Fix decklist card exclusion filter and add tests

app/resources/decklist_resource.rb

@@ -29,19 +29,18 @@ class DecklistResource < ApplicationResource
   # Will return decklists where all cards specified are present.
   filter :card_id, :string do
     eq do |scope, card_ids|
-      scope.joins(:decklist_cards)
-           .where(decklist_cards: { card_id: card_ids })
-           .group('decklists.id')
-           .having('COUNT(DISTINCT decklist_cards.card_id) = ?', card_ids.length)
+      matching = DecklistCard.where(card_id: card_ids)
+                             .group(:decklist_id)
+                             .having('COUNT(DISTINCT card_id) = ?', card_ids.length)
+                             .select(:decklist_id)
+      scope.where(id: matching)
     end
   end
 
   # Will return decklists that do NOT contain any of the specified cards.
   filter :exclude_card_id, :string do
     eq do |scope, card_ids|
-      scope.left_joins(:decklist_cards)
-           .group('decklists.id')
-           .having('COUNT(CASE WHEN decklists_cards.card_id IN (?) THEN 1 END) = 0', card_ids)
+      scope.where.not(id: DecklistCard.where(card_id: card_ids).select(:decklist_id))
     end
   end
 

spec/resources/decklist_resource_reads_spec.rb

@@ -96,6 +96,35 @@
         expect(decklist_ids).to include(runner_decklist.id)
       end
     end
+
+    context 'with card_id and exclude_card_id combined' do
+      let!(:corp_decklist) { Decklist.find('11111111-1111-1111-1111-111111111111') }
+      let!(:runner_decklist) { Decklist.find('22222222-2222-2222-2222-222222222222') }
+
+      it 'returns the decklist that contains the card and lacks the excluded card' do
+        params[:filter] = { card_id: { eq: 'pennyshaver' }, exclude_card_id: { eq: 'hedge_fund' } }
+        render
+        expect(d.map(&:id)).to eq([runner_decklist.id])
+      end
+
+      it 'returns no decklists when the contained card is also excluded' do
+        params[:filter] = { card_id: { eq: 'pennyshaver' }, exclude_card_id: { eq: 'pennyshaver' } }
+        render
+        expect(d).to be_empty
+      end
+
+      it 'returns no decklists when the only matching decklist also has the excluded card' do
+        params[:filter] = { card_id: { eq: 'pennyshaver' }, exclude_card_id: { eq: 'stargate' } }
+        render
+        expect(d).to be_empty
+      end
+
+      it 'returns the decklist when the excluded card is absent from the matching decklist' do
+        params[:filter] = { card_id: { eq: 'adonis_campaign' }, exclude_card_id: { eq: 'stargate' } }
+        render
+        expect(d.map(&:id)).to eq([corp_decklist.id])
+      end
+    end
   end
 
   describe 'sideloading' do