Add #on_weekend?, #next_weekday, and #prev_weekday methods to Date, Time, and DateTime

`#on_weekend?` returns true if the receiving date/time falls on a Saturday or
Sunday.

`#next_weekday` returns a new date/time representing the next day that does
not fall on a Saturday or Sunday.

`#prev_weekday` returns a new date/time representing the previous day that
does not fall on a Saturday or Sunday.

3 files changed, 84 insertions, 0 deletions

diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index aa2090b897..aec46f71ce 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,3 +1,17 @@
+*   Add `#on_weekend?`, `#next_weekday`, `#prev_weekday` methods to `Date`,
+    `Time`, and `DateTime`.
+
+    `#on_weekend?` returns true if the receiving date/time falls on a Saturday
+    or Sunday.
+
+    `#next_weekday` returns a new date/time representing the next day that does
+    not fall on a Saturday or Sunday.
+
+    `#prev_weekday` returns a new date/time representing the previous day that
+    does not fall on a Saturday or Sunday.
+
+    *George Claghorn*
+
 *   Change the default test order from `:sorted` to `:random`.
 
     *Rafael Mendonça França*
diff --git a/activesupport/lib/active_support/core_ext/date_and_time/calculations.rb b/activesupport/lib/active_support/core_ext/date_and_time/calculations.rb
index b85e49aca5..4e86b270f9 100644
--- a/activesupport/lib/active_support/core_ext/date_and_time/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/date_and_time/calculations.rb
@@ -9,6 +9,7 @@ module DateAndTime
       :saturday  => 5,
       :sunday    => 6
     }
+    WEEKEND_DAYS = [ 6, 0 ]
 
     # Returns a new date/time representing yesterday.
     def yesterday
@@ -35,6 +36,11 @@ module DateAndTime
       self > self.class.current
     end
 
+    # Returns true if the date/time falls on a Saturday or Sunday.
+    def on_weekend?
+      wday.in?(WEEKEND_DAYS)
+    end
+
     # Returns a new date/time the specified number of days ago.
     def days_ago(days)
       advance(:days => -days)
@@ -116,6 +122,15 @@ module DateAndTime
       first_hour(weeks_since(1).beginning_of_week.days_since(days_span(given_day_in_next_week)))
     end
 
+    # Returns a new date/time representing the next weekday.
+    def next_weekday
+      if tomorrow.on_weekend?
+        next_week(:monday).change(hour: hour, min: min, sec: sec, usec: try(:usec))
+      else
+        tomorrow
+      end
+    end
+
     # Short-hand for months_since(1).
     def next_month
       months_since(1)
@@ -140,6 +155,16 @@ module DateAndTime
     end
     alias_method :last_week, :prev_week
 
+    # Returns a new date/time representing the previous weekday.
+    def prev_weekday
+      if yesterday.on_weekend?
+        beginning_of_week(:friday).change(hour: hour, min: min, sec: sec, usec: try(:usec))
+      else
+        yesterday
+      end
+    end
+    alias_method :last_weekday, :prev_weekday
+
     # Short-hand for months_ago(1).
     def prev_month
       months_ago(1)
diff --git a/activesupport/test/core_ext/date_and_time_behavior.rb b/activesupport/test/core_ext/date_and_time_behavior.rb
index b4ef5a0597..a6a21f8de4 100644
--- a/activesupport/test/core_ext/date_and_time_behavior.rb
+++ b/activesupport/test/core_ext/date_and_time_behavior.rb
@@ -115,6 +115,21 @@ module DateAndTimeBehavior
     end
   end
 
+  def test_next_weekday_on_wednesday
+    assert_equal date_time_init(2015,1,8,0,0,0), date_time_init(2015,1,7,0,0,0).next_weekday
+    assert_equal date_time_init(2015,1,8,15,15,10), date_time_init(2015,1,7,15,15,10).next_weekday
+  end
+
+  def test_next_weekday_on_friday
+    assert_equal date_time_init(2015,1,5,0,0,0), date_time_init(2015,1,2,0,0,0).next_weekday
+    assert_equal date_time_init(2015,1,5,15,15,10), date_time_init(2015,1,2,15,15,10).next_weekday
+  end
+
+  def test_next_weekday_on_saturday
+    assert_equal date_time_init(2015,1,5,0,0,0), date_time_init(2015,1,3,0,0,0).next_weekday
+    assert_equal date_time_init(2015,1,5,15,15,10), date_time_init(2015,1,3,15,15,10).next_weekday
+  end
+
   def test_next_month_on_31st
     assert_equal date_time_init(2005,9,30,15,15,10), date_time_init(2005,8,31,15,15,10).next_month
   end
@@ -144,6 +159,21 @@ module DateAndTimeBehavior
     end
   end
 
+  def test_prev_weekday_on_wednesday
+    assert_equal date_time_init(2015,1,6,0,0,0), date_time_init(2015,1,7,0,0,0).prev_weekday
+    assert_equal date_time_init(2015,1,6,15,15,10), date_time_init(2015,1,7,15,15,10).prev_weekday
+  end
+
+  def test_prev_weekday_on_monday
+    assert_equal date_time_init(2015,1,2,0,0,0), date_time_init(2015,1,5,0,0,0).prev_weekday
+    assert_equal date_time_init(2015,1,2,15,15,10), date_time_init(2015,1,5,15,15,10).prev_weekday
+  end
+
+  def test_prev_weekday_on_sunday
+    assert_equal date_time_init(2015,1,2,0,0,0), date_time_init(2015,1,4,0,0,0).prev_weekday
+    assert_equal date_time_init(2015,1,2,15,15,10), date_time_init(2015,1,4,15,15,10).prev_weekday
+  end
+
   def test_prev_month_on_31st
     assert_equal date_time_init(2004,2,29,10,10,10), date_time_init(2004,3,31,10,10,10).prev_month
   end
@@ -231,6 +261,21 @@ module DateAndTimeBehavior
     end
   end
 
+  def test_on_weekend_on_saturday
+    assert date_time_init(2015,1,3,0,0,0).on_weekend?
+    assert date_time_init(2015,1,3,15,15,10).on_weekend?
+  end
+
+  def test_on_weekend_on_sunday
+    assert date_time_init(2015,1,4,0,0,0).on_weekend?
+    assert date_time_init(2015,1,4,15,15,10).on_weekend?
+  end
+
+  def test_on_weekend_on_monday
+    assert_not date_time_init(2015,1,5,0,0,0).on_weekend?
+    assert_not date_time_init(2015,1,5,15,15,10).on_weekend?
+  end
+
   def with_bw_default(bw = :monday)
     old_bw = Date.beginning_of_week
     Date.beginning_of_week = bw