module Icalendar
  # date = date-fullyear date-month date-mday
  # date-fullyear = 4 DIGIT
  # date-month = 2 DIGIT
  # date-mday = 2 DIGIT
  DATE = '(\d\d\d\d)(\d\d)(\d\d)'

  # time = time-hour [":"] time-minute [":"] time-second [time-secfrac] [time-zone]
  # time-hour = 2 DIGIT
  # time-minute = 2 DIGIT
  # time-second = 2 DIGIT
  # time-secfrac = "," 1*DIGIT
  # time-zone = "Z" / time-numzone
  # time-numzome = sign time-hour [":"] time-minute
  TIME = '(\d\d)(\d\d)(\d\d)(Z)?'


  # Maps to dtstart property
  # TODO: Look into having the DateTime library do more of the work...
  module Dtstart

    # Set the starting DateTime of an Event, Todo,
    # Freebusy or Timezone component.  If utc is set to true
    # then this time represents absolute time without regard for
    # timezone information.
    def setStart(start, utc = false)
      if start.respond_to?(:year) # Date format
        s = ""

        # 4 digit year
        s << start.year.to_s
        
        # Double digit month
        s << "0" unless start.month > 9 
        s << start.month.to_s

        # Double digit day
        s << "0" unless start.day > 9 
        s << start.day.to_s
      else
        raise InvalidPropertyValue, "Cannot access year on start argument object!"
      end
      
      if start.respond_to?(:hour) # include Time format if possible
        s << "T"
        
        # Double digit hour
        s << "0" unless start.hour > 9 
        s << start.hour.to_s

        # Double digit minute
        s << "0" unless start.min > 9 
        s << start.min.to_s

        # Double digit second
        s << "0" unless start.sec > 9 
        s << start.sec.to_s
      end

      # UTC time gets a Z suffix
      if utc
        s << "Z"
      end

      @properties["DTSTART"] = s
    end

    # Returns the starting DateTime of an Event, Todo, Freebusy or
    # Timezone component.
    def getStart
      # If we don't have a start time then return nil.
      unless @properties.has_key?("DTSTART")
        return nil
      end
      s = @properties["DTSTART"]
      
      # If we can't parse the start time figure its bad and return nil.
      unless s =~ %r{#{DATE}}i
        return nil
      end

      # We can at least create a Date object
      year = $1
      month = $2
      day = $3

      puts "s: #{s}"
      puts "#{DATE}T#{TIME}"
      # We might be able to get the time too
      if s =~ %r{"#{DATE}T#{TIME}"}i
        hour = $5
        min = $6
        sec = $7

        puts "Hour: #{hour.to_s}"
        
        return DateTime.new(year, month, day, hour, min, sec)
      else
        return Date.new(year.to_i, month.to_i, day.to_i)
      end    
    end
  end
end