/*
	pscalendar
 
	Unix C tool for generating continuous calendar pages in Postscript
	Copyright (C) 2004 Dave Bayer. Subject to the terms and conditions of the MIT License.

	This tool has no interface; to adjust settings, change the program constants below.
	To compile, type
 
		gcc pscalendar.c -o pscalendar
 
	To execute, type
 
		./pscalendar
*/

/* output file name */

 char file_name[] = "calendar.ps";

/* starting day, month, year */

unsigned firstday = 28;
unsigned firstmonth = 12;
int firstyear = 2003;

/* columns, rows, pages */

unsigned cols = 7;
unsigned rows = 6;
unsigned pages = 20;

/* font */

char font_name[] = "Times-Roman";
unsigned font_size = 12;

/* define units, e.g. 1 inch = 72 points, 1 cm = 28.3 points */

unsigned points_per_unit = 72;

/* page dimensions in chosen units */

double pagewidth = 8.5;
double pageheight = 11;

double leftmargin = 0.2;
double rightmargin = 0.2;
double topmargin = 0.2;
double bottommargin = 0.2;

double gap_between_boxes = 0.03;
double text_offset_x = 0.1;
double text_offset_y = 0.2;

/*------------------------------------------------------------------------------------------------*/

#include <stdio.h>
#define LEN 256

int month_length[13] =
{
	0,
	31, 28, 31, 30, 31, 30,
	31, 31, 30, 31, 30, 31
};

char *month_name[13] =
{
	"",
	"Jan", "Feb", "Mar", "Apr", "May", "Jun",
	"Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
};

typedef struct date
{
	unsigned day;
	unsigned month;
	int year;
} date;

static void date_advance( date *d )
{
	int day, month, year;
	
	day = d->day;
	month = d->month;
	year = d->year;
	
	if ( day == 28 && month == 2 && year % 4 == 0 && ( year % 100 != 0 || year % 400 == 0 )) {}
	else if ( day >= month_length[month] )
	{
		day = 0;
		if ( ++month == 13 )
		{
			month = 1;
			++year;
		}
	}
	++day;
	
	d->day = day;
	d->month = month;
	d->year = year;
}

static char *date_string( date *d, int level )
{
	static char s[LEN];
	
	if ( d->day == 1 ) level = 2;
	switch ( level )
	{
		case 2:
			sprintf( s, "%d %s %02d", d->day, month_name[d->month], d->year % 100 );
			break;
		default:
			sprintf( s, "%d", d->day );
			break;
	}
	return s;	
}

char *ps_header[] =
{
	"%!PS-Adobe-3.0",
	"%%Creator: Dave Bayer",
	"%%EndComments",
	"",
	"/choosefont",
	"{",
	"	exch findfont",
	"	exch scalefont",
	"	setfont",
	"} def",
	"",
	"/daybox",
	"{",
	"	/text exch def",
	"	/uly exch units def",
	"	/ulx exch units def",
	"	0.75 setlinewidth",
	"	newpath",
	"	ulx uly moveto",
	"	0 height neg rlineto",
	"	width 0 rlineto",
	"	0 height rlineto",
	"	closepath",
	"	stroke",
	"	ulx xoff add uly yoff sub moveto",
	"	text show	",
	"} def",
	"",
	0
};

char ps_constants[] =
	"/units {%d mul} def\n"
	"/width %.4f units def\n"
	"/height %.4f units def\n"
	"/xoff %.4f units def\n"
	"/yoff %.4f units def\n"
	"/%s %d choosefont\n\n"
;

char ps_daybox[] = "%.4f %.4f (%s) daybox\n";
char ps_page[] = "\nshowpage\n\n";

static void calendar ( FILE *fout )
{
	char **p;
	int i, j, k, level;
	double xinc, yinc;
	
	date d = {
		firstday, firstmonth, firstyear
	};
	
	xinc = ( pagewidth - leftmargin - rightmargin + gap_between_boxes ) / cols;
	yinc = ( pageheight - topmargin - bottommargin + gap_between_boxes ) / rows;
	
	for ( p=ps_header; *p!=0; ++p )
		fprintf( fout, "%s\n", *p );
	
	fprintf( fout, ps_constants, points_per_unit,
			xinc - gap_between_boxes, yinc - gap_between_boxes, text_offset_x, text_offset_y, font_name, font_size );
	
	for ( k=0; k<pages; ++k )
	{
		for ( i=0; i<rows; ++i )
			for ( j=0; j<cols; ++j )
			{
				level = ( i == 0 && j == 0 ) ? 2 : 1;
				fprintf( fout, ps_daybox, leftmargin + j*xinc, pageheight - topmargin - i*yinc, date_string( &d, level ));
				date_advance( &d );
			}
		fprintf( fout, ps_page );
	}
}

int main (int argc, const char * argv[])
{
	FILE *fout;
	
	fout = fopen( file_name, "w" );
	calendar( fout );
	return 0;
}