#!/bin/perl
################################################################################
# jdate.pl                                                                     #
# Purpose: Calculates the julian date from date or vice-versa.                 #
# Written by: Kelly Cash on November 30, 2001                                  #
#                                                                              #
# Required files: getopt.pl - Hardcoded location below; find it on your system #
#                                                                              #
# Switches: -2 - Specifies 2-character year  eg: 01151                         #
#           -4 - Specifies 4-character year  eg: 2001151                       #
#                Default is 2-character year format (5-char julian date)       #
#           -r - Reverse mode: derive YYYYMODY date format from supplied jdate #
#                                                                              #
# Args:  YR MO DY - Specify the date to be converted to julian.                #
#                   Arguments are positionally dependent.                      #
#                   Default is the current day.                                #
#                                                                              #
# Notes: Command-line switches and arguments are all optional.                 #
#                                                                              #
#        Command-line switches must precede command-line arguments.            #
#                                                                              #
#        If you specify -4 AND a date to convert, you'd better supply a        #
#        4-character year (eg: 1999) for me!  (I'm not doing it for you)       #
#                                                                              #
#        Reverse mode requires julian date in 4-char year format               #
#                                                                              #
#        Reverse mode is mutually exclusive with all other switches and args   #
#                                                                              #
# Usage examples:  jdate.pl -2             Returns today's jdate, 2-char year  #
#                  jdate.pl 99 10 26       Returns jdate for 10/20/1999        #
#                  jdate.pl -4 02 01 01    Returns 20020101                    #
#                  jdate.pl -r 2001336     Returns 12/02/2001                  #
#                                                                              #
# Called by: check_in.pl                                                       #
#            check_in_daemon.pl                                                #
#                                                                              #
# Revision history:                                                            #
# KAC  2001/11/30  Initial implementation                                      #
# KAC  2001/12/01  Added reverse mode functionality                            #
# KAC  2001/12/29  Fixed bug in losing a digit from Jan 01 - Jan 09.           #
#                  (ex: 2002003 was incorrectly reported as 200203)            #
################################################################################

require "/usr/local/lib/perl5/getopts.pl";

# open(DEBUG, ">jdate.debug");

# To calculate the jdate, all days of previous months must be added to day
#             J  F   M   A    M    J    J    A    S    O    N    D
@dayadd = (0, 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334);
#          ^--  Dummy to offset values to start at @dayadd[1]

&Getopts('24r');	# -2, -4 and -r switches allowed

# printf DEBUG "Switches are: 2: %s    4: %s    r: %s\n", $opt_2, $opt_4, $opt_r;
# printf DEBUG "Args are:%s %s %s %s %s %s %s %s %s %s %s %s\n", @ARGV;

if ($opt_r ne "") {
	# Reverse mode.  Take supplied switch argument and convert back to YYYYMODY.
	$jday = substr(@ARGV[0],4,3);
	$mo = 12;
	$mo-- while ($dayadd[$mo] >= $jday); 
	$dy = $jday - $dayadd[$mo];
	$dy = substr("0".$dy,-2,2);	# zero-pad the day
	$mo = substr("0".$mo,-2,2);	# zero-pad the month

	printf "%s/%s/%s\n", $mo, $dy, substr(@ARGV[0],0,4);
} else {
	# Regular mode.  Calculate julian date from today's date or supplied arguments.
	if (@ARGV[0] ne "") {
		# Arguments were passed, take them as the date
		$yr = @ARGV[0];
		$mo = @ARGV[1];
		$dy = @ARGV[2];
	} else {
		# No args passed, use today's date
		$date = `date '+%Y%m%d'`;
		$yr = substr($date,0,4);
		$mo = substr($date,4,2);
		$dy = substr($date,6,2);
	}
	
	# If not returning a 4-character year, remove the leading two chars 
	$yr = substr($yr,-2,2) if ($opt_4 == 0);
		
	# printf DEBUG "JDATE: Year:%s   Month:%s   Day:%s\n", $yr, $mo, $dy;
	
	$jdate = $dy + $dayadd[$mo];
	$jdate = substr("00".$jdate,-3,3);	# zero-pad the number
	if ($jdate > 59) {
		# We're past Feb 28th. Check and correct for leap year.
		# If year is evenly divisible by 4, add the leap day.
		$jdate++ if ($yr/4 == 0);
	}
	
	printf "%s\n", $yr.$jdate;
}

# close(DEBUG);