Add card set filter on decklist search

app/resources/decklist_resource.rb

@@ -44,6 +44,16 @@ class DecklistResource < ApplicationResource
     end
   end
 
+  # Will return decklists where every card has at least one printing in the specified card set(s).
+  # Multiple values are treated as the union of card sets, matching the legacy /decklist/find?packs[] behavior.
+  filter :card_set_id, :string do
+    eq do |scope, card_set_ids|
+      card_ids = Printing.where(card_set_id: card_set_ids).select(:card_id)
+      decklists_with_other_cards = DecklistCard.where.not(card_id: card_ids).select(:decklist_id)
+      scope.where.not(id: decklists_with_other_cards)
+    end
+  end
+
   attribute :card_slots, :hash
   attribute :num_cards, :integer
   attribute :influence_spent, :integer

db/migrate/20260522120000_add_card_id_decklist_id_index_to_decklists_cards.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+class AddCardIdDecklistIdIndexToDecklistsCards < ActiveRecord::Migration[8.1]
+  def change
+    add_index :decklists_cards, %i[card_id decklist_id]
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.1].define(version: 2026_05_20_044700) do
+ActiveRecord::Schema[8.1].define(version: 2026_05_22_120000) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "pg_catalog.plpgsql"
   enable_extension "pgcrypto"
@@ -182,6 +182,7 @@
     t.string "card_id", null: false
     t.uuid "decklist_id", null: false
     t.integer "quantity", null: false
+    t.index ["card_id", "decklist_id"], name: "index_decklists_cards_on_card_id_and_decklist_id"
     t.index ["decklist_id", "card_id"], name: "index_decklists_cards_on_decklist_id_and_card_id", unique: true
   end
 

spec/resources/decklist_resource_reads_spec.rb

@@ -97,6 +97,44 @@
       end
     end
 
+    context 'with card_set_id' do
+      let!(:corp_decklist) { Decklist.find('11111111-1111-1111-1111-111111111111') }
+      let!(:runner_decklist) { Decklist.find('22222222-2222-2222-2222-222222222222') }
+
+      it 'returns decklists whose cards all have a printing in the set' do
+        params[:filter] = { card_set_id: { eq: 'core' } }
+        render
+        decklist_ids = d.map(&:id)
+
+        expect(decklist_ids).to include(corp_decklist.id)
+        expect(decklist_ids).to include(runner_decklist.id)
+      end
+
+      it 'excludes decklists with any card not printed in the set' do
+        params[:filter] = { card_set_id: { eq: 'midnight_sun' } }
+        render
+        decklist_ids = d.map(&:id)
+
+        expect(decklist_ids).not_to include(corp_decklist.id)
+        expect(decklist_ids).not_to include(runner_decklist.id)
+      end
+
+      it 'treats multiple card sets as a union of legal cards' do
+        params[:filter] = { card_set_id: { eq: 'core,midnight_sun' } }
+        render
+        decklist_ids = d.map(&:id)
+
+        expect(decklist_ids).to include(corp_decklist.id)
+        expect(decklist_ids).to include(runner_decklist.id)
+      end
+
+      it 'combines with faction_id' do
+        params[:filter] = { card_set_id: { eq: 'core' }, faction_id: { eq: 'criminal' } }
+        render
+        expect(d.map(&:id)).to eq([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') }