require 'time_crisis/tzinfo/timezone'

module TimeCrisis
  module TZInfo

    # A proxy class representing a timezone with a given identifier. TimezoneProxy
    # inherits from Timezone and can be treated like any Timezone loaded with
    # Timezone.get.
    #
    # The first time an attempt is made to access the data for the timezone, the
    # real Timezone is loaded. If the proxy's identifier was not valid, then an
    # exception will be raised at this point.
    class TimezoneProxy < Timezone
      # Construct a new TimezoneProxy for the given identifier. The identifier
      # is not checked when constructing the proxy. It will be validated on the
      # when the real Timezone is loaded.
      def self.new(identifier)
        # Need to override new to undo the behaviour introduced in Timezone#new.
        tzp = super()
        tzp.send(:setup, identifier)
        tzp
      end

      # The identifier of the timezone, e.g. "Europe/Paris".
      def identifier
        @real_timezone ? @real_timezone.identifier : @identifier
      end

      # 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).
      def period_for_utc(utc)
        real_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.
      # Returns an empty array if no periods are found for the given time.
      def periods_for_local(local)
        real_timezone.periods_for_local(local)
      end

      # Dumps this TimezoneProxy for marshalling.
      def _dump(limit)
        identifier
      end

      # Loads a marshalled TimezoneProxy.
      def self._load(data)
        TimezoneProxy.new(data)
      end

      private
      def setup(identifier)
        @identifier = identifier
        @real_timezone = nil
      end

      def real_timezone
        @real_timezone ||= Timezone.get(@identifier)
      end
    end
  end
end