# Calendar-Generator
#
# J. Nagasaki, Jan. 2006
# Last change: 2007-04-07
#


# Predefines

$dash = "-------------------------";
$ddash = "=========================";
$space = "                                                                                       ";
$width = 10;	# min = 5

@ultimo = (0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);
@dayname = ("Mo", "Tu", "We", "Th", "Fr", "Sa", "Su");
@month1 = ("JAN", "FEB", "MAR", "APR", "MAY", "JUN",
           "JUL", "AUG", "SEP", "OCT", "NOV", "DEC");
@month2 = ("January", "February", "March", "April", "May", "June",
           "July", "August", "September", "October", "November", "December");

$args = @ARGV;

print "\n Calendar Calculation\n";
print "======================\n\n";
print "J. Nagasaki, Jan. 2006\n\n";


# ======= check arguments ========

if ($args < 1)
{
	print "Usage:\n";
	print "perl calendar.pl <n> <2YYY> <output file>\n\n";
	print "<n> = cloumn width (min. 5)\n\n";
	print "Year must be greater than 2000 and less than 2200.\n\n";
	exit (1);
}

$width = $ARGV[0];

if (($width < 5) || ($width > 25))
{
	print "Please give clumn width greater than 4 and smaller than 26.\n\n";
	exit(1);
}

$year = $ARGV[1];

if ((!($year =~ /2[0-1][0-9][0-9]/)) || ($year < 2001))
{
	print "Please use year greater than 2000 and number format 2YYY for year number!\n\n";
	exit (1);
}

$filename = $ARGV[2];

print "Calendar for $year will be generated ...\n\n";


# Usage of month name or abbreviation according to column width

if ($width > 10)
{
	@month = @month2;
}
else
{
	@month = @month1;
}


# Calculation of format of column width to center month name ontop table head

$dstr = substr($dash, 0, $width);	# width for "----- ..."
$ddstr = substr($ddash, 0, $width);	# width for "===== ..."

@prmonat = "";				# Space place holder field of month names (@month)

$i = 0;					# place holder left and right of month name and name to @prmonat-strings
foreach (@month)
{
	$sp1 = int($width / 2 - length($month[$i]) / 2);
	$sp2 = $width - length($month[$i]) - $sp1;
	
	$prmonat[$i] = 	substr($space, 0, $sp1).$month[$i].substr($space, 0, $sp2);
	$i++;
}
	

# ========= calendar precalculations ===========

# calculation of leap-years

$leapdays = 0;
for ($fyear = 2001; $fyear <= ($year - 1); $fyear++)
{
	$leapdays++ if (($fyear / 4) == int($fyear  / 4));
	$leapdays-- if (($fyear / 400) == int($fyear / 400));
	#$leapdays = 0 if ($fyear == 2000);			# 2000 NO leap-year!
}


# calculation of day (name) of 1st January (2001-01-01 was a Monday == 0)

$primo[1] = (($year - 2001) + $leapdays) % 7;


# calculation if actual year is a leap-year

$leapdays = 0;
$fyear = $year;
$leapdays++ if (($fyear  / 4) == int($fyear  / 4));
$leapdays-- if (($fyear  / 400) == int($fyear / 400));

$ultimo[2] = $ultimo[2] + $leapdays;				# adapt February


# calculation of first days of weak for the remaining months

for ($i = 2; $i <= 12; $i++)
{
	$primo[$i] = ($primo[$i - 1] + $ultimo[$i - 1]) % 7;
}


# ========== Output of Calendar Table ==========

@outfile = "";

for ($l = 0; $l < 2; $l++)
{
	push (@outfile, "\n");
	
	$indent = substr($space, 0, (3 * $width - 5));
	
	if ($l == 0)
	{
		$halfyear = "1st";
	}
	else
	{
		$halfyear = "2nd";
	}
	
	push (@outfile, "$indent$halfyear HALFYEAR $year\n\n");
	
	push (@outfile, ".$dstr.$dstr.$dstr.$dstr.$dstr.$dstr.\n");
	
	if (!$l)
	{
		push (@outfile, "|$prmonat[0]|$prmonat[1]|$prmonat[2]|$prmonat[3]|$prmonat[4]|$prmonat[5]|\n");
	}
	else
	{
		push (@outfile, "|$prmonat[6]|$prmonat[7]|$prmonat[8]|$prmonat[9]|$prmonat[10]|$prmonat[11]|\n");
	}

	push (@outfile, "|$ddstr|$ddstr|$ddstr|$ddstr|$ddstr|$ddstr|\n");

	for ($dayname = 0; $dayname <= 30; $dayname++)
	{
		push (@outfile, "|");

		for ($j = (($l * 6) + 1); $j <= (($l * 6) + 6); $j++)
		{
			$k = ($primo[$j] + $dayname) % 7;

			if (($dayname + 1) <= $ultimo[$j])
			{
				push (@outfile, "$dayname[$k] ");
				push (@outfile, " ") if (($dayname + 1) < 10);
				push (@outfile, ($dayname + 1));
				$sp = substr($space, 0, $width - 5);
				push (@outfile, "$sp|");
			}
			else
			{
				$sp = substr($space, 0, $width);
				push (@outfile, "$sp|");
			}
		}
		push (@outfile, "\n");

		if ($dayname == 30)
		{
			push (@outfile, "'");
		}
		else
		{
			push (@outfile, "|");
		}
	
		for ($j = (($l * 6) + 1); $j <= (($l * 6) + 6); $j++)
		{
			$k = ($primo[$j] + $dayname) % 7;

			if ((($dayname + 1) <= $ultimo[$j]) && ($k == 6))
			{
				push (@outfile, "$ddstr");
			}
			else
			{
				push (@outfile, "$dstr");
			}
			
			if ($dayname == 30)
			{
				push (@outfile, "'");
			}
			else
			{
				push (@outfile, "|");
			}
		}
		push (@outfile, "\n");
	}
	push (@outfile, "\n\n\n");
}

print "Done!\n\n";

open(FILE, ">$filename");
print FILE @outfile;
close(FILE);