module TZInfo

  # A Timezone based on a LinkedTimezoneInfo.
  #
  # @private
  class LinkedTimezone < InfoTimezone #:nodoc:
    # Returns the TimezonePeriod for the given UTC time. utc can either be
    # a DateTime, Time or integer timestamp (Time.to_i). Any timezone 
    # information in utc is ignored (it is treated as a UTC time).        
    #
    # If no TimezonePeriod could be found, PeriodNotFound is raised.
    def period_for_utc(utc)
      @linked_timezone.period_for_utc(utc)
    end
    
    # Returns the set of TimezonePeriod instances that are valid for the given
    # local time as an array. If you just want a single period, use 
    # period_for_local instead and specify how abiguities should be resolved.
    # Raises PeriodNotFound if no periods are found for the given time.
    def periods_for_local(local)
      @linked_timezone.periods_for_local(local)
    end
    
    # Returns an Array of TimezoneTransition instances representing the times
    # where the UTC offset of the timezone changes.
    #
    # Transitions are returned up to a given date and time up to a given date 
    # and time, specified in UTC (utc_to).
    #
    # A from date and time may also be supplied using the utc_from parameter
    # (also specified in UTC). If utc_from is not nil, only transitions from 
    # that date and time onwards will be returned.
    #
    # Comparisons with utc_to are exclusive. Comparisons with utc_from are
    # inclusive. If a transition falls precisely on utc_to, it will be excluded.
    # If a transition falls on utc_from, it will be included.
    #
    # Transitions returned are ordered by when they occur, from earliest to 
    # latest.
    #
    # utc_to and utc_from can be specified using either DateTime, Time or 
    # integer timestamps (Time.to_i).
    #
    # If utc_from is specified and utc_to is not greater than utc_from, then
    # transitions_up_to raises an ArgumentError exception.
    def transitions_up_to(utc_to, utc_from = nil)
      @linked_timezone.transitions_up_to(utc_to, utc_from)
    end
    
    # Returns the canonical zone for this Timezone.
    #
    # For a LinkedTimezone, this is the canonical zone of the link target.
    def canonical_zone
      @linked_timezone.canonical_zone
    end
    
    protected
      def setup(info)
        super(info)
        @linked_timezone = Timezone.get(info.link_to_identifier)
      end
  end
end