Introduce ActiveSupport::TimeWithZone, for wrapping Time instances with a TimeZone. Introduce instance methods to Time for creating TimeWithZone instances, and class methods for managing a global time zone

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@8696 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

1 files changed, 156 insertions, 0 deletions

diff --git a/activesupport/lib/active_support/time_with_zone.rb b/activesupport/lib/active_support/time_with_zone.rb
new file mode 100644
index 0000000000..dcd55ae93d
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+++ b/activesupport/lib/active_support/time_with_zone.rb
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+module ActiveSupport
+  # A Time-like class that can represent a time in any time zone. Necessary because standard Ruby Time instances are 
+  # limited to UTC and the system's ENV['TZ'] zone
+  class TimeWithZone
+    include Comparable
+    attr_reader :time_zone
+  
+    def initialize(utc_time, time_zone = nil, local_time = nil)
+      @utc = utc_time
+      @time = local_time
+      @time_zone = time_zone
+    end
+  
+    # Returns a Time instance that represents the time in time_zone
+    def time
+      @time ||= utc? ? @utc : time_zone.utc_to_local(@utc)
+    end
+
+    # Returns a Time instance that represents the time in UTC
+    def utc
+      @utc ||= utc? ? @time : time_zone.local_to_utc(@time)
+    end
+    alias_method :comparable_time, :utc
+  
+    # Returns the underlying TZInfo::TimezonePeriod for the local time
+    def period
+      @period ||= get_period_for_local
+    end
+
+    # Returns the simultaneous time in the specified zone
+    def in_time_zone(new_zone)
+      utc.in_time_zone(new_zone)
+    end
+  
+    # Returns the simultaneous time in Time.zone
+    def in_current_time_zone
+      utc.in_current_time_zone
+    end
+  
+    # Changes the time zone without converting the time
+    def change_time_zone(new_zone)
+      time.change_time_zone(new_zone)
+    end
+  
+    # Changes the time zone to Time.zone without converting the time
+    def change_time_zone_to_current
+      time.change_time_zone_to_current
+    end
+  
+    # Returns a Time.local() instance of the simultaneous time in your system's ENV['TZ'] zone
+    def localtime
+      utc.dup.localtime # use #dup because Time#localtime is destructive
+    end
+  
+    def dst?
+      utc? ? false : period.dst?
+    end
+  
+    # The TimeZone class has no zone for UTC, so this class uses the absence of a time zone to indicate UTC
+    def utc?
+      !time_zone
+    end
+  
+    def utc_offset
+      utc? ? 0 : period.utc_total_offset
+    end
+  
+    def formatted_offset(colon = true, alternate_utc_string = nil)
+      utc? && alternate_utc_string || utc_offset.to_utc_offset_s(colon)
+    end
+  
+    # Time uses #zone to display the time zone abbreviation, so we're duck-typing it
+    def zone
+      utc? ? 'UTC' : period.abbreviation.to_s
+    end
+  
+    def inspect
+      "#{time.strftime('%a, %d %b %Y %H:%M:%S')} #{zone} #{formatted_offset}"
+    end
+
+    def xmlschema
+      "#{time.strftime("%Y-%m-%dT%H:%M:%S")}#{formatted_offset(true, 'Z')}"
+    end
+  
+    def to_json(options = nil)
+      %("#{time.strftime("%Y/%m/%d %H:%M:%S")} #{formatted_offset(false)}")
+    end
+  
+    # :db format outputs time in UTC; all others output time in local. Uses TimeWithZone's strftime, so %Z and %z work correctly
+    def to_s(format = :default) 
+      return utc.to_s(format) if format == :db
+      if formatter = ::Time::DATE_FORMATS[format]
+        formatter.respond_to?(:call) ? formatter.call(self).to_s : strftime(formatter)
+      else
+        "#{time.strftime("%Y-%m-%d %H:%M:%S")} #{formatted_offset(false, 'UTC')}" # mimicking Ruby 1.9 Time#to_s format
+      end
+    end
+    
+    # Replaces %Z and %z directives with #zone and #formatted_offset, respectively, before passing to 
+    # Time#strftime, so that zone information is correct
+    def strftime(format)
+      format = format.gsub('%Z', zone).gsub('%z', formatted_offset(false))
+      time.strftime(format)
+    end
+  
+    # Use the time in UTC for comparisons
+    def <=>(other)
+      other = other.comparable_time if other.respond_to?(:comparable_time) # to coerce time from TimeWithZone
+      utc <=> other
+    end
+  
+    # A TimeProxy acts like a Time, so just return self
+    def to_time
+      self
+    end
+    
+    # so that self acts_like?(:time)
+    def acts_like_time?
+      true
+    end
+  
+    # Say we're a Time to thwart type checking
+    def is_a?(klass)
+      klass == ::Time || super
+    end
+    alias_method :kind_of?, :is_a?
+  
+    # Neuter freeze because freezing can cause problems with lazy loading of attributes
+    def freeze
+      self
+    end
+  
+    # Ensure proxy class responds to all methods that underlying time instance responds to
+    def respond_to?(sym)
+      super || time.respond_to?(sym)
+    end
+  
+    # Send the missing method to time instance, and wrap result in a new TimeWithZone with the existing time_zone
+    def method_missing(sym, *args, &block)
+      result = time.__send__(sym, *args, &block)
+      result = result.change_time_zone(time_zone) if result.acts_like?(:time)
+      result
+    end
+  
+    private
+      def get_period_for_local
+        t = time
+        begin
+          time_zone.period_for_local(t, true)
+        rescue ::TZInfo::PeriodNotFound # failover logic from TzTime
+          t -= 1.hour
+          retry
+        end
+      end
+  end
+end