module TimeCrisis
  module TZInfo
    # Represents an offset defined in a Timezone data file.
    class TimezoneOffsetInfo #:nodoc:
      # The base offset of the timezone from UTC in seconds.
      attr_reader :utc_offset

      # The offset from standard time for the zone in seconds (i.e. non-zero if
      # daylight savings is being observed).
      attr_reader :std_offset

      # The total offset of this observance from UTC in seconds
      # (utc_offset + std_offset).
      attr_reader :utc_total_offset

      # The abbreviation that identifies this observance, e.g. "GMT"
      # (Greenwich Mean Time) or "BST" (British Summer Time) for "Europe/London". The returned identifier is a
      # symbol.
      attr_reader :abbreviation

      # Constructs a new TimezoneOffsetInfo. utc_offset and std_offset are
      # specified in seconds.
      def initialize(utc_offset, std_offset, abbreviation)
        @utc_offset = utc_offset
        @std_offset = std_offset
        @abbreviation = abbreviation

        @utc_total_offset = @utc_offset + @std_offset
      end

      # True if std_offset is non-zero.
      def dst?
        @std_offset != 0
      end

      # Converts a UTC DateTime to local time based on the offset of this period.
      def to_local(utc)
        TimeOrDateTime.wrap(utc) {|wrapped|
          wrapped + @utc_total_offset
        }
      end

      # Converts a local DateTime to UTC based on the offset of this period.
      def to_utc(local)
        TimeOrDateTime.wrap(local) {|wrapped|
          wrapped - @utc_total_offset
        }
      end

      # Returns true if and only if toi has the same utc_offset, std_offset
      # and abbreviation as this TimezoneOffsetInfo.
      def ==(toi)
        toi.respond_to?(:utc_offset) && toi.respond_to?(:std_offset) && toi.respond_to?(:abbreviation) &&
                utc_offset == toi.utc_offset && std_offset == toi.std_offset && abbreviation == toi.abbreviation
      end

      # Returns true if and only if toi has the same utc_offset, std_offset
      # and abbreviation as this TimezoneOffsetInfo.
      def eql?(toi)
        self == toi
      end

      # Returns a hash of this TimezoneOffsetInfo.
      def hash
        utc_offset.hash ^ std_offset.hash ^ abbreviation.hash
      end

      # Returns internal object state as a programmer-readable string.
      def inspect
        "#<#{self.class}: #@utc_offset,#@std_offset,#@abbreviation>"
      end
    end
  end

end