DateTime calculations analogous to the Date and Time extensions. Closes #7693.

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@6303 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

1 files changed, 173 insertions, 0 deletions

diff --git a/activesupport/lib/active_support/core_ext/date_time/calculations.rb b/activesupport/lib/active_support/core_ext/date_time/calculations.rb
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+++ b/activesupport/lib/active_support/core_ext/date_time/calculations.rb
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+require 'rational'
+
+module ActiveSupport #:nodoc:
+  module CoreExtensions #:nodoc:
+    module DateTime #:nodoc:
+      # Enables the use of time calculations within DateTime itself
+      module Calculations
+
+        # Seconds since midnight: DateTime.now.seconds_since_midnight
+        def seconds_since_midnight
+          self.sec + (self.min * 60) + (self.hour * 3600)
+        end
+
+        # Returns a new DateTime where one or more of the elements have been changed according to the +options+ parameter. The time options
+        # (hour, minute, sec) reset cascadingly, so if only the hour is passed, then minute and sec is set to 0. If the hour and
+        # minute is passed, then sec is set to 0.
+        def change(options)
+          ::DateTime.civil(
+            options[:year]  || self.year,
+            options[:month] || self.month,
+            options[:mday]  || self.mday,
+            options[:hour]  || self.hour,
+            options[:min]   || (options[:hour] ? 0 : self.min),
+            options[:sec]   || ((options[:hour] || options[:min]) ? 0 : self.sec),
+            options[:offset]  || self.offset,
+            options[:start]  || self.start
+          )
+        end
+
+        # Uses Date to provide precise Time calculations for years, months, and days.  The +options+ parameter takes a hash with
+        # any of these keys: :months, :days, :years.
+        def advance(options)
+          d = ::Date.new(year + (options.delete(:years) || 0), month, day)
+          d = d >> options.delete(:months) if options[:months]
+          d = d +  options.delete(:days)   if options[:days]
+          change(options.merge(:year => d.year, :month => d.month, :mday => d.day))
+        end
+
+        # Returns a new DateTime representing the time a number of seconds ago
+        # Do not use this method in combination with x.months, use months_ago instead!
+        def ago(seconds)
+          self.since(-seconds)
+        end
+
+        # Returns a new DateTime representing the time a number of seconds since the instance time
+        # Do not use this method in combination with x.months, use months_since instead!
+        def since(seconds)
+          self + Rational(seconds, 86400)
+        end
+        alias :in :since
+
+        # Returns a new DateTime representing the time a number of specified months ago
+         def months_ago(months)
+           months_since(-months)
+         end
+
+         def months_since(months)
+           year, month, mday = self.year, self.month, self.mday
+
+           month += months
+
+           # in case months is negative
+           while month < 1
+             month += 12
+             year -= 1
+           end
+
+           # in case months is positive
+           while month > 12
+             month -= 12
+             year += 1
+           end
+
+           max = ::Time.days_in_month(month, year)
+           mday = max if mday > max
+
+           change(:year => year, :month => month, :mday => mday)
+         end
+
+         # Returns a new DateTime representing the time a number of specified years ago
+         def years_ago(years)
+           change(:year => self.year - years)
+         end
+
+         def years_since(years)
+           change(:year => self.year + years)
+         end
+
+         # Short-hand for years_ago(1)
+         def last_year
+           years_ago(1)
+         end
+
+         # Short-hand for years_since(1)
+         def next_year
+           years_since(1)
+         end
+
+         # Short-hand for months_ago(1)
+         def last_month
+           months_ago(1)
+         end
+
+         # Short-hand for months_since(1)
+         def next_month
+           months_since(1)
+         end
+
+         # Returns a new DateTime representing the "start" of this week (Monday, 0:00)
+         def beginning_of_week
+           days_to_monday = self.wday!=0 ? self.wday-1 : 6
+           (self - days_to_monday).midnight
+         end
+         alias :monday :beginning_of_week
+         alias :at_beginning_of_week :beginning_of_week
+
+         # Returns a new DateTime representing the start of the given day in next week (default is Monday).
+         def next_week(day = :monday)
+           days_into_week = { :monday => 0, :tuesday => 1, :wednesday => 2, :thursday => 3, :friday => 4, :saturday => 5, :sunday => 6}
+           ((self + 7).beginning_of_week + days_into_week[day]).change(:hour => 0)
+         end
+
+         # Returns a new DateTime representing the start of the day (0:00)
+         def beginning_of_day
+           change(:hour => 0)
+         end
+         alias :midnight :beginning_of_day
+         alias :at_midnight :beginning_of_day
+         alias :at_beginning_of_day :beginning_of_day
+
+         # Returns a new DateTime representing the end of the day (23:59:59)
+         def end_of_day
+           change(:hour => 23, :min => 59, :sec => 59)
+         end
+
+         # Returns a new DateTime representing the start of the month (1st of the month, 0:00)
+         def beginning_of_month
+           change(:mday => 1,:hour => 0, :min => 0, :sec => 0)
+         end
+         alias :at_beginning_of_month :beginning_of_month
+
+         # Returns a new DateTime representing the end of the month (last day of the month, 0:00)
+         def end_of_month
+           last_day = ::Time.days_in_month( self.month, self.year )
+           change(:mday => last_day,:hour => 0, :min => 0, :sec => 0)
+         end
+         alias :at_end_of_month :end_of_month
+
+         # Returns  a new DateTime representing the start of the quarter (1st of january, april, july, october, 0:00)
+         def beginning_of_quarter
+           beginning_of_month.change(:month => [10, 7, 4, 1].detect { |m| m <= self.month })
+         end
+         alias :at_beginning_of_quarter :beginning_of_quarter
+
+         # Returns  a new DateTime representing the start of the year (1st of january, 0:00)
+         def beginning_of_year
+           change(:month => 1,:mday => 1,:hour => 0, :min => 0, :sec => 0)
+         end
+         alias :at_beginning_of_year :beginning_of_year
+
+         # Convenience method which returns a new DateTime representing the time 1 day ago
+         def yesterday
+           self - 1
+         end
+
+         # Convenience method which returns a new DateTime representing the time 1 day since the instance time
+         def tomorrow
+           self + 1
+         end
+      end
+    end
+  end
+end