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

1 files changed, 88 insertions, 0 deletions

diff --git a/activesupport/lib/active_support/duration.rb b/activesupport/lib/active_support/duration.rb
new file mode 100644
index 0000000000..66b6941c5c
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+++ 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
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