Add shift.overlaps? and shift.contains?

README.markdown

@@ -139,6 +139,29 @@ Include?
     Shift.new(TimeOfDay.new(20), TimeOfDay.new(4)).include?(TimeOfDay.new(2))  # => true
     Shift.new(TimeOfDay.new(20), TimeOfDay.new(4)).include?(TimeOfDay.new(18)) # => false
 
+
+Overlap?
+--------------------
+    breakfast = Shift.new(TimeOfDay.new(8), TimeOfDay.new(11))
+    lunch = Shift.new(TimeOfDay.new(10), TimeOfDay.new(14))
+    breakfast.overlaps?(lunch) # => true
+    lunch.overlaps?(breakfast) # => true
+
+    dinner = Shift.new(TimeOfDay.new(18), TimeOfDay.new(20))
+    dinner.overlaps?(lunch) # => false
+
+
+Contains?
+--------------------
+    workday = Shift.new(TimeOfDay.new(9), TimeOfDay.new(17))
+    lunch = Shift.new(TimeOfDay.new(10), TimeOfDay.new(14))
+    workday.contains?(lunch) # => true
+    lunch.contains?(workday) # => false
+
+    dinner = Shift.new(TimeOfDay.new(18), TimeOfDay.new(20))
+    dinner.overlaps?(lunch) # => false
+
+
 Rails Time Zone Support
 =======================
 

lib/tod/shift.rb

@@ -22,6 +22,17 @@ def include?(tod)
       end
     end
 
+    def overlaps?(shift)
+      self.include?(shift.beginning) || 
+        self.include?(shift.ending) || 
+        shift.include?(self.beginning) ||
+        shift.include?(self.ending)
+    end
+
+    def contains?(shift)
+      self.include?(shift.beginning) && self.include?(shift.ending)
+    end
+
     # Return shift duration in seconds.
     # if ending is lower than beginning this method will calculate the duration as the ending time is from the following day
     def duration

test/tod/shift_test.rb

@@ -27,6 +27,46 @@ class ShiftTest < Test::Unit::TestCase
     end
   end
 
+  context "overlaps?" do
+    should "be true when shifts overlap" do
+      shift1 = Shift.new(TimeOfDay.new(12), TimeOfDay.new(18))
+      shift2 = Shift.new(TimeOfDay.new(13), TimeOfDay.new(15))
+      assert_true shift1.overlaps?(shift2)
+    end
+
+    should "be false when shifts don't overlap" do
+      shift1 = Shift.new(TimeOfDay.new(1), TimeOfDay.new(5))
+      shift2 = Shift.new(TimeOfDay.new(9), TimeOfDay.new(12))
+      assert_false shift1.overlaps?(shift2)
+    end
+
+    should "be true when shifts touch" do
+      shift1 = Shift.new(TimeOfDay.new(1), TimeOfDay.new(5))
+      shift2 = Shift.new(TimeOfDay.new(5), TimeOfDay.new(12))
+      assert_true shift1.overlaps?(shift2)
+    end
+  end
+
+  context "contains?" do
+    should "be true when one shift contains another" do
+      outside = Shift.new(TimeOfDay.new(12), TimeOfDay.new(18))
+      inside = Shift.new(TimeOfDay.new(13), TimeOfDay.new(15))
+      assert_true outside.contains?(inside)
+    end
+
+    should "be false when a shift is contained by another" do
+      outside = Shift.new(TimeOfDay.new(12), TimeOfDay.new(18))
+      inside = Shift.new(TimeOfDay.new(13), TimeOfDay.new(15))
+      assert_false inside.contains?(outside)
+    end
+
+    should "be false when shifts don't even overlap" do
+      shift1 = Shift.new(TimeOfDay.new(12), TimeOfDay.new(15))
+      shift2 = Shift.new(TimeOfDay.new(18), TimeOfDay.new(19))
+      assert_false shift1.contains?(shift2)
+    end
+  end
+
   context "include?" do
     # |------------------------|--------T1----V----T2----|------------------------|
     should "be true when value is between ToDs and boths tods are in the same day" do