Implement Black Lotus card

lib/magic/cards/black_lotus.rb

@@ -0,0 +1,17 @@
+module Magic
+  module Cards
+    BlackLotus = Artifact("Black Lotus") do
+      cost generic: 0
+    end
+
+    class BlackLotus < Artifact
+      class ManaAbility < Magic::ManaAbility
+        costs "{T}, Sacrifice {this}"
+        choices :all
+        amount 3
+      end
+
+      def activated_abilities = [ManaAbility]
+    end
+  end
+end

lib/magic/mana_ability.rb

@@ -10,6 +10,10 @@ def self.choices(*choices)
       end
     end
 
+    def self.amount(value)
+      define_method(:amount) { value }
+    end
+
     def initialize(**args)
       super(**args)
     end
@@ -22,11 +26,19 @@ def choose(color)
       @choice = color
     end
 
-    def resolve!
+    def amount
+      1
+    end
+
+    def validate_choice!
       @choice ||= choices.first if choices.length == 1
 
       raise "Invalid choice made for mana ability. Choice: #{choice}, Choices: #{choices}" unless choices.include?(choice)
-      source.controller.add_mana(choice => 1)
+    end
+
+    def resolve!
+      validate_choice!
+      source.controller.add_mana(choice => amount)
     end
   end
 end

spec/cards/black_lotus_spec.rb

@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Magic::Cards::BlackLotus do
+  include_context "two player game"
+  subject { ResolvePermanent("Black Lotus", owner: p1) }
+
+  context "tap and sacrifice" do
+    it "adds three mana of chosen color" do
+      ability = subject.activated_abilities.first
+      ability.choose(:green)
+      p1.activate_ability(ability: ability)
+      expect(p1.mana_pool[:green]).to eq(3)
+    end
+
+    it "sacrifices the artifact when activated" do
+      ability = subject.activated_abilities.first
+      ability.choose(:blue)
+      expect {
+        p1.activate_ability(ability: ability)
+      }.to change { p1.permanents.count }.by(-1)
+      expect(p1.graveyard.map(&:name)).to include("Black Lotus")
+    end
+
+    it "can add mana of different colors" do
+      # Test red
+      lotus = ResolvePermanent("Black Lotus", owner: p1)
+      ability = lotus.activated_abilities.first
+      ability.choose(:red)
+      p1.activate_ability(ability: ability)
+      expect(p1.mana_pool[:red]).to eq(3)
+
+      # Test white
+      lotus2 = ResolvePermanent("Black Lotus", owner: p1)
+      ability2 = lotus2.activated_abilities.first
+      ability2.choose(:white)
+      p1.activate_ability(ability: ability2)
+      expect(p1.mana_pool[:white]).to eq(3)
+    end
+  end
+end