Implement remaining Academy Elite ability

lib/magic/cards/academy_elite.rb

@@ -16,7 +16,23 @@ def perform
       end
 
       def etb_triggers = [ETB]
-    end
 
+      class ActivatedAbility < ActivatedAbility
+        def costs
+          [
+            Costs::Mana.new(generic: 2, blue: 1),
+            Costs::RemoveCounter.new(source, Counters::Plus1Plus1),
+          ]
+        end
+
+        def resolve!
+          game.add_effect(Effects::DrawCards.new(source: source, player: source.controller))
+
+          game.choices.add(Magic::Choice::Discard.new(player: source.controller))
+        end
+      end
+
+      def activated_abilities = [ActivatedAbility]
+    end
   end
 end

lib/magic/costs/remove_counter.rb

@@ -0,0 +1,20 @@
+module Magic
+  module Costs
+    class RemoveCounter
+      attr_reader :source, :counter_class
+
+      def initialize(source, counter_class)
+        @source = source
+        @counter_class = counter_class
+      end
+
+      def can_pay?
+        source.counters.count(counter_class) > 0
+      end
+
+      def finalize!(_player)
+        source.remove_counter(counter_class)
+      end
+    end
+  end
+end

lib/magic/events/counter_removed.rb

@@ -0,0 +1,18 @@
+module Magic
+  module Events
+    class CounterRemoved
+      attr_reader :permanent, :player, :counter_type, :amount
+
+      def initialize(permanent: nil, player: nil, counter_type:, amount:)
+        @permanent = permanent
+        @player = player
+        @counter_type = counter_type
+        @amount = amount
+      end
+
+      def inspect
+        "#<Events::CounterRemoved player: #{player&.name}, permanent: #{permanent&.name}, type: #{counter_type}, amount: #{amount}>"
+      end
+    end
+  end
+end

lib/magic/permanent.rb

@@ -261,6 +261,25 @@ def add_counter(counter_type, amount: 1)
       game.notify!(counter_added)
     end
 
+    def remove_counter(counter_type, amount: 1)
+      removable_counters = @counters.select { |counter| counter.is_a?(counter_type) }.first(amount)
+      if removable_counters.count < amount
+        raise "Not enough #{counter_type} counters to remove"
+      end
+
+      events = []
+      removable_counters.each do |counter|
+        @counters.delete(counter)
+        events << Events::CounterRemoved.new(
+          permanent: self,
+          counter_type: counter_type,
+          amount: amount
+        )
+      end
+
+      game.notify!(events)
+    end
+
     def target_choices
       card.target_choices(self)
     end

spec/cards/academy_elite_spec.rb

@@ -3,55 +3,78 @@
 RSpec.describe Magic::Cards::AcademyElite do
   include_context "two player game"
 
-  subject(:academy_elite) { Card("Academy Elite") }
+  context "ETB effects" do
+    subject(:academy_elite) { Card("Academy Elite", owner: p1) }
 
-  before do
-    p1.hand.add(subject)
-  end
-
-  context "when there's a single instant in opponent's graveyard" do
     before do
-      p2.graveyard.add(Card("Shock"))
+      p1.hand.add(subject)
     end
 
-    context "when it enters the battlefield" do
-      it "gets 1 +1/+1 counter" do
-        p1.add_mana(blue: 4)
-        p1.cast(card: academy_elite) do
-          _1.pay_mana(generic: { blue: 3 }, blue: 1)
+    context "when there's a single instant in opponent's graveyard" do
+      before do
+        p2.graveyard.add(Card("Shock"))
+      end
+
+      context "when it enters the battlefield" do
+        it "gets 1 +1/+1 counter" do
+          p1.add_mana(blue: 4)
+          p1.cast(card: academy_elite) do
+            _1.pay_mana(generic: { blue: 3 }, blue: 1)
+          end
+          game.tick!
+
+          permanent = p1.permanents.last
+          expect(permanent.counters.first).to be_a(Magic::Counters::Plus1Plus1)
+          expect(permanent.power).to eq(1)
+          expect(permanent.toughness).to eq(1)
         end
-        game.tick!
+      end
+    end
 
-        permanent = p1.permanents.last
-        expect(permanent.counters.first).to be_a(Magic::Counters::Plus1Plus1)
-        expect(permanent.power).to eq(1)
-        expect(permanent.toughness).to eq(1)
+    context "when there's an instant and sorcery in opponent's graveyard" do
+      before do
+        p2.graveyard.add(Card("Shock"))
+        p2.graveyard.add(Card("Legion's Judgement"))
+      end
+
+      context "when it enters the battlefield" do
+        it "gets 2 +1/+1 counters" do
+          p1.add_mana(blue: 4)
+          p1.cast(card: academy_elite) do
+            _1.pay_mana(generic: { blue: 3 }, blue: 1)
+          end
+          game.tick!
+
+          permanent = p1.permanents.last
+          expect(permanent.counters.first).to be_a(Magic::Counters::Plus1Plus1)
+          expect(permanent.power).to eq(2)
+          expect(permanent.toughness).to eq(2)
+        end
       end
     end
   end
 
-  context "when there's an instant and sorcery in opponent's graveyard" do
+  context "activated ability" do
+    let(:academy_elite) { ResolvePermanent("Academy Elite", owner: p1) }
+
     before do
-      p2.graveyard.add(Card("Shock"))
-      p2.graveyard.add(Card("Legion's Judgement"))
+      academy_elite.add_counter(Magic::Counters::Plus1Plus1)
     end
 
-    context "when it enters the battlefield" do
-      it "gets 2 +1/+1 counters" do
-        p1.add_mana(blue: 4)
-        p1.cast(card: academy_elite) do
-          _1.pay_mana(generic: { blue: 3 }, blue: 1)
-        end
-        game.tick!
-
-        permanent = p1.permanents.last
-        expect(permanent.counters.first).to be_a(Magic::Counters::Plus1Plus1)
-        expect(permanent.power).to eq(2)
-        expect(permanent.toughness).to eq(2)
+    it "removes a +1/+1 counter, draws a card and discards a card" do
+      expect(p1).to receive(:draw!)
 
+      p1.add_mana(blue: 3)
+      p1.activate_ability(ability: academy_elite.activated_abilities.first) do
+        _1.pay_mana(generic: { blue: 2 }, blue: 1)
       end
+
+      expect(academy_elite.counters.count).to eq(0)
+
+      choice = game.choices.last
+      expect(choice).to be_a(Magic::Choice::Discard)
+      choice.choose(p1.hand.cards.first)
+      expect(p1.graveyard.cards.count).to eq(1)
     end
   end
-
-  it "activated ability to loot a card"
 end