_trending_ids(true, -1)
+      else
+        Trends.links.currently_trending_ids(false, -1)
+      end
+    end
+
+    if ids.empty?
+      PreviewCard.none
+    else
+      PreviewCard.joins("join unnest(array[#{ids.map(&:to_i).join(',')}]::integer[]) with ordinality as x (id, ordering) on preview_cards.id = x.id").order('x.ordering')
+    end
+  end
+end