Implement Peer Into The Abyss

Fixes #371

lib/magic/cards/peer_into_the_abyss.rb

@@ -0,0 +1,23 @@
+module Magic
+  module Cards
+    PeerIntoTheAbyss = Sorcery("Peer Into the Abyss") do
+      cost black: 3, generic: 4
+
+      def single_target?
+        true
+      end
+
+      def target_choices
+        game.players
+      end
+
+      def resolve!(target:)
+        effect = Magic::Effects::DrawCards.new(source: self, player: target, number_to_draw: (target.library.count / 2.0).ceil)
+        game.add_effect(effect)
+
+        effect = Magic::Effects::LoseLife.new(source: self, targets: [target], life: (target.life / 2.0).ceil)
+        game.add_effect(effect)
+      end
+    end
+  end
+end

spec/cards/peer_into_the_abyss_spec.rb

@@ -0,0 +1,20 @@
+require 'spec_helper'
+
+RSpec.describe Magic::Cards::PeerIntoTheAbyss do
+  include_context "two player game"
+  subject(:peer_into_the_abyss) { Card("Peer Into The Abyss") }
+
+  it "p2 draws half their library, and loses half their life, rounded up" do
+    3.times { p2.library.add(Card("Forest")) }
+    p2.lose_life(1)
+    p1.add_mana(black: 7)
+    p1.cast(card: peer_into_the_abyss) do
+      _1.targeting(p2)
+      _1.pay_mana(black: 3, generic: { black: 4 })
+    end
+    game.tick!
+
+    expect(p2.library.count).to eq(1)
+    expect(p2.life).to eq(9)
+  end
+end