Make 1.months and friends accurate by introducing a Duration class. #6835 [eventualbuddha]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@5940 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

9 files changed, 245 insertions, 11 deletions

diff --git a/activesupport/CHANGELOG b/activesupport/CHANGELOG
index f26c99b7b7..148feff061 100644
--- a/activesupport/CHANGELOG
+++ b/activesupport/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* Make 1.months and friends accurate by introducing a Duration class.  #6835 [eventualbuddha]
+
 * Document Inflector.ordinalize and merge docs from String inflections.  #7023 [smeade]
 
 * Unbundle flexmock.  [Jeremy Kemper]
diff --git a/activesupport/lib/active_support.rb b/activesupport/lib/active_support.rb
index 5504fa8f01..e094cbe0fe 100644
--- a/activesupport/lib/active_support.rb
+++ b/activesupport/lib/active_support.rb
@@ -38,6 +38,7 @@ require 'active_support/ordered_options'
 require 'active_support/option_merger'
 
 require 'active_support/values/time_zone'
+require 'active_support/duration'
 
 require 'active_support/json'
 
diff --git a/activesupport/lib/active_support/core_ext/date.rb b/activesupport/lib/active_support/core_ext/date.rb
index 239b8c140a..effb749c25 100644
--- a/activesupport/lib/active_support/core_ext/date.rb
+++ b/activesupport/lib/active_support/core_ext/date.rb
@@ -1,6 +1,8 @@
 require 'date'
+require File.dirname(__FILE__) + '/date/calculations'
 require File.dirname(__FILE__) + '/date/conversions'
 
 class Date#:nodoc:
+  include ActiveSupport::CoreExtensions::Date::Calculations
   include ActiveSupport::CoreExtensions::Date::Conversions
 end
diff --git a/activesupport/lib/active_support/core_ext/date/calculations.rb b/activesupport/lib/active_support/core_ext/date/calculations.rb
new file mode 100644
index 0000000000..f81cd9187e
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/date/calculations.rb
@@ -0,0 +1,41 @@
+module ActiveSupport #:nodoc:
+  module CoreExtensions #:nodoc:
+    module Date #:nodoc:
+      # Enables the use of time calculations within Time itself
+      module Calculations
+        def self.included(base) #:nodoc:
+          base.send(:include, ClassMethods)
+          
+          base.send(:alias_method, :plus_without_duration, :+)
+          base.send(:alias_method, :+, :plus_with_duration)
+          
+          base.send(:alias_method, :minus_without_duration, :-)
+          base.send(:alias_method, :-, :minus_with_duration)
+        end
+
+        module ClassMethods
+          def plus_with_duration(other) #:nodoc:
+            if ActiveSupport::Duration === other
+              other.since(self)
+            else
+              plus_without_duration(other)
+            end
+          end
+          
+          def minus_with_duration(other) #:nodoc:
+            self.plus_with_duration(-other)
+          end
+          
+          # Provides precise Date 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]
+            d
+          end
+        end
+      end
+    end
+  end
+end
\ No newline at end of file
diff --git a/activesupport/lib/active_support/core_ext/numeric/time.rb b/activesupport/lib/active_support/core_ext/numeric/time.rb
index 93740046db..aac698f7a8 100644
--- a/activesupport/lib/active_support/core_ext/numeric/time.rb
+++ b/activesupport/lib/active_support/core_ext/numeric/time.rb
@@ -3,51 +3,70 @@ module ActiveSupport #:nodoc:
     module Numeric #:nodoc:
       # Enables the use of time calculations and declarations, like 45.minutes + 2.hours + 4.years.
       #
-      # If you need precise date calculations that doesn't just treat months as 30 days, then have
-      # a look at Time#advance.
+      # These methods use Time#advance for precise date calculations when using from_now, ago, etc. 
+      # as well as adding or subtracting their results from a Time object. For example:
+      #
+      #   # equivalent to Time.now.advance(:months => 1)
+      #   1.month.from_now
+      #
+      #   # equivalent to Time.now.advance(:years => 2)
+      #   2.years.from_now
+      #
+      #   # equivalent to Time.now.advance(:months => 4, :years => 5)
+      #   (4.months + 5.years).from_now
       # 
-      # Some of these methods are approximations, Ruby's core 
+      # While these methods provide precise calculation when used as in the examples above, care
+      # should be taken to note that this is not true if the result of `months', `years', etc is
+      # converted before use:
+      #
+      #   # equivalent to 30.days.to_i.from_now
+      #   1.month.to_i.from_now
+      #
+      #   # equivalent to 365.25.days.to_f.from_now
+      #   1.year.to_f.from_now
+      #
+      # In such cases, Ruby's core 
       # Date[http://stdlib.rubyonrails.org/libdoc/date/rdoc/index.html] and 
       # Time[http://stdlib.rubyonrails.org/libdoc/time/rdoc/index.html] should be used for precision
       # date and time arithmetic
       module Time
         def seconds
-          self
+          ActiveSupport::Duration.new(self, [[:seconds, self]])
         end
         alias :second :seconds
 
         def minutes
-          self * 60
+          ActiveSupport::Duration.new(self * 60, [[:seconds, self * 60]])
         end
         alias :minute :minutes  
         
         def hours
-          self * 60.minutes
+          ActiveSupport::Duration.new(self * 3600, [[:seconds, self * 3600]])
         end
         alias :hour :hours
         
         def days
-          self * 24.hours
+          ActiveSupport::Duration.new(self * 24.hours, [[:days, self]])
         end
         alias :day :days
 
         def weeks
-          self * 7.days
+          ActiveSupport::Duration.new(self * 7.days, [[:days, self * 7]])
         end
         alias :week :weeks
         
         def fortnights
-          self * 2.weeks
+          ActiveSupport::Duration.new(self * 2.weeks, [[:days, self * 14]])
         end
         alias :fortnight :fortnights
         
         def months
-          self * 30.days
+          ActiveSupport::Duration.new(self * 30.days, [[:months, self]])
         end
         alias :month :months
 
         def years
-          (self * 365.25.days).to_i
+          ActiveSupport::Duration.new(self * 365.25.days, [[:years, self]])
         end
         alias :year :years
 
diff --git a/activesupport/lib/active_support/core_ext/time/calculations.rb b/activesupport/lib/active_support/core_ext/time/calculations.rb
index cd412368dc..70a4768d13 100644
--- a/activesupport/lib/active_support/core_ext/time/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/time/calculations.rb
@@ -5,6 +5,11 @@ module ActiveSupport #:nodoc:
       module Calculations
         def self.included(base) #:nodoc:
           base.extend(ClassMethods)
+          
+          base.send(:alias_method, :plus_without_duration, :+)
+          base.send(:alias_method, :+, :plus_with_duration)
+          base.send(:alias_method, :minus_without_duration, :-)
+          base.send(:alias_method, :-, :minus_with_duration)
         end
 
         module ClassMethods
@@ -190,6 +195,22 @@ module ActiveSupport #:nodoc:
         def tomorrow
           self.since(1.day)
         end
+        
+        def plus_with_duration(other) #:nodoc:
+          if ActiveSupport::Duration === other
+            other.since(self)
+          else
+            plus_without_duration(other)
+          end
+        end
+
+        def minus_with_duration(other) #:nodoc:
+          if ActiveSupport::Duration === other
+            other.until(self)
+          else
+            minus_without_duration(other)
+          end
+        end
       end
     end
   end
diff --git a/activesupport/lib/active_support/duration.rb b/activesupport/lib/active_support/duration.rb
new file mode 100644
index 0000000000..66b6941c5c
--- /dev/null
+++ b/activesupport/lib/active_support/duration.rb
@@ -0,0 +1,88 @@
+module ActiveSupport
+  # Provides accurate date and time measurements using Date#advance and 
+  # Time#advance, respectively. It mainly supports the methods on Numeric,
+  # such as in this example:
+  #
+  #   1.month.ago       # equivalent to Time.now.advance(:months => -1)
+  class Duration < Builder::BlankSlate
+    attr_accessor :value, :parts
+    
+    def initialize(value, parts) #:nodoc:
+      @value, @parts = value, parts
+    end
+    
+    # Adds another Duration or a Numeric to this Duration. Numeric values
+    # are treated as seconds.
+    def +(other)
+      if Duration === other
+        Duration.new(value + other.value, @parts + other.parts)
+      else
+        Duration.new(value + other, @parts + [[:seconds, other]])
+      end
+    end
+    
+    # Subtracts another Duration or a Numeric from this Duration. Numeric
+    # values are treated as seconds.
+    def -(other)
+      self + (-other)
+    end
+    
+    def -@ #:nodoc:
+      Duration.new(-value, parts.map { |type,number| [type, -number] })
+    end
+    
+    def is_a?(klass) #:nodoc:
+      klass == Duration || super
+    end
+    
+    def self.===(other) #:nodoc:
+      other.is_a?(Duration) rescue super
+    end
+    
+    # Calculates a new Time or Date that is as far in the future
+    # as this Duration represents.
+    def since(time = ::Time.now)
+      sum(1, time)
+    end
+    alias :from_now :since
+    
+    # Calculates a new Time or Date that is as far in the past
+    # as this Duration represents.
+    def ago(time = ::Time.now)
+      sum(-1, time)
+    end
+    alias :until :ago
+    
+    def inspect #:nodoc:
+      consolidated = parts.inject(Hash.new(0)) { |h,part| h[part.first] += part.last; h }
+      [:years, :months, :days, :hours, :minutes, :seconds].map do |length|
+        n = consolidated[length]
+        "#{n} #{n == 1 ? length.to_s.singularize : length.to_s}" if n.nonzero?
+      end.compact.to_sentence
+    end
+    
+    protected
+    
+    def sum(sign, time = ::Time.now) #:nodoc:
+      parts.inject(time) do |t,(type,number)|
+        case t
+        when ::Time
+          if type == :seconds
+            t + (sign * number)
+          else
+            t.advance(type => sign * number)
+          end
+        when ::Date
+          raise ArgumentError, "Adding seconds to a Date does not make sense" if type == :seconds
+          t.advance(type => sign * number)
+        end
+      end
+    end
+    
+    private
+    
+    def method_missing(method, *args, &block) #:nodoc:
+      value.send(method, *args)
+    end
+  end
+end
\ No newline at end of file
diff --git a/activesupport/test/core_ext/duration_test.rb b/activesupport/test/core_ext/duration_test.rb
new file mode 100644
index 0000000000..78fc999052
--- /dev/null
+++ b/activesupport/test/core_ext/duration_test.rb
@@ -0,0 +1,13 @@
+require File.dirname(__FILE__) + '/../abstract_unit'
+
+class DurationTest < Test::Unit::TestCase
+  def test_inspect
+    assert_equal '1 month',                         1.month.inspect
+    assert_equal '1 month and 1 day',               (1.month + 1.day).inspect
+    assert_equal '6 months and -2 days',            (6.months - 2.days).inspect
+    assert_equal '10 seconds',                      10.seconds.inspect
+    assert_equal '10 years, 2 months, and 1 day',   (10.years + 2.months + 1.day).inspect
+    assert_equal '7 days',                          1.week.inspect
+    assert_equal '14 days',                         1.fortnight.inspect
+  end
+end
\ No newline at end of file
diff --git a/activesupport/test/core_ext/numeric_ext_test.rb b/activesupport/test/core_ext/numeric_ext_test.rb
index 1d04cf7fe8..a594d25805 100644
--- a/activesupport/test/core_ext/numeric_ext_test.rb
+++ b/activesupport/test/core_ext/numeric_ext_test.rb
@@ -34,6 +34,53 @@ class NumericExtTimeTest < Test::Unit::TestCase
       assert seconds.from_now >= now + seconds
     end
   end
+  
+  def test_irregular_durations
+    assert_equal @now.advance(:days => 3000), 3000.days.since(@now)
+    assert_equal @now.advance(:months => 1), 1.month.since(@now)
+    assert_equal @now.advance(:months => -1), 1.month.until(@now)
+    assert_equal @now.advance(:years => 20), 20.years.since(@now)
+  end
+  
+  def test_duration_addition
+    assert_equal @now.advance(:days => 1, :months => 1), (1.day + 1.month).since(@now)
+    assert_equal @now.advance(:days => 7), (1.week + 5.seconds - 5.seconds).since(@now)
+    assert_equal @now.advance(:years => 2), (4.years - 2.years).since(@now)
+  end
+  
+  def test_time_plus_duration
+    assert_equal @now + 8, @now + 8.seconds
+    assert_equal @now + 22.9, @now + 22.9.seconds
+    assert_equal @now.advance(:days => 15), @now + 15.days
+    assert_equal @now.advance(:months => 1), @now + 1.month
+  end
+  
+  def test_chaining_duration_operations
+    assert_equal @now.advance(:days => 2, :months => -3), @now + 2.days - 3.months
+    assert_equal @now.advance(:days => 1, :months => 2), @now + 1.day + 2.months
+  end
+  
+  def test_duration_after_convertion_is_no_longer_accurate
+    assert_equal 30.days.to_i.since(@now), 1.month.to_i.since(@now)
+    assert_equal 365.25.days.to_f.since(@now), 1.year.to_f.since(@now)
+  end
+end
+
+class NumericExtDateTest < Test::Unit::TestCase
+  def setup
+    @today = Date.today
+  end
+
+  def test_date_plus_duration
+    assert_equal @today + 1, @today + 1.day
+    assert_equal @today >> 1, @today + 1.month
+    assert_raises(ArgumentError) { @today + 1.second }
+  end
+  
+  def test_chaining_duration_operations
+    assert_equal @today.advance(:days => 2, :months => -3), @today + 2.days - 3.months
+    assert_equal @today.advance(:days => 1, :months => 2), @today + 1.day + 2.months
+  end
 end
 
 class NumericExtSizeTest < Test::Unit::TestCase