/* use the javascript canvas to paint a polyomino tiling
 * from its letter matrix */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define BOARDWIDTH 250

static const int y0 = 20;
static int y1;
static int x0, x1;
static int dpl; /* dots per letter */
static int width; /* in letters */
static int lineno; /* line number */
#define xloc(n) ((n)*dpl + x0)

static char thisline[BOARDWIDTH+6], lastline[BOARDWIDTH+6];

static void setScale(void)
{
dpl = 20;
while(dpl*width > 760) --dpl;
if(dpl < 7) {
fprintf(stderr, "dpl %d too small\n", dpl);
exit(1);
}
x0 = 400 - dpl * width / 2;
x1 = xloc(width);
} /* setScale */

static void printRow(void)
{
int agree, i, y2;

if(!lineno) {
/* top line of the rectangle */
printf("cvx.moveTo(%d,%d);\n", x0, y0);
printf("cvx.lineTo(%d,%d);\n", x1, y0);
y1 = y0;
} else {
/* borders with previous row */
agree = -1;
for(i=0; i<width; ++i) {
if(thisline[i] != lastline[i])
continue;
if(agree+1 < i) {
/* region of disagreeing letters, draw line */
printf("cvx.moveTo(%d,%d);\n", xloc(agree+1), y1);
printf("cvx.lineTo(%d,%d);\n", xloc(i), y1);
}
agree = i;
}
if(agree+1 < i) {
printf("cvx.moveTo(%d,%d);\n", xloc(agree+1), y1);
printf("cvx.lineTo(%d,%d);\n", xloc(i), y1);
}
}

y2 = y1 + dpl;
/* left and right border */
printf("cvx.moveTo(%d,%d);\n", x0, y1);
printf("cvx.lineTo(%d,%d);\n", x0, y2);
printf("cvx.moveTo(%d,%d);\n", x1, y1);
printf("cvx.lineTo(%d,%d);\n", x1, y2);

for(i=1; i<width; ++i) {
if(thisline[i] == thisline[i-1])
continue;
printf("cvx.moveTo(%d,%d);\n", xloc(i), y1);
printf("cvx.lineTo(%d,%d);\n", xloc(i), y2);
}

y1 = y2;
++lineno;
} /* printRow */

int main(int argc, char **argv)
{
FILE *f;
int w;
char *s;

if(argc != 2) {
fprintf(stderr, "usage:  canvas letterfile\n");
exit(1);
}

f = fopen(argv[1], "r");
if(!f) {
fprintf(stderr, "canvas cannot open %s\n", argv[1]);
exit(1);
}

puts("<script language=JavaScript>");
puts("cv=document.getElementById('myCanvas');");
puts("cvx=cv.getContext('2d');");
puts("cvx.beginPath();");

while(fgets(thisline, sizeof(thisline), f)) {
s = strpbrk(thisline, "\r\n");
if(s) *s = 0;
w = strlen(thisline);
if(!lineno) {
width = w;
setScale();
} else if(width != w) {
fprintf(stderr, "width mismatch %d versus %d\n", width, w);
exit(1);
}
printRow();
strcpy(lastline, thisline);
}

/* bottom line */
printf("cvx.moveTo(%d,%d);\n", x0, y1);
printf("cvx.lineTo(%d,%d);\n", x1, y1);
printf("cvx.moveTo(%d,%d);\n", x0, y1+20);
puts("cvx.stroke();");
puts("</script>");
} /* main */