require 'win32ole'
require 'socket'
require 'date'
require 'time'

# The Sys module serves as a namespace only.
module Sys
   
   # The Uptime class encapsulates various bits of information regarding your
   # system's uptime, including boot time.
   class Uptime
      
      # Error typically raised in one of the Uptime methods should fail.
      class Error < StandardError; end

      # The version of this library.
      VERSION = '0.5.3'

      # Returns the boot time as a Time object.
      #
      # Example:
      #
      #    Sys::Uptime.boot_time # => Fri Dec 12 20:18:58 -0700 2008
      #
      def self.boot_time(host=Socket.gethostname)
         cs = "winmgmts://#{host}/root/cimv2"
         begin
            wmi = WIN32OLE.connect(cs)
         rescue WIN32OLERuntimeError => e
            raise Error, e
         else
            query = "select LastBootupTime from Win32_OperatingSystem"
            results = wmi.ExecQuery(query)
            results.each{ |ole|
               time_array = parse_ms_date(ole.LastBootupTime)
               return Time.mktime(*time_array)
            }
         end
      end
      
      # Calculates and returns the number of days, hours, minutes and
      # seconds the +host+ has been running as a colon-separated string.
      #
      # The localhost is used if no +host+ is provided.
      #
      # Example:
      #
      #    Sys::Uptime.uptime # => "1:9:55:11"
      #
      def self.uptime(host=Socket.gethostname)
         get_dhms(host).join(':')
      end
      
      # Calculates and returns the number of days, hours, minutes and
      # seconds the +host+ has been running as a four-element Array.
      # The localhost is used if no +host+ is provided.
      #
      # Example:
      #
      #    Sys::Uptime.dhms # => [1, 9, 55, 11]
      #
      def self.dhms(host=Socket.gethostname)
         get_dhms(host)
      end
      
      # Returns the total number of days the system has been up on +host+,
      # or the localhost if no host is provided.
      #
      # Example:
      #
      #    Sys::Uptime.days # => 1
      #
      def self.days(host=Socket.gethostname)
         hours(host) / 24
      end
      
      # Returns the total number of hours the system has been up on +host+,
      # or the localhost if no host is provided.
      #
      # Example:
      #
      #    Sys::Uptime.hours # => 33
      #
      def self.hours(host=Socket.gethostname)
         minutes(host) / 60
      end
      
      # Returns the total number of minutes the system has been up on +host+,
      # or the localhost if no host is provided.
      #
      # Example:
      #
      #    Sys::Uptime.minutes # => 1980
      #
      def self.minutes(host=Socket.gethostname)
         seconds(host) / 60
      end
      
      # Returns the total number of seconds the system has been up on +host+,
      # or the localhost if no host is provided.
      #
      # Example:
      #
      #    Sys::Uptime.seconds # => 118800
      #
      def self.seconds(host=Socket.gethostname)
         get_seconds(host)
      end
      
      private
      
      # Converts a string in the format '20040703074625.015625-360' into a
      # Ruby Time object.
      #
      def self.parse_ms_date(str)
         return if str.nil?
         return Time.parse(str.split('.').first)
      end
      
      # Get the actual days, hours, minutes and seconds since boot using WMI.
      #
      def self.get_dhms(host)
         seconds = get_seconds(host)

         days = (seconds / 86400).to_i
         seconds -= days * 86400
         hours = seconds / 3600
         seconds -= hours * 3600
         minutes = seconds / 60
         seconds -= minutes * 60

         [days, hours, minutes, seconds]
      end

      # Returns the number of seconds since boot.
      #
      def self.get_seconds(host)
         cs = "winmgmts://#{host}/root/cimv2"
         begin
            wmi = WIN32OLE.connect(cs)
         rescue WIN32OLERuntimeError => e
            raise Error, e
         else
            query = "select LastBootupTime from Win32_OperatingSystem"
            results = wmi.ExecQuery(query)
            now = Time.now
            
            results.each{ |ole|
               time_array = parse_ms_date(ole.LastBootupTime)
               boot_time = Time.mktime(*time_array)
               break
            }
         end
            
         (now - boot_time).to_i
      end
   end
end