adding direction_of_stairs ability

lib/ruby_warrior.rb

@@ -32,3 +32,4 @@
 require 'ruby_warrior/abilities/distance'
 require 'ruby_warrior/abilities/bind'
 require 'ruby_warrior/abilities/listen'
+require 'ruby_warrior/abilities/direction_of_stairs'

lib/ruby_warrior/abilities/direction_of_stairs.rb

@@ -0,0 +1,17 @@
+module RubyWarrior
+  module Abilities
+    class DirectionOfStairs < Base
+      def description
+        "Returns the direction (:left, :right, :forward, :backward) the stairs are from your location."
+      end
+
+      def possible_arguments
+        [[]]
+      end
+
+      def perform
+        @unit.position.relative_direction_of_stairs
+      end
+    end
+  end
+end

lib/ruby_warrior/position.rb

@@ -2,6 +2,7 @@ module RubyWarrior
   class Position
     attr_reader :floor
     DIRECTIONS = [:north, :east, :south, :west]
+    RELATIVE_DIRECTIONS = [:forward, :right, :backward, :left]
 
     def initialize(floor, x, y, direction = nil)
       @floor = floor
@@ -41,6 +42,32 @@ def distance_from_stairs
       (@x - stairs_x).abs + (@y - stairs_y).abs
     end
 
+    def relative_direction_of_stairs
+      relative_direction(direction_of_stairs)
+    end
+
+    def direction_of_stairs
+      stairs_x, stairs_y = *@floor.stairs_location
+      if (@x - stairs_x).abs > (@y - stairs_y).abs
+        if stairs_x > @x
+          :west
+        else
+          :east
+        end
+      elsif stairs_y > @y
+        :south
+      else
+        :north
+      end
+    end
+
+    def relative_direction(direction)
+      offset = DIRECTIONS.index(direction) - @direction_index
+      offset -= 4 while offset > 3
+      offset += 4 while offset < 0
+      RELATIVE_DIRECTIONS[offset]
+    end
+
     private
 
     def translate_offset(forward, right)

spec/ruby_warrior/abilities/direction_of_stairs_spec.rb

@@ -0,0 +1,13 @@
+require File.dirname(__FILE__) + '/../../spec_helper'
+
+describe RubyWarrior::Abilities::DirectionOfStairs do
+  before(:each) do
+    @position = stub
+    @distance = RubyWarrior::Abilities::DirectionOfStairs.new(stub(:position => @position, :say => nil))
+  end
+
+  it "should return relative direction of stairs" do
+    @position.stubs(:relative_direction_of_stairs).returns(:left)
+    @distance.perform.should == :left
+  end
+end

spec/ruby_warrior/position_spec.rb

@@ -72,4 +72,22 @@
     @floor.place_stairs(0, 3)
     @position.distance_from_stairs.should == 2
   end
+
+  it "should return direction and relative direction of stairs" do
+    @floor.place_stairs(0, 0)
+    @position.direction_of_stairs.should == :north
+    @position.relative_direction_of_stairs.should == :forward
+  end
+
+  it "should be able to determine relative direction" do
+    @position.relative_direction(:north).should == :forward
+    @position.rotate 1
+    @position.relative_direction(:north).should == :left
+    @position.rotate 1
+    @position.relative_direction(:north).should == :backward
+    @position.rotate 1
+    @position.relative_direction(:north).should == :right
+    @position.rotate 1
+    @position.relative_direction(:south).should == :backward
+  end
 end