From 8c26e22b39871f64db49e7d6d6726e27dc459a9e Mon Sep 17 00:00:00 2001
From: Dan Barry <dan@bakineggs.com>
Date: Sun, 12 Oct 2008 22:05:41 -0500
Subject: [PATCH] Date.durations_between: Date.days_between, Date.weeks_between, Date.months_between, Date.years_between

---
 .../active_support/core_ext/date/calculations.rb   |   30 +++++++++++++
 activesupport/lib/active_support/duration.rb       |    8 ++++
 activesupport/test/core_ext/date_ext_test.rb       |   44 ++++++++++++++++++++
 activesupport/test/core_ext/duration_test.rb       |   17 ++++++++
 4 files changed, 99 insertions(+), 0 deletions(-)

diff --git a/activesupport/lib/active_support/core_ext/date/calculations.rb b/activesupport/lib/active_support/core_ext/date/calculations.rb
index 43d70c7..7bd4847 100644
--- a/activesupport/lib/active_support/core_ext/date/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/date/calculations.rb
@@ -30,6 +30,36 @@ module ActiveSupport #:nodoc:
           def current
             ::Time.zone_default ? ::Time.zone.today : ::Date.today
           end
+
+          def durations_between(start, finish, duration)
+            return durations_between(finish, start, duration) if start > finish
+            count = 0
+            multiplier = 512
+            while (multiplier > 0)
+              while ((check = start + duration * multiplier) <= finish)
+                count += multiplier
+                start = check
+              end
+              multiplier /= 2
+            end
+            count + ((finish - start) / (finish + duration - finish))
+          end
+
+          def days_between(start, finish)
+            durations_between(start, finish, 1.day)
+          end
+
+          def weeks_between(start, finish)
+            durations_between(start, finish, 1.week)
+          end
+
+          def months_between(start, finish)
+            durations_between(start, finish, 1.month)
+          end
+
+          def years_between(start, finish)
+            durations_between(start, finish, 1.year)
+          end
         end
 
         # Tells whether the Date object's date lies in the past
diff --git a/activesupport/lib/active_support/duration.rb b/activesupport/lib/active_support/duration.rb
index 8eae85d..3739ce4 100644
--- a/activesupport/lib/active_support/duration.rb
+++ b/activesupport/lib/active_support/duration.rb
@@ -31,6 +31,14 @@ module ActiveSupport
       Duration.new(-value, parts.map { |type,number| [type, -number] })
     end
 
+    def *(count)
+      Duration.new(value * count, parts.map { |type, number| [type, number * count] })
+    end
+
+    def /(divisor)
+      self * (1.0 / divisor)
+    end
+
     def is_a?(klass) #:nodoc:
       klass == Duration || super
     end
diff --git a/activesupport/test/core_ext/date_ext_test.rb b/activesupport/test/core_ext/date_ext_test.rb
index b53c754..a5fad46 100644
--- a/activesupport/test/core_ext/date_ext_test.rb
+++ b/activesupport/test/core_ext/date_ext_test.rb
@@ -256,6 +256,50 @@ class DateExtCalculationsTest < Test::Unit::TestCase
     end
   end
 
+  def test_durations_between
+    assert_equal 2, Date.durations_between(Date.new(1999, 12, 29), Date.new(1999, 12, 31), 1.day)
+  end
+
+  def test_durations_between_wrapping
+    assert_equal 1, Date.durations_between(Date.new(1999, 12, 31), Date.new(2000, 1, 1), 1.day)
+  end
+
+  def test_durations_between_fractions
+    assert_equal 1.25, Date.durations_between(Date.new(1999, 12, 25), Date.new(1999, 12, 30), 4.days)
+  end
+
+  def test_days_between
+    assert_equal 2, Date.days_between(Date.new(1999, 12, 29), Date.new(1999, 12, 31))
+  end
+
+  def test_days_between_wrapping
+    assert_equal 3, Date.days_between(Date.new(1999, 12, 30), Date.new(2000, 1, 2))
+  end
+
+  def test_weeks_between
+    assert_equal 2, Date.weeks_between(Date.new(1999, 12, 5), Date.new(1999, 12, 19))
+  end
+
+  def test_months_between
+    assert_equal 2, Date.months_between(Date.new(1999, 10, 1), Date.new(1999, 12, 1))
+  end
+
+  def test_months_between_wrapping
+    assert_equal 4, Date.months_between(Date.new(1999, 10, 1), Date.new(2000, 2, 1))
+  end
+
+  def test_months_between_fractions
+    assert_equal 1.5, Date.months_between(Date.new(1999, 10, 15), Date.new(1999, 11, 30))
+  end
+
+  def test_years_between
+    assert_equal 2, Date.years_between(Date.new(1999, 12, 31), Date.new(2001, 12, 31))
+  end
+
+  def test_years_between_fractions
+    assert_equal 1.2, Date.years_between(Date.new(1999, 6, 1), Date.new(2000, 8, 13))
+  end
+
   protected
     def with_env_tz(new_tz = 'US/Eastern')
       old_tz, ENV['TZ'] = ENV['TZ'], new_tz
diff --git a/activesupport/test/core_ext/duration_test.rb b/activesupport/test/core_ext/duration_test.rb
index f802ed8..7f73a4b 100644
--- a/activesupport/test/core_ext/duration_test.rb
+++ b/activesupport/test/core_ext/duration_test.rb
@@ -19,6 +19,23 @@ class DurationTest < Test::Unit::TestCase
     assert_equal 1 + 1.second, 1.second + 1, "Duration + Numeric should == Numeric + Duration"
   end
 
+  def test_multiplication
+    assert_equal 2.months, 1.month * 2
+    assert_equal 18.months - 6.days, (6.months - 2.days) * 3
+    assert_equal -40.years - 8.months - 4.days, (10.years + 2.months + 1.day) * -4
+  end
+
+  def test_multiplication_associativity
+    assert_equal 1.month * 2, 2 * 1.month
+    assert_equal 1.month * 1.5, 1.5 * 1.month
+  end
+
+  def test_division
+    assert_equal 1.month, 2.months / 2
+    assert_equal 6.months - 2.days, (18.months - 6.days) / 3
+    assert_equal -10.years - 2.months - 1.day, (40.years + 8.months + 4.days) / -4
+  end
+
   def test_argument_error
     begin
       1.second.ago('')
-- 
1.5.4.2