#!/usr/bin/env ruby

class GPSTime
  def GPSTime::itow(utc = Time::now)
    sec = utc - Time::gm(1980, 1, 6, 0, 0, 0)
    if sec < 0 then return nil end
    
    [
      Time::gm(1981, 7, 1, 0, 0, 0),
      Time::gm(1982, 7, 1, 0, 0, 0),
      Time::gm(1983, 7, 1, 0, 0, 0),
      Time::gm(1985, 7, 1, 0, 0, 0),
      Time::gm(1988, 1, 1, 0, 0, 0),
      Time::gm(1990, 1, 1, 0, 0, 0),
      Time::gm(1991, 1, 1, 0, 0, 0),
      Time::gm(1992, 7, 1, 0, 0, 0),
      Time::gm(1993, 7, 1, 0, 0, 0),
      Time::gm(1994, 7, 1, 0, 0, 0),
      Time::gm(1996, 1, 1, 0, 0, 0),
      Time::gm(1997, 7, 1, 0, 0, 0),
      Time::gm(1999, 1, 1, 0, 0, 0),
      Time::gm(2006, 1, 1, 0, 0, 0),
      Time::gm(2009, 1, 1, 0, 0, 0)
    ].each{|item| if utc > item then sec += 1 end}
    cycle = (sec / (1024 * 7 * 24 * 60 * 60)).to_i
    sec = sec % (1024 * 7 * 24 * 60 * 60)
    week = (sec / (7 * 24 * 60 * 60)).to_i
    [cycle, week, sec % (7 * 24 * 60 * 60)]
  end
end

if $0 == __FILE__ then
  if ARGV.empty? then
    p GPSTime::itow
  else
    require 'time'
    p GPSTime::itow(Time::parse(ARGV.join(' ')))
  end
end